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mirror_zfs/module/zfs/arc.c
shodanshok 7aef672b77 Read prefetched buffers from L2ARC 
Prefetched buffers are currently read from L2ARC if, and only if,
l2arc_noprefetch is set to non-default value of 0. This means that
a streaming read which can be served from L2ARC will instead engage
the main pool.

For example, consider what happens when a file is sequentially read:
- application requests contiguous data, engaging the prefetcher;
- ARC buffers are initially marked as prefetched but, as the calling
application consumes data, the prefetch tag is cleared;
- these "normal" buffers become eligible for L2ARC and are copied to it;
- re-reading the same file will *not* engage L2ARC even if it contains
the required buffers;
- main pool has to suffer another sequential read load, which (due to
most NCQ-enabled HDDs preferring sequential loads) can dramatically
increase latency for uncached random reads.

In other words, current behavior is to write data to L2ARC (wearing it)
without using the very same cache when reading back the same data. This
was probably useful many years ago to preserve L2ARC read bandwidth but,
with current SSD speed/size/price, it is vastly sub-optimal.

Setting l2arc_noprefetch=1, while enabling L2ARC to serve these reads,
means that even prefetched but unused buffers will be copied into L2ARC,
further increasing wear and load for potentially not-useful data.

This patch enable prefetched buffer to be read from L2ARC even when
l2arc_noprefetch=1 (default), increasing sequential read speed and
reducing load on the main pool without polluting L2ARC with not-useful
(ie: unused) prefetched data. Moreover, it clear users confusion about
L2ARC size increasing but not serving any IO when doing sequential
reads.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Gionatan Danti <g.danti@assyoma.it>
Closes #15451
2023-11-06 16:47:51 -08:00

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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or https://opensource.org/licenses/CDDL-1.0.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2018, Joyent, Inc.
* Copyright (c) 2011, 2020, Delphix. All rights reserved.
* Copyright (c) 2014, Saso Kiselkov. All rights reserved.
* Copyright (c) 2017, Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2019, loli10K <ezomori.nozomu@gmail.com>. All rights reserved.
* Copyright (c) 2020, George Amanakis. All rights reserved.
* Copyright (c) 2019, Klara Inc.
* Copyright (c) 2019, Allan Jude
* Copyright (c) 2020, The FreeBSD Foundation [1]
*
* [1] Portions of this software were developed by Allan Jude
* under sponsorship from the FreeBSD Foundation.
*/
/*
* DVA-based Adjustable Replacement Cache
*
* While much of the theory of operation used here is
* based on the self-tuning, low overhead replacement cache
* presented by Megiddo and Modha at FAST 2003, there are some
* significant differences:
*
* 1. The Megiddo and Modha model assumes any page is evictable.
* Pages in its cache cannot be "locked" into memory. This makes
* the eviction algorithm simple: evict the last page in the list.
* This also make the performance characteristics easy to reason
* about. Our cache is not so simple. At any given moment, some
* subset of the blocks in the cache are un-evictable because we
* have handed out a reference to them. Blocks are only evictable
* when there are no external references active. This makes
* eviction far more problematic: we choose to evict the evictable
* blocks that are the "lowest" in the list.
*
* There are times when it is not possible to evict the requested
* space. In these circumstances we are unable to adjust the cache
* size. To prevent the cache growing unbounded at these times we
* implement a "cache throttle" that slows the flow of new data
* into the cache until we can make space available.
*
* 2. The Megiddo and Modha model assumes a fixed cache size.
* Pages are evicted when the cache is full and there is a cache
* miss. Our model has a variable sized cache. It grows with
* high use, but also tries to react to memory pressure from the
* operating system: decreasing its size when system memory is
* tight.
*
* 3. The Megiddo and Modha model assumes a fixed page size. All
* elements of the cache are therefore exactly the same size. So
* when adjusting the cache size following a cache miss, its simply
* a matter of choosing a single page to evict. In our model, we
* have variable sized cache blocks (ranging from 512 bytes to
* 128K bytes). We therefore choose a set of blocks to evict to make
* space for a cache miss that approximates as closely as possible
* the space used by the new block.
*
* See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
* by N. Megiddo & D. Modha, FAST 2003
*/
/*
* The locking model:
*
* A new reference to a cache buffer can be obtained in two
* ways: 1) via a hash table lookup using the DVA as a key,
* or 2) via one of the ARC lists. The arc_read() interface
* uses method 1, while the internal ARC algorithms for
* adjusting the cache use method 2. We therefore provide two
* types of locks: 1) the hash table lock array, and 2) the
* ARC list locks.
*
* Buffers do not have their own mutexes, rather they rely on the
* hash table mutexes for the bulk of their protection (i.e. most
* fields in the arc_buf_hdr_t are protected by these mutexes).
*
* buf_hash_find() returns the appropriate mutex (held) when it
* locates the requested buffer in the hash table. It returns
* NULL for the mutex if the buffer was not in the table.
*
* buf_hash_remove() expects the appropriate hash mutex to be
* already held before it is invoked.
*
* Each ARC state also has a mutex which is used to protect the
* buffer list associated with the state. When attempting to
* obtain a hash table lock while holding an ARC list lock you
* must use: mutex_tryenter() to avoid deadlock. Also note that
* the active state mutex must be held before the ghost state mutex.
*
* It as also possible to register a callback which is run when the
* metadata limit is reached and no buffers can be safely evicted. In
* this case the arc user should drop a reference on some arc buffers so
* they can be reclaimed. For example, when using the ZPL each dentry
* holds a references on a znode. These dentries must be pruned before
* the arc buffer holding the znode can be safely evicted.
*
* Note that the majority of the performance stats are manipulated
* with atomic operations.
*
* The L2ARC uses the l2ad_mtx on each vdev for the following:
*
* - L2ARC buflist creation
* - L2ARC buflist eviction
* - L2ARC write completion, which walks L2ARC buflists
* - ARC header destruction, as it removes from L2ARC buflists
* - ARC header release, as it removes from L2ARC buflists
*/
/*
* ARC operation:
*
* Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
* This structure can point either to a block that is still in the cache or to
* one that is only accessible in an L2 ARC device, or it can provide
* information about a block that was recently evicted. If a block is
* only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
* information to retrieve it from the L2ARC device. This information is
* stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
* that is in this state cannot access the data directly.
*
* Blocks that are actively being referenced or have not been evicted
* are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
* the arc_buf_hdr_t that will point to the data block in memory. A block can
* only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
* caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
* also in the arc_buf_hdr_t's private physical data block pointer (b_pabd).
*
* The L1ARC's data pointer may or may not be uncompressed. The ARC has the
* ability to store the physical data (b_pabd) associated with the DVA of the
* arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block,
* it will match its on-disk compression characteristics. This behavior can be
* disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
* compressed ARC functionality is disabled, the b_pabd will point to an
* uncompressed version of the on-disk data.
*
* Data in the L1ARC is not accessed by consumers of the ARC directly. Each
* arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
* Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
* consumer. The ARC will provide references to this data and will keep it
* cached until it is no longer in use. The ARC caches only the L1ARC's physical
* data block and will evict any arc_buf_t that is no longer referenced. The
* amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
* "overhead_size" kstat.
*
* Depending on the consumer, an arc_buf_t can be requested in uncompressed or
* compressed form. The typical case is that consumers will want uncompressed
* data, and when that happens a new data buffer is allocated where the data is
* decompressed for them to use. Currently the only consumer who wants
* compressed arc_buf_t's is "zfs send", when it streams data exactly as it
* exists on disk. When this happens, the arc_buf_t's data buffer is shared
* with the arc_buf_hdr_t.
*
* Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
* first one is owned by a compressed send consumer (and therefore references
* the same compressed data buffer as the arc_buf_hdr_t) and the second could be
* used by any other consumer (and has its own uncompressed copy of the data
* buffer).
*
* arc_buf_hdr_t
* +-----------+
* | fields |
* | common to |
* | L1- and |
* | L2ARC |
* +-----------+
* | l2arc_buf_hdr_t
* | |
* +-----------+
* | l1arc_buf_hdr_t
* | | arc_buf_t
* | b_buf +------------>+-----------+ arc_buf_t
* | b_pabd +-+ |b_next +---->+-----------+
* +-----------+ | |-----------| |b_next +-->NULL
* | |b_comp = T | +-----------+
* | |b_data +-+ |b_comp = F |
* | +-----------+ | |b_data +-+
* +->+------+ | +-----------+ |
* compressed | | | |
* data | |<--------------+ | uncompressed
* +------+ compressed, | data
* shared +-->+------+
* data | |
* | |
* +------+
*
* When a consumer reads a block, the ARC must first look to see if the
* arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
* arc_buf_t and either copies uncompressed data into a new data buffer from an
* existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a
* new data buffer, or shares the hdr's b_pabd buffer, depending on whether the
* hdr is compressed and the desired compression characteristics of the
* arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
* arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
* the last buffer in the hdr's b_buf list, however a shared compressed buf can
* be anywhere in the hdr's list.
*
* The diagram below shows an example of an uncompressed ARC hdr that is
* sharing its data with an arc_buf_t (note that the shared uncompressed buf is
* the last element in the buf list):
*
* arc_buf_hdr_t
* +-----------+
* | |
* | |
* | |
* +-----------+
* l2arc_buf_hdr_t| |
* | |
* +-----------+
* l1arc_buf_hdr_t| |
* | | arc_buf_t (shared)
* | b_buf +------------>+---------+ arc_buf_t
* | | |b_next +---->+---------+
* | b_pabd +-+ |---------| |b_next +-->NULL
* +-----------+ | | | +---------+
* | |b_data +-+ | |
* | +---------+ | |b_data +-+
* +->+------+ | +---------+ |
* | | | |
* uncompressed | | | |
* data +------+ | |
* ^ +->+------+ |
* | uncompressed | | |
* | data | | |
* | +------+ |
* +---------------------------------+
*
* Writing to the ARC requires that the ARC first discard the hdr's b_pabd
* since the physical block is about to be rewritten. The new data contents
* will be contained in the arc_buf_t. As the I/O pipeline performs the write,
* it may compress the data before writing it to disk. The ARC will be called
* with the transformed data and will memcpy the transformed on-disk block into
* a newly allocated b_pabd. Writes are always done into buffers which have
* either been loaned (and hence are new and don't have other readers) or
* buffers which have been released (and hence have their own hdr, if there
* were originally other readers of the buf's original hdr). This ensures that
* the ARC only needs to update a single buf and its hdr after a write occurs.
*
* When the L2ARC is in use, it will also take advantage of the b_pabd. The
* L2ARC will always write the contents of b_pabd to the L2ARC. This means
* that when compressed ARC is enabled that the L2ARC blocks are identical
* to the on-disk block in the main data pool. This provides a significant
* advantage since the ARC can leverage the bp's checksum when reading from the
* L2ARC to determine if the contents are valid. However, if the compressed
* ARC is disabled, then the L2ARC's block must be transformed to look
* like the physical block in the main data pool before comparing the
* checksum and determining its validity.
*
* The L1ARC has a slightly different system for storing encrypted data.
* Raw (encrypted + possibly compressed) data has a few subtle differences from
* data that is just compressed. The biggest difference is that it is not
* possible to decrypt encrypted data (or vice-versa) if the keys aren't loaded.
* The other difference is that encryption cannot be treated as a suggestion.
* If a caller would prefer compressed data, but they actually wind up with
* uncompressed data the worst thing that could happen is there might be a
* performance hit. If the caller requests encrypted data, however, we must be
* sure they actually get it or else secret information could be leaked. Raw
* data is stored in hdr->b_crypt_hdr.b_rabd. An encrypted header, therefore,
* may have both an encrypted version and a decrypted version of its data at
* once. When a caller needs a raw arc_buf_t, it is allocated and the data is
* copied out of this header. To avoid complications with b_pabd, raw buffers
* cannot be shared.
*/
#include <sys/spa.h>
#include <sys/zio.h>
#include <sys/spa_impl.h>
#include <sys/zio_compress.h>
#include <sys/zio_checksum.h>
#include <sys/zfs_context.h>
#include <sys/arc.h>
#include <sys/zfs_refcount.h>
#include <sys/vdev.h>
#include <sys/vdev_impl.h>
#include <sys/dsl_pool.h>
#include <sys/multilist.h>
#include <sys/abd.h>
#include <sys/zil.h>
#include <sys/fm/fs/zfs.h>
#include <sys/callb.h>
#include <sys/kstat.h>
#include <sys/zthr.h>
#include <zfs_fletcher.h>
#include <sys/arc_impl.h>
#include <sys/trace_zfs.h>
#include <sys/aggsum.h>
#include <sys/wmsum.h>
#include <cityhash.h>
#include <sys/vdev_trim.h>
#include <sys/zfs_racct.h>
#include <sys/zstd/zstd.h>
#ifndef _KERNEL
/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
boolean_t arc_watch = B_FALSE;
#endif
/*
* This thread's job is to keep enough free memory in the system, by
* calling arc_kmem_reap_soon() plus arc_reduce_target_size(), which improves
* arc_available_memory().
*/
static zthr_t *arc_reap_zthr;
/*
* This thread's job is to keep arc_size under arc_c, by calling
* arc_evict(), which improves arc_is_overflowing().
*/
static zthr_t *arc_evict_zthr;
static arc_buf_hdr_t **arc_state_evict_markers;
static int arc_state_evict_marker_count;
static kmutex_t arc_evict_lock;
static boolean_t arc_evict_needed = B_FALSE;
static clock_t arc_last_uncached_flush;
/*
* Count of bytes evicted since boot.
*/
static uint64_t arc_evict_count;
/*
* List of arc_evict_waiter_t's, representing threads waiting for the
* arc_evict_count to reach specific values.
*/
static list_t arc_evict_waiters;
/*
* When arc_is_overflowing(), arc_get_data_impl() waits for this percent of
* the requested amount of data to be evicted. For example, by default for
* every 2KB that's evicted, 1KB of it may be "reused" by a new allocation.
* Since this is above 100%, it ensures that progress is made towards getting
* arc_size under arc_c. Since this is finite, it ensures that allocations
* can still happen, even during the potentially long time that arc_size is
* more than arc_c.
*/
static uint_t zfs_arc_eviction_pct = 200;
/*
* The number of headers to evict in arc_evict_state_impl() before
* dropping the sublist lock and evicting from another sublist. A lower
* value means we're more likely to evict the "correct" header (i.e. the
* oldest header in the arc state), but comes with higher overhead
* (i.e. more invocations of arc_evict_state_impl()).
*/
static uint_t zfs_arc_evict_batch_limit = 10;
/* number of seconds before growing cache again */
uint_t arc_grow_retry = 5;
/*
* Minimum time between calls to arc_kmem_reap_soon().
*/
static const int arc_kmem_cache_reap_retry_ms = 1000;
/* shift of arc_c for calculating overflow limit in arc_get_data_impl */
static int zfs_arc_overflow_shift = 8;
/* log2(fraction of arc to reclaim) */
uint_t arc_shrink_shift = 7;
/* percent of pagecache to reclaim arc to */
#ifdef _KERNEL
uint_t zfs_arc_pc_percent = 0;
#endif
/*
* log2(fraction of ARC which must be free to allow growing).
* I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
* when reading a new block into the ARC, we will evict an equal-sized block
* from the ARC.
*
* This must be less than arc_shrink_shift, so that when we shrink the ARC,
* we will still not allow it to grow.
*/
uint_t arc_no_grow_shift = 5;
/*
* minimum lifespan of a prefetch block in clock ticks
* (initialized in arc_init())
*/
static uint_t arc_min_prefetch_ms;
static uint_t arc_min_prescient_prefetch_ms;
/*
* If this percent of memory is free, don't throttle.
*/
uint_t arc_lotsfree_percent = 10;
/*
* The arc has filled available memory and has now warmed up.
*/
boolean_t arc_warm;
/*
* These tunables are for performance analysis.
*/
uint64_t zfs_arc_max = 0;
uint64_t zfs_arc_min = 0;
static uint64_t zfs_arc_dnode_limit = 0;
static uint_t zfs_arc_dnode_reduce_percent = 10;
static uint_t zfs_arc_grow_retry = 0;
static uint_t zfs_arc_shrink_shift = 0;
uint_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
/*
* ARC dirty data constraints for arc_tempreserve_space() throttle:
* * total dirty data limit
* * anon block dirty limit
* * each pool's anon allowance
*/
static const unsigned long zfs_arc_dirty_limit_percent = 50;
static const unsigned long zfs_arc_anon_limit_percent = 25;
static const unsigned long zfs_arc_pool_dirty_percent = 20;
/*
* Enable or disable compressed arc buffers.
*/
int zfs_compressed_arc_enabled = B_TRUE;
/*
* Balance between metadata and data on ghost hits. Values above 100
* increase metadata caching by proportionally reducing effect of ghost
* data hits on target data/metadata rate.
*/
static uint_t zfs_arc_meta_balance = 500;
/*
* Percentage that can be consumed by dnodes of ARC meta buffers.
*/
static uint_t zfs_arc_dnode_limit_percent = 10;
/*
* These tunables are Linux-specific
*/
static uint64_t zfs_arc_sys_free = 0;
static uint_t zfs_arc_min_prefetch_ms = 0;
static uint_t zfs_arc_min_prescient_prefetch_ms = 0;
static uint_t zfs_arc_lotsfree_percent = 10;
/*
* Number of arc_prune threads
*/
static int zfs_arc_prune_task_threads = 1;
/* The 7 states: */
arc_state_t ARC_anon;
arc_state_t ARC_mru;
arc_state_t ARC_mru_ghost;
arc_state_t ARC_mfu;
arc_state_t ARC_mfu_ghost;
arc_state_t ARC_l2c_only;
arc_state_t ARC_uncached;
arc_stats_t arc_stats = {
{ "hits", KSTAT_DATA_UINT64 },
{ "iohits", KSTAT_DATA_UINT64 },
{ "misses", KSTAT_DATA_UINT64 },
{ "demand_data_hits", KSTAT_DATA_UINT64 },
{ "demand_data_iohits", KSTAT_DATA_UINT64 },
{ "demand_data_misses", KSTAT_DATA_UINT64 },
{ "demand_metadata_hits", KSTAT_DATA_UINT64 },
{ "demand_metadata_iohits", KSTAT_DATA_UINT64 },
{ "demand_metadata_misses", KSTAT_DATA_UINT64 },
{ "prefetch_data_hits", KSTAT_DATA_UINT64 },
{ "prefetch_data_iohits", KSTAT_DATA_UINT64 },
{ "prefetch_data_misses", KSTAT_DATA_UINT64 },
{ "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
{ "prefetch_metadata_iohits", KSTAT_DATA_UINT64 },
{ "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
{ "mru_hits", KSTAT_DATA_UINT64 },
{ "mru_ghost_hits", KSTAT_DATA_UINT64 },
{ "mfu_hits", KSTAT_DATA_UINT64 },
{ "mfu_ghost_hits", KSTAT_DATA_UINT64 },
{ "uncached_hits", KSTAT_DATA_UINT64 },
{ "deleted", KSTAT_DATA_UINT64 },
{ "mutex_miss", KSTAT_DATA_UINT64 },
{ "access_skip", KSTAT_DATA_UINT64 },
{ "evict_skip", KSTAT_DATA_UINT64 },
{ "evict_not_enough", KSTAT_DATA_UINT64 },
{ "evict_l2_cached", KSTAT_DATA_UINT64 },
{ "evict_l2_eligible", KSTAT_DATA_UINT64 },
{ "evict_l2_eligible_mfu", KSTAT_DATA_UINT64 },
{ "evict_l2_eligible_mru", KSTAT_DATA_UINT64 },
{ "evict_l2_ineligible", KSTAT_DATA_UINT64 },
{ "evict_l2_skip", KSTAT_DATA_UINT64 },
{ "hash_elements", KSTAT_DATA_UINT64 },
{ "hash_elements_max", KSTAT_DATA_UINT64 },
{ "hash_collisions", KSTAT_DATA_UINT64 },
{ "hash_chains", KSTAT_DATA_UINT64 },
{ "hash_chain_max", KSTAT_DATA_UINT64 },
{ "meta", KSTAT_DATA_UINT64 },
{ "pd", KSTAT_DATA_UINT64 },
{ "pm", KSTAT_DATA_UINT64 },
{ "c", KSTAT_DATA_UINT64 },
{ "c_min", KSTAT_DATA_UINT64 },
{ "c_max", KSTAT_DATA_UINT64 },
{ "size", KSTAT_DATA_UINT64 },
{ "compressed_size", KSTAT_DATA_UINT64 },
{ "uncompressed_size", KSTAT_DATA_UINT64 },
{ "overhead_size", KSTAT_DATA_UINT64 },
{ "hdr_size", KSTAT_DATA_UINT64 },
{ "data_size", KSTAT_DATA_UINT64 },
{ "metadata_size", KSTAT_DATA_UINT64 },
{ "dbuf_size", KSTAT_DATA_UINT64 },
{ "dnode_size", KSTAT_DATA_UINT64 },
{ "bonus_size", KSTAT_DATA_UINT64 },
#if defined(COMPAT_FREEBSD11)
{ "other_size", KSTAT_DATA_UINT64 },
#endif
{ "anon_size", KSTAT_DATA_UINT64 },
{ "anon_data", KSTAT_DATA_UINT64 },
{ "anon_metadata", KSTAT_DATA_UINT64 },
{ "anon_evictable_data", KSTAT_DATA_UINT64 },
{ "anon_evictable_metadata", KSTAT_DATA_UINT64 },
{ "mru_size", KSTAT_DATA_UINT64 },
{ "mru_data", KSTAT_DATA_UINT64 },
{ "mru_metadata", KSTAT_DATA_UINT64 },
{ "mru_evictable_data", KSTAT_DATA_UINT64 },
{ "mru_evictable_metadata", KSTAT_DATA_UINT64 },
{ "mru_ghost_size", KSTAT_DATA_UINT64 },
{ "mru_ghost_data", KSTAT_DATA_UINT64 },
{ "mru_ghost_metadata", KSTAT_DATA_UINT64 },
{ "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
{ "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
{ "mfu_size", KSTAT_DATA_UINT64 },
{ "mfu_data", KSTAT_DATA_UINT64 },
{ "mfu_metadata", KSTAT_DATA_UINT64 },
{ "mfu_evictable_data", KSTAT_DATA_UINT64 },
{ "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
{ "mfu_ghost_size", KSTAT_DATA_UINT64 },
{ "mfu_ghost_data", KSTAT_DATA_UINT64 },
{ "mfu_ghost_metadata", KSTAT_DATA_UINT64 },
{ "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
{ "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
{ "uncached_size", KSTAT_DATA_UINT64 },
{ "uncached_data", KSTAT_DATA_UINT64 },
{ "uncached_metadata", KSTAT_DATA_UINT64 },
{ "uncached_evictable_data", KSTAT_DATA_UINT64 },
{ "uncached_evictable_metadata", KSTAT_DATA_UINT64 },
{ "l2_hits", KSTAT_DATA_UINT64 },
{ "l2_misses", KSTAT_DATA_UINT64 },
{ "l2_prefetch_asize", KSTAT_DATA_UINT64 },
{ "l2_mru_asize", KSTAT_DATA_UINT64 },
{ "l2_mfu_asize", KSTAT_DATA_UINT64 },
{ "l2_bufc_data_asize", KSTAT_DATA_UINT64 },
{ "l2_bufc_metadata_asize", KSTAT_DATA_UINT64 },
{ "l2_feeds", KSTAT_DATA_UINT64 },
{ "l2_rw_clash", KSTAT_DATA_UINT64 },
{ "l2_read_bytes", KSTAT_DATA_UINT64 },
{ "l2_write_bytes", KSTAT_DATA_UINT64 },
{ "l2_writes_sent", KSTAT_DATA_UINT64 },
{ "l2_writes_done", KSTAT_DATA_UINT64 },
{ "l2_writes_error", KSTAT_DATA_UINT64 },
{ "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
{ "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
{ "l2_evict_reading", KSTAT_DATA_UINT64 },
{ "l2_evict_l1cached", KSTAT_DATA_UINT64 },
{ "l2_free_on_write", KSTAT_DATA_UINT64 },
{ "l2_abort_lowmem", KSTAT_DATA_UINT64 },
{ "l2_cksum_bad", KSTAT_DATA_UINT64 },
{ "l2_io_error", KSTAT_DATA_UINT64 },
{ "l2_size", KSTAT_DATA_UINT64 },
{ "l2_asize", KSTAT_DATA_UINT64 },
{ "l2_hdr_size", KSTAT_DATA_UINT64 },
{ "l2_log_blk_writes", KSTAT_DATA_UINT64 },
{ "l2_log_blk_avg_asize", KSTAT_DATA_UINT64 },
{ "l2_log_blk_asize", KSTAT_DATA_UINT64 },
{ "l2_log_blk_count", KSTAT_DATA_UINT64 },
{ "l2_data_to_meta_ratio", KSTAT_DATA_UINT64 },
{ "l2_rebuild_success", KSTAT_DATA_UINT64 },
{ "l2_rebuild_unsupported", KSTAT_DATA_UINT64 },
{ "l2_rebuild_io_errors", KSTAT_DATA_UINT64 },
{ "l2_rebuild_dh_errors", KSTAT_DATA_UINT64 },
{ "l2_rebuild_cksum_lb_errors", KSTAT_DATA_UINT64 },
{ "l2_rebuild_lowmem", KSTAT_DATA_UINT64 },
{ "l2_rebuild_size", KSTAT_DATA_UINT64 },
{ "l2_rebuild_asize", KSTAT_DATA_UINT64 },
{ "l2_rebuild_bufs", KSTAT_DATA_UINT64 },
{ "l2_rebuild_bufs_precached", KSTAT_DATA_UINT64 },
{ "l2_rebuild_log_blks", KSTAT_DATA_UINT64 },
{ "memory_throttle_count", KSTAT_DATA_UINT64 },
{ "memory_direct_count", KSTAT_DATA_UINT64 },
{ "memory_indirect_count", KSTAT_DATA_UINT64 },
{ "memory_all_bytes", KSTAT_DATA_UINT64 },
{ "memory_free_bytes", KSTAT_DATA_UINT64 },
{ "memory_available_bytes", KSTAT_DATA_INT64 },
{ "arc_no_grow", KSTAT_DATA_UINT64 },
{ "arc_tempreserve", KSTAT_DATA_UINT64 },
{ "arc_loaned_bytes", KSTAT_DATA_UINT64 },
{ "arc_prune", KSTAT_DATA_UINT64 },
{ "arc_meta_used", KSTAT_DATA_UINT64 },
{ "arc_dnode_limit", KSTAT_DATA_UINT64 },
{ "async_upgrade_sync", KSTAT_DATA_UINT64 },
{ "predictive_prefetch", KSTAT_DATA_UINT64 },
{ "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
{ "demand_iohit_predictive_prefetch", KSTAT_DATA_UINT64 },
{ "prescient_prefetch", KSTAT_DATA_UINT64 },
{ "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 },
{ "demand_iohit_prescient_prefetch", KSTAT_DATA_UINT64 },
{ "arc_need_free", KSTAT_DATA_UINT64 },
{ "arc_sys_free", KSTAT_DATA_UINT64 },
{ "arc_raw_size", KSTAT_DATA_UINT64 },
{ "cached_only_in_progress", KSTAT_DATA_UINT64 },
{ "abd_chunk_waste_size", KSTAT_DATA_UINT64 },
};
arc_sums_t arc_sums;
#define ARCSTAT_MAX(stat, val) { \
uint64_t m; \
while ((val) > (m = arc_stats.stat.value.ui64) && \
(m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
continue; \
}
/*
* We define a macro to allow ARC hits/misses to be easily broken down by
* two separate conditions, giving a total of four different subtypes for
* each of hits and misses (so eight statistics total).
*/
#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
if (cond1) { \
if (cond2) { \
ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
} else { \
ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
} \
} else { \
if (cond2) { \
ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
} else { \
ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
} \
}
/*
* This macro allows us to use kstats as floating averages. Each time we
* update this kstat, we first factor it and the update value by
* ARCSTAT_AVG_FACTOR to shrink the new value's contribution to the overall
* average. This macro assumes that integer loads and stores are atomic, but
* is not safe for multiple writers updating the kstat in parallel (only the
* last writer's update will remain).
*/
#define ARCSTAT_F_AVG_FACTOR 3
#define ARCSTAT_F_AVG(stat, value) \
do { \
uint64_t x = ARCSTAT(stat); \
x = x - x / ARCSTAT_F_AVG_FACTOR + \
(value) / ARCSTAT_F_AVG_FACTOR; \
ARCSTAT(stat) = x; \
} while (0)
static kstat_t *arc_ksp;
/*
* There are several ARC variables that are critical to export as kstats --
* but we don't want to have to grovel around in the kstat whenever we wish to
* manipulate them. For these variables, we therefore define them to be in
* terms of the statistic variable. This assures that we are not introducing
* the possibility of inconsistency by having shadow copies of the variables,
* while still allowing the code to be readable.
*/
#define arc_tempreserve ARCSTAT(arcstat_tempreserve)
#define arc_loaned_bytes ARCSTAT(arcstat_loaned_bytes)
#define arc_dnode_limit ARCSTAT(arcstat_dnode_limit) /* max size for dnodes */
#define arc_need_free ARCSTAT(arcstat_need_free) /* waiting to be evicted */
hrtime_t arc_growtime;
list_t arc_prune_list;
kmutex_t arc_prune_mtx;
taskq_t *arc_prune_taskq;
#define GHOST_STATE(state) \
((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
(state) == arc_l2c_only)
#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
#define HDR_PRESCIENT_PREFETCH(hdr) \
((hdr)->b_flags & ARC_FLAG_PRESCIENT_PREFETCH)
#define HDR_COMPRESSION_ENABLED(hdr) \
((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
#define HDR_UNCACHED(hdr) ((hdr)->b_flags & ARC_FLAG_UNCACHED)
#define HDR_L2_READING(hdr) \
(((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
#define HDR_PROTECTED(hdr) ((hdr)->b_flags & ARC_FLAG_PROTECTED)
#define HDR_NOAUTH(hdr) ((hdr)->b_flags & ARC_FLAG_NOAUTH)
#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
#define HDR_ISTYPE_METADATA(hdr) \
((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
#define HDR_HAS_RABD(hdr) \
(HDR_HAS_L1HDR(hdr) && HDR_PROTECTED(hdr) && \
(hdr)->b_crypt_hdr.b_rabd != NULL)
#define HDR_ENCRYPTED(hdr) \
(HDR_PROTECTED(hdr) && DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot))
#define HDR_AUTHENTICATED(hdr) \
(HDR_PROTECTED(hdr) && !DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot))
/* For storing compression mode in b_flags */
#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
#define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
#define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
#define ARC_BUF_ENCRYPTED(buf) ((buf)->b_flags & ARC_BUF_FLAG_ENCRYPTED)
/*
* Other sizes
*/
#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
/*
* Hash table routines
*/
#define BUF_LOCKS 2048
typedef struct buf_hash_table {
uint64_t ht_mask;
arc_buf_hdr_t **ht_table;
kmutex_t ht_locks[BUF_LOCKS] ____cacheline_aligned;
} buf_hash_table_t;
static buf_hash_table_t buf_hash_table;
#define BUF_HASH_INDEX(spa, dva, birth) \
(buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
#define BUF_HASH_LOCK(idx) (&buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
#define HDR_LOCK(hdr) \
(BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
uint64_t zfs_crc64_table[256];
/*
* Level 2 ARC
*/
#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
#define L2ARC_HEADROOM 2 /* num of writes */
/*
* If we discover during ARC scan any buffers to be compressed, we boost
* our headroom for the next scanning cycle by this percentage multiple.
*/
#define L2ARC_HEADROOM_BOOST 200
#define L2ARC_FEED_SECS 1 /* caching interval secs */
#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
/*
* We can feed L2ARC from two states of ARC buffers, mru and mfu,
* and each of the state has two types: data and metadata.
*/
#define L2ARC_FEED_TYPES 4
/* L2ARC Performance Tunables */
uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* def max write size */
uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra warmup write */
uint64_t l2arc_headroom = L2ARC_HEADROOM; /* # of dev writes */
uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval msecs */
int l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
int l2arc_feed_again = B_TRUE; /* turbo warmup */
int l2arc_norw = B_FALSE; /* no reads during writes */
static uint_t l2arc_meta_percent = 33; /* limit on headers size */
/*
* L2ARC Internals
*/
static list_t L2ARC_dev_list; /* device list */
static list_t *l2arc_dev_list; /* device list pointer */
static kmutex_t l2arc_dev_mtx; /* device list mutex */
static l2arc_dev_t *l2arc_dev_last; /* last device used */
static list_t L2ARC_free_on_write; /* free after write buf list */
static list_t *l2arc_free_on_write; /* free after write list ptr */
static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
static uint64_t l2arc_ndev; /* number of devices */
typedef struct l2arc_read_callback {
arc_buf_hdr_t *l2rcb_hdr; /* read header */
blkptr_t l2rcb_bp; /* original blkptr */
zbookmark_phys_t l2rcb_zb; /* original bookmark */
int l2rcb_flags; /* original flags */
abd_t *l2rcb_abd; /* temporary buffer */
} l2arc_read_callback_t;
typedef struct l2arc_data_free {
/* protected by l2arc_free_on_write_mtx */
abd_t *l2df_abd;
size_t l2df_size;
arc_buf_contents_t l2df_type;
list_node_t l2df_list_node;
} l2arc_data_free_t;
typedef enum arc_fill_flags {
ARC_FILL_LOCKED = 1 << 0, /* hdr lock is held */
ARC_FILL_COMPRESSED = 1 << 1, /* fill with compressed data */
ARC_FILL_ENCRYPTED = 1 << 2, /* fill with encrypted data */
ARC_FILL_NOAUTH = 1 << 3, /* don't attempt to authenticate */
ARC_FILL_IN_PLACE = 1 << 4 /* fill in place (special case) */
} arc_fill_flags_t;
typedef enum arc_ovf_level {
ARC_OVF_NONE, /* ARC within target size. */
ARC_OVF_SOME, /* ARC is slightly overflowed. */
ARC_OVF_SEVERE /* ARC is severely overflowed. */
} arc_ovf_level_t;
static kmutex_t l2arc_feed_thr_lock;
static kcondvar_t l2arc_feed_thr_cv;
static uint8_t l2arc_thread_exit;
static kmutex_t l2arc_rebuild_thr_lock;
static kcondvar_t l2arc_rebuild_thr_cv;
enum arc_hdr_alloc_flags {
ARC_HDR_ALLOC_RDATA = 0x1,
ARC_HDR_USE_RESERVE = 0x4,
ARC_HDR_ALLOC_LINEAR = 0x8,
};
static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, const void *, int);
static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, const void *);
static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, const void *, int);
static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, const void *);
static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, const void *);
static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size,
const void *tag);
static void arc_hdr_free_abd(arc_buf_hdr_t *, boolean_t);
static void arc_hdr_alloc_abd(arc_buf_hdr_t *, int);
static void arc_hdr_destroy(arc_buf_hdr_t *);
static void arc_access(arc_buf_hdr_t *, arc_flags_t, boolean_t);
static void arc_buf_watch(arc_buf_t *);
static void arc_change_state(arc_state_t *, arc_buf_hdr_t *);
static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
static void l2arc_read_done(zio_t *);
static void l2arc_do_free_on_write(void);
static void l2arc_hdr_arcstats_update(arc_buf_hdr_t *hdr, boolean_t incr,
boolean_t state_only);
#define l2arc_hdr_arcstats_increment(hdr) \
l2arc_hdr_arcstats_update((hdr), B_TRUE, B_FALSE)
#define l2arc_hdr_arcstats_decrement(hdr) \
l2arc_hdr_arcstats_update((hdr), B_FALSE, B_FALSE)
#define l2arc_hdr_arcstats_increment_state(hdr) \
l2arc_hdr_arcstats_update((hdr), B_TRUE, B_TRUE)
#define l2arc_hdr_arcstats_decrement_state(hdr) \
l2arc_hdr_arcstats_update((hdr), B_FALSE, B_TRUE)
/*
* l2arc_exclude_special : A zfs module parameter that controls whether buffers
* present on special vdevs are eligibile for caching in L2ARC. If
* set to 1, exclude dbufs on special vdevs from being cached to
* L2ARC.
*/
int l2arc_exclude_special = 0;
/*
* l2arc_mfuonly : A ZFS module parameter that controls whether only MFU
* metadata and data are cached from ARC into L2ARC.
*/
static int l2arc_mfuonly = 0;
/*
* L2ARC TRIM
* l2arc_trim_ahead : A ZFS module parameter that controls how much ahead of
* the current write size (l2arc_write_max) we should TRIM if we
* have filled the device. It is defined as a percentage of the
* write size. If set to 100 we trim twice the space required to
* accommodate upcoming writes. A minimum of 64MB will be trimmed.
* It also enables TRIM of the whole L2ARC device upon creation or
* addition to an existing pool or if the header of the device is
* invalid upon importing a pool or onlining a cache device. The
* default is 0, which disables TRIM on L2ARC altogether as it can
* put significant stress on the underlying storage devices. This
* will vary depending of how well the specific device handles
* these commands.
*/
static uint64_t l2arc_trim_ahead = 0;
/*
* Performance tuning of L2ARC persistence:
*
* l2arc_rebuild_enabled : A ZFS module parameter that controls whether adding
* an L2ARC device (either at pool import or later) will attempt
* to rebuild L2ARC buffer contents.
* l2arc_rebuild_blocks_min_l2size : A ZFS module parameter that controls
* whether log blocks are written to the L2ARC device. If the L2ARC
* device is less than 1GB, the amount of data l2arc_evict()
* evicts is significant compared to the amount of restored L2ARC
* data. In this case do not write log blocks in L2ARC in order
* not to waste space.
*/
static int l2arc_rebuild_enabled = B_TRUE;
static uint64_t l2arc_rebuild_blocks_min_l2size = 1024 * 1024 * 1024;
/* L2ARC persistence rebuild control routines. */
void l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen);
static __attribute__((noreturn)) void l2arc_dev_rebuild_thread(void *arg);
static int l2arc_rebuild(l2arc_dev_t *dev);
/* L2ARC persistence read I/O routines. */
static int l2arc_dev_hdr_read(l2arc_dev_t *dev);
static int l2arc_log_blk_read(l2arc_dev_t *dev,
const l2arc_log_blkptr_t *this_lp, const l2arc_log_blkptr_t *next_lp,
l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb,
zio_t *this_io, zio_t **next_io);
static zio_t *l2arc_log_blk_fetch(vdev_t *vd,
const l2arc_log_blkptr_t *lp, l2arc_log_blk_phys_t *lb);
static void l2arc_log_blk_fetch_abort(zio_t *zio);
/* L2ARC persistence block restoration routines. */
static void l2arc_log_blk_restore(l2arc_dev_t *dev,
const l2arc_log_blk_phys_t *lb, uint64_t lb_asize);
static void l2arc_hdr_restore(const l2arc_log_ent_phys_t *le,
l2arc_dev_t *dev);
/* L2ARC persistence write I/O routines. */
static uint64_t l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio,
l2arc_write_callback_t *cb);
/* L2ARC persistence auxiliary routines. */
boolean_t l2arc_log_blkptr_valid(l2arc_dev_t *dev,
const l2arc_log_blkptr_t *lbp);
static boolean_t l2arc_log_blk_insert(l2arc_dev_t *dev,
const arc_buf_hdr_t *ab);
boolean_t l2arc_range_check_overlap(uint64_t bottom,
uint64_t top, uint64_t check);
static void l2arc_blk_fetch_done(zio_t *zio);
static inline uint64_t
l2arc_log_blk_overhead(uint64_t write_sz, l2arc_dev_t *dev);
/*
* We use Cityhash for this. It's fast, and has good hash properties without
* requiring any large static buffers.
*/
static uint64_t
buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
{
return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth));
}
#define HDR_EMPTY(hdr) \
((hdr)->b_dva.dva_word[0] == 0 && \
(hdr)->b_dva.dva_word[1] == 0)
#define HDR_EMPTY_OR_LOCKED(hdr) \
(HDR_EMPTY(hdr) || MUTEX_HELD(HDR_LOCK(hdr)))
#define HDR_EQUAL(spa, dva, birth, hdr) \
((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
static void
buf_discard_identity(arc_buf_hdr_t *hdr)
{
hdr->b_dva.dva_word[0] = 0;
hdr->b_dva.dva_word[1] = 0;
hdr->b_birth = 0;
}
static arc_buf_hdr_t *
buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
{
const dva_t *dva = BP_IDENTITY(bp);
uint64_t birth = BP_PHYSICAL_BIRTH(bp);
uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
arc_buf_hdr_t *hdr;
mutex_enter(hash_lock);
for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
hdr = hdr->b_hash_next) {
if (HDR_EQUAL(spa, dva, birth, hdr)) {
*lockp = hash_lock;
return (hdr);
}
}
mutex_exit(hash_lock);
*lockp = NULL;
return (NULL);
}
/*
* Insert an entry into the hash table. If there is already an element
* equal to elem in the hash table, then the already existing element
* will be returned and the new element will not be inserted.
* Otherwise returns NULL.
* If lockp == NULL, the caller is assumed to already hold the hash lock.
*/
static arc_buf_hdr_t *
buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
{
uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
arc_buf_hdr_t *fhdr;
uint32_t i;
ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
ASSERT(hdr->b_birth != 0);
ASSERT(!HDR_IN_HASH_TABLE(hdr));
if (lockp != NULL) {
*lockp = hash_lock;
mutex_enter(hash_lock);
} else {
ASSERT(MUTEX_HELD(hash_lock));
}
for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
fhdr = fhdr->b_hash_next, i++) {
if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
return (fhdr);
}
hdr->b_hash_next = buf_hash_table.ht_table[idx];
buf_hash_table.ht_table[idx] = hdr;
arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
/* collect some hash table performance data */
if (i > 0) {
ARCSTAT_BUMP(arcstat_hash_collisions);
if (i == 1)
ARCSTAT_BUMP(arcstat_hash_chains);
ARCSTAT_MAX(arcstat_hash_chain_max, i);
}
uint64_t he = atomic_inc_64_nv(
&arc_stats.arcstat_hash_elements.value.ui64);
ARCSTAT_MAX(arcstat_hash_elements_max, he);
return (NULL);
}
static void
buf_hash_remove(arc_buf_hdr_t *hdr)
{
arc_buf_hdr_t *fhdr, **hdrp;
uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
ASSERT(HDR_IN_HASH_TABLE(hdr));
hdrp = &buf_hash_table.ht_table[idx];
while ((fhdr = *hdrp) != hdr) {
ASSERT3P(fhdr, !=, NULL);
hdrp = &fhdr->b_hash_next;
}
*hdrp = hdr->b_hash_next;
hdr->b_hash_next = NULL;
arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
/* collect some hash table performance data */
atomic_dec_64(&arc_stats.arcstat_hash_elements.value.ui64);
if (buf_hash_table.ht_table[idx] &&
buf_hash_table.ht_table[idx]->b_hash_next == NULL)
ARCSTAT_BUMPDOWN(arcstat_hash_chains);
}
/*
* Global data structures and functions for the buf kmem cache.
*/
static kmem_cache_t *hdr_full_cache;
static kmem_cache_t *hdr_l2only_cache;
static kmem_cache_t *buf_cache;
static void
buf_fini(void)
{
#if defined(_KERNEL)
/*
* Large allocations which do not require contiguous pages
* should be using vmem_free() in the linux kernel\
*/
vmem_free(buf_hash_table.ht_table,
(buf_hash_table.ht_mask + 1) * sizeof (void *));
#else
kmem_free(buf_hash_table.ht_table,
(buf_hash_table.ht_mask + 1) * sizeof (void *));
#endif
for (int i = 0; i < BUF_LOCKS; i++)
mutex_destroy(BUF_HASH_LOCK(i));
kmem_cache_destroy(hdr_full_cache);
kmem_cache_destroy(hdr_l2only_cache);
kmem_cache_destroy(buf_cache);
}
/*
* Constructor callback - called when the cache is empty
* and a new buf is requested.
*/
static int
hdr_full_cons(void *vbuf, void *unused, int kmflag)
{
(void) unused, (void) kmflag;
arc_buf_hdr_t *hdr = vbuf;
memset(hdr, 0, HDR_FULL_SIZE);
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
zfs_refcount_create(&hdr->b_l1hdr.b_refcnt);
#ifdef ZFS_DEBUG
mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
#endif
multilist_link_init(&hdr->b_l1hdr.b_arc_node);
list_link_init(&hdr->b_l2hdr.b_l2node);
arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
return (0);
}
static int
hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
{
(void) unused, (void) kmflag;
arc_buf_hdr_t *hdr = vbuf;
memset(hdr, 0, HDR_L2ONLY_SIZE);
arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
return (0);
}
static int
buf_cons(void *vbuf, void *unused, int kmflag)
{
(void) unused, (void) kmflag;
arc_buf_t *buf = vbuf;
memset(buf, 0, sizeof (arc_buf_t));
arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
return (0);
}
/*
* Destructor callback - called when a cached buf is
* no longer required.
*/
static void
hdr_full_dest(void *vbuf, void *unused)
{
(void) unused;
arc_buf_hdr_t *hdr = vbuf;
ASSERT(HDR_EMPTY(hdr));
zfs_refcount_destroy(&hdr->b_l1hdr.b_refcnt);
#ifdef ZFS_DEBUG
mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
#endif
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
}
static void
hdr_l2only_dest(void *vbuf, void *unused)
{
(void) unused;
arc_buf_hdr_t *hdr = vbuf;
ASSERT(HDR_EMPTY(hdr));
arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
}
static void
buf_dest(void *vbuf, void *unused)
{
(void) unused;
(void) vbuf;
arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
}
static void
buf_init(void)
{
uint64_t *ct = NULL;
uint64_t hsize = 1ULL << 12;
int i, j;
/*
* The hash table is big enough to fill all of physical memory
* with an average block size of zfs_arc_average_blocksize (default 8K).
* By default, the table will take up
* totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
*/
while (hsize * zfs_arc_average_blocksize < arc_all_memory())
hsize <<= 1;
retry:
buf_hash_table.ht_mask = hsize - 1;
#if defined(_KERNEL)
/*
* Large allocations which do not require contiguous pages
* should be using vmem_alloc() in the linux kernel
*/
buf_hash_table.ht_table =
vmem_zalloc(hsize * sizeof (void*), KM_SLEEP);
#else
buf_hash_table.ht_table =
kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
#endif
if (buf_hash_table.ht_table == NULL) {
ASSERT(hsize > (1ULL << 8));
hsize >>= 1;
goto retry;
}
hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
0, hdr_full_cons, hdr_full_dest, NULL, NULL, NULL, 0);
hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, NULL,
NULL, NULL, 0);
buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
for (i = 0; i < 256; i++)
for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
*ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
for (i = 0; i < BUF_LOCKS; i++)
mutex_init(BUF_HASH_LOCK(i), NULL, MUTEX_DEFAULT, NULL);
}
#define ARC_MINTIME (hz>>4) /* 62 ms */
/*
* This is the size that the buf occupies in memory. If the buf is compressed,
* it will correspond to the compressed size. You should use this method of
* getting the buf size unless you explicitly need the logical size.
*/
uint64_t
arc_buf_size(arc_buf_t *buf)
{
return (ARC_BUF_COMPRESSED(buf) ?
HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
}
uint64_t
arc_buf_lsize(arc_buf_t *buf)
{
return (HDR_GET_LSIZE(buf->b_hdr));
}
/*
* This function will return B_TRUE if the buffer is encrypted in memory.
* This buffer can be decrypted by calling arc_untransform().
*/
boolean_t
arc_is_encrypted(arc_buf_t *buf)
{
return (ARC_BUF_ENCRYPTED(buf) != 0);
}
/*
* Returns B_TRUE if the buffer represents data that has not had its MAC
* verified yet.
*/
boolean_t
arc_is_unauthenticated(arc_buf_t *buf)
{
return (HDR_NOAUTH(buf->b_hdr) != 0);
}
void
arc_get_raw_params(arc_buf_t *buf, boolean_t *byteorder, uint8_t *salt,
uint8_t *iv, uint8_t *mac)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT(HDR_PROTECTED(hdr));
memcpy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
memcpy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
memcpy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
*byteorder = (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ?
ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER;
}
/*
* Indicates how this buffer is compressed in memory. If it is not compressed
* the value will be ZIO_COMPRESS_OFF. It can be made normally readable with
* arc_untransform() as long as it is also unencrypted.
*/
enum zio_compress
arc_get_compression(arc_buf_t *buf)
{
return (ARC_BUF_COMPRESSED(buf) ?
HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
}
/*
* Return the compression algorithm used to store this data in the ARC. If ARC
* compression is enabled or this is an encrypted block, this will be the same
* as what's used to store it on-disk. Otherwise, this will be ZIO_COMPRESS_OFF.
*/
static inline enum zio_compress
arc_hdr_get_compress(arc_buf_hdr_t *hdr)
{
return (HDR_COMPRESSION_ENABLED(hdr) ?
HDR_GET_COMPRESS(hdr) : ZIO_COMPRESS_OFF);
}
uint8_t
arc_get_complevel(arc_buf_t *buf)
{
return (buf->b_hdr->b_complevel);
}
static inline boolean_t
arc_buf_is_shared(arc_buf_t *buf)
{
boolean_t shared = (buf->b_data != NULL &&
buf->b_hdr->b_l1hdr.b_pabd != NULL &&
abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
EQUIV(shared, ARC_BUF_SHARED(buf));
IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
/*
* It would be nice to assert arc_can_share() too, but the "hdr isn't
* already being shared" requirement prevents us from doing that.
*/
return (shared);
}
/*
* Free the checksum associated with this header. If there is no checksum, this
* is a no-op.
*/
static inline void
arc_cksum_free(arc_buf_hdr_t *hdr)
{
#ifdef ZFS_DEBUG
ASSERT(HDR_HAS_L1HDR(hdr));
mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
hdr->b_l1hdr.b_freeze_cksum = NULL;
}
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
#endif
}
/*
* Return true iff at least one of the bufs on hdr is not compressed.
* Encrypted buffers count as compressed.
*/
static boolean_t
arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
{
ASSERT(hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY_OR_LOCKED(hdr));
for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
if (!ARC_BUF_COMPRESSED(b)) {
return (B_TRUE);
}
}
return (B_FALSE);
}
/*
* If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
* matches the checksum that is stored in the hdr. If there is no checksum,
* or if the buf is compressed, this is a no-op.
*/
static void
arc_cksum_verify(arc_buf_t *buf)
{
#ifdef ZFS_DEBUG
arc_buf_hdr_t *hdr = buf->b_hdr;
zio_cksum_t zc;
if (!(zfs_flags & ZFS_DEBUG_MODIFY))
return;
if (ARC_BUF_COMPRESSED(buf))
return;
ASSERT(HDR_HAS_L1HDR(hdr));
mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
return;
}
fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
panic("buffer modified while frozen!");
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
#endif
}
/*
* This function makes the assumption that data stored in the L2ARC
* will be transformed exactly as it is in the main pool. Because of
* this we can verify the checksum against the reading process's bp.
*/
static boolean_t
arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
{
ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
/*
* Block pointers always store the checksum for the logical data.
* If the block pointer has the gang bit set, then the checksum
* it represents is for the reconstituted data and not for an
* individual gang member. The zio pipeline, however, must be able to
* determine the checksum of each of the gang constituents so it
* treats the checksum comparison differently than what we need
* for l2arc blocks. This prevents us from using the
* zio_checksum_error() interface directly. Instead we must call the
* zio_checksum_error_impl() so that we can ensure the checksum is
* generated using the correct checksum algorithm and accounts for the
* logical I/O size and not just a gang fragment.
*/
return (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
zio->io_offset, NULL) == 0);
}
/*
* Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
* checksum and attaches it to the buf's hdr so that we can ensure that the buf
* isn't modified later on. If buf is compressed or there is already a checksum
* on the hdr, this is a no-op (we only checksum uncompressed bufs).
*/
static void
arc_cksum_compute(arc_buf_t *buf)
{
if (!(zfs_flags & ZFS_DEBUG_MODIFY))
return;
#ifdef ZFS_DEBUG
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT(HDR_HAS_L1HDR(hdr));
mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
if (hdr->b_l1hdr.b_freeze_cksum != NULL || ARC_BUF_COMPRESSED(buf)) {
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
return;
}
ASSERT(!ARC_BUF_ENCRYPTED(buf));
ASSERT(!ARC_BUF_COMPRESSED(buf));
hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
KM_SLEEP);
fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
hdr->b_l1hdr.b_freeze_cksum);
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
#endif
arc_buf_watch(buf);
}
#ifndef _KERNEL
void
arc_buf_sigsegv(int sig, siginfo_t *si, void *unused)
{
(void) sig, (void) unused;
panic("Got SIGSEGV at address: 0x%lx\n", (long)si->si_addr);
}
#endif
static void
arc_buf_unwatch(arc_buf_t *buf)
{
#ifndef _KERNEL
if (arc_watch) {
ASSERT0(mprotect(buf->b_data, arc_buf_size(buf),
PROT_READ | PROT_WRITE));
}
#else
(void) buf;
#endif
}
static void
arc_buf_watch(arc_buf_t *buf)
{
#ifndef _KERNEL
if (arc_watch)
ASSERT0(mprotect(buf->b_data, arc_buf_size(buf),
PROT_READ));
#else
(void) buf;
#endif
}
static arc_buf_contents_t
arc_buf_type(arc_buf_hdr_t *hdr)
{
arc_buf_contents_t type;
if (HDR_ISTYPE_METADATA(hdr)) {
type = ARC_BUFC_METADATA;
} else {
type = ARC_BUFC_DATA;
}
VERIFY3U(hdr->b_type, ==, type);
return (type);
}
boolean_t
arc_is_metadata(arc_buf_t *buf)
{
return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
}
static uint32_t
arc_bufc_to_flags(arc_buf_contents_t type)
{
switch (type) {
case ARC_BUFC_DATA:
/* metadata field is 0 if buffer contains normal data */
return (0);
case ARC_BUFC_METADATA:
return (ARC_FLAG_BUFC_METADATA);
default:
break;
}
panic("undefined ARC buffer type!");
return ((uint32_t)-1);
}
void
arc_buf_thaw(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
arc_cksum_verify(buf);
/*
* Compressed buffers do not manipulate the b_freeze_cksum.
*/
if (ARC_BUF_COMPRESSED(buf))
return;
ASSERT(HDR_HAS_L1HDR(hdr));
arc_cksum_free(hdr);
arc_buf_unwatch(buf);
}
void
arc_buf_freeze(arc_buf_t *buf)
{
if (!(zfs_flags & ZFS_DEBUG_MODIFY))
return;
if (ARC_BUF_COMPRESSED(buf))
return;
ASSERT(HDR_HAS_L1HDR(buf->b_hdr));
arc_cksum_compute(buf);
}
/*
* The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
* the following functions should be used to ensure that the flags are
* updated in a thread-safe way. When manipulating the flags either
* the hash_lock must be held or the hdr must be undiscoverable. This
* ensures that we're not racing with any other threads when updating
* the flags.
*/
static inline void
arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
{
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
hdr->b_flags |= flags;
}
static inline void
arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
{
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
hdr->b_flags &= ~flags;
}
/*
* Setting the compression bits in the arc_buf_hdr_t's b_flags is
* done in a special way since we have to clear and set bits
* at the same time. Consumers that wish to set the compression bits
* must use this function to ensure that the flags are updated in
* thread-safe manner.
*/
static void
arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
{
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
/*
* Holes and embedded blocks will always have a psize = 0 so
* we ignore the compression of the blkptr and set the
* want to uncompress them. Mark them as uncompressed.
*/
if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
} else {
arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
ASSERT(HDR_COMPRESSION_ENABLED(hdr));
}
HDR_SET_COMPRESS(hdr, cmp);
ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
}
/*
* Looks for another buf on the same hdr which has the data decompressed, copies
* from it, and returns true. If no such buf exists, returns false.
*/
static boolean_t
arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
boolean_t copied = B_FALSE;
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT3P(buf->b_data, !=, NULL);
ASSERT(!ARC_BUF_COMPRESSED(buf));
for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
from = from->b_next) {
/* can't use our own data buffer */
if (from == buf) {
continue;
}
if (!ARC_BUF_COMPRESSED(from)) {
memcpy(buf->b_data, from->b_data, arc_buf_size(buf));
copied = B_TRUE;
break;
}
}
#ifdef ZFS_DEBUG
/*
* There were no decompressed bufs, so there should not be a
* checksum on the hdr either.
*/
if (zfs_flags & ZFS_DEBUG_MODIFY)
EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
#endif
return (copied);
}
/*
* Allocates an ARC buf header that's in an evicted & L2-cached state.
* This is used during l2arc reconstruction to make empty ARC buffers
* which circumvent the regular disk->arc->l2arc path and instead come
* into being in the reverse order, i.e. l2arc->arc.
*/
static arc_buf_hdr_t *
arc_buf_alloc_l2only(size_t size, arc_buf_contents_t type, l2arc_dev_t *dev,
dva_t dva, uint64_t daddr, int32_t psize, uint64_t birth,
enum zio_compress compress, uint8_t complevel, boolean_t protected,
boolean_t prefetch, arc_state_type_t arcs_state)
{
arc_buf_hdr_t *hdr;
ASSERT(size != 0);
hdr = kmem_cache_alloc(hdr_l2only_cache, KM_SLEEP);
hdr->b_birth = birth;
hdr->b_type = type;
hdr->b_flags = 0;
arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L2HDR);
HDR_SET_LSIZE(hdr, size);
HDR_SET_PSIZE(hdr, psize);
arc_hdr_set_compress(hdr, compress);
hdr->b_complevel = complevel;
if (protected)
arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
if (prefetch)
arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
hdr->b_spa = spa_load_guid(dev->l2ad_vdev->vdev_spa);
hdr->b_dva = dva;
hdr->b_l2hdr.b_dev = dev;
hdr->b_l2hdr.b_daddr = daddr;
hdr->b_l2hdr.b_arcs_state = arcs_state;
return (hdr);
}
/*
* Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
*/
static uint64_t
arc_hdr_size(arc_buf_hdr_t *hdr)
{
uint64_t size;
if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF &&
HDR_GET_PSIZE(hdr) > 0) {
size = HDR_GET_PSIZE(hdr);
} else {
ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
size = HDR_GET_LSIZE(hdr);
}
return (size);
}
static int
arc_hdr_authenticate(arc_buf_hdr_t *hdr, spa_t *spa, uint64_t dsobj)
{
int ret;
uint64_t csize;
uint64_t lsize = HDR_GET_LSIZE(hdr);
uint64_t psize = HDR_GET_PSIZE(hdr);
void *tmpbuf = NULL;
abd_t *abd = hdr->b_l1hdr.b_pabd;
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
ASSERT(HDR_AUTHENTICATED(hdr));
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
/*
* The MAC is calculated on the compressed data that is stored on disk.
* However, if compressed arc is disabled we will only have the
* decompressed data available to us now. Compress it into a temporary
* abd so we can verify the MAC. The performance overhead of this will
* be relatively low, since most objects in an encrypted objset will
* be encrypted (instead of authenticated) anyway.
*/
if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
!HDR_COMPRESSION_ENABLED(hdr)) {
csize = zio_compress_data(HDR_GET_COMPRESS(hdr),
hdr->b_l1hdr.b_pabd, &tmpbuf, lsize, hdr->b_complevel);
ASSERT3P(tmpbuf, !=, NULL);
ASSERT3U(csize, <=, psize);
abd = abd_get_from_buf(tmpbuf, lsize);
abd_take_ownership_of_buf(abd, B_TRUE);
abd_zero_off(abd, csize, psize - csize);
}
/*
* Authentication is best effort. We authenticate whenever the key is
* available. If we succeed we clear ARC_FLAG_NOAUTH.
*/
if (hdr->b_crypt_hdr.b_ot == DMU_OT_OBJSET) {
ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
ASSERT3U(lsize, ==, psize);
ret = spa_do_crypt_objset_mac_abd(B_FALSE, spa, dsobj, abd,
psize, hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
} else {
ret = spa_do_crypt_mac_abd(B_FALSE, spa, dsobj, abd, psize,
hdr->b_crypt_hdr.b_mac);
}
if (ret == 0)
arc_hdr_clear_flags(hdr, ARC_FLAG_NOAUTH);
else if (ret != ENOENT)
goto error;
if (tmpbuf != NULL)
abd_free(abd);
return (0);
error:
if (tmpbuf != NULL)
abd_free(abd);
return (ret);
}
/*
* This function will take a header that only has raw encrypted data in
* b_crypt_hdr.b_rabd and decrypt it into a new buffer which is stored in
* b_l1hdr.b_pabd. If designated in the header flags, this function will
* also decompress the data.
*/
static int
arc_hdr_decrypt(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb)
{
int ret;
abd_t *cabd = NULL;
void *tmp = NULL;
boolean_t no_crypt = B_FALSE;
boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
ASSERT(HDR_ENCRYPTED(hdr));
arc_hdr_alloc_abd(hdr, 0);
ret = spa_do_crypt_abd(B_FALSE, spa, zb, hdr->b_crypt_hdr.b_ot,
B_FALSE, bswap, hdr->b_crypt_hdr.b_salt, hdr->b_crypt_hdr.b_iv,
hdr->b_crypt_hdr.b_mac, HDR_GET_PSIZE(hdr), hdr->b_l1hdr.b_pabd,
hdr->b_crypt_hdr.b_rabd, &no_crypt);
if (ret != 0)
goto error;
if (no_crypt) {
abd_copy(hdr->b_l1hdr.b_pabd, hdr->b_crypt_hdr.b_rabd,
HDR_GET_PSIZE(hdr));
}
/*
* If this header has disabled arc compression but the b_pabd is
* compressed after decrypting it, we need to decompress the newly
* decrypted data.
*/
if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
!HDR_COMPRESSION_ENABLED(hdr)) {
/*
* We want to make sure that we are correctly honoring the
* zfs_abd_scatter_enabled setting, so we allocate an abd here
* and then loan a buffer from it, rather than allocating a
* linear buffer and wrapping it in an abd later.
*/
cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr, 0);
tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr));
ret = zio_decompress_data(HDR_GET_COMPRESS(hdr),
hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr),
HDR_GET_LSIZE(hdr), &hdr->b_complevel);
if (ret != 0) {
abd_return_buf(cabd, tmp, arc_hdr_size(hdr));
goto error;
}
abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
arc_hdr_size(hdr), hdr);
hdr->b_l1hdr.b_pabd = cabd;
}
return (0);
error:
arc_hdr_free_abd(hdr, B_FALSE);
if (cabd != NULL)
arc_free_data_buf(hdr, cabd, arc_hdr_size(hdr), hdr);
return (ret);
}
/*
* This function is called during arc_buf_fill() to prepare the header's
* abd plaintext pointer for use. This involves authenticated protected
* data and decrypting encrypted data into the plaintext abd.
*/
static int
arc_fill_hdr_crypt(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, spa_t *spa,
const zbookmark_phys_t *zb, boolean_t noauth)
{
int ret;
ASSERT(HDR_PROTECTED(hdr));
if (hash_lock != NULL)
mutex_enter(hash_lock);
if (HDR_NOAUTH(hdr) && !noauth) {
/*
* The caller requested authenticated data but our data has
* not been authenticated yet. Verify the MAC now if we can.
*/
ret = arc_hdr_authenticate(hdr, spa, zb->zb_objset);
if (ret != 0)
goto error;
} else if (HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd == NULL) {
/*
* If we only have the encrypted version of the data, but the
* unencrypted version was requested we take this opportunity
* to store the decrypted version in the header for future use.
*/
ret = arc_hdr_decrypt(hdr, spa, zb);
if (ret != 0)
goto error;
}
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
if (hash_lock != NULL)
mutex_exit(hash_lock);
return (0);
error:
if (hash_lock != NULL)
mutex_exit(hash_lock);
return (ret);
}
/*
* This function is used by the dbuf code to decrypt bonus buffers in place.
* The dbuf code itself doesn't have any locking for decrypting a shared dnode
* block, so we use the hash lock here to protect against concurrent calls to
* arc_buf_fill().
*/
static void
arc_buf_untransform_in_place(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT(HDR_ENCRYPTED(hdr));
ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE);
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
zio_crypt_copy_dnode_bonus(hdr->b_l1hdr.b_pabd, buf->b_data,
arc_buf_size(buf));
buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
}
/*
* Given a buf that has a data buffer attached to it, this function will
* efficiently fill the buf with data of the specified compression setting from
* the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
* are already sharing a data buf, no copy is performed.
*
* If the buf is marked as compressed but uncompressed data was requested, this
* will allocate a new data buffer for the buf, remove that flag, and fill the
* buf with uncompressed data. You can't request a compressed buf on a hdr with
* uncompressed data, and (since we haven't added support for it yet) if you
* want compressed data your buf must already be marked as compressed and have
* the correct-sized data buffer.
*/
static int
arc_buf_fill(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
arc_fill_flags_t flags)
{
int error = 0;
arc_buf_hdr_t *hdr = buf->b_hdr;
boolean_t hdr_compressed =
(arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
boolean_t compressed = (flags & ARC_FILL_COMPRESSED) != 0;
boolean_t encrypted = (flags & ARC_FILL_ENCRYPTED) != 0;
dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
kmutex_t *hash_lock = (flags & ARC_FILL_LOCKED) ? NULL : HDR_LOCK(hdr);
ASSERT3P(buf->b_data, !=, NULL);
IMPLY(compressed, hdr_compressed || ARC_BUF_ENCRYPTED(buf));
IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
IMPLY(encrypted, HDR_ENCRYPTED(hdr));
IMPLY(encrypted, ARC_BUF_ENCRYPTED(buf));
IMPLY(encrypted, ARC_BUF_COMPRESSED(buf));
IMPLY(encrypted, !arc_buf_is_shared(buf));
/*
* If the caller wanted encrypted data we just need to copy it from
* b_rabd and potentially byteswap it. We won't be able to do any
* further transforms on it.
*/
if (encrypted) {
ASSERT(HDR_HAS_RABD(hdr));
abd_copy_to_buf(buf->b_data, hdr->b_crypt_hdr.b_rabd,
HDR_GET_PSIZE(hdr));
goto byteswap;
}
/*
* Adjust encrypted and authenticated headers to accommodate
* the request if needed. Dnode blocks (ARC_FILL_IN_PLACE) are
* allowed to fail decryption due to keys not being loaded
* without being marked as an IO error.
*/
if (HDR_PROTECTED(hdr)) {
error = arc_fill_hdr_crypt(hdr, hash_lock, spa,
zb, !!(flags & ARC_FILL_NOAUTH));
if (error == EACCES && (flags & ARC_FILL_IN_PLACE) != 0) {
return (error);
} else if (error != 0) {
if (hash_lock != NULL)
mutex_enter(hash_lock);
arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
if (hash_lock != NULL)
mutex_exit(hash_lock);
return (error);
}
}
/*
* There is a special case here for dnode blocks which are
* decrypting their bonus buffers. These blocks may request to
* be decrypted in-place. This is necessary because there may
* be many dnodes pointing into this buffer and there is
* currently no method to synchronize replacing the backing
* b_data buffer and updating all of the pointers. Here we use
* the hash lock to ensure there are no races. If the need
* arises for other types to be decrypted in-place, they must
* add handling here as well.
*/
if ((flags & ARC_FILL_IN_PLACE) != 0) {
ASSERT(!hdr_compressed);
ASSERT(!compressed);
ASSERT(!encrypted);
if (HDR_ENCRYPTED(hdr) && ARC_BUF_ENCRYPTED(buf)) {
ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE);
if (hash_lock != NULL)
mutex_enter(hash_lock);
arc_buf_untransform_in_place(buf);
if (hash_lock != NULL)
mutex_exit(hash_lock);
/* Compute the hdr's checksum if necessary */
arc_cksum_compute(buf);
}
return (0);
}
if (hdr_compressed == compressed) {
if (ARC_BUF_SHARED(buf)) {
ASSERT(arc_buf_is_shared(buf));
} else {
abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
arc_buf_size(buf));
}
} else {
ASSERT(hdr_compressed);
ASSERT(!compressed);
/*
* If the buf is sharing its data with the hdr, unlink it and
* allocate a new data buffer for the buf.
*/
if (ARC_BUF_SHARED(buf)) {
ASSERT(ARC_BUF_COMPRESSED(buf));
/* We need to give the buf its own b_data */
buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
buf->b_data =
arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
/* Previously overhead was 0; just add new overhead */
ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
} else if (ARC_BUF_COMPRESSED(buf)) {
ASSERT(!arc_buf_is_shared(buf));
/* We need to reallocate the buf's b_data */
arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
buf);
buf->b_data =
arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
/* We increased the size of b_data; update overhead */
ARCSTAT_INCR(arcstat_overhead_size,
HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
}
/*
* Regardless of the buf's previous compression settings, it
* should not be compressed at the end of this function.
*/
buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
/*
* Try copying the data from another buf which already has a
* decompressed version. If that's not possible, it's time to
* bite the bullet and decompress the data from the hdr.
*/
if (arc_buf_try_copy_decompressed_data(buf)) {
/* Skip byteswapping and checksumming (already done) */
return (0);
} else {
error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
hdr->b_l1hdr.b_pabd, buf->b_data,
HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr),
&hdr->b_complevel);
/*
* Absent hardware errors or software bugs, this should
* be impossible, but log it anyway so we can debug it.
*/
if (error != 0) {
zfs_dbgmsg(
"hdr %px, compress %d, psize %d, lsize %d",
hdr, arc_hdr_get_compress(hdr),
HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
if (hash_lock != NULL)
mutex_enter(hash_lock);
arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
if (hash_lock != NULL)
mutex_exit(hash_lock);
return (SET_ERROR(EIO));
}
}
}
byteswap:
/* Byteswap the buf's data if necessary */
if (bswap != DMU_BSWAP_NUMFUNCS) {
ASSERT(!HDR_SHARED_DATA(hdr));
ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
}
/* Compute the hdr's checksum if necessary */
arc_cksum_compute(buf);
return (0);
}
/*
* If this function is being called to decrypt an encrypted buffer or verify an
* authenticated one, the key must be loaded and a mapping must be made
* available in the keystore via spa_keystore_create_mapping() or one of its
* callers.
*/
int
arc_untransform(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
boolean_t in_place)
{
int ret;
arc_fill_flags_t flags = 0;
if (in_place)
flags |= ARC_FILL_IN_PLACE;
ret = arc_buf_fill(buf, spa, zb, flags);
if (ret == ECKSUM) {
/*
* Convert authentication and decryption errors to EIO
* (and generate an ereport) before leaving the ARC.
*/
ret = SET_ERROR(EIO);
spa_log_error(spa, zb, &buf->b_hdr->b_birth);
(void) zfs_ereport_post(FM_EREPORT_ZFS_AUTHENTICATION,
spa, NULL, zb, NULL, 0);
}
return (ret);
}
/*
* Increment the amount of evictable space in the arc_state_t's refcount.
* We account for the space used by the hdr and the arc buf individually
* so that we can add and remove them from the refcount individually.
*/
static void
arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
{
arc_buf_contents_t type = arc_buf_type(hdr);
ASSERT(HDR_HAS_L1HDR(hdr));
if (GHOST_STATE(state)) {
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!HDR_HAS_RABD(hdr));
(void) zfs_refcount_add_many(&state->arcs_esize[type],
HDR_GET_LSIZE(hdr), hdr);
return;
}
if (hdr->b_l1hdr.b_pabd != NULL) {
(void) zfs_refcount_add_many(&state->arcs_esize[type],
arc_hdr_size(hdr), hdr);
}
if (HDR_HAS_RABD(hdr)) {
(void) zfs_refcount_add_many(&state->arcs_esize[type],
HDR_GET_PSIZE(hdr), hdr);
}
for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
buf = buf->b_next) {
if (ARC_BUF_SHARED(buf))
continue;
(void) zfs_refcount_add_many(&state->arcs_esize[type],
arc_buf_size(buf), buf);
}
}
/*
* Decrement the amount of evictable space in the arc_state_t's refcount.
* We account for the space used by the hdr and the arc buf individually
* so that we can add and remove them from the refcount individually.
*/
static void
arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
{
arc_buf_contents_t type = arc_buf_type(hdr);
ASSERT(HDR_HAS_L1HDR(hdr));
if (GHOST_STATE(state)) {
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!HDR_HAS_RABD(hdr));
(void) zfs_refcount_remove_many(&state->arcs_esize[type],
HDR_GET_LSIZE(hdr), hdr);
return;
}
if (hdr->b_l1hdr.b_pabd != NULL) {
(void) zfs_refcount_remove_many(&state->arcs_esize[type],
arc_hdr_size(hdr), hdr);
}
if (HDR_HAS_RABD(hdr)) {
(void) zfs_refcount_remove_many(&state->arcs_esize[type],
HDR_GET_PSIZE(hdr), hdr);
}
for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
buf = buf->b_next) {
if (ARC_BUF_SHARED(buf))
continue;
(void) zfs_refcount_remove_many(&state->arcs_esize[type],
arc_buf_size(buf), buf);
}
}
/*
* Add a reference to this hdr indicating that someone is actively
* referencing that memory. When the refcount transitions from 0 to 1,
* we remove it from the respective arc_state_t list to indicate that
* it is not evictable.
*/
static void
add_reference(arc_buf_hdr_t *hdr, const void *tag)
{
arc_state_t *state = hdr->b_l1hdr.b_state;
ASSERT(HDR_HAS_L1HDR(hdr));
if (!HDR_EMPTY(hdr) && !MUTEX_HELD(HDR_LOCK(hdr))) {
ASSERT(state == arc_anon);
ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
}
if ((zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
state != arc_anon && state != arc_l2c_only) {
/* We don't use the L2-only state list. */
multilist_remove(&state->arcs_list[arc_buf_type(hdr)], hdr);
arc_evictable_space_decrement(hdr, state);
}
}
/*
* Remove a reference from this hdr. When the reference transitions from
* 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
* list making it eligible for eviction.
*/
static int
remove_reference(arc_buf_hdr_t *hdr, const void *tag)
{
int cnt;
arc_state_t *state = hdr->b_l1hdr.b_state;
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(state == arc_anon || MUTEX_HELD(HDR_LOCK(hdr)));
ASSERT(!GHOST_STATE(state)); /* arc_l2c_only counts as a ghost. */
if ((cnt = zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) != 0)
return (cnt);
if (state == arc_anon) {
arc_hdr_destroy(hdr);
return (0);
}
if (state == arc_uncached && !HDR_PREFETCH(hdr)) {
arc_change_state(arc_anon, hdr);
arc_hdr_destroy(hdr);
return (0);
}
multilist_insert(&state->arcs_list[arc_buf_type(hdr)], hdr);
arc_evictable_space_increment(hdr, state);
return (0);
}
/*
* Returns detailed information about a specific arc buffer. When the
* state_index argument is set the function will calculate the arc header
* list position for its arc state. Since this requires a linear traversal
* callers are strongly encourage not to do this. However, it can be helpful
* for targeted analysis so the functionality is provided.
*/
void
arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index)
{
(void) state_index;
arc_buf_hdr_t *hdr = ab->b_hdr;
l1arc_buf_hdr_t *l1hdr = NULL;
l2arc_buf_hdr_t *l2hdr = NULL;
arc_state_t *state = NULL;
memset(abi, 0, sizeof (arc_buf_info_t));
if (hdr == NULL)
return;
abi->abi_flags = hdr->b_flags;
if (HDR_HAS_L1HDR(hdr)) {
l1hdr = &hdr->b_l1hdr;
state = l1hdr->b_state;
}
if (HDR_HAS_L2HDR(hdr))
l2hdr = &hdr->b_l2hdr;
if (l1hdr) {
abi->abi_bufcnt = 0;
for (arc_buf_t *buf = l1hdr->b_buf; buf; buf = buf->b_next)
abi->abi_bufcnt++;
abi->abi_access = l1hdr->b_arc_access;
abi->abi_mru_hits = l1hdr->b_mru_hits;
abi->abi_mru_ghost_hits = l1hdr->b_mru_ghost_hits;
abi->abi_mfu_hits = l1hdr->b_mfu_hits;
abi->abi_mfu_ghost_hits = l1hdr->b_mfu_ghost_hits;
abi->abi_holds = zfs_refcount_count(&l1hdr->b_refcnt);
}
if (l2hdr) {
abi->abi_l2arc_dattr = l2hdr->b_daddr;
abi->abi_l2arc_hits = l2hdr->b_hits;
}
abi->abi_state_type = state ? state->arcs_state : ARC_STATE_ANON;
abi->abi_state_contents = arc_buf_type(hdr);
abi->abi_size = arc_hdr_size(hdr);
}
/*
* Move the supplied buffer to the indicated state. The hash lock
* for the buffer must be held by the caller.
*/
static void
arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr)
{
arc_state_t *old_state;
int64_t refcnt;
boolean_t update_old, update_new;
arc_buf_contents_t type = arc_buf_type(hdr);
/*
* We almost always have an L1 hdr here, since we call arc_hdr_realloc()
* in arc_read() when bringing a buffer out of the L2ARC. However, the
* L1 hdr doesn't always exist when we change state to arc_anon before
* destroying a header, in which case reallocating to add the L1 hdr is
* pointless.
*/
if (HDR_HAS_L1HDR(hdr)) {
old_state = hdr->b_l1hdr.b_state;
refcnt = zfs_refcount_count(&hdr->b_l1hdr.b_refcnt);
update_old = (hdr->b_l1hdr.b_buf != NULL ||
hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
IMPLY(GHOST_STATE(old_state), hdr->b_l1hdr.b_buf == NULL);
IMPLY(GHOST_STATE(new_state), hdr->b_l1hdr.b_buf == NULL);
IMPLY(old_state == arc_anon, hdr->b_l1hdr.b_buf == NULL ||
ARC_BUF_LAST(hdr->b_l1hdr.b_buf));
} else {
old_state = arc_l2c_only;
refcnt = 0;
update_old = B_FALSE;
}
update_new = update_old;
if (GHOST_STATE(old_state))
update_old = B_TRUE;
if (GHOST_STATE(new_state))
update_new = B_TRUE;
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
ASSERT3P(new_state, !=, old_state);
/*
* If this buffer is evictable, transfer it from the
* old state list to the new state list.
*/
if (refcnt == 0) {
if (old_state != arc_anon && old_state != arc_l2c_only) {
ASSERT(HDR_HAS_L1HDR(hdr));
/* remove_reference() saves on insert. */
if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
multilist_remove(&old_state->arcs_list[type],
hdr);
arc_evictable_space_decrement(hdr, old_state);
}
}
if (new_state != arc_anon && new_state != arc_l2c_only) {
/*
* An L1 header always exists here, since if we're
* moving to some L1-cached state (i.e. not l2c_only or
* anonymous), we realloc the header to add an L1hdr
* beforehand.
*/
ASSERT(HDR_HAS_L1HDR(hdr));
multilist_insert(&new_state->arcs_list[type], hdr);
arc_evictable_space_increment(hdr, new_state);
}
}
ASSERT(!HDR_EMPTY(hdr));
if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
buf_hash_remove(hdr);
/* adjust state sizes (ignore arc_l2c_only) */
if (update_new && new_state != arc_l2c_only) {
ASSERT(HDR_HAS_L1HDR(hdr));
if (GHOST_STATE(new_state)) {
/*
* When moving a header to a ghost state, we first
* remove all arc buffers. Thus, we'll have no arc
* buffer to use for the reference. As a result, we
* use the arc header pointer for the reference.
*/
(void) zfs_refcount_add_many(
&new_state->arcs_size[type],
HDR_GET_LSIZE(hdr), hdr);
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!HDR_HAS_RABD(hdr));
} else {
/*
* Each individual buffer holds a unique reference,
* thus we must remove each of these references one
* at a time.
*/
for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
buf = buf->b_next) {
/*
* When the arc_buf_t is sharing the data
* block with the hdr, the owner of the
* reference belongs to the hdr. Only
* add to the refcount if the arc_buf_t is
* not shared.
*/
if (ARC_BUF_SHARED(buf))
continue;
(void) zfs_refcount_add_many(
&new_state->arcs_size[type],
arc_buf_size(buf), buf);
}
if (hdr->b_l1hdr.b_pabd != NULL) {
(void) zfs_refcount_add_many(
&new_state->arcs_size[type],
arc_hdr_size(hdr), hdr);
}
if (HDR_HAS_RABD(hdr)) {
(void) zfs_refcount_add_many(
&new_state->arcs_size[type],
HDR_GET_PSIZE(hdr), hdr);
}
}
}
if (update_old && old_state != arc_l2c_only) {
ASSERT(HDR_HAS_L1HDR(hdr));
if (GHOST_STATE(old_state)) {
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!HDR_HAS_RABD(hdr));
/*
* When moving a header off of a ghost state,
* the header will not contain any arc buffers.
* We use the arc header pointer for the reference
* which is exactly what we did when we put the
* header on the ghost state.
*/
(void) zfs_refcount_remove_many(
&old_state->arcs_size[type],
HDR_GET_LSIZE(hdr), hdr);
} else {
/*
* Each individual buffer holds a unique reference,
* thus we must remove each of these references one
* at a time.
*/
for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
buf = buf->b_next) {
/*
* When the arc_buf_t is sharing the data
* block with the hdr, the owner of the
* reference belongs to the hdr. Only
* add to the refcount if the arc_buf_t is
* not shared.
*/
if (ARC_BUF_SHARED(buf))
continue;
(void) zfs_refcount_remove_many(
&old_state->arcs_size[type],
arc_buf_size(buf), buf);
}
ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
HDR_HAS_RABD(hdr));
if (hdr->b_l1hdr.b_pabd != NULL) {
(void) zfs_refcount_remove_many(
&old_state->arcs_size[type],
arc_hdr_size(hdr), hdr);
}
if (HDR_HAS_RABD(hdr)) {
(void) zfs_refcount_remove_many(
&old_state->arcs_size[type],
HDR_GET_PSIZE(hdr), hdr);
}
}
}
if (HDR_HAS_L1HDR(hdr)) {
hdr->b_l1hdr.b_state = new_state;
if (HDR_HAS_L2HDR(hdr) && new_state != arc_l2c_only) {
l2arc_hdr_arcstats_decrement_state(hdr);
hdr->b_l2hdr.b_arcs_state = new_state->arcs_state;
l2arc_hdr_arcstats_increment_state(hdr);
}
}
}
void
arc_space_consume(uint64_t space, arc_space_type_t type)
{
ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
switch (type) {
default:
break;
case ARC_SPACE_DATA:
ARCSTAT_INCR(arcstat_data_size, space);
break;
case ARC_SPACE_META:
ARCSTAT_INCR(arcstat_metadata_size, space);
break;
case ARC_SPACE_BONUS:
ARCSTAT_INCR(arcstat_bonus_size, space);
break;
case ARC_SPACE_DNODE:
ARCSTAT_INCR(arcstat_dnode_size, space);
break;
case ARC_SPACE_DBUF:
ARCSTAT_INCR(arcstat_dbuf_size, space);
break;
case ARC_SPACE_HDRS:
ARCSTAT_INCR(arcstat_hdr_size, space);
break;
case ARC_SPACE_L2HDRS:
aggsum_add(&arc_sums.arcstat_l2_hdr_size, space);
break;
case ARC_SPACE_ABD_CHUNK_WASTE:
/*
* Note: this includes space wasted by all scatter ABD's, not
* just those allocated by the ARC. But the vast majority of
* scatter ABD's come from the ARC, because other users are
* very short-lived.
*/
ARCSTAT_INCR(arcstat_abd_chunk_waste_size, space);
break;
}
if (type != ARC_SPACE_DATA && type != ARC_SPACE_ABD_CHUNK_WASTE)
ARCSTAT_INCR(arcstat_meta_used, space);
aggsum_add(&arc_sums.arcstat_size, space);
}
void
arc_space_return(uint64_t space, arc_space_type_t type)
{
ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
switch (type) {
default:
break;
case ARC_SPACE_DATA:
ARCSTAT_INCR(arcstat_data_size, -space);
break;
case ARC_SPACE_META:
ARCSTAT_INCR(arcstat_metadata_size, -space);
break;
case ARC_SPACE_BONUS:
ARCSTAT_INCR(arcstat_bonus_size, -space);
break;
case ARC_SPACE_DNODE:
ARCSTAT_INCR(arcstat_dnode_size, -space);
break;
case ARC_SPACE_DBUF:
ARCSTAT_INCR(arcstat_dbuf_size, -space);
break;
case ARC_SPACE_HDRS:
ARCSTAT_INCR(arcstat_hdr_size, -space);
break;
case ARC_SPACE_L2HDRS:
aggsum_add(&arc_sums.arcstat_l2_hdr_size, -space);
break;
case ARC_SPACE_ABD_CHUNK_WASTE:
ARCSTAT_INCR(arcstat_abd_chunk_waste_size, -space);
break;
}
if (type != ARC_SPACE_DATA && type != ARC_SPACE_ABD_CHUNK_WASTE)
ARCSTAT_INCR(arcstat_meta_used, -space);
ASSERT(aggsum_compare(&arc_sums.arcstat_size, space) >= 0);
aggsum_add(&arc_sums.arcstat_size, -space);
}
/*
* Given a hdr and a buf, returns whether that buf can share its b_data buffer
* with the hdr's b_pabd.
*/
static boolean_t
arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
{
/*
* The criteria for sharing a hdr's data are:
* 1. the buffer is not encrypted
* 2. the hdr's compression matches the buf's compression
* 3. the hdr doesn't need to be byteswapped
* 4. the hdr isn't already being shared
* 5. the buf is either compressed or it is the last buf in the hdr list
*
* Criterion #5 maintains the invariant that shared uncompressed
* bufs must be the final buf in the hdr's b_buf list. Reading this, you
* might ask, "if a compressed buf is allocated first, won't that be the
* last thing in the list?", but in that case it's impossible to create
* a shared uncompressed buf anyway (because the hdr must be compressed
* to have the compressed buf). You might also think that #3 is
* sufficient to make this guarantee, however it's possible
* (specifically in the rare L2ARC write race mentioned in
* arc_buf_alloc_impl()) there will be an existing uncompressed buf that
* is shareable, but wasn't at the time of its allocation. Rather than
* allow a new shared uncompressed buf to be created and then shuffle
* the list around to make it the last element, this simply disallows
* sharing if the new buf isn't the first to be added.
*/
ASSERT3P(buf->b_hdr, ==, hdr);
boolean_t hdr_compressed =
arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF;
boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
return (!ARC_BUF_ENCRYPTED(buf) &&
buf_compressed == hdr_compressed &&
hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
!HDR_SHARED_DATA(hdr) &&
(ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
}
/*
* Allocate a buf for this hdr. If you care about the data that's in the hdr,
* or if you want a compressed buffer, pass those flags in. Returns 0 if the
* copy was made successfully, or an error code otherwise.
*/
static int
arc_buf_alloc_impl(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb,
const void *tag, boolean_t encrypted, boolean_t compressed,
boolean_t noauth, boolean_t fill, arc_buf_t **ret)
{
arc_buf_t *buf;
arc_fill_flags_t flags = ARC_FILL_LOCKED;
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
VERIFY(hdr->b_type == ARC_BUFC_DATA ||
hdr->b_type == ARC_BUFC_METADATA);
ASSERT3P(ret, !=, NULL);
ASSERT3P(*ret, ==, NULL);
IMPLY(encrypted, compressed);
buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
buf->b_hdr = hdr;
buf->b_data = NULL;
buf->b_next = hdr->b_l1hdr.b_buf;
buf->b_flags = 0;
add_reference(hdr, tag);
/*
* We're about to change the hdr's b_flags. We must either
* hold the hash_lock or be undiscoverable.
*/
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
/*
* Only honor requests for compressed bufs if the hdr is actually
* compressed. This must be overridden if the buffer is encrypted since
* encrypted buffers cannot be decompressed.
*/
if (encrypted) {
buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
buf->b_flags |= ARC_BUF_FLAG_ENCRYPTED;
flags |= ARC_FILL_COMPRESSED | ARC_FILL_ENCRYPTED;
} else if (compressed &&
arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
flags |= ARC_FILL_COMPRESSED;
}
if (noauth) {
ASSERT0(encrypted);
flags |= ARC_FILL_NOAUTH;
}
/*
* If the hdr's data can be shared then we share the data buffer and
* set the appropriate bit in the hdr's b_flags to indicate the hdr is
* sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new
* buffer to store the buf's data.
*
* There are two additional restrictions here because we're sharing
* hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
* actively involved in an L2ARC write, because if this buf is used by
* an arc_write() then the hdr's data buffer will be released when the
* write completes, even though the L2ARC write might still be using it.
* Second, the hdr's ABD must be linear so that the buf's user doesn't
* need to be ABD-aware. It must be allocated via
* zio_[data_]buf_alloc(), not as a page, because we need to be able
* to abd_release_ownership_of_buf(), which isn't allowed on "linear
* page" buffers because the ABD code needs to handle freeing them
* specially.
*/
boolean_t can_share = arc_can_share(hdr, buf) &&
!HDR_L2_WRITING(hdr) &&
hdr->b_l1hdr.b_pabd != NULL &&
abd_is_linear(hdr->b_l1hdr.b_pabd) &&
!abd_is_linear_page(hdr->b_l1hdr.b_pabd);
/* Set up b_data and sharing */
if (can_share) {
buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
buf->b_flags |= ARC_BUF_FLAG_SHARED;
arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
} else {
buf->b_data =
arc_get_data_buf(hdr, arc_buf_size(buf), buf);
ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
}
VERIFY3P(buf->b_data, !=, NULL);
hdr->b_l1hdr.b_buf = buf;
/*
* If the user wants the data from the hdr, we need to either copy or
* decompress the data.
*/
if (fill) {
ASSERT3P(zb, !=, NULL);
return (arc_buf_fill(buf, spa, zb, flags));
}
return (0);
}
static const char *arc_onloan_tag = "onloan";
static inline void
arc_loaned_bytes_update(int64_t delta)
{
atomic_add_64(&arc_loaned_bytes, delta);
/* assert that it did not wrap around */
ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
}
/*
* Loan out an anonymous arc buffer. Loaned buffers are not counted as in
* flight data by arc_tempreserve_space() until they are "returned". Loaned
* buffers must be returned to the arc before they can be used by the DMU or
* freed.
*/
arc_buf_t *
arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
{
arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
arc_loaned_bytes_update(arc_buf_size(buf));
return (buf);
}
arc_buf_t *
arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
enum zio_compress compression_type, uint8_t complevel)
{
arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
psize, lsize, compression_type, complevel);
arc_loaned_bytes_update(arc_buf_size(buf));
return (buf);
}
arc_buf_t *
arc_loan_raw_buf(spa_t *spa, uint64_t dsobj, boolean_t byteorder,
const uint8_t *salt, const uint8_t *iv, const uint8_t *mac,
dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
enum zio_compress compression_type, uint8_t complevel)
{
arc_buf_t *buf = arc_alloc_raw_buf(spa, arc_onloan_tag, dsobj,
byteorder, salt, iv, mac, ot, psize, lsize, compression_type,
complevel);
atomic_add_64(&arc_loaned_bytes, psize);
return (buf);
}
/*
* Return a loaned arc buffer to the arc.
*/
void
arc_return_buf(arc_buf_t *buf, const void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT3P(buf->b_data, !=, NULL);
ASSERT(HDR_HAS_L1HDR(hdr));
(void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
(void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
arc_loaned_bytes_update(-arc_buf_size(buf));
}
/* Detach an arc_buf from a dbuf (tag) */
void
arc_loan_inuse_buf(arc_buf_t *buf, const void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT3P(buf->b_data, !=, NULL);
ASSERT(HDR_HAS_L1HDR(hdr));
(void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
(void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
arc_loaned_bytes_update(arc_buf_size(buf));
}
static void
l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
{
l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
df->l2df_abd = abd;
df->l2df_size = size;
df->l2df_type = type;
mutex_enter(&l2arc_free_on_write_mtx);
list_insert_head(l2arc_free_on_write, df);
mutex_exit(&l2arc_free_on_write_mtx);
}
static void
arc_hdr_free_on_write(arc_buf_hdr_t *hdr, boolean_t free_rdata)
{
arc_state_t *state = hdr->b_l1hdr.b_state;
arc_buf_contents_t type = arc_buf_type(hdr);
uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr);
/* protected by hash lock, if in the hash table */
if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT(state != arc_anon && state != arc_l2c_only);
(void) zfs_refcount_remove_many(&state->arcs_esize[type],
size, hdr);
}
(void) zfs_refcount_remove_many(&state->arcs_size[type], size, hdr);
if (type == ARC_BUFC_METADATA) {
arc_space_return(size, ARC_SPACE_META);
} else {
ASSERT(type == ARC_BUFC_DATA);
arc_space_return(size, ARC_SPACE_DATA);
}
if (free_rdata) {
l2arc_free_abd_on_write(hdr->b_crypt_hdr.b_rabd, size, type);
} else {
l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
}
}
/*
* Share the arc_buf_t's data with the hdr. Whenever we are sharing the
* data buffer, we transfer the refcount ownership to the hdr and update
* the appropriate kstats.
*/
static void
arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
{
ASSERT(arc_can_share(hdr, buf));
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!ARC_BUF_ENCRYPTED(buf));
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
/*
* Start sharing the data buffer. We transfer the
* refcount ownership to the hdr since it always owns
* the refcount whenever an arc_buf_t is shared.
*/
zfs_refcount_transfer_ownership_many(
&hdr->b_l1hdr.b_state->arcs_size[arc_buf_type(hdr)],
arc_hdr_size(hdr), buf, hdr);
hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
HDR_ISTYPE_METADATA(hdr));
arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
buf->b_flags |= ARC_BUF_FLAG_SHARED;
/*
* Since we've transferred ownership to the hdr we need
* to increment its compressed and uncompressed kstats and
* decrement the overhead size.
*/
ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
}
static void
arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
{
ASSERT(arc_buf_is_shared(buf));
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
/*
* We are no longer sharing this buffer so we need
* to transfer its ownership to the rightful owner.
*/
zfs_refcount_transfer_ownership_many(
&hdr->b_l1hdr.b_state->arcs_size[arc_buf_type(hdr)],
arc_hdr_size(hdr), hdr, buf);
arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
abd_free(hdr->b_l1hdr.b_pabd);
hdr->b_l1hdr.b_pabd = NULL;
buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
/*
* Since the buffer is no longer shared between
* the arc buf and the hdr, count it as overhead.
*/
ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
}
/*
* Remove an arc_buf_t from the hdr's buf list and return the last
* arc_buf_t on the list. If no buffers remain on the list then return
* NULL.
*/
static arc_buf_t *
arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
{
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
arc_buf_t *lastbuf = NULL;
/*
* Remove the buf from the hdr list and locate the last
* remaining buffer on the list.
*/
while (*bufp != NULL) {
if (*bufp == buf)
*bufp = buf->b_next;
/*
* If we've removed a buffer in the middle of
* the list then update the lastbuf and update
* bufp.
*/
if (*bufp != NULL) {
lastbuf = *bufp;
bufp = &(*bufp)->b_next;
}
}
buf->b_next = NULL;
ASSERT3P(lastbuf, !=, buf);
IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
return (lastbuf);
}
/*
* Free up buf->b_data and pull the arc_buf_t off of the arc_buf_hdr_t's
* list and free it.
*/
static void
arc_buf_destroy_impl(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
/*
* Free up the data associated with the buf but only if we're not
* sharing this with the hdr. If we are sharing it with the hdr, the
* hdr is responsible for doing the free.
*/
if (buf->b_data != NULL) {
/*
* We're about to change the hdr's b_flags. We must either
* hold the hash_lock or be undiscoverable.
*/
ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
arc_cksum_verify(buf);
arc_buf_unwatch(buf);
if (ARC_BUF_SHARED(buf)) {
arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
} else {
ASSERT(!arc_buf_is_shared(buf));
uint64_t size = arc_buf_size(buf);
arc_free_data_buf(hdr, buf->b_data, size, buf);
ARCSTAT_INCR(arcstat_overhead_size, -size);
}
buf->b_data = NULL;
/*
* If we have no more encrypted buffers and we've already
* gotten a copy of the decrypted data we can free b_rabd
* to save some space.
*/
if (ARC_BUF_ENCRYPTED(buf) && HDR_HAS_RABD(hdr) &&
hdr->b_l1hdr.b_pabd != NULL && !HDR_IO_IN_PROGRESS(hdr)) {
arc_buf_t *b;
for (b = hdr->b_l1hdr.b_buf; b; b = b->b_next) {
if (b != buf && ARC_BUF_ENCRYPTED(b))
break;
}
if (b == NULL)
arc_hdr_free_abd(hdr, B_TRUE);
}
}
arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
/*
* If the current arc_buf_t is sharing its data buffer with the
* hdr, then reassign the hdr's b_pabd to share it with the new
* buffer at the end of the list. The shared buffer is always
* the last one on the hdr's buffer list.
*
* There is an equivalent case for compressed bufs, but since
* they aren't guaranteed to be the last buf in the list and
* that is an exceedingly rare case, we just allow that space be
* wasted temporarily. We must also be careful not to share
* encrypted buffers, since they cannot be shared.
*/
if (lastbuf != NULL && !ARC_BUF_ENCRYPTED(lastbuf)) {
/* Only one buf can be shared at once */
ASSERT(!arc_buf_is_shared(lastbuf));
/* hdr is uncompressed so can't have compressed buf */
ASSERT(!ARC_BUF_COMPRESSED(lastbuf));
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
arc_hdr_free_abd(hdr, B_FALSE);
/*
* We must setup a new shared block between the
* last buffer and the hdr. The data would have
* been allocated by the arc buf so we need to transfer
* ownership to the hdr since it's now being shared.
*/
arc_share_buf(hdr, lastbuf);
}
} else if (HDR_SHARED_DATA(hdr)) {
/*
* Uncompressed shared buffers are always at the end
* of the list. Compressed buffers don't have the
* same requirements. This makes it hard to
* simply assert that the lastbuf is shared so
* we rely on the hdr's compression flags to determine
* if we have a compressed, shared buffer.
*/
ASSERT3P(lastbuf, !=, NULL);
ASSERT(arc_buf_is_shared(lastbuf) ||
arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
}
/*
* Free the checksum if we're removing the last uncompressed buf from
* this hdr.
*/
if (!arc_hdr_has_uncompressed_buf(hdr)) {
arc_cksum_free(hdr);
}
/* clean up the buf */
buf->b_hdr = NULL;
kmem_cache_free(buf_cache, buf);
}
static void
arc_hdr_alloc_abd(arc_buf_hdr_t *hdr, int alloc_flags)
{
uint64_t size;
boolean_t alloc_rdata = ((alloc_flags & ARC_HDR_ALLOC_RDATA) != 0);
ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(!HDR_SHARED_DATA(hdr) || alloc_rdata);
IMPLY(alloc_rdata, HDR_PROTECTED(hdr));
if (alloc_rdata) {
size = HDR_GET_PSIZE(hdr);
ASSERT3P(hdr->b_crypt_hdr.b_rabd, ==, NULL);
hdr->b_crypt_hdr.b_rabd = arc_get_data_abd(hdr, size, hdr,
alloc_flags);
ASSERT3P(hdr->b_crypt_hdr.b_rabd, !=, NULL);
ARCSTAT_INCR(arcstat_raw_size, size);
} else {
size = arc_hdr_size(hdr);
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, size, hdr,
alloc_flags);
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
}
ARCSTAT_INCR(arcstat_compressed_size, size);
ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
}
static void
arc_hdr_free_abd(arc_buf_hdr_t *hdr, boolean_t free_rdata)
{
uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr);
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
IMPLY(free_rdata, HDR_HAS_RABD(hdr));
/*
* If the hdr is currently being written to the l2arc then
* we defer freeing the data by adding it to the l2arc_free_on_write
* list. The l2arc will free the data once it's finished
* writing it to the l2arc device.
*/
if (HDR_L2_WRITING(hdr)) {
arc_hdr_free_on_write(hdr, free_rdata);
ARCSTAT_BUMP(arcstat_l2_free_on_write);
} else if (free_rdata) {
arc_free_data_abd(hdr, hdr->b_crypt_hdr.b_rabd, size, hdr);
} else {
arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, size, hdr);
}
if (free_rdata) {
hdr->b_crypt_hdr.b_rabd = NULL;
ARCSTAT_INCR(arcstat_raw_size, -size);
} else {
hdr->b_l1hdr.b_pabd = NULL;
}
if (hdr->b_l1hdr.b_pabd == NULL && !HDR_HAS_RABD(hdr))
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
ARCSTAT_INCR(arcstat_compressed_size, -size);
ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
}
/*
* Allocate empty anonymous ARC header. The header will get its identity
* assigned and buffers attached later as part of read or write operations.
*
* In case of read arc_read() assigns header its identify (b_dva + b_birth),
* inserts it into ARC hash to become globally visible and allocates physical
* (b_pabd) or raw (b_rabd) ABD buffer to read into from disk. On disk read
* completion arc_read_done() allocates ARC buffer(s) as needed, potentially
* sharing one of them with the physical ABD buffer.
*
* In case of write arc_alloc_buf() allocates ARC buffer to be filled with
* data. Then after compression and/or encryption arc_write_ready() allocates
* and fills (or potentially shares) physical (b_pabd) or raw (b_rabd) ABD
* buffer. On disk write completion arc_write_done() assigns the header its
* new identity (b_dva + b_birth) and inserts into ARC hash.
*
* In case of partial overwrite the old data is read first as described. Then
* arc_release() either allocates new anonymous ARC header and moves the ARC
* buffer to it, or reuses the old ARC header by discarding its identity and
* removing it from ARC hash. After buffer modification normal write process
* follows as described.
*/
static arc_buf_hdr_t *
arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
boolean_t protected, enum zio_compress compression_type, uint8_t complevel,
arc_buf_contents_t type)
{
arc_buf_hdr_t *hdr;
VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
ASSERT(HDR_EMPTY(hdr));
#ifdef ZFS_DEBUG
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
#endif
HDR_SET_PSIZE(hdr, psize);
HDR_SET_LSIZE(hdr, lsize);
hdr->b_spa = spa;
hdr->b_type = type;
hdr->b_flags = 0;
arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
arc_hdr_set_compress(hdr, compression_type);
hdr->b_complevel = complevel;
if (protected)
arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
hdr->b_l1hdr.b_state = arc_anon;
hdr->b_l1hdr.b_arc_access = 0;
hdr->b_l1hdr.b_mru_hits = 0;
hdr->b_l1hdr.b_mru_ghost_hits = 0;
hdr->b_l1hdr.b_mfu_hits = 0;
hdr->b_l1hdr.b_mfu_ghost_hits = 0;
hdr->b_l1hdr.b_buf = NULL;
ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
return (hdr);
}
/*
* Transition between the two allocation states for the arc_buf_hdr struct.
* The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
* (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
* version is used when a cache buffer is only in the L2ARC in order to reduce
* memory usage.
*/
static arc_buf_hdr_t *
arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
{
ASSERT(HDR_HAS_L2HDR(hdr));
arc_buf_hdr_t *nhdr;
l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
(old == hdr_l2only_cache && new == hdr_full_cache));
nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
buf_hash_remove(hdr);
memcpy(nhdr, hdr, HDR_L2ONLY_SIZE);
if (new == hdr_full_cache) {
arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
/*
* arc_access and arc_change_state need to be aware that a
* header has just come out of L2ARC, so we set its state to
* l2c_only even though it's about to change.
*/
nhdr->b_l1hdr.b_state = arc_l2c_only;
/* Verify previous threads set to NULL before freeing */
ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!HDR_HAS_RABD(hdr));
} else {
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
#ifdef ZFS_DEBUG
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
#endif
/*
* If we've reached here, We must have been called from
* arc_evict_hdr(), as such we should have already been
* removed from any ghost list we were previously on
* (which protects us from racing with arc_evict_state),
* thus no locking is needed during this check.
*/
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
/*
* A buffer must not be moved into the arc_l2c_only
* state if it's not finished being written out to the
* l2arc device. Otherwise, the b_l1hdr.b_pabd field
* might try to be accessed, even though it was removed.
*/
VERIFY(!HDR_L2_WRITING(hdr));
VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!HDR_HAS_RABD(hdr));
arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
}
/*
* The header has been reallocated so we need to re-insert it into any
* lists it was on.
*/
(void) buf_hash_insert(nhdr, NULL);
ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
mutex_enter(&dev->l2ad_mtx);
/*
* We must place the realloc'ed header back into the list at
* the same spot. Otherwise, if it's placed earlier in the list,
* l2arc_write_buffers() could find it during the function's
* write phase, and try to write it out to the l2arc.
*/
list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
list_remove(&dev->l2ad_buflist, hdr);
mutex_exit(&dev->l2ad_mtx);
/*
* Since we're using the pointer address as the tag when
* incrementing and decrementing the l2ad_alloc refcount, we
* must remove the old pointer (that we're about to destroy) and
* add the new pointer to the refcount. Otherwise we'd remove
* the wrong pointer address when calling arc_hdr_destroy() later.
*/
(void) zfs_refcount_remove_many(&dev->l2ad_alloc,
arc_hdr_size(hdr), hdr);
(void) zfs_refcount_add_many(&dev->l2ad_alloc,
arc_hdr_size(nhdr), nhdr);
buf_discard_identity(hdr);
kmem_cache_free(old, hdr);
return (nhdr);
}
/*
* This function is used by the send / receive code to convert a newly
* allocated arc_buf_t to one that is suitable for a raw encrypted write. It
* is also used to allow the root objset block to be updated without altering
* its embedded MACs. Both block types will always be uncompressed so we do not
* have to worry about compression type or psize.
*/
void
arc_convert_to_raw(arc_buf_t *buf, uint64_t dsobj, boolean_t byteorder,
dmu_object_type_t ot, const uint8_t *salt, const uint8_t *iv,
const uint8_t *mac)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT(ot == DMU_OT_DNODE || ot == DMU_OT_OBJSET);
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
buf->b_flags |= (ARC_BUF_FLAG_COMPRESSED | ARC_BUF_FLAG_ENCRYPTED);
arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
hdr->b_crypt_hdr.b_dsobj = dsobj;
hdr->b_crypt_hdr.b_ot = ot;
hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ?
DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot);
if (!arc_hdr_has_uncompressed_buf(hdr))
arc_cksum_free(hdr);
if (salt != NULL)
memcpy(hdr->b_crypt_hdr.b_salt, salt, ZIO_DATA_SALT_LEN);
if (iv != NULL)
memcpy(hdr->b_crypt_hdr.b_iv, iv, ZIO_DATA_IV_LEN);
if (mac != NULL)
memcpy(hdr->b_crypt_hdr.b_mac, mac, ZIO_DATA_MAC_LEN);
}
/*
* Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
* The buf is returned thawed since we expect the consumer to modify it.
*/
arc_buf_t *
arc_alloc_buf(spa_t *spa, const void *tag, arc_buf_contents_t type,
int32_t size)
{
arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
B_FALSE, ZIO_COMPRESS_OFF, 0, type);
arc_buf_t *buf = NULL;
VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE, B_FALSE,
B_FALSE, B_FALSE, &buf));
arc_buf_thaw(buf);
return (buf);
}
/*
* Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
* for bufs containing metadata.
*/
arc_buf_t *
arc_alloc_compressed_buf(spa_t *spa, const void *tag, uint64_t psize,
uint64_t lsize, enum zio_compress compression_type, uint8_t complevel)
{
ASSERT3U(lsize, >, 0);
ASSERT3U(lsize, >=, psize);
ASSERT3U(compression_type, >, ZIO_COMPRESS_OFF);
ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS);
arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
B_FALSE, compression_type, complevel, ARC_BUFC_DATA);
arc_buf_t *buf = NULL;
VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE,
B_TRUE, B_FALSE, B_FALSE, &buf));
arc_buf_thaw(buf);
/*
* To ensure that the hdr has the correct data in it if we call
* arc_untransform() on this buf before it's been written to disk,
* it's easiest if we just set up sharing between the buf and the hdr.
*/
arc_share_buf(hdr, buf);
return (buf);
}
arc_buf_t *
arc_alloc_raw_buf(spa_t *spa, const void *tag, uint64_t dsobj,
boolean_t byteorder, const uint8_t *salt, const uint8_t *iv,
const uint8_t *mac, dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
enum zio_compress compression_type, uint8_t complevel)
{
arc_buf_hdr_t *hdr;
arc_buf_t *buf;
arc_buf_contents_t type = DMU_OT_IS_METADATA(ot) ?
ARC_BUFC_METADATA : ARC_BUFC_DATA;
ASSERT3U(lsize, >, 0);
ASSERT3U(lsize, >=, psize);
ASSERT3U(compression_type, >=, ZIO_COMPRESS_OFF);
ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS);
hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, B_TRUE,
compression_type, complevel, type);
hdr->b_crypt_hdr.b_dsobj = dsobj;
hdr->b_crypt_hdr.b_ot = ot;
hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ?
DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot);
memcpy(hdr->b_crypt_hdr.b_salt, salt, ZIO_DATA_SALT_LEN);
memcpy(hdr->b_crypt_hdr.b_iv, iv, ZIO_DATA_IV_LEN);
memcpy(hdr->b_crypt_hdr.b_mac, mac, ZIO_DATA_MAC_LEN);
/*
* This buffer will be considered encrypted even if the ot is not an
* encrypted type. It will become authenticated instead in
* arc_write_ready().
*/
buf = NULL;
VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_TRUE, B_TRUE,
B_FALSE, B_FALSE, &buf));
arc_buf_thaw(buf);
return (buf);
}
static void
l2arc_hdr_arcstats_update(arc_buf_hdr_t *hdr, boolean_t incr,
boolean_t state_only)
{
l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
l2arc_dev_t *dev = l2hdr->b_dev;
uint64_t lsize = HDR_GET_LSIZE(hdr);
uint64_t psize = HDR_GET_PSIZE(hdr);
uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
arc_buf_contents_t type = hdr->b_type;
int64_t lsize_s;
int64_t psize_s;
int64_t asize_s;
if (incr) {
lsize_s = lsize;
psize_s = psize;
asize_s = asize;
} else {
lsize_s = -lsize;
psize_s = -psize;
asize_s = -asize;
}
/* If the buffer is a prefetch, count it as such. */
if (HDR_PREFETCH(hdr)) {
ARCSTAT_INCR(arcstat_l2_prefetch_asize, asize_s);
} else {
/*
* We use the value stored in the L2 header upon initial
* caching in L2ARC. This value will be updated in case
* an MRU/MRU_ghost buffer transitions to MFU but the L2ARC
* metadata (log entry) cannot currently be updated. Having
* the ARC state in the L2 header solves the problem of a
* possibly absent L1 header (apparent in buffers restored
* from persistent L2ARC).
*/
switch (hdr->b_l2hdr.b_arcs_state) {
case ARC_STATE_MRU_GHOST:
case ARC_STATE_MRU:
ARCSTAT_INCR(arcstat_l2_mru_asize, asize_s);
break;
case ARC_STATE_MFU_GHOST:
case ARC_STATE_MFU:
ARCSTAT_INCR(arcstat_l2_mfu_asize, asize_s);
break;
default:
break;
}
}
if (state_only)
return;
ARCSTAT_INCR(arcstat_l2_psize, psize_s);
ARCSTAT_INCR(arcstat_l2_lsize, lsize_s);
switch (type) {
case ARC_BUFC_DATA:
ARCSTAT_INCR(arcstat_l2_bufc_data_asize, asize_s);
break;
case ARC_BUFC_METADATA:
ARCSTAT_INCR(arcstat_l2_bufc_metadata_asize, asize_s);
break;
default:
break;
}
}
static void
arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
{
l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
l2arc_dev_t *dev = l2hdr->b_dev;
uint64_t psize = HDR_GET_PSIZE(hdr);
uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
ASSERT(HDR_HAS_L2HDR(hdr));
list_remove(&dev->l2ad_buflist, hdr);
l2arc_hdr_arcstats_decrement(hdr);
vdev_space_update(dev->l2ad_vdev, -asize, 0, 0);
(void) zfs_refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr),
hdr);
arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
}
static void
arc_hdr_destroy(arc_buf_hdr_t *hdr)
{
if (HDR_HAS_L1HDR(hdr)) {
ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
}
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT(!HDR_IN_HASH_TABLE(hdr));
if (HDR_HAS_L2HDR(hdr)) {
l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
if (!buflist_held)
mutex_enter(&dev->l2ad_mtx);
/*
* Even though we checked this conditional above, we
* need to check this again now that we have the
* l2ad_mtx. This is because we could be racing with
* another thread calling l2arc_evict() which might have
* destroyed this header's L2 portion as we were waiting
* to acquire the l2ad_mtx. If that happens, we don't
* want to re-destroy the header's L2 portion.
*/
if (HDR_HAS_L2HDR(hdr)) {
if (!HDR_EMPTY(hdr))
buf_discard_identity(hdr);
arc_hdr_l2hdr_destroy(hdr);
}
if (!buflist_held)
mutex_exit(&dev->l2ad_mtx);
}
/*
* The header's identify can only be safely discarded once it is no
* longer discoverable. This requires removing it from the hash table
* and the l2arc header list. After this point the hash lock can not
* be used to protect the header.
*/
if (!HDR_EMPTY(hdr))
buf_discard_identity(hdr);
if (HDR_HAS_L1HDR(hdr)) {
arc_cksum_free(hdr);
while (hdr->b_l1hdr.b_buf != NULL)
arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
if (hdr->b_l1hdr.b_pabd != NULL)
arc_hdr_free_abd(hdr, B_FALSE);
if (HDR_HAS_RABD(hdr))
arc_hdr_free_abd(hdr, B_TRUE);
}
ASSERT3P(hdr->b_hash_next, ==, NULL);
if (HDR_HAS_L1HDR(hdr)) {
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
#ifdef ZFS_DEBUG
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
#endif
kmem_cache_free(hdr_full_cache, hdr);
} else {
kmem_cache_free(hdr_l2only_cache, hdr);
}
}
void
arc_buf_destroy(arc_buf_t *buf, const void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
if (hdr->b_l1hdr.b_state == arc_anon) {
ASSERT3P(hdr->b_l1hdr.b_buf, ==, buf);
ASSERT(ARC_BUF_LAST(buf));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
VERIFY0(remove_reference(hdr, tag));
return;
}
kmutex_t *hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
ASSERT3P(hdr, ==, buf->b_hdr);
ASSERT3P(hdr->b_l1hdr.b_buf, !=, NULL);
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
ASSERT3P(buf->b_data, !=, NULL);
arc_buf_destroy_impl(buf);
(void) remove_reference(hdr, tag);
mutex_exit(hash_lock);
}
/*
* Evict the arc_buf_hdr that is provided as a parameter. The resultant
* state of the header is dependent on its state prior to entering this
* function. The following transitions are possible:
*
* - arc_mru -> arc_mru_ghost
* - arc_mfu -> arc_mfu_ghost
* - arc_mru_ghost -> arc_l2c_only
* - arc_mru_ghost -> deleted
* - arc_mfu_ghost -> arc_l2c_only
* - arc_mfu_ghost -> deleted
* - arc_uncached -> deleted
*
* Return total size of evicted data buffers for eviction progress tracking.
* When evicting from ghost states return logical buffer size to make eviction
* progress at the same (or at least comparable) rate as from non-ghost states.
*
* Return *real_evicted for actual ARC size reduction to wake up threads
* waiting for it. For non-ghost states it includes size of evicted data
* buffers (the headers are not freed there). For ghost states it includes
* only the evicted headers size.
*/
static int64_t
arc_evict_hdr(arc_buf_hdr_t *hdr, uint64_t *real_evicted)
{
arc_state_t *evicted_state, *state;
int64_t bytes_evicted = 0;
uint_t min_lifetime = HDR_PRESCIENT_PREFETCH(hdr) ?
arc_min_prescient_prefetch_ms : arc_min_prefetch_ms;
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt));
*real_evicted = 0;
state = hdr->b_l1hdr.b_state;
if (GHOST_STATE(state)) {
/*
* l2arc_write_buffers() relies on a header's L1 portion
* (i.e. its b_pabd field) during it's write phase.
* Thus, we cannot push a header onto the arc_l2c_only
* state (removing its L1 piece) until the header is
* done being written to the l2arc.
*/
if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
ARCSTAT_BUMP(arcstat_evict_l2_skip);
return (bytes_evicted);
}
ARCSTAT_BUMP(arcstat_deleted);
bytes_evicted += HDR_GET_LSIZE(hdr);
DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
if (HDR_HAS_L2HDR(hdr)) {
ASSERT(hdr->b_l1hdr.b_pabd == NULL);
ASSERT(!HDR_HAS_RABD(hdr));
/*
* This buffer is cached on the 2nd Level ARC;
* don't destroy the header.
*/
arc_change_state(arc_l2c_only, hdr);
/*
* dropping from L1+L2 cached to L2-only,
* realloc to remove the L1 header.
*/
(void) arc_hdr_realloc(hdr, hdr_full_cache,
hdr_l2only_cache);
*real_evicted += HDR_FULL_SIZE - HDR_L2ONLY_SIZE;
} else {
arc_change_state(arc_anon, hdr);
arc_hdr_destroy(hdr);
*real_evicted += HDR_FULL_SIZE;
}
return (bytes_evicted);
}
ASSERT(state == arc_mru || state == arc_mfu || state == arc_uncached);
evicted_state = (state == arc_uncached) ? arc_anon :
((state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost);
/* prefetch buffers have a minimum lifespan */
if ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
MSEC_TO_TICK(min_lifetime)) {
ARCSTAT_BUMP(arcstat_evict_skip);
return (bytes_evicted);
}
if (HDR_HAS_L2HDR(hdr)) {
ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
} else {
if (l2arc_write_eligible(hdr->b_spa, hdr)) {
ARCSTAT_INCR(arcstat_evict_l2_eligible,
HDR_GET_LSIZE(hdr));
switch (state->arcs_state) {
case ARC_STATE_MRU:
ARCSTAT_INCR(
arcstat_evict_l2_eligible_mru,
HDR_GET_LSIZE(hdr));
break;
case ARC_STATE_MFU:
ARCSTAT_INCR(
arcstat_evict_l2_eligible_mfu,
HDR_GET_LSIZE(hdr));
break;
default:
break;
}
} else {
ARCSTAT_INCR(arcstat_evict_l2_ineligible,
HDR_GET_LSIZE(hdr));
}
}
bytes_evicted += arc_hdr_size(hdr);
*real_evicted += arc_hdr_size(hdr);
/*
* If this hdr is being evicted and has a compressed buffer then we
* discard it here before we change states. This ensures that the
* accounting is updated correctly in arc_free_data_impl().
*/
if (hdr->b_l1hdr.b_pabd != NULL)
arc_hdr_free_abd(hdr, B_FALSE);
if (HDR_HAS_RABD(hdr))
arc_hdr_free_abd(hdr, B_TRUE);
arc_change_state(evicted_state, hdr);
DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
if (evicted_state == arc_anon) {
arc_hdr_destroy(hdr);
*real_evicted += HDR_FULL_SIZE;
} else {
ASSERT(HDR_IN_HASH_TABLE(hdr));
}
return (bytes_evicted);
}
static void
arc_set_need_free(void)
{
ASSERT(MUTEX_HELD(&arc_evict_lock));
int64_t remaining = arc_free_memory() - arc_sys_free / 2;
arc_evict_waiter_t *aw = list_tail(&arc_evict_waiters);
if (aw == NULL) {
arc_need_free = MAX(-remaining, 0);
} else {
arc_need_free =
MAX(-remaining, (int64_t)(aw->aew_count - arc_evict_count));
}
}
static uint64_t
arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
uint64_t spa, uint64_t bytes)
{
multilist_sublist_t *mls;
uint64_t bytes_evicted = 0, real_evicted = 0;
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
uint_t evict_count = zfs_arc_evict_batch_limit;
ASSERT3P(marker, !=, NULL);
mls = multilist_sublist_lock(ml, idx);
for (hdr = multilist_sublist_prev(mls, marker); likely(hdr != NULL);
hdr = multilist_sublist_prev(mls, marker)) {
if ((evict_count == 0) || (bytes_evicted >= bytes))
break;
/*
* To keep our iteration location, move the marker
* forward. Since we're not holding hdr's hash lock, we
* must be very careful and not remove 'hdr' from the
* sublist. Otherwise, other consumers might mistake the
* 'hdr' as not being on a sublist when they call the
* multilist_link_active() function (they all rely on
* the hash lock protecting concurrent insertions and
* removals). multilist_sublist_move_forward() was
* specifically implemented to ensure this is the case
* (only 'marker' will be removed and re-inserted).
*/
multilist_sublist_move_forward(mls, marker);
/*
* The only case where the b_spa field should ever be
* zero, is the marker headers inserted by
* arc_evict_state(). It's possible for multiple threads
* to be calling arc_evict_state() concurrently (e.g.
* dsl_pool_close() and zio_inject_fault()), so we must
* skip any markers we see from these other threads.
*/
if (hdr->b_spa == 0)
continue;
/* we're only interested in evicting buffers of a certain spa */
if (spa != 0 && hdr->b_spa != spa) {
ARCSTAT_BUMP(arcstat_evict_skip);
continue;
}
hash_lock = HDR_LOCK(hdr);
/*
* We aren't calling this function from any code path
* that would already be holding a hash lock, so we're
* asserting on this assumption to be defensive in case
* this ever changes. Without this check, it would be
* possible to incorrectly increment arcstat_mutex_miss
* below (e.g. if the code changed such that we called
* this function with a hash lock held).
*/
ASSERT(!MUTEX_HELD(hash_lock));
if (mutex_tryenter(hash_lock)) {
uint64_t revicted;
uint64_t evicted = arc_evict_hdr(hdr, &revicted);
mutex_exit(hash_lock);
bytes_evicted += evicted;
real_evicted += revicted;
/*
* If evicted is zero, arc_evict_hdr() must have
* decided to skip this header, don't increment
* evict_count in this case.
*/
if (evicted != 0)
evict_count--;
} else {
ARCSTAT_BUMP(arcstat_mutex_miss);
}
}
multilist_sublist_unlock(mls);
/*
* Increment the count of evicted bytes, and wake up any threads that
* are waiting for the count to reach this value. Since the list is
* ordered by ascending aew_count, we pop off the beginning of the
* list until we reach the end, or a waiter that's past the current
* "count". Doing this outside the loop reduces the number of times
* we need to acquire the global arc_evict_lock.
*
* Only wake when there's sufficient free memory in the system
* (specifically, arc_sys_free/2, which by default is a bit more than
* 1/64th of RAM). See the comments in arc_wait_for_eviction().
*/
mutex_enter(&arc_evict_lock);
arc_evict_count += real_evicted;
if (arc_free_memory() > arc_sys_free / 2) {
arc_evict_waiter_t *aw;
while ((aw = list_head(&arc_evict_waiters)) != NULL &&
aw->aew_count <= arc_evict_count) {
list_remove(&arc_evict_waiters, aw);
cv_broadcast(&aw->aew_cv);
}
}
arc_set_need_free();
mutex_exit(&arc_evict_lock);
/*
* If the ARC size is reduced from arc_c_max to arc_c_min (especially
* if the average cached block is small), eviction can be on-CPU for
* many seconds. To ensure that other threads that may be bound to
* this CPU are able to make progress, make a voluntary preemption
* call here.
*/
kpreempt(KPREEMPT_SYNC);
return (bytes_evicted);
}
/*
* Allocate an array of buffer headers used as placeholders during arc state
* eviction.
*/
static arc_buf_hdr_t **
arc_state_alloc_markers(int count)
{
arc_buf_hdr_t **markers;
markers = kmem_zalloc(sizeof (*markers) * count, KM_SLEEP);
for (int i = 0; i < count; i++) {
markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
/*
* A b_spa of 0 is used to indicate that this header is
* a marker. This fact is used in arc_evict_state_impl().
*/
markers[i]->b_spa = 0;
}
return (markers);
}
static void
arc_state_free_markers(arc_buf_hdr_t **markers, int count)
{
for (int i = 0; i < count; i++)
kmem_cache_free(hdr_full_cache, markers[i]);
kmem_free(markers, sizeof (*markers) * count);
}
/*
* Evict buffers from the given arc state, until we've removed the
* specified number of bytes. Move the removed buffers to the
* appropriate evict state.
*
* This function makes a "best effort". It skips over any buffers
* it can't get a hash_lock on, and so, may not catch all candidates.
* It may also return without evicting as much space as requested.
*
* If bytes is specified using the special value ARC_EVICT_ALL, this
* will evict all available (i.e. unlocked and evictable) buffers from
* the given arc state; which is used by arc_flush().
*/
static uint64_t
arc_evict_state(arc_state_t *state, arc_buf_contents_t type, uint64_t spa,
uint64_t bytes)
{
uint64_t total_evicted = 0;
multilist_t *ml = &state->arcs_list[type];
int num_sublists;
arc_buf_hdr_t **markers;
num_sublists = multilist_get_num_sublists(ml);
/*
* If we've tried to evict from each sublist, made some
* progress, but still have not hit the target number of bytes
* to evict, we want to keep trying. The markers allow us to
* pick up where we left off for each individual sublist, rather
* than starting from the tail each time.
*/
if (zthr_iscurthread(arc_evict_zthr)) {
markers = arc_state_evict_markers;
ASSERT3S(num_sublists, <=, arc_state_evict_marker_count);
} else {
markers = arc_state_alloc_markers(num_sublists);
}
for (int i = 0; i < num_sublists; i++) {
multilist_sublist_t *mls;
mls = multilist_sublist_lock(ml, i);
multilist_sublist_insert_tail(mls, markers[i]);
multilist_sublist_unlock(mls);
}
/*
* While we haven't hit our target number of bytes to evict, or
* we're evicting all available buffers.
*/
while (total_evicted < bytes) {
int sublist_idx = multilist_get_random_index(ml);
uint64_t scan_evicted = 0;
/*
* Start eviction using a randomly selected sublist,
* this is to try and evenly balance eviction across all
* sublists. Always starting at the same sublist
* (e.g. index 0) would cause evictions to favor certain
* sublists over others.
*/
for (int i = 0; i < num_sublists; i++) {
uint64_t bytes_remaining;
uint64_t bytes_evicted;
if (total_evicted < bytes)
bytes_remaining = bytes - total_evicted;
else
break;
bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
markers[sublist_idx], spa, bytes_remaining);
scan_evicted += bytes_evicted;
total_evicted += bytes_evicted;
/* we've reached the end, wrap to the beginning */
if (++sublist_idx >= num_sublists)
sublist_idx = 0;
}
/*
* If we didn't evict anything during this scan, we have
* no reason to believe we'll evict more during another
* scan, so break the loop.
*/
if (scan_evicted == 0) {
/* This isn't possible, let's make that obvious */
ASSERT3S(bytes, !=, 0);
/*
* When bytes is ARC_EVICT_ALL, the only way to
* break the loop is when scan_evicted is zero.
* In that case, we actually have evicted enough,
* so we don't want to increment the kstat.
*/
if (bytes != ARC_EVICT_ALL) {
ASSERT3S(total_evicted, <, bytes);
ARCSTAT_BUMP(arcstat_evict_not_enough);
}
break;
}
}
for (int i = 0; i < num_sublists; i++) {
multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
multilist_sublist_remove(mls, markers[i]);
multilist_sublist_unlock(mls);
}
if (markers != arc_state_evict_markers)
arc_state_free_markers(markers, num_sublists);
return (total_evicted);
}
/*
* Flush all "evictable" data of the given type from the arc state
* specified. This will not evict any "active" buffers (i.e. referenced).
*
* When 'retry' is set to B_FALSE, the function will make a single pass
* over the state and evict any buffers that it can. Since it doesn't
* continually retry the eviction, it might end up leaving some buffers
* in the ARC due to lock misses.
*
* When 'retry' is set to B_TRUE, the function will continually retry the
* eviction until *all* evictable buffers have been removed from the
* state. As a result, if concurrent insertions into the state are
* allowed (e.g. if the ARC isn't shutting down), this function might
* wind up in an infinite loop, continually trying to evict buffers.
*/
static uint64_t
arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
boolean_t retry)
{
uint64_t evicted = 0;
while (zfs_refcount_count(&state->arcs_esize[type]) != 0) {
evicted += arc_evict_state(state, type, spa, ARC_EVICT_ALL);
if (!retry)
break;
}
return (evicted);
}
/*
* Evict the specified number of bytes from the state specified. This
* function prevents us from trying to evict more from a state's list
* than is "evictable", and to skip evicting altogether when passed a
* negative value for "bytes". In contrast, arc_evict_state() will
* evict everything it can, when passed a negative value for "bytes".
*/
static uint64_t
arc_evict_impl(arc_state_t *state, arc_buf_contents_t type, int64_t bytes)
{
uint64_t delta;
if (bytes > 0 && zfs_refcount_count(&state->arcs_esize[type]) > 0) {
delta = MIN(zfs_refcount_count(&state->arcs_esize[type]),
bytes);
return (arc_evict_state(state, type, 0, delta));
}
return (0);
}
/*
* Adjust specified fraction, taking into account initial ghost state(s) size,
* ghost hit bytes towards increasing the fraction, ghost hit bytes towards
* decreasing it, plus a balance factor, controlling the decrease rate, used
* to balance metadata vs data.
*/
static uint64_t
arc_evict_adj(uint64_t frac, uint64_t total, uint64_t up, uint64_t down,
uint_t balance)
{
if (total < 8 || up + down == 0)
return (frac);
/*
* We should not have more ghost hits than ghost size, but they
* may get close. Restrict maximum adjustment in that case.
*/
if (up + down >= total / 4) {
uint64_t scale = (up + down) / (total / 8);
up /= scale;
down /= scale;
}
/* Get maximal dynamic range by choosing optimal shifts. */
int s = highbit64(total);
s = MIN(64 - s, 32);
uint64_t ofrac = (1ULL << 32) - frac;
if (frac >= 4 * ofrac)
up /= frac / (2 * ofrac + 1);
up = (up << s) / (total >> (32 - s));
if (ofrac >= 4 * frac)
down /= ofrac / (2 * frac + 1);
down = (down << s) / (total >> (32 - s));
down = down * 100 / balance;
return (frac + up - down);
}
/*
* Evict buffers from the cache, such that arcstat_size is capped by arc_c.
*/
static uint64_t
arc_evict(void)
{
uint64_t asize, bytes, total_evicted = 0;
int64_t e, mrud, mrum, mfud, mfum, w;
static uint64_t ogrd, ogrm, ogfd, ogfm;
static uint64_t gsrd, gsrm, gsfd, gsfm;
uint64_t ngrd, ngrm, ngfd, ngfm;
/* Get current size of ARC states we can evict from. */
mrud = zfs_refcount_count(&arc_mru->arcs_size[ARC_BUFC_DATA]) +
zfs_refcount_count(&arc_anon->arcs_size[ARC_BUFC_DATA]);
mrum = zfs_refcount_count(&arc_mru->arcs_size[ARC_BUFC_METADATA]) +
zfs_refcount_count(&arc_anon->arcs_size[ARC_BUFC_METADATA]);
mfud = zfs_refcount_count(&arc_mfu->arcs_size[ARC_BUFC_DATA]);
mfum = zfs_refcount_count(&arc_mfu->arcs_size[ARC_BUFC_METADATA]);
uint64_t d = mrud + mfud;
uint64_t m = mrum + mfum;
uint64_t t = d + m;
/* Get ARC ghost hits since last eviction. */
ngrd = wmsum_value(&arc_mru_ghost->arcs_hits[ARC_BUFC_DATA]);
uint64_t grd = ngrd - ogrd;
ogrd = ngrd;
ngrm = wmsum_value(&arc_mru_ghost->arcs_hits[ARC_BUFC_METADATA]);
uint64_t grm = ngrm - ogrm;
ogrm = ngrm;
ngfd = wmsum_value(&arc_mfu_ghost->arcs_hits[ARC_BUFC_DATA]);
uint64_t gfd = ngfd - ogfd;
ogfd = ngfd;
ngfm = wmsum_value(&arc_mfu_ghost->arcs_hits[ARC_BUFC_METADATA]);
uint64_t gfm = ngfm - ogfm;
ogfm = ngfm;
/* Adjust ARC states balance based on ghost hits. */
arc_meta = arc_evict_adj(arc_meta, gsrd + gsrm + gsfd + gsfm,
grm + gfm, grd + gfd, zfs_arc_meta_balance);
arc_pd = arc_evict_adj(arc_pd, gsrd + gsfd, grd, gfd, 100);
arc_pm = arc_evict_adj(arc_pm, gsrm + gsfm, grm, gfm, 100);
asize = aggsum_value(&arc_sums.arcstat_size);
int64_t wt = t - (asize - arc_c);
/*
* Try to reduce pinned dnodes if more than 3/4 of wanted metadata
* target is not evictable or if they go over arc_dnode_limit.
*/
int64_t prune = 0;
int64_t dn = wmsum_value(&arc_sums.arcstat_dnode_size);
w = wt * (int64_t)(arc_meta >> 16) >> 16;
if (zfs_refcount_count(&arc_mru->arcs_size[ARC_BUFC_METADATA]) +
zfs_refcount_count(&arc_mfu->arcs_size[ARC_BUFC_METADATA]) -
zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_METADATA]) -
zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]) >
w * 3 / 4) {
prune = dn / sizeof (dnode_t) *
zfs_arc_dnode_reduce_percent / 100;
} else if (dn > arc_dnode_limit) {
prune = (dn - arc_dnode_limit) / sizeof (dnode_t) *
zfs_arc_dnode_reduce_percent / 100;
}
if (prune > 0)
arc_prune_async(prune);
/* Evict MRU metadata. */
w = wt * (int64_t)(arc_meta * arc_pm >> 48) >> 16;
e = MIN((int64_t)(asize - arc_c), (int64_t)(mrum - w));
bytes = arc_evict_impl(arc_mru, ARC_BUFC_METADATA, e);
total_evicted += bytes;
mrum -= bytes;
asize -= bytes;
/* Evict MFU metadata. */
w = wt * (int64_t)(arc_meta >> 16) >> 16;
e = MIN((int64_t)(asize - arc_c), (int64_t)(m - w));
bytes = arc_evict_impl(arc_mfu, ARC_BUFC_METADATA, e);
total_evicted += bytes;
mfum -= bytes;
asize -= bytes;
/* Evict MRU data. */
wt -= m - total_evicted;
w = wt * (int64_t)(arc_pd >> 16) >> 16;
e = MIN((int64_t)(asize - arc_c), (int64_t)(mrud - w));
bytes = arc_evict_impl(arc_mru, ARC_BUFC_DATA, e);
total_evicted += bytes;
mrud -= bytes;
asize -= bytes;
/* Evict MFU data. */
e = asize - arc_c;
bytes = arc_evict_impl(arc_mfu, ARC_BUFC_DATA, e);
mfud -= bytes;
total_evicted += bytes;
/*
* Evict ghost lists
*
* Size of each state's ghost list represents how much that state
* may grow by shrinking the other states. Would it need to shrink
* other states to zero (that is unlikely), its ghost size would be
* equal to sum of other three state sizes. But excessive ghost
* size may result in false ghost hits (too far back), that may
* never result in real cache hits if several states are competing.
* So choose some arbitraty point of 1/2 of other state sizes.
*/
gsrd = (mrum + mfud + mfum) / 2;
e = zfs_refcount_count(&arc_mru_ghost->arcs_size[ARC_BUFC_DATA]) -
gsrd;
(void) arc_evict_impl(arc_mru_ghost, ARC_BUFC_DATA, e);
gsrm = (mrud + mfud + mfum) / 2;
e = zfs_refcount_count(&arc_mru_ghost->arcs_size[ARC_BUFC_METADATA]) -
gsrm;
(void) arc_evict_impl(arc_mru_ghost, ARC_BUFC_METADATA, e);
gsfd = (mrud + mrum + mfum) / 2;
e = zfs_refcount_count(&arc_mfu_ghost->arcs_size[ARC_BUFC_DATA]) -
gsfd;
(void) arc_evict_impl(arc_mfu_ghost, ARC_BUFC_DATA, e);
gsfm = (mrud + mrum + mfud) / 2;
e = zfs_refcount_count(&arc_mfu_ghost->arcs_size[ARC_BUFC_METADATA]) -
gsfm;
(void) arc_evict_impl(arc_mfu_ghost, ARC_BUFC_METADATA, e);
return (total_evicted);
}
void
arc_flush(spa_t *spa, boolean_t retry)
{
uint64_t guid = 0;
/*
* If retry is B_TRUE, a spa must not be specified since we have
* no good way to determine if all of a spa's buffers have been
* evicted from an arc state.
*/
ASSERT(!retry || spa == NULL);
if (spa != NULL)
guid = spa_load_guid(spa);
(void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
(void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
(void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
(void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
(void) arc_flush_state(arc_uncached, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_uncached, guid, ARC_BUFC_METADATA, retry);
}
void
arc_reduce_target_size(int64_t to_free)
{
uint64_t c = arc_c;
if (c <= arc_c_min)
return;
/*
* All callers want the ARC to actually evict (at least) this much
* memory. Therefore we reduce from the lower of the current size and
* the target size. This way, even if arc_c is much higher than
* arc_size (as can be the case after many calls to arc_freed(), we will
* immediately have arc_c < arc_size and therefore the arc_evict_zthr
* will evict.
*/
uint64_t asize = aggsum_value(&arc_sums.arcstat_size);
if (asize < c)
to_free += c - asize;
arc_c = MAX((int64_t)c - to_free, (int64_t)arc_c_min);
/* See comment in arc_evict_cb_check() on why lock+flag */
mutex_enter(&arc_evict_lock);
arc_evict_needed = B_TRUE;
mutex_exit(&arc_evict_lock);
zthr_wakeup(arc_evict_zthr);
}
/*
* Determine if the system is under memory pressure and is asking
* to reclaim memory. A return value of B_TRUE indicates that the system
* is under memory pressure and that the arc should adjust accordingly.
*/
boolean_t
arc_reclaim_needed(void)
{
return (arc_available_memory() < 0);
}
void
arc_kmem_reap_soon(void)
{
size_t i;
kmem_cache_t *prev_cache = NULL;
kmem_cache_t *prev_data_cache = NULL;
#ifdef _KERNEL
#if defined(_ILP32)
/*
* Reclaim unused memory from all kmem caches.
*/
kmem_reap();
#endif
#endif
for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
#if defined(_ILP32)
/* reach upper limit of cache size on 32-bit */
if (zio_buf_cache[i] == NULL)
break;
#endif
if (zio_buf_cache[i] != prev_cache) {
prev_cache = zio_buf_cache[i];
kmem_cache_reap_now(zio_buf_cache[i]);
}
if (zio_data_buf_cache[i] != prev_data_cache) {
prev_data_cache = zio_data_buf_cache[i];
kmem_cache_reap_now(zio_data_buf_cache[i]);
}
}
kmem_cache_reap_now(buf_cache);
kmem_cache_reap_now(hdr_full_cache);
kmem_cache_reap_now(hdr_l2only_cache);
kmem_cache_reap_now(zfs_btree_leaf_cache);
abd_cache_reap_now();
}
static boolean_t
arc_evict_cb_check(void *arg, zthr_t *zthr)
{
(void) arg, (void) zthr;
#ifdef ZFS_DEBUG
/*
* This is necessary in order to keep the kstat information
* up to date for tools that display kstat data such as the
* mdb ::arc dcmd and the Linux crash utility. These tools
* typically do not call kstat's update function, but simply
* dump out stats from the most recent update. Without
* this call, these commands may show stale stats for the
* anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
* with this call, the data might be out of date if the
* evict thread hasn't been woken recently; but that should
* suffice. The arc_state_t structures can be queried
* directly if more accurate information is needed.
*/
if (arc_ksp != NULL)
arc_ksp->ks_update(arc_ksp, KSTAT_READ);
#endif
/*
* We have to rely on arc_wait_for_eviction() to tell us when to
* evict, rather than checking if we are overflowing here, so that we
* are sure to not leave arc_wait_for_eviction() waiting on aew_cv.
* If we have become "not overflowing" since arc_wait_for_eviction()
* checked, we need to wake it up. We could broadcast the CV here,
* but arc_wait_for_eviction() may have not yet gone to sleep. We
* would need to use a mutex to ensure that this function doesn't
* broadcast until arc_wait_for_eviction() has gone to sleep (e.g.
* the arc_evict_lock). However, the lock ordering of such a lock
* would necessarily be incorrect with respect to the zthr_lock,
* which is held before this function is called, and is held by
* arc_wait_for_eviction() when it calls zthr_wakeup().
*/
if (arc_evict_needed)
return (B_TRUE);
/*
* If we have buffers in uncached state, evict them periodically.
*/
return ((zfs_refcount_count(&arc_uncached->arcs_esize[ARC_BUFC_DATA]) +
zfs_refcount_count(&arc_uncached->arcs_esize[ARC_BUFC_METADATA]) &&
ddi_get_lbolt() - arc_last_uncached_flush >
MSEC_TO_TICK(arc_min_prefetch_ms / 2)));
}
/*
* Keep arc_size under arc_c by running arc_evict which evicts data
* from the ARC.
*/
static void
arc_evict_cb(void *arg, zthr_t *zthr)
{
(void) arg, (void) zthr;
uint64_t evicted = 0;
fstrans_cookie_t cookie = spl_fstrans_mark();
/* Always try to evict from uncached state. */
arc_last_uncached_flush = ddi_get_lbolt();
evicted += arc_flush_state(arc_uncached, 0, ARC_BUFC_DATA, B_FALSE);
evicted += arc_flush_state(arc_uncached, 0, ARC_BUFC_METADATA, B_FALSE);
/* Evict from other states only if told to. */
if (arc_evict_needed)
evicted += arc_evict();
/*
* If evicted is zero, we couldn't evict anything
* via arc_evict(). This could be due to hash lock
* collisions, but more likely due to the majority of
* arc buffers being unevictable. Therefore, even if
* arc_size is above arc_c, another pass is unlikely to
* be helpful and could potentially cause us to enter an
* infinite loop. Additionally, zthr_iscancelled() is
* checked here so that if the arc is shutting down, the
* broadcast will wake any remaining arc evict waiters.
*/
mutex_enter(&arc_evict_lock);
arc_evict_needed = !zthr_iscancelled(arc_evict_zthr) &&
evicted > 0 && aggsum_compare(&arc_sums.arcstat_size, arc_c) > 0;
if (!arc_evict_needed) {
/*
* We're either no longer overflowing, or we
* can't evict anything more, so we should wake
* arc_get_data_impl() sooner.
*/
arc_evict_waiter_t *aw;
while ((aw = list_remove_head(&arc_evict_waiters)) != NULL) {
cv_broadcast(&aw->aew_cv);
}
arc_set_need_free();
}
mutex_exit(&arc_evict_lock);
spl_fstrans_unmark(cookie);
}
static boolean_t
arc_reap_cb_check(void *arg, zthr_t *zthr)
{
(void) arg, (void) zthr;
int64_t free_memory = arc_available_memory();
static int reap_cb_check_counter = 0;
/*
* If a kmem reap is already active, don't schedule more. We must
* check for this because kmem_cache_reap_soon() won't actually
* block on the cache being reaped (this is to prevent callers from
* becoming implicitly blocked by a system-wide kmem reap -- which,
* on a system with many, many full magazines, can take minutes).
*/
if (!kmem_cache_reap_active() && free_memory < 0) {
arc_no_grow = B_TRUE;
arc_warm = B_TRUE;
/*
* Wait at least zfs_grow_retry (default 5) seconds
* before considering growing.
*/
arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
return (B_TRUE);
} else if (free_memory < arc_c >> arc_no_grow_shift) {
arc_no_grow = B_TRUE;
} else if (gethrtime() >= arc_growtime) {
arc_no_grow = B_FALSE;
}
/*
* Called unconditionally every 60 seconds to reclaim unused
* zstd compression and decompression context. This is done
* here to avoid the need for an independent thread.
*/
if (!((reap_cb_check_counter++) % 60))
zfs_zstd_cache_reap_now();
return (B_FALSE);
}
/*
* Keep enough free memory in the system by reaping the ARC's kmem
* caches. To cause more slabs to be reapable, we may reduce the
* target size of the cache (arc_c), causing the arc_evict_cb()
* to free more buffers.
*/
static void
arc_reap_cb(void *arg, zthr_t *zthr)
{
(void) arg, (void) zthr;
int64_t free_memory;
fstrans_cookie_t cookie = spl_fstrans_mark();
/*
* Kick off asynchronous kmem_reap()'s of all our caches.
*/
arc_kmem_reap_soon();
/*
* Wait at least arc_kmem_cache_reap_retry_ms between
* arc_kmem_reap_soon() calls. Without this check it is possible to
* end up in a situation where we spend lots of time reaping
* caches, while we're near arc_c_min. Waiting here also gives the
* subsequent free memory check a chance of finding that the
* asynchronous reap has already freed enough memory, and we don't
* need to call arc_reduce_target_size().
*/
delay((hz * arc_kmem_cache_reap_retry_ms + 999) / 1000);
/*
* Reduce the target size as needed to maintain the amount of free
* memory in the system at a fraction of the arc_size (1/128th by
* default). If oversubscribed (free_memory < 0) then reduce the
* target arc_size by the deficit amount plus the fractional
* amount. If free memory is positive but less than the fractional
* amount, reduce by what is needed to hit the fractional amount.
*/
free_memory = arc_available_memory();
int64_t can_free = arc_c - arc_c_min;
if (can_free > 0) {
int64_t to_free = (can_free >> arc_shrink_shift) - free_memory;
if (to_free > 0)
arc_reduce_target_size(to_free);
}
spl_fstrans_unmark(cookie);
}
#ifdef _KERNEL
/*
* Determine the amount of memory eligible for eviction contained in the
* ARC. All clean data reported by the ghost lists can always be safely
* evicted. Due to arc_c_min, the same does not hold for all clean data
* contained by the regular mru and mfu lists.
*
* In the case of the regular mru and mfu lists, we need to report as
* much clean data as possible, such that evicting that same reported
* data will not bring arc_size below arc_c_min. Thus, in certain
* circumstances, the total amount of clean data in the mru and mfu
* lists might not actually be evictable.
*
* The following two distinct cases are accounted for:
*
* 1. The sum of the amount of dirty data contained by both the mru and
* mfu lists, plus the ARC's other accounting (e.g. the anon list),
* is greater than or equal to arc_c_min.
* (i.e. amount of dirty data >= arc_c_min)
*
* This is the easy case; all clean data contained by the mru and mfu
* lists is evictable. Evicting all clean data can only drop arc_size
* to the amount of dirty data, which is greater than arc_c_min.
*
* 2. The sum of the amount of dirty data contained by both the mru and
* mfu lists, plus the ARC's other accounting (e.g. the anon list),
* is less than arc_c_min.
* (i.e. arc_c_min > amount of dirty data)
*
* 2.1. arc_size is greater than or equal arc_c_min.
* (i.e. arc_size >= arc_c_min > amount of dirty data)
*
* In this case, not all clean data from the regular mru and mfu
* lists is actually evictable; we must leave enough clean data
* to keep arc_size above arc_c_min. Thus, the maximum amount of
* evictable data from the two lists combined, is exactly the
* difference between arc_size and arc_c_min.
*
* 2.2. arc_size is less than arc_c_min
* (i.e. arc_c_min > arc_size > amount of dirty data)
*
* In this case, none of the data contained in the mru and mfu
* lists is evictable, even if it's clean. Since arc_size is
* already below arc_c_min, evicting any more would only
* increase this negative difference.
*/
#endif /* _KERNEL */
/*
* Adapt arc info given the number of bytes we are trying to add and
* the state that we are coming from. This function is only called
* when we are adding new content to the cache.
*/
static void
arc_adapt(uint64_t bytes)
{
/*
* Wake reap thread if we do not have any available memory
*/
if (arc_reclaim_needed()) {
zthr_wakeup(arc_reap_zthr);
return;
}
if (arc_no_grow)
return;
if (arc_c >= arc_c_max)
return;
/*
* If we're within (2 * maxblocksize) bytes of the target
* cache size, increment the target cache size
*/
if (aggsum_upper_bound(&arc_sums.arcstat_size) +
2 * SPA_MAXBLOCKSIZE >= arc_c) {
uint64_t dc = MAX(bytes, SPA_OLD_MAXBLOCKSIZE);
if (atomic_add_64_nv(&arc_c, dc) > arc_c_max)
arc_c = arc_c_max;
}
}
/*
* Check if arc_size has grown past our upper threshold, determined by
* zfs_arc_overflow_shift.
*/
static arc_ovf_level_t
arc_is_overflowing(boolean_t use_reserve)
{
/* Always allow at least one block of overflow */
int64_t overflow = MAX(SPA_MAXBLOCKSIZE,
arc_c >> zfs_arc_overflow_shift);
/*
* We just compare the lower bound here for performance reasons. Our
* primary goals are to make sure that the arc never grows without
* bound, and that it can reach its maximum size. This check
* accomplishes both goals. The maximum amount we could run over by is
* 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block
* in the ARC. In practice, that's in the tens of MB, which is low
* enough to be safe.
*/
int64_t over = aggsum_lower_bound(&arc_sums.arcstat_size) -
arc_c - overflow / 2;
if (!use_reserve)
overflow /= 2;
return (over < 0 ? ARC_OVF_NONE :
over < overflow ? ARC_OVF_SOME : ARC_OVF_SEVERE);
}
static abd_t *
arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, const void *tag,
int alloc_flags)
{
arc_buf_contents_t type = arc_buf_type(hdr);
arc_get_data_impl(hdr, size, tag, alloc_flags);
if (alloc_flags & ARC_HDR_ALLOC_LINEAR)
return (abd_alloc_linear(size, type == ARC_BUFC_METADATA));
else
return (abd_alloc(size, type == ARC_BUFC_METADATA));
}
static void *
arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, const void *tag)
{
arc_buf_contents_t type = arc_buf_type(hdr);
arc_get_data_impl(hdr, size, tag, 0);
if (type == ARC_BUFC_METADATA) {
return (zio_buf_alloc(size));
} else {
ASSERT(type == ARC_BUFC_DATA);
return (zio_data_buf_alloc(size));
}
}
/*
* Wait for the specified amount of data (in bytes) to be evicted from the
* ARC, and for there to be sufficient free memory in the system. Waiting for
* eviction ensures that the memory used by the ARC decreases. Waiting for
* free memory ensures that the system won't run out of free pages, regardless
* of ARC behavior and settings. See arc_lowmem_init().
*/
void
arc_wait_for_eviction(uint64_t amount, boolean_t use_reserve)
{
switch (arc_is_overflowing(use_reserve)) {
case ARC_OVF_NONE:
return;
case ARC_OVF_SOME:
/*
* This is a bit racy without taking arc_evict_lock, but the
* worst that can happen is we either call zthr_wakeup() extra
* time due to race with other thread here, or the set flag
* get cleared by arc_evict_cb(), which is unlikely due to
* big hysteresis, but also not important since at this level
* of overflow the eviction is purely advisory. Same time
* taking the global lock here every time without waiting for
* the actual eviction creates a significant lock contention.
*/
if (!arc_evict_needed) {
arc_evict_needed = B_TRUE;
zthr_wakeup(arc_evict_zthr);
}
return;
case ARC_OVF_SEVERE:
default:
{
arc_evict_waiter_t aw;
list_link_init(&aw.aew_node);
cv_init(&aw.aew_cv, NULL, CV_DEFAULT, NULL);
uint64_t last_count = 0;
mutex_enter(&arc_evict_lock);
if (!list_is_empty(&arc_evict_waiters)) {
arc_evict_waiter_t *last =
list_tail(&arc_evict_waiters);
last_count = last->aew_count;
} else if (!arc_evict_needed) {
arc_evict_needed = B_TRUE;
zthr_wakeup(arc_evict_zthr);
}
/*
* Note, the last waiter's count may be less than
* arc_evict_count if we are low on memory in which
* case arc_evict_state_impl() may have deferred
* wakeups (but still incremented arc_evict_count).
*/
aw.aew_count = MAX(last_count, arc_evict_count) + amount;
list_insert_tail(&arc_evict_waiters, &aw);
arc_set_need_free();
DTRACE_PROBE3(arc__wait__for__eviction,
uint64_t, amount,
uint64_t, arc_evict_count,
uint64_t, aw.aew_count);
/*
* We will be woken up either when arc_evict_count reaches
* aew_count, or when the ARC is no longer overflowing and
* eviction completes.
* In case of "false" wakeup, we will still be on the list.
*/
do {
cv_wait(&aw.aew_cv, &arc_evict_lock);
} while (list_link_active(&aw.aew_node));
mutex_exit(&arc_evict_lock);
cv_destroy(&aw.aew_cv);
}
}
}
/*
* Allocate a block and return it to the caller. If we are hitting the
* hard limit for the cache size, we must sleep, waiting for the eviction
* thread to catch up. If we're past the target size but below the hard
* limit, we'll only signal the reclaim thread and continue on.
*/
static void
arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, const void *tag,
int alloc_flags)
{
arc_adapt(size);
/*
* If arc_size is currently overflowing, we must be adding data
* faster than we are evicting. To ensure we don't compound the
* problem by adding more data and forcing arc_size to grow even
* further past it's target size, we wait for the eviction thread to
* make some progress. We also wait for there to be sufficient free
* memory in the system, as measured by arc_free_memory().
*
* Specifically, we wait for zfs_arc_eviction_pct percent of the
* requested size to be evicted. This should be more than 100%, to
* ensure that that progress is also made towards getting arc_size
* under arc_c. See the comment above zfs_arc_eviction_pct.
*/
arc_wait_for_eviction(size * zfs_arc_eviction_pct / 100,
alloc_flags & ARC_HDR_USE_RESERVE);
arc_buf_contents_t type = arc_buf_type(hdr);
if (type == ARC_BUFC_METADATA) {
arc_space_consume(size, ARC_SPACE_META);
} else {
arc_space_consume(size, ARC_SPACE_DATA);
}
/*
* Update the state size. Note that ghost states have a
* "ghost size" and so don't need to be updated.
*/
arc_state_t *state = hdr->b_l1hdr.b_state;
if (!GHOST_STATE(state)) {
(void) zfs_refcount_add_many(&state->arcs_size[type], size,
tag);
/*
* If this is reached via arc_read, the link is
* protected by the hash lock. If reached via
* arc_buf_alloc, the header should not be accessed by
* any other thread. And, if reached via arc_read_done,
* the hash lock will protect it if it's found in the
* hash table; otherwise no other thread should be
* trying to [add|remove]_reference it.
*/
if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
(void) zfs_refcount_add_many(&state->arcs_esize[type],
size, tag);
}
}
}
static void
arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size,
const void *tag)
{
arc_free_data_impl(hdr, size, tag);
abd_free(abd);
}
static void
arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, const void *tag)
{
arc_buf_contents_t type = arc_buf_type(hdr);
arc_free_data_impl(hdr, size, tag);
if (type == ARC_BUFC_METADATA) {
zio_buf_free(buf, size);
} else {
ASSERT(type == ARC_BUFC_DATA);
zio_data_buf_free(buf, size);
}
}
/*
* Free the arc data buffer.
*/
static void
arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, const void *tag)
{
arc_state_t *state = hdr->b_l1hdr.b_state;
arc_buf_contents_t type = arc_buf_type(hdr);
/* protected by hash lock, if in the hash table */
if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT(state != arc_anon && state != arc_l2c_only);
(void) zfs_refcount_remove_many(&state->arcs_esize[type],
size, tag);
}
(void) zfs_refcount_remove_many(&state->arcs_size[type], size, tag);
VERIFY3U(hdr->b_type, ==, type);
if (type == ARC_BUFC_METADATA) {
arc_space_return(size, ARC_SPACE_META);
} else {
ASSERT(type == ARC_BUFC_DATA);
arc_space_return(size, ARC_SPACE_DATA);
}
}
/*
* This routine is called whenever a buffer is accessed.
*/
static void
arc_access(arc_buf_hdr_t *hdr, arc_flags_t arc_flags, boolean_t hit)
{
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
ASSERT(HDR_HAS_L1HDR(hdr));
/*
* Update buffer prefetch status.
*/
boolean_t was_prefetch = HDR_PREFETCH(hdr);
boolean_t now_prefetch = arc_flags & ARC_FLAG_PREFETCH;
if (was_prefetch != now_prefetch) {
if (was_prefetch) {
ARCSTAT_CONDSTAT(hit, demand_hit, demand_iohit,
HDR_PRESCIENT_PREFETCH(hdr), prescient, predictive,
prefetch);
}
if (HDR_HAS_L2HDR(hdr))
l2arc_hdr_arcstats_decrement_state(hdr);
if (was_prefetch) {
arc_hdr_clear_flags(hdr,
ARC_FLAG_PREFETCH | ARC_FLAG_PRESCIENT_PREFETCH);
} else {
arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
}
if (HDR_HAS_L2HDR(hdr))
l2arc_hdr_arcstats_increment_state(hdr);
}
if (now_prefetch) {
if (arc_flags & ARC_FLAG_PRESCIENT_PREFETCH) {
arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
ARCSTAT_BUMP(arcstat_prescient_prefetch);
} else {
ARCSTAT_BUMP(arcstat_predictive_prefetch);
}
}
if (arc_flags & ARC_FLAG_L2CACHE)
arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
clock_t now = ddi_get_lbolt();
if (hdr->b_l1hdr.b_state == arc_anon) {
arc_state_t *new_state;
/*
* This buffer is not in the cache, and does not appear in
* our "ghost" lists. Add it to the MRU or uncached state.
*/
ASSERT0(hdr->b_l1hdr.b_arc_access);
hdr->b_l1hdr.b_arc_access = now;
if (HDR_UNCACHED(hdr)) {
new_state = arc_uncached;
DTRACE_PROBE1(new_state__uncached, arc_buf_hdr_t *,
hdr);
} else {
new_state = arc_mru;
DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
}
arc_change_state(new_state, hdr);
} else if (hdr->b_l1hdr.b_state == arc_mru) {
/*
* This buffer has been accessed once recently and either
* its read is still in progress or it is in the cache.
*/
if (HDR_IO_IN_PROGRESS(hdr)) {
hdr->b_l1hdr.b_arc_access = now;
return;
}
hdr->b_l1hdr.b_mru_hits++;
ARCSTAT_BUMP(arcstat_mru_hits);
/*
* If the previous access was a prefetch, then it already
* handled possible promotion, so nothing more to do for now.
*/
if (was_prefetch) {
hdr->b_l1hdr.b_arc_access = now;
return;
}
/*
* If more than ARC_MINTIME have passed from the previous
* hit, promote the buffer to the MFU state.
*/
if (ddi_time_after(now, hdr->b_l1hdr.b_arc_access +
ARC_MINTIME)) {
hdr->b_l1hdr.b_arc_access = now;
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
arc_change_state(arc_mfu, hdr);
}
} else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
arc_state_t *new_state;
/*
* This buffer has been accessed once recently, but was
* evicted from the cache. Would we have bigger MRU, it
* would be an MRU hit, so handle it the same way, except
* we don't need to check the previous access time.
*/
hdr->b_l1hdr.b_mru_ghost_hits++;
ARCSTAT_BUMP(arcstat_mru_ghost_hits);
hdr->b_l1hdr.b_arc_access = now;
wmsum_add(&arc_mru_ghost->arcs_hits[arc_buf_type(hdr)],
arc_hdr_size(hdr));
if (was_prefetch) {
new_state = arc_mru;
DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
} else {
new_state = arc_mfu;
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
}
arc_change_state(new_state, hdr);
} else if (hdr->b_l1hdr.b_state == arc_mfu) {
/*
* This buffer has been accessed more than once and either
* still in the cache or being restored from one of ghosts.
*/
if (!HDR_IO_IN_PROGRESS(hdr)) {
hdr->b_l1hdr.b_mfu_hits++;
ARCSTAT_BUMP(arcstat_mfu_hits);
}
hdr->b_l1hdr.b_arc_access = now;
} else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
/*
* This buffer has been accessed more than once recently, but
* has been evicted from the cache. Would we have bigger MFU
* it would stay in cache, so move it back to MFU state.
*/
hdr->b_l1hdr.b_mfu_ghost_hits++;
ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
hdr->b_l1hdr.b_arc_access = now;
wmsum_add(&arc_mfu_ghost->arcs_hits[arc_buf_type(hdr)],
arc_hdr_size(hdr));
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
arc_change_state(arc_mfu, hdr);
} else if (hdr->b_l1hdr.b_state == arc_uncached) {
/*
* This buffer is uncacheable, but we got a hit. Probably
* a demand read after prefetch. Nothing more to do here.
*/
if (!HDR_IO_IN_PROGRESS(hdr))
ARCSTAT_BUMP(arcstat_uncached_hits);
hdr->b_l1hdr.b_arc_access = now;
} else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
/*
* This buffer is on the 2nd Level ARC and was not accessed
* for a long time, so treat it as new and put into MRU.
*/
hdr->b_l1hdr.b_arc_access = now;
DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
arc_change_state(arc_mru, hdr);
} else {
cmn_err(CE_PANIC, "invalid arc state 0x%p",
hdr->b_l1hdr.b_state);
}
}
/*
* This routine is called by dbuf_hold() to update the arc_access() state
* which otherwise would be skipped for entries in the dbuf cache.
*/
void
arc_buf_access(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
/*
* Avoid taking the hash_lock when possible as an optimization.
* The header must be checked again under the hash_lock in order
* to handle the case where it is concurrently being released.
*/
if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr))
return;
kmutex_t *hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_access_skip);
return;
}
ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
hdr->b_l1hdr.b_state == arc_mfu ||
hdr->b_l1hdr.b_state == arc_uncached);
DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
arc_access(hdr, 0, B_TRUE);
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_hits);
ARCSTAT_CONDSTAT(B_TRUE /* demand */, demand, prefetch,
!HDR_ISTYPE_METADATA(hdr), data, metadata, hits);
}
/* a generic arc_read_done_func_t which you can use */
void
arc_bcopy_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
arc_buf_t *buf, void *arg)
{
(void) zio, (void) zb, (void) bp;
if (buf == NULL)
return;
memcpy(arg, buf->b_data, arc_buf_size(buf));
arc_buf_destroy(buf, arg);
}
/* a generic arc_read_done_func_t */
void
arc_getbuf_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
arc_buf_t *buf, void *arg)
{
(void) zb, (void) bp;
arc_buf_t **bufp = arg;
if (buf == NULL) {
ASSERT(zio == NULL || zio->io_error != 0);
*bufp = NULL;
} else {
ASSERT(zio == NULL || zio->io_error == 0);
*bufp = buf;
ASSERT(buf->b_data != NULL);
}
}
static void
arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp)
{
if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
ASSERT3U(arc_hdr_get_compress(hdr), ==, ZIO_COMPRESS_OFF);
} else {
if (HDR_COMPRESSION_ENABLED(hdr)) {
ASSERT3U(arc_hdr_get_compress(hdr), ==,
BP_GET_COMPRESS(bp));
}
ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
ASSERT3U(!!HDR_PROTECTED(hdr), ==, BP_IS_PROTECTED(bp));
}
}
static void
arc_read_done(zio_t *zio)
{
blkptr_t *bp = zio->io_bp;
arc_buf_hdr_t *hdr = zio->io_private;
kmutex_t *hash_lock = NULL;
arc_callback_t *callback_list;
arc_callback_t *acb;
/*
* The hdr was inserted into hash-table and removed from lists
* prior to starting I/O. We should find this header, since
* it's in the hash table, and it should be legit since it's
* not possible to evict it during the I/O. The only possible
* reason for it not to be found is if we were freed during the
* read.
*/
if (HDR_IN_HASH_TABLE(hdr)) {
arc_buf_hdr_t *found;
ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
ASSERT3U(hdr->b_dva.dva_word[0], ==,
BP_IDENTITY(zio->io_bp)->dva_word[0]);
ASSERT3U(hdr->b_dva.dva_word[1], ==,
BP_IDENTITY(zio->io_bp)->dva_word[1]);
found = buf_hash_find(hdr->b_spa, zio->io_bp, &hash_lock);
ASSERT((found == hdr &&
DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
(found == hdr && HDR_L2_READING(hdr)));
ASSERT3P(hash_lock, !=, NULL);
}
if (BP_IS_PROTECTED(bp)) {
hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp);
hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset;
zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt,
hdr->b_crypt_hdr.b_iv);
if (zio->io_error == 0) {
if (BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG) {
void *tmpbuf;
tmpbuf = abd_borrow_buf_copy(zio->io_abd,
sizeof (zil_chain_t));
zio_crypt_decode_mac_zil(tmpbuf,
hdr->b_crypt_hdr.b_mac);
abd_return_buf(zio->io_abd, tmpbuf,
sizeof (zil_chain_t));
} else {
zio_crypt_decode_mac_bp(bp,
hdr->b_crypt_hdr.b_mac);
}
}
}
if (zio->io_error == 0) {
/* byteswap if necessary */
if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
if (BP_GET_LEVEL(zio->io_bp) > 0) {
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
} else {
hdr->b_l1hdr.b_byteswap =
DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
}
} else {
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
}
if (!HDR_L2_READING(hdr)) {
hdr->b_complevel = zio->io_prop.zp_complevel;
}
}
arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
if (l2arc_noprefetch && HDR_PREFETCH(hdr))
arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE);
callback_list = hdr->b_l1hdr.b_acb;
ASSERT3P(callback_list, !=, NULL);
hdr->b_l1hdr.b_acb = NULL;
/*
* If a read request has a callback (i.e. acb_done is not NULL), then we
* make a buf containing the data according to the parameters which were
* passed in. The implementation of arc_buf_alloc_impl() ensures that we
* aren't needlessly decompressing the data multiple times.
*/
int callback_cnt = 0;
for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
/* We need the last one to call below in original order. */
callback_list = acb;
if (!acb->acb_done || acb->acb_nobuf)
continue;
callback_cnt++;
if (zio->io_error != 0)
continue;
int error = arc_buf_alloc_impl(hdr, zio->io_spa,
&acb->acb_zb, acb->acb_private, acb->acb_encrypted,
acb->acb_compressed, acb->acb_noauth, B_TRUE,
&acb->acb_buf);
/*
* Assert non-speculative zios didn't fail because an
* encryption key wasn't loaded
*/
ASSERT((zio->io_flags & ZIO_FLAG_SPECULATIVE) ||
error != EACCES);
/*
* If we failed to decrypt, report an error now (as the zio
* layer would have done if it had done the transforms).
*/
if (error == ECKSUM) {
ASSERT(BP_IS_PROTECTED(bp));
error = SET_ERROR(EIO);
if ((zio->io_flags & ZIO_FLAG_SPECULATIVE) == 0) {
spa_log_error(zio->io_spa, &acb->acb_zb,
&zio->io_bp->blk_birth);
(void) zfs_ereport_post(
FM_EREPORT_ZFS_AUTHENTICATION,
zio->io_spa, NULL, &acb->acb_zb, zio, 0);
}
}
if (error != 0) {
/*
* Decompression or decryption failed. Set
* io_error so that when we call acb_done
* (below), we will indicate that the read
* failed. Note that in the unusual case
* where one callback is compressed and another
* uncompressed, we will mark all of them
* as failed, even though the uncompressed
* one can't actually fail. In this case,
* the hdr will not be anonymous, because
* if there are multiple callbacks, it's
* because multiple threads found the same
* arc buf in the hash table.
*/
zio->io_error = error;
}
}
/*
* If there are multiple callbacks, we must have the hash lock,
* because the only way for multiple threads to find this hdr is
* in the hash table. This ensures that if there are multiple
* callbacks, the hdr is not anonymous. If it were anonymous,
* we couldn't use arc_buf_destroy() in the error case below.
*/
ASSERT(callback_cnt < 2 || hash_lock != NULL);
if (zio->io_error == 0) {
arc_hdr_verify(hdr, zio->io_bp);
} else {
arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
if (hdr->b_l1hdr.b_state != arc_anon)
arc_change_state(arc_anon, hdr);
if (HDR_IN_HASH_TABLE(hdr))
buf_hash_remove(hdr);
}
arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
(void) remove_reference(hdr, hdr);
if (hash_lock != NULL)
mutex_exit(hash_lock);
/* execute each callback and free its structure */
while ((acb = callback_list) != NULL) {
if (acb->acb_done != NULL) {
if (zio->io_error != 0 && acb->acb_buf != NULL) {
/*
* If arc_buf_alloc_impl() fails during
* decompression, the buf will still be
* allocated, and needs to be freed here.
*/
arc_buf_destroy(acb->acb_buf,
acb->acb_private);
acb->acb_buf = NULL;
}
acb->acb_done(zio, &zio->io_bookmark, zio->io_bp,
acb->acb_buf, acb->acb_private);
}
if (acb->acb_zio_dummy != NULL) {
acb->acb_zio_dummy->io_error = zio->io_error;
zio_nowait(acb->acb_zio_dummy);
}
callback_list = acb->acb_prev;
if (acb->acb_wait) {
mutex_enter(&acb->acb_wait_lock);
acb->acb_wait_error = zio->io_error;
acb->acb_wait = B_FALSE;
cv_signal(&acb->acb_wait_cv);
mutex_exit(&acb->acb_wait_lock);
/* acb will be freed by the waiting thread. */
} else {
kmem_free(acb, sizeof (arc_callback_t));
}
}
}
/*
* "Read" the block at the specified DVA (in bp) via the
* cache. If the block is found in the cache, invoke the provided
* callback immediately and return. Note that the `zio' parameter
* in the callback will be NULL in this case, since no IO was
* required. If the block is not in the cache pass the read request
* on to the spa with a substitute callback function, so that the
* requested block will be added to the cache.
*
* If a read request arrives for a block that has a read in-progress,
* either wait for the in-progress read to complete (and return the
* results); or, if this is a read with a "done" func, add a record
* to the read to invoke the "done" func when the read completes,
* and return; or just return.
*
* arc_read_done() will invoke all the requested "done" functions
* for readers of this block.
*/
int
arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
arc_read_done_func_t *done, void *private, zio_priority_t priority,
int zio_flags, arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
{
arc_buf_hdr_t *hdr = NULL;
kmutex_t *hash_lock = NULL;
zio_t *rzio;
uint64_t guid = spa_load_guid(spa);
boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW_COMPRESS) != 0;
boolean_t encrypted_read = BP_IS_ENCRYPTED(bp) &&
(zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0;
boolean_t noauth_read = BP_IS_AUTHENTICATED(bp) &&
(zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0;
boolean_t embedded_bp = !!BP_IS_EMBEDDED(bp);
boolean_t no_buf = *arc_flags & ARC_FLAG_NO_BUF;
arc_buf_t *buf = NULL;
int rc = 0;
ASSERT(!embedded_bp ||
BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
ASSERT(!BP_IS_HOLE(bp));
ASSERT(!BP_IS_REDACTED(bp));
/*
* Normally SPL_FSTRANS will already be set since kernel threads which
* expect to call the DMU interfaces will set it when created. System
* calls are similarly handled by setting/cleaning the bit in the
* registered callback (module/os/.../zfs/zpl_*).
*
* External consumers such as Lustre which call the exported DMU
* interfaces may not have set SPL_FSTRANS. To avoid a deadlock
* on the hash_lock always set and clear the bit.
*/
fstrans_cookie_t cookie = spl_fstrans_mark();
top:
/*
* Verify the block pointer contents are reasonable. This should
* always be the case since the blkptr is protected by a checksum.
* However, if there is damage it's desirable to detect this early
* and treat it as a checksum error. This allows an alternate blkptr
* to be tried when one is available (e.g. ditto blocks).
*/
if (!zfs_blkptr_verify(spa, bp, (zio_flags & ZIO_FLAG_CONFIG_WRITER) ?
BLK_CONFIG_HELD : BLK_CONFIG_NEEDED, BLK_VERIFY_LOG)) {
rc = SET_ERROR(ECKSUM);
goto done;
}
if (!embedded_bp) {
/*
* Embedded BP's have no DVA and require no I/O to "read".
* Create an anonymous arc buf to back it.
*/
hdr = buf_hash_find(guid, bp, &hash_lock);
}
/*
* Determine if we have an L1 cache hit or a cache miss. For simplicity
* we maintain encrypted data separately from compressed / uncompressed
* data. If the user is requesting raw encrypted data and we don't have
* that in the header we will read from disk to guarantee that we can
* get it even if the encryption keys aren't loaded.
*/
if (hdr != NULL && HDR_HAS_L1HDR(hdr) && (HDR_HAS_RABD(hdr) ||
(hdr->b_l1hdr.b_pabd != NULL && !encrypted_read))) {
boolean_t is_data = !HDR_ISTYPE_METADATA(hdr);
if (HDR_IO_IN_PROGRESS(hdr)) {
if (*arc_flags & ARC_FLAG_CACHED_ONLY) {
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_cached_only_in_progress);
rc = SET_ERROR(ENOENT);
goto done;
}
zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head;
ASSERT3P(head_zio, !=, NULL);
if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
priority == ZIO_PRIORITY_SYNC_READ) {
/*
* This is a sync read that needs to wait for
* an in-flight async read. Request that the
* zio have its priority upgraded.
*/
zio_change_priority(head_zio, priority);
DTRACE_PROBE1(arc__async__upgrade__sync,
arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_async_upgrade_sync);
}
DTRACE_PROBE1(arc__iohit, arc_buf_hdr_t *, hdr);
arc_access(hdr, *arc_flags, B_FALSE);
/*
* If there are multiple threads reading the same block
* and that block is not yet in the ARC, then only one
* thread will do the physical I/O and all other
* threads will wait until that I/O completes.
* Synchronous reads use the acb_wait_cv whereas nowait
* reads register a callback. Both are signalled/called
* in arc_read_done.
*
* Errors of the physical I/O may need to be propagated.
* Synchronous read errors are returned here from
* arc_read_done via acb_wait_error. Nowait reads
* attach the acb_zio_dummy zio to pio and
* arc_read_done propagates the physical I/O's io_error
* to acb_zio_dummy, and thereby to pio.
*/
arc_callback_t *acb = NULL;
if (done || pio || *arc_flags & ARC_FLAG_WAIT) {
acb = kmem_zalloc(sizeof (arc_callback_t),
KM_SLEEP);
acb->acb_done = done;
acb->acb_private = private;
acb->acb_compressed = compressed_read;
acb->acb_encrypted = encrypted_read;
acb->acb_noauth = noauth_read;
acb->acb_nobuf = no_buf;
if (*arc_flags & ARC_FLAG_WAIT) {
acb->acb_wait = B_TRUE;
mutex_init(&acb->acb_wait_lock, NULL,
MUTEX_DEFAULT, NULL);
cv_init(&acb->acb_wait_cv, NULL,
CV_DEFAULT, NULL);
}
acb->acb_zb = *zb;
if (pio != NULL) {
acb->acb_zio_dummy = zio_null(pio,
spa, NULL, NULL, NULL, zio_flags);
}
acb->acb_zio_head = head_zio;
acb->acb_next = hdr->b_l1hdr.b_acb;
hdr->b_l1hdr.b_acb->acb_prev = acb;
hdr->b_l1hdr.b_acb = acb;
}
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_iohits);
ARCSTAT_CONDSTAT(!(*arc_flags & ARC_FLAG_PREFETCH),
demand, prefetch, is_data, data, metadata, iohits);
if (*arc_flags & ARC_FLAG_WAIT) {
mutex_enter(&acb->acb_wait_lock);
while (acb->acb_wait) {
cv_wait(&acb->acb_wait_cv,
&acb->acb_wait_lock);
}
rc = acb->acb_wait_error;
mutex_exit(&acb->acb_wait_lock);
mutex_destroy(&acb->acb_wait_lock);
cv_destroy(&acb->acb_wait_cv);
kmem_free(acb, sizeof (arc_callback_t));
}
goto out;
}
ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
hdr->b_l1hdr.b_state == arc_mfu ||
hdr->b_l1hdr.b_state == arc_uncached);
DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
arc_access(hdr, *arc_flags, B_TRUE);
if (done && !no_buf) {
ASSERT(!embedded_bp || !BP_IS_HOLE(bp));
/* Get a buf with the desired data in it. */
rc = arc_buf_alloc_impl(hdr, spa, zb, private,
encrypted_read, compressed_read, noauth_read,
B_TRUE, &buf);
if (rc == ECKSUM) {
/*
* Convert authentication and decryption errors
* to EIO (and generate an ereport if needed)
* before leaving the ARC.
*/
rc = SET_ERROR(EIO);
if ((zio_flags & ZIO_FLAG_SPECULATIVE) == 0) {
spa_log_error(spa, zb, &hdr->b_birth);
(void) zfs_ereport_post(
FM_EREPORT_ZFS_AUTHENTICATION,
spa, NULL, zb, NULL, 0);
}
}
if (rc != 0) {
arc_buf_destroy_impl(buf);
buf = NULL;
(void) remove_reference(hdr, private);
}
/* assert any errors weren't due to unloaded keys */
ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) ||
rc != EACCES);
}
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_hits);
ARCSTAT_CONDSTAT(!(*arc_flags & ARC_FLAG_PREFETCH),
demand, prefetch, is_data, data, metadata, hits);
*arc_flags |= ARC_FLAG_CACHED;
goto done;
} else {
uint64_t lsize = BP_GET_LSIZE(bp);
uint64_t psize = BP_GET_PSIZE(bp);
arc_callback_t *acb;
vdev_t *vd = NULL;
uint64_t addr = 0;
boolean_t devw = B_FALSE;
uint64_t size;
abd_t *hdr_abd;
int alloc_flags = encrypted_read ? ARC_HDR_ALLOC_RDATA : 0;
arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
if (*arc_flags & ARC_FLAG_CACHED_ONLY) {
if (hash_lock != NULL)
mutex_exit(hash_lock);
rc = SET_ERROR(ENOENT);
goto done;
}
if (hdr == NULL) {
/*
* This block is not in the cache or it has
* embedded data.
*/
arc_buf_hdr_t *exists = NULL;
hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
BP_IS_PROTECTED(bp), BP_GET_COMPRESS(bp), 0, type);
if (!embedded_bp) {
hdr->b_dva = *BP_IDENTITY(bp);
hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
exists = buf_hash_insert(hdr, &hash_lock);
}
if (exists != NULL) {
/* somebody beat us to the hash insert */
mutex_exit(hash_lock);
buf_discard_identity(hdr);
arc_hdr_destroy(hdr);
goto top; /* restart the IO request */
}
} else {
/*
* This block is in the ghost cache or encrypted data
* was requested and we didn't have it. If it was
* L2-only (and thus didn't have an L1 hdr),
* we realloc the header to add an L1 hdr.
*/
if (!HDR_HAS_L1HDR(hdr)) {
hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
hdr_full_cache);
}
if (GHOST_STATE(hdr->b_l1hdr.b_state)) {
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!HDR_HAS_RABD(hdr));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT0(zfs_refcount_count(
&hdr->b_l1hdr.b_refcnt));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
#ifdef ZFS_DEBUG
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
#endif
} else if (HDR_IO_IN_PROGRESS(hdr)) {
/*
* If this header already had an IO in progress
* and we are performing another IO to fetch
* encrypted data we must wait until the first
* IO completes so as not to confuse
* arc_read_done(). This should be very rare
* and so the performance impact shouldn't
* matter.
*/
arc_callback_t *acb = kmem_zalloc(
sizeof (arc_callback_t), KM_SLEEP);
acb->acb_wait = B_TRUE;
mutex_init(&acb->acb_wait_lock, NULL,
MUTEX_DEFAULT, NULL);
cv_init(&acb->acb_wait_cv, NULL, CV_DEFAULT,
NULL);
acb->acb_zio_head =
hdr->b_l1hdr.b_acb->acb_zio_head;
acb->acb_next = hdr->b_l1hdr.b_acb;
hdr->b_l1hdr.b_acb->acb_prev = acb;
hdr->b_l1hdr.b_acb = acb;
mutex_exit(hash_lock);
mutex_enter(&acb->acb_wait_lock);
while (acb->acb_wait) {
cv_wait(&acb->acb_wait_cv,
&acb->acb_wait_lock);
}
mutex_exit(&acb->acb_wait_lock);
mutex_destroy(&acb->acb_wait_lock);
cv_destroy(&acb->acb_wait_cv);
kmem_free(acb, sizeof (arc_callback_t));
goto top;
}
}
if (*arc_flags & ARC_FLAG_UNCACHED) {
arc_hdr_set_flags(hdr, ARC_FLAG_UNCACHED);
if (!encrypted_read)
alloc_flags |= ARC_HDR_ALLOC_LINEAR;
}
/*
* Take additional reference for IO_IN_PROGRESS. It stops
* arc_access() from putting this header without any buffers
* and so other references but obviously nonevictable onto
* the evictable list of MRU or MFU state.
*/
add_reference(hdr, hdr);
if (!embedded_bp)
arc_access(hdr, *arc_flags, B_FALSE);
arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
arc_hdr_alloc_abd(hdr, alloc_flags);
if (encrypted_read) {
ASSERT(HDR_HAS_RABD(hdr));
size = HDR_GET_PSIZE(hdr);
hdr_abd = hdr->b_crypt_hdr.b_rabd;
zio_flags |= ZIO_FLAG_RAW;
} else {
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
size = arc_hdr_size(hdr);
hdr_abd = hdr->b_l1hdr.b_pabd;
if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
zio_flags |= ZIO_FLAG_RAW_COMPRESS;
}
/*
* For authenticated bp's, we do not ask the ZIO layer
* to authenticate them since this will cause the entire
* IO to fail if the key isn't loaded. Instead, we
* defer authentication until arc_buf_fill(), which will
* verify the data when the key is available.
*/
if (BP_IS_AUTHENTICATED(bp))
zio_flags |= ZIO_FLAG_RAW_ENCRYPT;
}
if (BP_IS_AUTHENTICATED(bp))
arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH);
if (BP_GET_LEVEL(bp) > 0)
arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
acb->acb_done = done;
acb->acb_private = private;
acb->acb_compressed = compressed_read;
acb->acb_encrypted = encrypted_read;
acb->acb_noauth = noauth_read;
acb->acb_zb = *zb;
ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
hdr->b_l1hdr.b_acb = acb;
if (HDR_HAS_L2HDR(hdr) &&
(vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
devw = hdr->b_l2hdr.b_dev->l2ad_writing;
addr = hdr->b_l2hdr.b_daddr;
/*
* Lock out L2ARC device removal.
*/
if (vdev_is_dead(vd) ||
!spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
vd = NULL;
}
/*
* We count both async reads and scrub IOs as asynchronous so
* that both can be upgraded in the event of a cache hit while
* the read IO is still in-flight.
*/
if (priority == ZIO_PRIORITY_ASYNC_READ ||
priority == ZIO_PRIORITY_SCRUB)
arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
else
arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
/*
* At this point, we have a level 1 cache miss or a blkptr
* with embedded data. Try again in L2ARC if possible.
*/
ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
/*
* Skip ARC stat bump for block pointers with embedded
* data. The data are read from the blkptr itself via
* decode_embedded_bp_compressed().
*/
if (!embedded_bp) {
DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr,
blkptr_t *, bp, uint64_t, lsize,
zbookmark_phys_t *, zb);
ARCSTAT_BUMP(arcstat_misses);
ARCSTAT_CONDSTAT(!(*arc_flags & ARC_FLAG_PREFETCH),
demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data,
metadata, misses);
zfs_racct_read(size, 1);
}
/* Check if the spa even has l2 configured */
const boolean_t spa_has_l2 = l2arc_ndev != 0 &&
spa->spa_l2cache.sav_count > 0;
if (vd != NULL && spa_has_l2 && !(l2arc_norw && devw)) {
/*
* Read from the L2ARC if the following are true:
* 1. The L2ARC vdev was previously cached.
* 2. This buffer still has L2ARC metadata.
* 3. This buffer isn't currently writing to the L2ARC.
* 4. The L2ARC entry wasn't evicted, which may
* also have invalidated the vdev.
*/
if (HDR_HAS_L2HDR(hdr) &&
!HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr)) {
l2arc_read_callback_t *cb;
abd_t *abd;
uint64_t asize;
DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_l2_hits);
hdr->b_l2hdr.b_hits++;
cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
KM_SLEEP);
cb->l2rcb_hdr = hdr;
cb->l2rcb_bp = *bp;
cb->l2rcb_zb = *zb;
cb->l2rcb_flags = zio_flags;
/*
* When Compressed ARC is disabled, but the
* L2ARC block is compressed, arc_hdr_size()
* will have returned LSIZE rather than PSIZE.
*/
if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
!HDR_COMPRESSION_ENABLED(hdr) &&
HDR_GET_PSIZE(hdr) != 0) {
size = HDR_GET_PSIZE(hdr);
}
asize = vdev_psize_to_asize(vd, size);
if (asize != size) {
abd = abd_alloc_for_io(asize,
HDR_ISTYPE_METADATA(hdr));
cb->l2rcb_abd = abd;
} else {
abd = hdr_abd;
}
ASSERT(addr >= VDEV_LABEL_START_SIZE &&
addr + asize <= vd->vdev_psize -
VDEV_LABEL_END_SIZE);
/*
* l2arc read. The SCL_L2ARC lock will be
* released by l2arc_read_done().
* Issue a null zio if the underlying buffer
* was squashed to zero size by compression.
*/
ASSERT3U(arc_hdr_get_compress(hdr), !=,
ZIO_COMPRESS_EMPTY);
rzio = zio_read_phys(pio, vd, addr,
asize, abd,
ZIO_CHECKSUM_OFF,
l2arc_read_done, cb, priority,
zio_flags | ZIO_FLAG_CANFAIL |
ZIO_FLAG_DONT_PROPAGATE |
ZIO_FLAG_DONT_RETRY, B_FALSE);
acb->acb_zio_head = rzio;
if (hash_lock != NULL)
mutex_exit(hash_lock);
DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
zio_t *, rzio);
ARCSTAT_INCR(arcstat_l2_read_bytes,
HDR_GET_PSIZE(hdr));
if (*arc_flags & ARC_FLAG_NOWAIT) {
zio_nowait(rzio);
goto out;
}
ASSERT(*arc_flags & ARC_FLAG_WAIT);
if (zio_wait(rzio) == 0)
goto out;
/* l2arc read error; goto zio_read() */
if (hash_lock != NULL)
mutex_enter(hash_lock);
} else {
DTRACE_PROBE1(l2arc__miss,
arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_l2_misses);
if (HDR_L2_WRITING(hdr))
ARCSTAT_BUMP(arcstat_l2_rw_clash);
spa_config_exit(spa, SCL_L2ARC, vd);
}
} else {
if (vd != NULL)
spa_config_exit(spa, SCL_L2ARC, vd);
/*
* Only a spa with l2 should contribute to l2
* miss stats. (Including the case of having a
* faulted cache device - that's also a miss.)
*/
if (spa_has_l2) {
/*
* Skip ARC stat bump for block pointers with
* embedded data. The data are read from the
* blkptr itself via
* decode_embedded_bp_compressed().
*/
if (!embedded_bp) {
DTRACE_PROBE1(l2arc__miss,
arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_l2_misses);
}
}
}
rzio = zio_read(pio, spa, bp, hdr_abd, size,
arc_read_done, hdr, priority, zio_flags, zb);
acb->acb_zio_head = rzio;
if (hash_lock != NULL)
mutex_exit(hash_lock);
if (*arc_flags & ARC_FLAG_WAIT) {
rc = zio_wait(rzio);
goto out;
}
ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
zio_nowait(rzio);
}
out:
/* embedded bps don't actually go to disk */
if (!embedded_bp)
spa_read_history_add(spa, zb, *arc_flags);
spl_fstrans_unmark(cookie);
return (rc);
done:
if (done)
done(NULL, zb, bp, buf, private);
if (pio && rc != 0) {
zio_t *zio = zio_null(pio, spa, NULL, NULL, NULL, zio_flags);
zio->io_error = rc;
zio_nowait(zio);
}
goto out;
}
arc_prune_t *
arc_add_prune_callback(arc_prune_func_t *func, void *private)
{
arc_prune_t *p;
p = kmem_alloc(sizeof (*p), KM_SLEEP);
p->p_pfunc = func;
p->p_private = private;
list_link_init(&p->p_node);
zfs_refcount_create(&p->p_refcnt);
mutex_enter(&arc_prune_mtx);
zfs_refcount_add(&p->p_refcnt, &arc_prune_list);
list_insert_head(&arc_prune_list, p);
mutex_exit(&arc_prune_mtx);
return (p);
}
void
arc_remove_prune_callback(arc_prune_t *p)
{
boolean_t wait = B_FALSE;
mutex_enter(&arc_prune_mtx);
list_remove(&arc_prune_list, p);
if (zfs_refcount_remove(&p->p_refcnt, &arc_prune_list) > 0)
wait = B_TRUE;
mutex_exit(&arc_prune_mtx);
/* wait for arc_prune_task to finish */
if (wait)
taskq_wait_outstanding(arc_prune_taskq, 0);
ASSERT0(zfs_refcount_count(&p->p_refcnt));
zfs_refcount_destroy(&p->p_refcnt);
kmem_free(p, sizeof (*p));
}
/*
* Notify the arc that a block was freed, and thus will never be used again.
*/
void
arc_freed(spa_t *spa, const blkptr_t *bp)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
uint64_t guid = spa_load_guid(spa);
ASSERT(!BP_IS_EMBEDDED(bp));
hdr = buf_hash_find(guid, bp, &hash_lock);
if (hdr == NULL)
return;
/*
* We might be trying to free a block that is still doing I/O
* (i.e. prefetch) or has some other reference (i.e. a dedup-ed,
* dmu_sync-ed block). A block may also have a reference if it is
* part of a dedup-ed, dmu_synced write. The dmu_sync() function would
* have written the new block to its final resting place on disk but
* without the dedup flag set. This would have left the hdr in the MRU
* state and discoverable. When the txg finally syncs it detects that
* the block was overridden in open context and issues an override I/O.
* Since this is a dedup block, the override I/O will determine if the
* block is already in the DDT. If so, then it will replace the io_bp
* with the bp from the DDT and allow the I/O to finish. When the I/O
* reaches the done callback, dbuf_write_override_done, it will
* check to see if the io_bp and io_bp_override are identical.
* If they are not, then it indicates that the bp was replaced with
* the bp in the DDT and the override bp is freed. This allows
* us to arrive here with a reference on a block that is being
* freed. So if we have an I/O in progress, or a reference to
* this hdr, then we don't destroy the hdr.
*/
if (!HDR_HAS_L1HDR(hdr) ||
zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
arc_change_state(arc_anon, hdr);
arc_hdr_destroy(hdr);
mutex_exit(hash_lock);
} else {
mutex_exit(hash_lock);
}
}
/*
* Release this buffer from the cache, making it an anonymous buffer. This
* must be done after a read and prior to modifying the buffer contents.
* If the buffer has more than one reference, we must make
* a new hdr for the buffer.
*/
void
arc_release(arc_buf_t *buf, const void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
/*
* It would be nice to assert that if its DMU metadata (level >
* 0 || it's the dnode file), then it must be syncing context.
* But we don't know that information at this level.
*/
ASSERT(HDR_HAS_L1HDR(hdr));
/*
* We don't grab the hash lock prior to this check, because if
* the buffer's header is in the arc_anon state, it won't be
* linked into the hash table.
*/
if (hdr->b_l1hdr.b_state == arc_anon) {
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT(!HDR_IN_HASH_TABLE(hdr));
ASSERT(!HDR_HAS_L2HDR(hdr));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, buf);
ASSERT(ARC_BUF_LAST(buf));
ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
hdr->b_l1hdr.b_arc_access = 0;
/*
* If the buf is being overridden then it may already
* have a hdr that is not empty.
*/
buf_discard_identity(hdr);
arc_buf_thaw(buf);
return;
}
kmutex_t *hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
/*
* This assignment is only valid as long as the hash_lock is
* held, we must be careful not to reference state or the
* b_state field after dropping the lock.
*/
arc_state_t *state = hdr->b_l1hdr.b_state;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
ASSERT3P(state, !=, arc_anon);
/* this buffer is not on any list */
ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
if (HDR_HAS_L2HDR(hdr)) {
mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
/*
* We have to recheck this conditional again now that
* we're holding the l2ad_mtx to prevent a race with
* another thread which might be concurrently calling
* l2arc_evict(). In that case, l2arc_evict() might have
* destroyed the header's L2 portion as we were waiting
* to acquire the l2ad_mtx.
*/
if (HDR_HAS_L2HDR(hdr))
arc_hdr_l2hdr_destroy(hdr);
mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
}
/*
* Do we have more than one buf?
*/
if (hdr->b_l1hdr.b_buf != buf || !ARC_BUF_LAST(buf)) {
arc_buf_hdr_t *nhdr;
uint64_t spa = hdr->b_spa;
uint64_t psize = HDR_GET_PSIZE(hdr);
uint64_t lsize = HDR_GET_LSIZE(hdr);
boolean_t protected = HDR_PROTECTED(hdr);
enum zio_compress compress = arc_hdr_get_compress(hdr);
arc_buf_contents_t type = arc_buf_type(hdr);
VERIFY3U(hdr->b_type, ==, type);
ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
VERIFY3S(remove_reference(hdr, tag), >, 0);
if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
ASSERT(ARC_BUF_LAST(buf));
}
/*
* Pull the data off of this hdr and attach it to
* a new anonymous hdr. Also find the last buffer
* in the hdr's buffer list.
*/
arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
ASSERT3P(lastbuf, !=, NULL);
/*
* If the current arc_buf_t and the hdr are sharing their data
* buffer, then we must stop sharing that block.
*/
if (ARC_BUF_SHARED(buf)) {
ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
ASSERT(!arc_buf_is_shared(lastbuf));
/*
* First, sever the block sharing relationship between
* buf and the arc_buf_hdr_t.
*/
arc_unshare_buf(hdr, buf);
/*
* Now we need to recreate the hdr's b_pabd. Since we
* have lastbuf handy, we try to share with it, but if
* we can't then we allocate a new b_pabd and copy the
* data from buf into it.
*/
if (arc_can_share(hdr, lastbuf)) {
arc_share_buf(hdr, lastbuf);
} else {
arc_hdr_alloc_abd(hdr, 0);
abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
buf->b_data, psize);
}
VERIFY3P(lastbuf->b_data, !=, NULL);
} else if (HDR_SHARED_DATA(hdr)) {
/*
* Uncompressed shared buffers are always at the end
* of the list. Compressed buffers don't have the
* same requirements. This makes it hard to
* simply assert that the lastbuf is shared so
* we rely on the hdr's compression flags to determine
* if we have a compressed, shared buffer.
*/
ASSERT(arc_buf_is_shared(lastbuf) ||
arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
ASSERT(!arc_buf_is_shared(buf));
}
ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
ASSERT3P(state, !=, arc_l2c_only);
(void) zfs_refcount_remove_many(&state->arcs_size[type],
arc_buf_size(buf), buf);
if (zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
ASSERT3P(state, !=, arc_l2c_only);
(void) zfs_refcount_remove_many(
&state->arcs_esize[type],
arc_buf_size(buf), buf);
}
arc_cksum_verify(buf);
arc_buf_unwatch(buf);
/* if this is the last uncompressed buf free the checksum */
if (!arc_hdr_has_uncompressed_buf(hdr))
arc_cksum_free(hdr);
mutex_exit(hash_lock);
nhdr = arc_hdr_alloc(spa, psize, lsize, protected,
compress, hdr->b_complevel, type);
ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
ASSERT0(zfs_refcount_count(&nhdr->b_l1hdr.b_refcnt));
VERIFY3U(nhdr->b_type, ==, type);
ASSERT(!HDR_SHARED_DATA(nhdr));
nhdr->b_l1hdr.b_buf = buf;
(void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
buf->b_hdr = nhdr;
(void) zfs_refcount_add_many(&arc_anon->arcs_size[type],
arc_buf_size(buf), buf);
} else {
ASSERT(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
/* protected by hash lock, or hdr is on arc_anon */
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
hdr->b_l1hdr.b_mru_hits = 0;
hdr->b_l1hdr.b_mru_ghost_hits = 0;
hdr->b_l1hdr.b_mfu_hits = 0;
hdr->b_l1hdr.b_mfu_ghost_hits = 0;
arc_change_state(arc_anon, hdr);
hdr->b_l1hdr.b_arc_access = 0;
mutex_exit(hash_lock);
buf_discard_identity(hdr);
arc_buf_thaw(buf);
}
}
int
arc_released(arc_buf_t *buf)
{
return (buf->b_data != NULL &&
buf->b_hdr->b_l1hdr.b_state == arc_anon);
}
#ifdef ZFS_DEBUG
int
arc_referenced(arc_buf_t *buf)
{
return (zfs_refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
}
#endif
static void
arc_write_ready(zio_t *zio)
{
arc_write_callback_t *callback = zio->io_private;
arc_buf_t *buf = callback->awcb_buf;
arc_buf_hdr_t *hdr = buf->b_hdr;
blkptr_t *bp = zio->io_bp;
uint64_t psize = BP_IS_HOLE(bp) ? 0 : BP_GET_PSIZE(bp);
fstrans_cookie_t cookie = spl_fstrans_mark();
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(!zfs_refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
ASSERT3P(hdr->b_l1hdr.b_buf, !=, NULL);
/*
* If we're reexecuting this zio because the pool suspended, then
* cleanup any state that was previously set the first time the
* callback was invoked.
*/
if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
arc_cksum_free(hdr);
arc_buf_unwatch(buf);
if (hdr->b_l1hdr.b_pabd != NULL) {
if (ARC_BUF_SHARED(buf)) {
arc_unshare_buf(hdr, buf);
} else {
ASSERT(!arc_buf_is_shared(buf));
arc_hdr_free_abd(hdr, B_FALSE);
}
}
if (HDR_HAS_RABD(hdr))
arc_hdr_free_abd(hdr, B_TRUE);
}
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
ASSERT(!HDR_HAS_RABD(hdr));
ASSERT(!HDR_SHARED_DATA(hdr));
ASSERT(!arc_buf_is_shared(buf));
callback->awcb_ready(zio, buf, callback->awcb_private);
if (HDR_IO_IN_PROGRESS(hdr)) {
ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
} else {
arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
add_reference(hdr, hdr); /* For IO_IN_PROGRESS. */
}
if (BP_IS_PROTECTED(bp)) {
/* ZIL blocks are written through zio_rewrite */
ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG);
if (BP_SHOULD_BYTESWAP(bp)) {
if (BP_GET_LEVEL(bp) > 0) {
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
} else {
hdr->b_l1hdr.b_byteswap =
DMU_OT_BYTESWAP(BP_GET_TYPE(bp));
}
} else {
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
}
arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp);
hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset;
zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt,
hdr->b_crypt_hdr.b_iv);
zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac);
} else {
arc_hdr_clear_flags(hdr, ARC_FLAG_PROTECTED);
}
/*
* If this block was written for raw encryption but the zio layer
* ended up only authenticating it, adjust the buffer flags now.
*/
if (BP_IS_AUTHENTICATED(bp) && ARC_BUF_ENCRYPTED(buf)) {
arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH);
buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
if (BP_GET_COMPRESS(bp) == ZIO_COMPRESS_OFF)
buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
} else if (BP_IS_HOLE(bp) && ARC_BUF_ENCRYPTED(buf)) {
buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
}
/* this must be done after the buffer flags are adjusted */
arc_cksum_compute(buf);
enum zio_compress compress;
if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
compress = ZIO_COMPRESS_OFF;
} else {
ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
compress = BP_GET_COMPRESS(bp);
}
HDR_SET_PSIZE(hdr, psize);
arc_hdr_set_compress(hdr, compress);
hdr->b_complevel = zio->io_prop.zp_complevel;
if (zio->io_error != 0 || psize == 0)
goto out;
/*
* Fill the hdr with data. If the buffer is encrypted we have no choice
* but to copy the data into b_radb. If the hdr is compressed, the data
* we want is available from the zio, otherwise we can take it from
* the buf.
*
* We might be able to share the buf's data with the hdr here. However,
* doing so would cause the ARC to be full of linear ABDs if we write a
* lot of shareable data. As a compromise, we check whether scattered
* ABDs are allowed, and assume that if they are then the user wants
* the ARC to be primarily filled with them regardless of the data being
* written. Therefore, if they're allowed then we allocate one and copy
* the data into it; otherwise, we share the data directly if we can.
*/
if (ARC_BUF_ENCRYPTED(buf)) {
ASSERT3U(psize, >, 0);
ASSERT(ARC_BUF_COMPRESSED(buf));
arc_hdr_alloc_abd(hdr, ARC_HDR_ALLOC_RDATA |
ARC_HDR_USE_RESERVE);
abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize);
} else if (!(HDR_UNCACHED(hdr) ||
abd_size_alloc_linear(arc_buf_size(buf))) ||
!arc_can_share(hdr, buf)) {
/*
* Ideally, we would always copy the io_abd into b_pabd, but the
* user may have disabled compressed ARC, thus we must check the
* hdr's compression setting rather than the io_bp's.
*/
if (BP_IS_ENCRYPTED(bp)) {
ASSERT3U(psize, >, 0);
arc_hdr_alloc_abd(hdr, ARC_HDR_ALLOC_RDATA |
ARC_HDR_USE_RESERVE);
abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize);
} else if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF &&
!ARC_BUF_COMPRESSED(buf)) {
ASSERT3U(psize, >, 0);
arc_hdr_alloc_abd(hdr, ARC_HDR_USE_RESERVE);
abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
} else {
ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
arc_hdr_alloc_abd(hdr, ARC_HDR_USE_RESERVE);
abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
arc_buf_size(buf));
}
} else {
ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, buf);
ASSERT(ARC_BUF_LAST(buf));
arc_share_buf(hdr, buf);
}
out:
arc_hdr_verify(hdr, bp);
spl_fstrans_unmark(cookie);
}
static void
arc_write_children_ready(zio_t *zio)
{
arc_write_callback_t *callback = zio->io_private;
arc_buf_t *buf = callback->awcb_buf;
callback->awcb_children_ready(zio, buf, callback->awcb_private);
}
static void
arc_write_done(zio_t *zio)
{
arc_write_callback_t *callback = zio->io_private;
arc_buf_t *buf = callback->awcb_buf;
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
if (zio->io_error == 0) {
arc_hdr_verify(hdr, zio->io_bp);
if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
buf_discard_identity(hdr);
} else {
hdr->b_dva = *BP_IDENTITY(zio->io_bp);
hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
}
} else {
ASSERT(HDR_EMPTY(hdr));
}
/*
* If the block to be written was all-zero or compressed enough to be
* embedded in the BP, no write was performed so there will be no
* dva/birth/checksum. The buffer must therefore remain anonymous
* (and uncached).
*/
if (!HDR_EMPTY(hdr)) {
arc_buf_hdr_t *exists;
kmutex_t *hash_lock;
ASSERT3U(zio->io_error, ==, 0);
arc_cksum_verify(buf);
exists = buf_hash_insert(hdr, &hash_lock);
if (exists != NULL) {
/*
* This can only happen if we overwrite for
* sync-to-convergence, because we remove
* buffers from the hash table when we arc_free().
*/
if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
panic("bad overwrite, hdr=%p exists=%p",
(void *)hdr, (void *)exists);
ASSERT(zfs_refcount_is_zero(
&exists->b_l1hdr.b_refcnt));
arc_change_state(arc_anon, exists);
arc_hdr_destroy(exists);
mutex_exit(hash_lock);
exists = buf_hash_insert(hdr, &hash_lock);
ASSERT3P(exists, ==, NULL);
} else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
/* nopwrite */
ASSERT(zio->io_prop.zp_nopwrite);
if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
panic("bad nopwrite, hdr=%p exists=%p",
(void *)hdr, (void *)exists);
} else {
/* Dedup */
ASSERT3P(hdr->b_l1hdr.b_buf, !=, NULL);
ASSERT(ARC_BUF_LAST(hdr->b_l1hdr.b_buf));
ASSERT(hdr->b_l1hdr.b_state == arc_anon);
ASSERT(BP_GET_DEDUP(zio->io_bp));
ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
}
}
arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
VERIFY3S(remove_reference(hdr, hdr), >, 0);
/* if it's not anon, we are doing a scrub */
if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
arc_access(hdr, 0, B_FALSE);
mutex_exit(hash_lock);
} else {
arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
VERIFY3S(remove_reference(hdr, hdr), >, 0);
}
callback->awcb_done(zio, buf, callback->awcb_private);
abd_free(zio->io_abd);
kmem_free(callback, sizeof (arc_write_callback_t));
}
zio_t *
arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
blkptr_t *bp, arc_buf_t *buf, boolean_t uncached, boolean_t l2arc,
const zio_prop_t *zp, arc_write_done_func_t *ready,
arc_write_done_func_t *children_ready, arc_write_done_func_t *done,
void *private, zio_priority_t priority, int zio_flags,
const zbookmark_phys_t *zb)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
arc_write_callback_t *callback;
zio_t *zio;
zio_prop_t localprop = *zp;
ASSERT3P(ready, !=, NULL);
ASSERT3P(done, !=, NULL);
ASSERT(!HDR_IO_ERROR(hdr));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
ASSERT3P(hdr->b_l1hdr.b_buf, !=, NULL);
if (uncached)
arc_hdr_set_flags(hdr, ARC_FLAG_UNCACHED);
else if (l2arc)
arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
if (ARC_BUF_ENCRYPTED(buf)) {
ASSERT(ARC_BUF_COMPRESSED(buf));
localprop.zp_encrypt = B_TRUE;
localprop.zp_compress = HDR_GET_COMPRESS(hdr);
localprop.zp_complevel = hdr->b_complevel;
localprop.zp_byteorder =
(hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ?
ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER;
memcpy(localprop.zp_salt, hdr->b_crypt_hdr.b_salt,
ZIO_DATA_SALT_LEN);
memcpy(localprop.zp_iv, hdr->b_crypt_hdr.b_iv,
ZIO_DATA_IV_LEN);
memcpy(localprop.zp_mac, hdr->b_crypt_hdr.b_mac,
ZIO_DATA_MAC_LEN);
if (DMU_OT_IS_ENCRYPTED(localprop.zp_type)) {
localprop.zp_nopwrite = B_FALSE;
localprop.zp_copies =
MIN(localprop.zp_copies, SPA_DVAS_PER_BP - 1);
}
zio_flags |= ZIO_FLAG_RAW;
} else if (ARC_BUF_COMPRESSED(buf)) {
ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
localprop.zp_compress = HDR_GET_COMPRESS(hdr);
localprop.zp_complevel = hdr->b_complevel;
zio_flags |= ZIO_FLAG_RAW_COMPRESS;
}
callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
callback->awcb_ready = ready;
callback->awcb_children_ready = children_ready;
callback->awcb_done = done;
callback->awcb_private = private;
callback->awcb_buf = buf;
/*
* The hdr's b_pabd is now stale, free it now. A new data block
* will be allocated when the zio pipeline calls arc_write_ready().
*/
if (hdr->b_l1hdr.b_pabd != NULL) {
/*
* If the buf is currently sharing the data block with
* the hdr then we need to break that relationship here.
* The hdr will remain with a NULL data pointer and the
* buf will take sole ownership of the block.
*/
if (ARC_BUF_SHARED(buf)) {
arc_unshare_buf(hdr, buf);
} else {
ASSERT(!arc_buf_is_shared(buf));
arc_hdr_free_abd(hdr, B_FALSE);
}
VERIFY3P(buf->b_data, !=, NULL);
}
if (HDR_HAS_RABD(hdr))
arc_hdr_free_abd(hdr, B_TRUE);
if (!(zio_flags & ZIO_FLAG_RAW))
arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
ASSERT(!arc_buf_is_shared(buf));
ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
zio = zio_write(pio, spa, txg, bp,
abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
(children_ready != NULL) ? arc_write_children_ready : NULL,
arc_write_done, callback, priority, zio_flags, zb);
return (zio);
}
void
arc_tempreserve_clear(uint64_t reserve)
{
atomic_add_64(&arc_tempreserve, -reserve);
ASSERT((int64_t)arc_tempreserve >= 0);
}
int
arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg)
{
int error;
uint64_t anon_size;
if (!arc_no_grow &&
reserve > arc_c/4 &&
reserve * 4 > (2ULL << SPA_MAXBLOCKSHIFT))
arc_c = MIN(arc_c_max, reserve * 4);
/*
* Throttle when the calculated memory footprint for the TXG
* exceeds the target ARC size.
*/
if (reserve > arc_c) {
DMU_TX_STAT_BUMP(dmu_tx_memory_reserve);
return (SET_ERROR(ERESTART));
}
/*
* Don't count loaned bufs as in flight dirty data to prevent long
* network delays from blocking transactions that are ready to be
* assigned to a txg.
*/
/* assert that it has not wrapped around */
ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
anon_size = MAX((int64_t)
(zfs_refcount_count(&arc_anon->arcs_size[ARC_BUFC_DATA]) +
zfs_refcount_count(&arc_anon->arcs_size[ARC_BUFC_METADATA]) -
arc_loaned_bytes), 0);
/*
* Writes will, almost always, require additional memory allocations
* in order to compress/encrypt/etc the data. We therefore need to
* make sure that there is sufficient available memory for this.
*/
error = arc_memory_throttle(spa, reserve, txg);
if (error != 0)
return (error);
/*
* Throttle writes when the amount of dirty data in the cache
* gets too large. We try to keep the cache less than half full
* of dirty blocks so that our sync times don't grow too large.
*
* In the case of one pool being built on another pool, we want
* to make sure we don't end up throttling the lower (backing)
* pool when the upper pool is the majority contributor to dirty
* data. To insure we make forward progress during throttling, we
* also check the current pool's net dirty data and only throttle
* if it exceeds zfs_arc_pool_dirty_percent of the anonymous dirty
* data in the cache.
*
* Note: if two requests come in concurrently, we might let them
* both succeed, when one of them should fail. Not a huge deal.
*/
uint64_t total_dirty = reserve + arc_tempreserve + anon_size;
uint64_t spa_dirty_anon = spa_dirty_data(spa);
uint64_t rarc_c = arc_warm ? arc_c : arc_c_max;
if (total_dirty > rarc_c * zfs_arc_dirty_limit_percent / 100 &&
anon_size > rarc_c * zfs_arc_anon_limit_percent / 100 &&
spa_dirty_anon > anon_size * zfs_arc_pool_dirty_percent / 100) {
#ifdef ZFS_DEBUG
uint64_t meta_esize = zfs_refcount_count(
&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
uint64_t data_esize =
zfs_refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
"anon_data=%lluK tempreserve=%lluK rarc_c=%lluK\n",
(u_longlong_t)arc_tempreserve >> 10,
(u_longlong_t)meta_esize >> 10,
(u_longlong_t)data_esize >> 10,
(u_longlong_t)reserve >> 10,
(u_longlong_t)rarc_c >> 10);
#endif
DMU_TX_STAT_BUMP(dmu_tx_dirty_throttle);
return (SET_ERROR(ERESTART));
}
atomic_add_64(&arc_tempreserve, reserve);
return (0);
}
static void
arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
kstat_named_t *data, kstat_named_t *metadata,
kstat_named_t *evict_data, kstat_named_t *evict_metadata)
{
data->value.ui64 =
zfs_refcount_count(&state->arcs_size[ARC_BUFC_DATA]);
metadata->value.ui64 =
zfs_refcount_count(&state->arcs_size[ARC_BUFC_METADATA]);
size->value.ui64 = data->value.ui64 + metadata->value.ui64;
evict_data->value.ui64 =
zfs_refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
evict_metadata->value.ui64 =
zfs_refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
}
static int
arc_kstat_update(kstat_t *ksp, int rw)
{
arc_stats_t *as = ksp->ks_data;
if (rw == KSTAT_WRITE)
return (SET_ERROR(EACCES));
as->arcstat_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_hits);
as->arcstat_iohits.value.ui64 =
wmsum_value(&arc_sums.arcstat_iohits);
as->arcstat_misses.value.ui64 =
wmsum_value(&arc_sums.arcstat_misses);
as->arcstat_demand_data_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_data_hits);
as->arcstat_demand_data_iohits.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_data_iohits);
as->arcstat_demand_data_misses.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_data_misses);
as->arcstat_demand_metadata_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_metadata_hits);
as->arcstat_demand_metadata_iohits.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_metadata_iohits);
as->arcstat_demand_metadata_misses.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_metadata_misses);
as->arcstat_prefetch_data_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_prefetch_data_hits);
as->arcstat_prefetch_data_iohits.value.ui64 =
wmsum_value(&arc_sums.arcstat_prefetch_data_iohits);
as->arcstat_prefetch_data_misses.value.ui64 =
wmsum_value(&arc_sums.arcstat_prefetch_data_misses);
as->arcstat_prefetch_metadata_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_prefetch_metadata_hits);
as->arcstat_prefetch_metadata_iohits.value.ui64 =
wmsum_value(&arc_sums.arcstat_prefetch_metadata_iohits);
as->arcstat_prefetch_metadata_misses.value.ui64 =
wmsum_value(&arc_sums.arcstat_prefetch_metadata_misses);
as->arcstat_mru_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_mru_hits);
as->arcstat_mru_ghost_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_mru_ghost_hits);
as->arcstat_mfu_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_mfu_hits);
as->arcstat_mfu_ghost_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_mfu_ghost_hits);
as->arcstat_uncached_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_uncached_hits);
as->arcstat_deleted.value.ui64 =
wmsum_value(&arc_sums.arcstat_deleted);
as->arcstat_mutex_miss.value.ui64 =
wmsum_value(&arc_sums.arcstat_mutex_miss);
as->arcstat_access_skip.value.ui64 =
wmsum_value(&arc_sums.arcstat_access_skip);
as->arcstat_evict_skip.value.ui64 =
wmsum_value(&arc_sums.arcstat_evict_skip);
as->arcstat_evict_not_enough.value.ui64 =
wmsum_value(&arc_sums.arcstat_evict_not_enough);
as->arcstat_evict_l2_cached.value.ui64 =
wmsum_value(&arc_sums.arcstat_evict_l2_cached);
as->arcstat_evict_l2_eligible.value.ui64 =
wmsum_value(&arc_sums.arcstat_evict_l2_eligible);
as->arcstat_evict_l2_eligible_mfu.value.ui64 =
wmsum_value(&arc_sums.arcstat_evict_l2_eligible_mfu);
as->arcstat_evict_l2_eligible_mru.value.ui64 =
wmsum_value(&arc_sums.arcstat_evict_l2_eligible_mru);
as->arcstat_evict_l2_ineligible.value.ui64 =
wmsum_value(&arc_sums.arcstat_evict_l2_ineligible);
as->arcstat_evict_l2_skip.value.ui64 =
wmsum_value(&arc_sums.arcstat_evict_l2_skip);
as->arcstat_hash_collisions.value.ui64 =
wmsum_value(&arc_sums.arcstat_hash_collisions);
as->arcstat_hash_chains.value.ui64 =
wmsum_value(&arc_sums.arcstat_hash_chains);
as->arcstat_size.value.ui64 =
aggsum_value(&arc_sums.arcstat_size);
as->arcstat_compressed_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_compressed_size);
as->arcstat_uncompressed_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_uncompressed_size);
as->arcstat_overhead_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_overhead_size);
as->arcstat_hdr_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_hdr_size);
as->arcstat_data_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_data_size);
as->arcstat_metadata_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_metadata_size);
as->arcstat_dbuf_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_dbuf_size);
#if defined(COMPAT_FREEBSD11)
as->arcstat_other_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_bonus_size) +
wmsum_value(&arc_sums.arcstat_dnode_size) +
wmsum_value(&arc_sums.arcstat_dbuf_size);
#endif
arc_kstat_update_state(arc_anon,
&as->arcstat_anon_size,
&as->arcstat_anon_data,
&as->arcstat_anon_metadata,
&as->arcstat_anon_evictable_data,
&as->arcstat_anon_evictable_metadata);
arc_kstat_update_state(arc_mru,
&as->arcstat_mru_size,
&as->arcstat_mru_data,
&as->arcstat_mru_metadata,
&as->arcstat_mru_evictable_data,
&as->arcstat_mru_evictable_metadata);
arc_kstat_update_state(arc_mru_ghost,
&as->arcstat_mru_ghost_size,
&as->arcstat_mru_ghost_data,
&as->arcstat_mru_ghost_metadata,
&as->arcstat_mru_ghost_evictable_data,
&as->arcstat_mru_ghost_evictable_metadata);
arc_kstat_update_state(arc_mfu,
&as->arcstat_mfu_size,
&as->arcstat_mfu_data,
&as->arcstat_mfu_metadata,
&as->arcstat_mfu_evictable_data,
&as->arcstat_mfu_evictable_metadata);
arc_kstat_update_state(arc_mfu_ghost,
&as->arcstat_mfu_ghost_size,
&as->arcstat_mfu_ghost_data,
&as->arcstat_mfu_ghost_metadata,
&as->arcstat_mfu_ghost_evictable_data,
&as->arcstat_mfu_ghost_evictable_metadata);
arc_kstat_update_state(arc_uncached,
&as->arcstat_uncached_size,
&as->arcstat_uncached_data,
&as->arcstat_uncached_metadata,
&as->arcstat_uncached_evictable_data,
&as->arcstat_uncached_evictable_metadata);
as->arcstat_dnode_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_dnode_size);
as->arcstat_bonus_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_bonus_size);
as->arcstat_l2_hits.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_hits);
as->arcstat_l2_misses.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_misses);
as->arcstat_l2_prefetch_asize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_prefetch_asize);
as->arcstat_l2_mru_asize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_mru_asize);
as->arcstat_l2_mfu_asize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_mfu_asize);
as->arcstat_l2_bufc_data_asize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_bufc_data_asize);
as->arcstat_l2_bufc_metadata_asize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_bufc_metadata_asize);
as->arcstat_l2_feeds.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_feeds);
as->arcstat_l2_rw_clash.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rw_clash);
as->arcstat_l2_read_bytes.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_read_bytes);
as->arcstat_l2_write_bytes.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_write_bytes);
as->arcstat_l2_writes_sent.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_writes_sent);
as->arcstat_l2_writes_done.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_writes_done);
as->arcstat_l2_writes_error.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_writes_error);
as->arcstat_l2_writes_lock_retry.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_writes_lock_retry);
as->arcstat_l2_evict_lock_retry.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_evict_lock_retry);
as->arcstat_l2_evict_reading.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_evict_reading);
as->arcstat_l2_evict_l1cached.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_evict_l1cached);
as->arcstat_l2_free_on_write.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_free_on_write);
as->arcstat_l2_abort_lowmem.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_abort_lowmem);
as->arcstat_l2_cksum_bad.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_cksum_bad);
as->arcstat_l2_io_error.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_io_error);
as->arcstat_l2_lsize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_lsize);
as->arcstat_l2_psize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_psize);
as->arcstat_l2_hdr_size.value.ui64 =
aggsum_value(&arc_sums.arcstat_l2_hdr_size);
as->arcstat_l2_log_blk_writes.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_log_blk_writes);
as->arcstat_l2_log_blk_asize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_log_blk_asize);
as->arcstat_l2_log_blk_count.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_log_blk_count);
as->arcstat_l2_rebuild_success.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_success);
as->arcstat_l2_rebuild_abort_unsupported.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_abort_unsupported);
as->arcstat_l2_rebuild_abort_io_errors.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_abort_io_errors);
as->arcstat_l2_rebuild_abort_dh_errors.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_abort_dh_errors);
as->arcstat_l2_rebuild_abort_cksum_lb_errors.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_abort_cksum_lb_errors);
as->arcstat_l2_rebuild_abort_lowmem.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_abort_lowmem);
as->arcstat_l2_rebuild_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_size);
as->arcstat_l2_rebuild_asize.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_asize);
as->arcstat_l2_rebuild_bufs.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_bufs);
as->arcstat_l2_rebuild_bufs_precached.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_bufs_precached);
as->arcstat_l2_rebuild_log_blks.value.ui64 =
wmsum_value(&arc_sums.arcstat_l2_rebuild_log_blks);
as->arcstat_memory_throttle_count.value.ui64 =
wmsum_value(&arc_sums.arcstat_memory_throttle_count);
as->arcstat_memory_direct_count.value.ui64 =
wmsum_value(&arc_sums.arcstat_memory_direct_count);
as->arcstat_memory_indirect_count.value.ui64 =
wmsum_value(&arc_sums.arcstat_memory_indirect_count);
as->arcstat_memory_all_bytes.value.ui64 =
arc_all_memory();
as->arcstat_memory_free_bytes.value.ui64 =
arc_free_memory();
as->arcstat_memory_available_bytes.value.i64 =
arc_available_memory();
as->arcstat_prune.value.ui64 =
wmsum_value(&arc_sums.arcstat_prune);
as->arcstat_meta_used.value.ui64 =
wmsum_value(&arc_sums.arcstat_meta_used);
as->arcstat_async_upgrade_sync.value.ui64 =
wmsum_value(&arc_sums.arcstat_async_upgrade_sync);
as->arcstat_predictive_prefetch.value.ui64 =
wmsum_value(&arc_sums.arcstat_predictive_prefetch);
as->arcstat_demand_hit_predictive_prefetch.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_hit_predictive_prefetch);
as->arcstat_demand_iohit_predictive_prefetch.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_iohit_predictive_prefetch);
as->arcstat_prescient_prefetch.value.ui64 =
wmsum_value(&arc_sums.arcstat_prescient_prefetch);
as->arcstat_demand_hit_prescient_prefetch.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_hit_prescient_prefetch);
as->arcstat_demand_iohit_prescient_prefetch.value.ui64 =
wmsum_value(&arc_sums.arcstat_demand_iohit_prescient_prefetch);
as->arcstat_raw_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_raw_size);
as->arcstat_cached_only_in_progress.value.ui64 =
wmsum_value(&arc_sums.arcstat_cached_only_in_progress);
as->arcstat_abd_chunk_waste_size.value.ui64 =
wmsum_value(&arc_sums.arcstat_abd_chunk_waste_size);
return (0);
}
/*
* This function *must* return indices evenly distributed between all
* sublists of the multilist. This is needed due to how the ARC eviction
* code is laid out; arc_evict_state() assumes ARC buffers are evenly
* distributed between all sublists and uses this assumption when
* deciding which sublist to evict from and how much to evict from it.
*/
static unsigned int
arc_state_multilist_index_func(multilist_t *ml, void *obj)
{
arc_buf_hdr_t *hdr = obj;
/*
* We rely on b_dva to generate evenly distributed index
* numbers using buf_hash below. So, as an added precaution,
* let's make sure we never add empty buffers to the arc lists.
*/
ASSERT(!HDR_EMPTY(hdr));
/*
* The assumption here, is the hash value for a given
* arc_buf_hdr_t will remain constant throughout its lifetime
* (i.e. its b_spa, b_dva, and b_birth fields don't change).
* Thus, we don't need to store the header's sublist index
* on insertion, as this index can be recalculated on removal.
*
* Also, the low order bits of the hash value are thought to be
* distributed evenly. Otherwise, in the case that the multilist
* has a power of two number of sublists, each sublists' usage
* would not be evenly distributed. In this context full 64bit
* division would be a waste of time, so limit it to 32 bits.
*/
return ((unsigned int)buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
multilist_get_num_sublists(ml));
}
static unsigned int
arc_state_l2c_multilist_index_func(multilist_t *ml, void *obj)
{
panic("Header %p insert into arc_l2c_only %p", obj, ml);
}
#define WARN_IF_TUNING_IGNORED(tuning, value, do_warn) do { \
if ((do_warn) && (tuning) && ((tuning) != (value))) { \
cmn_err(CE_WARN, \
"ignoring tunable %s (using %llu instead)", \
(#tuning), (u_longlong_t)(value)); \
} \
} while (0)
/*
* Called during module initialization and periodically thereafter to
* apply reasonable changes to the exposed performance tunings. Can also be
* called explicitly by param_set_arc_*() functions when ARC tunables are
* updated manually. Non-zero zfs_* values which differ from the currently set
* values will be applied.
*/
void
arc_tuning_update(boolean_t verbose)
{
uint64_t allmem = arc_all_memory();
/* Valid range: 32M - <arc_c_max> */
if ((zfs_arc_min) && (zfs_arc_min != arc_c_min) &&
(zfs_arc_min >= 2ULL << SPA_MAXBLOCKSHIFT) &&
(zfs_arc_min <= arc_c_max)) {
arc_c_min = zfs_arc_min;
arc_c = MAX(arc_c, arc_c_min);
}
WARN_IF_TUNING_IGNORED(zfs_arc_min, arc_c_min, verbose);
/* Valid range: 64M - <all physical memory> */
if ((zfs_arc_max) && (zfs_arc_max != arc_c_max) &&
(zfs_arc_max >= MIN_ARC_MAX) && (zfs_arc_max < allmem) &&
(zfs_arc_max > arc_c_min)) {
arc_c_max = zfs_arc_max;
arc_c = MIN(arc_c, arc_c_max);
if (arc_dnode_limit > arc_c_max)
arc_dnode_limit = arc_c_max;
}
WARN_IF_TUNING_IGNORED(zfs_arc_max, arc_c_max, verbose);
/* Valid range: 0 - <all physical memory> */
arc_dnode_limit = zfs_arc_dnode_limit ? zfs_arc_dnode_limit :
MIN(zfs_arc_dnode_limit_percent, 100) * arc_c_max / 100;
WARN_IF_TUNING_IGNORED(zfs_arc_dnode_limit, arc_dnode_limit, verbose);
/* Valid range: 1 - N */
if (zfs_arc_grow_retry)
arc_grow_retry = zfs_arc_grow_retry;
/* Valid range: 1 - N */
if (zfs_arc_shrink_shift) {
arc_shrink_shift = zfs_arc_shrink_shift;
arc_no_grow_shift = MIN(arc_no_grow_shift, arc_shrink_shift -1);
}
/* Valid range: 1 - N ms */
if (zfs_arc_min_prefetch_ms)
arc_min_prefetch_ms = zfs_arc_min_prefetch_ms;
/* Valid range: 1 - N ms */
if (zfs_arc_min_prescient_prefetch_ms) {
arc_min_prescient_prefetch_ms =
zfs_arc_min_prescient_prefetch_ms;
}
/* Valid range: 0 - 100 */
if (zfs_arc_lotsfree_percent <= 100)
arc_lotsfree_percent = zfs_arc_lotsfree_percent;
WARN_IF_TUNING_IGNORED(zfs_arc_lotsfree_percent, arc_lotsfree_percent,
verbose);
/* Valid range: 0 - <all physical memory> */
if ((zfs_arc_sys_free) && (zfs_arc_sys_free != arc_sys_free))
arc_sys_free = MIN(zfs_arc_sys_free, allmem);
WARN_IF_TUNING_IGNORED(zfs_arc_sys_free, arc_sys_free, verbose);
}
static void
arc_state_multilist_init(multilist_t *ml,
multilist_sublist_index_func_t *index_func, int *maxcountp)
{
multilist_create(ml, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), index_func);
*maxcountp = MAX(*maxcountp, multilist_get_num_sublists(ml));
}
static void
arc_state_init(void)
{
int num_sublists = 0;
arc_state_multilist_init(&arc_mru->arcs_list[ARC_BUFC_METADATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_mru->arcs_list[ARC_BUFC_DATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_mfu->arcs_list[ARC_BUFC_DATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_uncached->arcs_list[ARC_BUFC_METADATA],
arc_state_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_uncached->arcs_list[ARC_BUFC_DATA],
arc_state_multilist_index_func, &num_sublists);
/*
* L2 headers should never be on the L2 state list since they don't
* have L1 headers allocated. Special index function asserts that.
*/
arc_state_multilist_init(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
arc_state_l2c_multilist_index_func, &num_sublists);
arc_state_multilist_init(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
arc_state_l2c_multilist_index_func, &num_sublists);
/*
* Keep track of the number of markers needed to reclaim buffers from
* any ARC state. The markers will be pre-allocated so as to minimize
* the number of memory allocations performed by the eviction thread.
*/
arc_state_evict_marker_count = num_sublists;
zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_uncached->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_uncached->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_anon->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_anon->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_mru->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_mru->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_mru_ghost->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_mru_ghost->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_mfu->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_mfu->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_mfu_ghost->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_mfu_ghost->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_l2c_only->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_l2c_only->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_create(&arc_uncached->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_create(&arc_uncached->arcs_size[ARC_BUFC_METADATA]);
wmsum_init(&arc_mru_ghost->arcs_hits[ARC_BUFC_DATA], 0);
wmsum_init(&arc_mru_ghost->arcs_hits[ARC_BUFC_METADATA], 0);
wmsum_init(&arc_mfu_ghost->arcs_hits[ARC_BUFC_DATA], 0);
wmsum_init(&arc_mfu_ghost->arcs_hits[ARC_BUFC_METADATA], 0);
wmsum_init(&arc_sums.arcstat_hits, 0);
wmsum_init(&arc_sums.arcstat_iohits, 0);
wmsum_init(&arc_sums.arcstat_misses, 0);
wmsum_init(&arc_sums.arcstat_demand_data_hits, 0);
wmsum_init(&arc_sums.arcstat_demand_data_iohits, 0);
wmsum_init(&arc_sums.arcstat_demand_data_misses, 0);
wmsum_init(&arc_sums.arcstat_demand_metadata_hits, 0);
wmsum_init(&arc_sums.arcstat_demand_metadata_iohits, 0);
wmsum_init(&arc_sums.arcstat_demand_metadata_misses, 0);
wmsum_init(&arc_sums.arcstat_prefetch_data_hits, 0);
wmsum_init(&arc_sums.arcstat_prefetch_data_iohits, 0);
wmsum_init(&arc_sums.arcstat_prefetch_data_misses, 0);
wmsum_init(&arc_sums.arcstat_prefetch_metadata_hits, 0);
wmsum_init(&arc_sums.arcstat_prefetch_metadata_iohits, 0);
wmsum_init(&arc_sums.arcstat_prefetch_metadata_misses, 0);
wmsum_init(&arc_sums.arcstat_mru_hits, 0);
wmsum_init(&arc_sums.arcstat_mru_ghost_hits, 0);
wmsum_init(&arc_sums.arcstat_mfu_hits, 0);
wmsum_init(&arc_sums.arcstat_mfu_ghost_hits, 0);
wmsum_init(&arc_sums.arcstat_uncached_hits, 0);
wmsum_init(&arc_sums.arcstat_deleted, 0);
wmsum_init(&arc_sums.arcstat_mutex_miss, 0);
wmsum_init(&arc_sums.arcstat_access_skip, 0);
wmsum_init(&arc_sums.arcstat_evict_skip, 0);
wmsum_init(&arc_sums.arcstat_evict_not_enough, 0);
wmsum_init(&arc_sums.arcstat_evict_l2_cached, 0);
wmsum_init(&arc_sums.arcstat_evict_l2_eligible, 0);
wmsum_init(&arc_sums.arcstat_evict_l2_eligible_mfu, 0);
wmsum_init(&arc_sums.arcstat_evict_l2_eligible_mru, 0);
wmsum_init(&arc_sums.arcstat_evict_l2_ineligible, 0);
wmsum_init(&arc_sums.arcstat_evict_l2_skip, 0);
wmsum_init(&arc_sums.arcstat_hash_collisions, 0);
wmsum_init(&arc_sums.arcstat_hash_chains, 0);
aggsum_init(&arc_sums.arcstat_size, 0);
wmsum_init(&arc_sums.arcstat_compressed_size, 0);
wmsum_init(&arc_sums.arcstat_uncompressed_size, 0);
wmsum_init(&arc_sums.arcstat_overhead_size, 0);
wmsum_init(&arc_sums.arcstat_hdr_size, 0);
wmsum_init(&arc_sums.arcstat_data_size, 0);
wmsum_init(&arc_sums.arcstat_metadata_size, 0);
wmsum_init(&arc_sums.arcstat_dbuf_size, 0);
wmsum_init(&arc_sums.arcstat_dnode_size, 0);
wmsum_init(&arc_sums.arcstat_bonus_size, 0);
wmsum_init(&arc_sums.arcstat_l2_hits, 0);
wmsum_init(&arc_sums.arcstat_l2_misses, 0);
wmsum_init(&arc_sums.arcstat_l2_prefetch_asize, 0);
wmsum_init(&arc_sums.arcstat_l2_mru_asize, 0);
wmsum_init(&arc_sums.arcstat_l2_mfu_asize, 0);
wmsum_init(&arc_sums.arcstat_l2_bufc_data_asize, 0);
wmsum_init(&arc_sums.arcstat_l2_bufc_metadata_asize, 0);
wmsum_init(&arc_sums.arcstat_l2_feeds, 0);
wmsum_init(&arc_sums.arcstat_l2_rw_clash, 0);
wmsum_init(&arc_sums.arcstat_l2_read_bytes, 0);
wmsum_init(&arc_sums.arcstat_l2_write_bytes, 0);
wmsum_init(&arc_sums.arcstat_l2_writes_sent, 0);
wmsum_init(&arc_sums.arcstat_l2_writes_done, 0);
wmsum_init(&arc_sums.arcstat_l2_writes_error, 0);
wmsum_init(&arc_sums.arcstat_l2_writes_lock_retry, 0);
wmsum_init(&arc_sums.arcstat_l2_evict_lock_retry, 0);
wmsum_init(&arc_sums.arcstat_l2_evict_reading, 0);
wmsum_init(&arc_sums.arcstat_l2_evict_l1cached, 0);
wmsum_init(&arc_sums.arcstat_l2_free_on_write, 0);
wmsum_init(&arc_sums.arcstat_l2_abort_lowmem, 0);
wmsum_init(&arc_sums.arcstat_l2_cksum_bad, 0);
wmsum_init(&arc_sums.arcstat_l2_io_error, 0);
wmsum_init(&arc_sums.arcstat_l2_lsize, 0);
wmsum_init(&arc_sums.arcstat_l2_psize, 0);
aggsum_init(&arc_sums.arcstat_l2_hdr_size, 0);
wmsum_init(&arc_sums.arcstat_l2_log_blk_writes, 0);
wmsum_init(&arc_sums.arcstat_l2_log_blk_asize, 0);
wmsum_init(&arc_sums.arcstat_l2_log_blk_count, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_success, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_abort_unsupported, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_abort_io_errors, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_abort_dh_errors, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_abort_cksum_lb_errors, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_abort_lowmem, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_size, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_asize, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_bufs, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_bufs_precached, 0);
wmsum_init(&arc_sums.arcstat_l2_rebuild_log_blks, 0);
wmsum_init(&arc_sums.arcstat_memory_throttle_count, 0);
wmsum_init(&arc_sums.arcstat_memory_direct_count, 0);
wmsum_init(&arc_sums.arcstat_memory_indirect_count, 0);
wmsum_init(&arc_sums.arcstat_prune, 0);
wmsum_init(&arc_sums.arcstat_meta_used, 0);
wmsum_init(&arc_sums.arcstat_async_upgrade_sync, 0);
wmsum_init(&arc_sums.arcstat_predictive_prefetch, 0);
wmsum_init(&arc_sums.arcstat_demand_hit_predictive_prefetch, 0);
wmsum_init(&arc_sums.arcstat_demand_iohit_predictive_prefetch, 0);
wmsum_init(&arc_sums.arcstat_prescient_prefetch, 0);
wmsum_init(&arc_sums.arcstat_demand_hit_prescient_prefetch, 0);
wmsum_init(&arc_sums.arcstat_demand_iohit_prescient_prefetch, 0);
wmsum_init(&arc_sums.arcstat_raw_size, 0);
wmsum_init(&arc_sums.arcstat_cached_only_in_progress, 0);
wmsum_init(&arc_sums.arcstat_abd_chunk_waste_size, 0);
arc_anon->arcs_state = ARC_STATE_ANON;
arc_mru->arcs_state = ARC_STATE_MRU;
arc_mru_ghost->arcs_state = ARC_STATE_MRU_GHOST;
arc_mfu->arcs_state = ARC_STATE_MFU;
arc_mfu_ghost->arcs_state = ARC_STATE_MFU_GHOST;
arc_l2c_only->arcs_state = ARC_STATE_L2C_ONLY;
arc_uncached->arcs_state = ARC_STATE_UNCACHED;
}
static void
arc_state_fini(void)
{
zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_uncached->arcs_esize[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_uncached->arcs_esize[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_anon->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_anon->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_mru->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_mru->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_mru_ghost->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_mru_ghost->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_mfu->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_mfu->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_mfu_ghost->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_mfu_ghost->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_l2c_only->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_l2c_only->arcs_size[ARC_BUFC_METADATA]);
zfs_refcount_destroy(&arc_uncached->arcs_size[ARC_BUFC_DATA]);
zfs_refcount_destroy(&arc_uncached->arcs_size[ARC_BUFC_METADATA]);
multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]);
multilist_destroy(&arc_uncached->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(&arc_uncached->arcs_list[ARC_BUFC_DATA]);
wmsum_fini(&arc_mru_ghost->arcs_hits[ARC_BUFC_DATA]);
wmsum_fini(&arc_mru_ghost->arcs_hits[ARC_BUFC_METADATA]);
wmsum_fini(&arc_mfu_ghost->arcs_hits[ARC_BUFC_DATA]);
wmsum_fini(&arc_mfu_ghost->arcs_hits[ARC_BUFC_METADATA]);
wmsum_fini(&arc_sums.arcstat_hits);
wmsum_fini(&arc_sums.arcstat_iohits);
wmsum_fini(&arc_sums.arcstat_misses);
wmsum_fini(&arc_sums.arcstat_demand_data_hits);
wmsum_fini(&arc_sums.arcstat_demand_data_iohits);
wmsum_fini(&arc_sums.arcstat_demand_data_misses);
wmsum_fini(&arc_sums.arcstat_demand_metadata_hits);
wmsum_fini(&arc_sums.arcstat_demand_metadata_iohits);
wmsum_fini(&arc_sums.arcstat_demand_metadata_misses);
wmsum_fini(&arc_sums.arcstat_prefetch_data_hits);
wmsum_fini(&arc_sums.arcstat_prefetch_data_iohits);
wmsum_fini(&arc_sums.arcstat_prefetch_data_misses);
wmsum_fini(&arc_sums.arcstat_prefetch_metadata_hits);
wmsum_fini(&arc_sums.arcstat_prefetch_metadata_iohits);
wmsum_fini(&arc_sums.arcstat_prefetch_metadata_misses);
wmsum_fini(&arc_sums.arcstat_mru_hits);
wmsum_fini(&arc_sums.arcstat_mru_ghost_hits);
wmsum_fini(&arc_sums.arcstat_mfu_hits);
wmsum_fini(&arc_sums.arcstat_mfu_ghost_hits);
wmsum_fini(&arc_sums.arcstat_uncached_hits);
wmsum_fini(&arc_sums.arcstat_deleted);
wmsum_fini(&arc_sums.arcstat_mutex_miss);
wmsum_fini(&arc_sums.arcstat_access_skip);
wmsum_fini(&arc_sums.arcstat_evict_skip);
wmsum_fini(&arc_sums.arcstat_evict_not_enough);
wmsum_fini(&arc_sums.arcstat_evict_l2_cached);
wmsum_fini(&arc_sums.arcstat_evict_l2_eligible);
wmsum_fini(&arc_sums.arcstat_evict_l2_eligible_mfu);
wmsum_fini(&arc_sums.arcstat_evict_l2_eligible_mru);
wmsum_fini(&arc_sums.arcstat_evict_l2_ineligible);
wmsum_fini(&arc_sums.arcstat_evict_l2_skip);
wmsum_fini(&arc_sums.arcstat_hash_collisions);
wmsum_fini(&arc_sums.arcstat_hash_chains);
aggsum_fini(&arc_sums.arcstat_size);
wmsum_fini(&arc_sums.arcstat_compressed_size);
wmsum_fini(&arc_sums.arcstat_uncompressed_size);
wmsum_fini(&arc_sums.arcstat_overhead_size);
wmsum_fini(&arc_sums.arcstat_hdr_size);
wmsum_fini(&arc_sums.arcstat_data_size);
wmsum_fini(&arc_sums.arcstat_metadata_size);
wmsum_fini(&arc_sums.arcstat_dbuf_size);
wmsum_fini(&arc_sums.arcstat_dnode_size);
wmsum_fini(&arc_sums.arcstat_bonus_size);
wmsum_fini(&arc_sums.arcstat_l2_hits);
wmsum_fini(&arc_sums.arcstat_l2_misses);
wmsum_fini(&arc_sums.arcstat_l2_prefetch_asize);
wmsum_fini(&arc_sums.arcstat_l2_mru_asize);
wmsum_fini(&arc_sums.arcstat_l2_mfu_asize);
wmsum_fini(&arc_sums.arcstat_l2_bufc_data_asize);
wmsum_fini(&arc_sums.arcstat_l2_bufc_metadata_asize);
wmsum_fini(&arc_sums.arcstat_l2_feeds);
wmsum_fini(&arc_sums.arcstat_l2_rw_clash);
wmsum_fini(&arc_sums.arcstat_l2_read_bytes);
wmsum_fini(&arc_sums.arcstat_l2_write_bytes);
wmsum_fini(&arc_sums.arcstat_l2_writes_sent);
wmsum_fini(&arc_sums.arcstat_l2_writes_done);
wmsum_fini(&arc_sums.arcstat_l2_writes_error);
wmsum_fini(&arc_sums.arcstat_l2_writes_lock_retry);
wmsum_fini(&arc_sums.arcstat_l2_evict_lock_retry);
wmsum_fini(&arc_sums.arcstat_l2_evict_reading);
wmsum_fini(&arc_sums.arcstat_l2_evict_l1cached);
wmsum_fini(&arc_sums.arcstat_l2_free_on_write);
wmsum_fini(&arc_sums.arcstat_l2_abort_lowmem);
wmsum_fini(&arc_sums.arcstat_l2_cksum_bad);
wmsum_fini(&arc_sums.arcstat_l2_io_error);
wmsum_fini(&arc_sums.arcstat_l2_lsize);
wmsum_fini(&arc_sums.arcstat_l2_psize);
aggsum_fini(&arc_sums.arcstat_l2_hdr_size);
wmsum_fini(&arc_sums.arcstat_l2_log_blk_writes);
wmsum_fini(&arc_sums.arcstat_l2_log_blk_asize);
wmsum_fini(&arc_sums.arcstat_l2_log_blk_count);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_success);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_abort_unsupported);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_abort_io_errors);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_abort_dh_errors);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_abort_cksum_lb_errors);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_abort_lowmem);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_size);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_asize);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_bufs);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_bufs_precached);
wmsum_fini(&arc_sums.arcstat_l2_rebuild_log_blks);
wmsum_fini(&arc_sums.arcstat_memory_throttle_count);
wmsum_fini(&arc_sums.arcstat_memory_direct_count);
wmsum_fini(&arc_sums.arcstat_memory_indirect_count);
wmsum_fini(&arc_sums.arcstat_prune);
wmsum_fini(&arc_sums.arcstat_meta_used);
wmsum_fini(&arc_sums.arcstat_async_upgrade_sync);
wmsum_fini(&arc_sums.arcstat_predictive_prefetch);
wmsum_fini(&arc_sums.arcstat_demand_hit_predictive_prefetch);
wmsum_fini(&arc_sums.arcstat_demand_iohit_predictive_prefetch);
wmsum_fini(&arc_sums.arcstat_prescient_prefetch);
wmsum_fini(&arc_sums.arcstat_demand_hit_prescient_prefetch);
wmsum_fini(&arc_sums.arcstat_demand_iohit_prescient_prefetch);
wmsum_fini(&arc_sums.arcstat_raw_size);
wmsum_fini(&arc_sums.arcstat_cached_only_in_progress);
wmsum_fini(&arc_sums.arcstat_abd_chunk_waste_size);
}
uint64_t
arc_target_bytes(void)
{
return (arc_c);
}
void
arc_set_limits(uint64_t allmem)
{
/* Set min cache to 1/32 of all memory, or 32MB, whichever is more. */
arc_c_min = MAX(allmem / 32, 2ULL << SPA_MAXBLOCKSHIFT);
/* How to set default max varies by platform. */
arc_c_max = arc_default_max(arc_c_min, allmem);
}
void
arc_init(void)
{
uint64_t percent, allmem = arc_all_memory();
mutex_init(&arc_evict_lock, NULL, MUTEX_DEFAULT, NULL);
list_create(&arc_evict_waiters, sizeof (arc_evict_waiter_t),
offsetof(arc_evict_waiter_t, aew_node));
arc_min_prefetch_ms = 1000;
arc_min_prescient_prefetch_ms = 6000;
#if defined(_KERNEL)
arc_lowmem_init();
#endif
arc_set_limits(allmem);
#ifdef _KERNEL
/*
* If zfs_arc_max is non-zero at init, meaning it was set in the kernel
* environment before the module was loaded, don't block setting the
* maximum because it is less than arc_c_min, instead, reset arc_c_min
* to a lower value.
* zfs_arc_min will be handled by arc_tuning_update().
*/
if (zfs_arc_max != 0 && zfs_arc_max >= MIN_ARC_MAX &&
zfs_arc_max < allmem) {
arc_c_max = zfs_arc_max;
if (arc_c_min >= arc_c_max) {
arc_c_min = MAX(zfs_arc_max / 2,
2ULL << SPA_MAXBLOCKSHIFT);
}
}
#else
/*
* In userland, there's only the memory pressure that we artificially
* create (see arc_available_memory()). Don't let arc_c get too
* small, because it can cause transactions to be larger than
* arc_c, causing arc_tempreserve_space() to fail.
*/
arc_c_min = MAX(arc_c_max / 2, 2ULL << SPA_MAXBLOCKSHIFT);
#endif
arc_c = arc_c_min;
/*
* 32-bit fixed point fractions of metadata from total ARC size,
* MRU data from all data and MRU metadata from all metadata.
*/
arc_meta = (1ULL << 32) / 4; /* Metadata is 25% of arc_c. */
arc_pd = (1ULL << 32) / 2; /* Data MRU is 50% of data. */
arc_pm = (1ULL << 32) / 2; /* Metadata MRU is 50% of metadata. */
percent = MIN(zfs_arc_dnode_limit_percent, 100);
arc_dnode_limit = arc_c_max * percent / 100;
/* Apply user specified tunings */
arc_tuning_update(B_TRUE);
/* if kmem_flags are set, lets try to use less memory */
if (kmem_debugging())
arc_c = arc_c / 2;
if (arc_c < arc_c_min)
arc_c = arc_c_min;
arc_register_hotplug();
arc_state_init();
buf_init();
list_create(&arc_prune_list, sizeof (arc_prune_t),
offsetof(arc_prune_t, p_node));
mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL);
arc_prune_taskq = taskq_create("arc_prune", zfs_arc_prune_task_threads,
defclsyspri, 100, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
if (arc_ksp != NULL) {
arc_ksp->ks_data = &arc_stats;
arc_ksp->ks_update = arc_kstat_update;
kstat_install(arc_ksp);
}
arc_state_evict_markers =
arc_state_alloc_markers(arc_state_evict_marker_count);
arc_evict_zthr = zthr_create_timer("arc_evict",
arc_evict_cb_check, arc_evict_cb, NULL, SEC2NSEC(1), defclsyspri);
arc_reap_zthr = zthr_create_timer("arc_reap",
arc_reap_cb_check, arc_reap_cb, NULL, SEC2NSEC(1), minclsyspri);
arc_warm = B_FALSE;
/*
* Calculate maximum amount of dirty data per pool.
*
* If it has been set by a module parameter, take that.
* Otherwise, use a percentage of physical memory defined by
* zfs_dirty_data_max_percent (default 10%) with a cap at
* zfs_dirty_data_max_max (default 4G or 25% of physical memory).
*/
#ifdef __LP64__
if (zfs_dirty_data_max_max == 0)
zfs_dirty_data_max_max = MIN(4ULL * 1024 * 1024 * 1024,
allmem * zfs_dirty_data_max_max_percent / 100);
#else
if (zfs_dirty_data_max_max == 0)
zfs_dirty_data_max_max = MIN(1ULL * 1024 * 1024 * 1024,
allmem * zfs_dirty_data_max_max_percent / 100);
#endif
if (zfs_dirty_data_max == 0) {
zfs_dirty_data_max = allmem *
zfs_dirty_data_max_percent / 100;
zfs_dirty_data_max = MIN(zfs_dirty_data_max,
zfs_dirty_data_max_max);
}
if (zfs_wrlog_data_max == 0) {
/*
* dp_wrlog_total is reduced for each txg at the end of
* spa_sync(). However, dp_dirty_total is reduced every time
* a block is written out. Thus under normal operation,
* dp_wrlog_total could grow 2 times as big as
* zfs_dirty_data_max.
*/
zfs_wrlog_data_max = zfs_dirty_data_max * 2;
}
}
void
arc_fini(void)
{
arc_prune_t *p;
#ifdef _KERNEL
arc_lowmem_fini();
#endif /* _KERNEL */
/* Use B_TRUE to ensure *all* buffers are evicted */
arc_flush(NULL, B_TRUE);
if (arc_ksp != NULL) {
kstat_delete(arc_ksp);
arc_ksp = NULL;
}
taskq_wait(arc_prune_taskq);
taskq_destroy(arc_prune_taskq);
mutex_enter(&arc_prune_mtx);
while ((p = list_remove_head(&arc_prune_list)) != NULL) {
zfs_refcount_remove(&p->p_refcnt, &arc_prune_list);
zfs_refcount_destroy(&p->p_refcnt);
kmem_free(p, sizeof (*p));
}
mutex_exit(&arc_prune_mtx);
list_destroy(&arc_prune_list);
mutex_destroy(&arc_prune_mtx);
(void) zthr_cancel(arc_evict_zthr);
(void) zthr_cancel(arc_reap_zthr);
arc_state_free_markers(arc_state_evict_markers,
arc_state_evict_marker_count);
mutex_destroy(&arc_evict_lock);
list_destroy(&arc_evict_waiters);
/*
* Free any buffers that were tagged for destruction. This needs
* to occur before arc_state_fini() runs and destroys the aggsum
* values which are updated when freeing scatter ABDs.
*/
l2arc_do_free_on_write();
/*
* buf_fini() must proceed arc_state_fini() because buf_fin() may
* trigger the release of kmem magazines, which can callback to
* arc_space_return() which accesses aggsums freed in act_state_fini().
*/
buf_fini();
arc_state_fini();
arc_unregister_hotplug();
/*
* We destroy the zthrs after all the ARC state has been
* torn down to avoid the case of them receiving any
* wakeup() signals after they are destroyed.
*/
zthr_destroy(arc_evict_zthr);
zthr_destroy(arc_reap_zthr);
ASSERT0(arc_loaned_bytes);
}
/*
* Level 2 ARC
*
* The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
* It uses dedicated storage devices to hold cached data, which are populated
* using large infrequent writes. The main role of this cache is to boost
* the performance of random read workloads. The intended L2ARC devices
* include short-stroked disks, solid state disks, and other media with
* substantially faster read latency than disk.
*
* +-----------------------+
* | ARC |
* +-----------------------+
* | ^ ^
* | | |
* l2arc_feed_thread() arc_read()
* | | |
* | l2arc read |
* V | |
* +---------------+ |
* | L2ARC | |
* +---------------+ |
* | ^ |
* l2arc_write() | |
* | | |
* V | |
* +-------+ +-------+
* | vdev | | vdev |
* | cache | | cache |
* +-------+ +-------+
* +=========+ .-----.
* : L2ARC : |-_____-|
* : devices : | Disks |
* +=========+ `-_____-'
*
* Read requests are satisfied from the following sources, in order:
*
* 1) ARC
* 2) vdev cache of L2ARC devices
* 3) L2ARC devices
* 4) vdev cache of disks
* 5) disks
*
* Some L2ARC device types exhibit extremely slow write performance.
* To accommodate for this there are some significant differences between
* the L2ARC and traditional cache design:
*
* 1. There is no eviction path from the ARC to the L2ARC. Evictions from
* the ARC behave as usual, freeing buffers and placing headers on ghost
* lists. The ARC does not send buffers to the L2ARC during eviction as
* this would add inflated write latencies for all ARC memory pressure.
*
* 2. The L2ARC attempts to cache data from the ARC before it is evicted.
* It does this by periodically scanning buffers from the eviction-end of
* the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
* not already there. It scans until a headroom of buffers is satisfied,
* which itself is a buffer for ARC eviction. If a compressible buffer is
* found during scanning and selected for writing to an L2ARC device, we
* temporarily boost scanning headroom during the next scan cycle to make
* sure we adapt to compression effects (which might significantly reduce
* the data volume we write to L2ARC). The thread that does this is
* l2arc_feed_thread(), illustrated below; example sizes are included to
* provide a better sense of ratio than this diagram:
*
* head --> tail
* +---------------------+----------+
* ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
* +---------------------+----------+ | o L2ARC eligible
* ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
* +---------------------+----------+ |
* 15.9 Gbytes ^ 32 Mbytes |
* headroom |
* l2arc_feed_thread()
* |
* l2arc write hand <--[oooo]--'
* | 8 Mbyte
* | write max
* V
* +==============================+
* L2ARC dev |####|#|###|###| |####| ... |
* +==============================+
* 32 Gbytes
*
* 3. If an ARC buffer is copied to the L2ARC but then hit instead of
* evicted, then the L2ARC has cached a buffer much sooner than it probably
* needed to, potentially wasting L2ARC device bandwidth and storage. It is
* safe to say that this is an uncommon case, since buffers at the end of
* the ARC lists have moved there due to inactivity.
*
* 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
* then the L2ARC simply misses copying some buffers. This serves as a
* pressure valve to prevent heavy read workloads from both stalling the ARC
* with waits and clogging the L2ARC with writes. This also helps prevent
* the potential for the L2ARC to churn if it attempts to cache content too
* quickly, such as during backups of the entire pool.
*
* 5. After system boot and before the ARC has filled main memory, there are
* no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
* lists can remain mostly static. Instead of searching from tail of these
* lists as pictured, the l2arc_feed_thread() will search from the list heads
* for eligible buffers, greatly increasing its chance of finding them.
*
* The L2ARC device write speed is also boosted during this time so that
* the L2ARC warms up faster. Since there have been no ARC evictions yet,
* there are no L2ARC reads, and no fear of degrading read performance
* through increased writes.
*
* 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
* the vdev queue can aggregate them into larger and fewer writes. Each
* device is written to in a rotor fashion, sweeping writes through
* available space then repeating.
*
* 7. The L2ARC does not store dirty content. It never needs to flush
* write buffers back to disk based storage.
*
* 8. If an ARC buffer is written (and dirtied) which also exists in the
* L2ARC, the now stale L2ARC buffer is immediately dropped.
*
* The performance of the L2ARC can be tweaked by a number of tunables, which
* may be necessary for different workloads:
*
* l2arc_write_max max write bytes per interval
* l2arc_write_boost extra write bytes during device warmup
* l2arc_noprefetch skip caching prefetched buffers
* l2arc_headroom number of max device writes to precache
* l2arc_headroom_boost when we find compressed buffers during ARC
* scanning, we multiply headroom by this
* percentage factor for the next scan cycle,
* since more compressed buffers are likely to
* be present
* l2arc_feed_secs seconds between L2ARC writing
*
* Tunables may be removed or added as future performance improvements are
* integrated, and also may become zpool properties.
*
* There are three key functions that control how the L2ARC warms up:
*
* l2arc_write_eligible() check if a buffer is eligible to cache
* l2arc_write_size() calculate how much to write
* l2arc_write_interval() calculate sleep delay between writes
*
* These three functions determine what to write, how much, and how quickly
* to send writes.
*
* L2ARC persistence:
*
* When writing buffers to L2ARC, we periodically add some metadata to
* make sure we can pick them up after reboot, thus dramatically reducing
* the impact that any downtime has on the performance of storage systems
* with large caches.
*
* The implementation works fairly simply by integrating the following two
* modifications:
*
* *) When writing to the L2ARC, we occasionally write a "l2arc log block",
* which is an additional piece of metadata which describes what's been
* written. This allows us to rebuild the arc_buf_hdr_t structures of the
* main ARC buffers. There are 2 linked-lists of log blocks headed by
* dh_start_lbps[2]. We alternate which chain we append to, so they are
* time-wise and offset-wise interleaved, but that is an optimization rather
* than for correctness. The log block also includes a pointer to the
* previous block in its chain.
*
* *) We reserve SPA_MINBLOCKSIZE of space at the start of each L2ARC device
* for our header bookkeeping purposes. This contains a device header,
* which contains our top-level reference structures. We update it each
* time we write a new log block, so that we're able to locate it in the
* L2ARC device. If this write results in an inconsistent device header
* (e.g. due to power failure), we detect this by verifying the header's
* checksum and simply fail to reconstruct the L2ARC after reboot.
*
* Implementation diagram:
*
* +=== L2ARC device (not to scale) ======================================+
* | ___two newest log block pointers__.__________ |
* | / \dh_start_lbps[1] |
* | / \ \dh_start_lbps[0]|
* |.___/__. V V |
* ||L2 dev|....|lb |bufs |lb |bufs |lb |bufs |lb |bufs |lb |---(empty)---|
* || hdr| ^ /^ /^ / / |
* |+------+ ...--\-------/ \-----/--\------/ / |
* | \--------------/ \--------------/ |
* +======================================================================+
*
* As can be seen on the diagram, rather than using a simple linked list,
* we use a pair of linked lists with alternating elements. This is a
* performance enhancement due to the fact that we only find out the
* address of the next log block access once the current block has been
* completely read in. Obviously, this hurts performance, because we'd be
* keeping the device's I/O queue at only a 1 operation deep, thus
* incurring a large amount of I/O round-trip latency. Having two lists
* allows us to fetch two log blocks ahead of where we are currently
* rebuilding L2ARC buffers.
*
* On-device data structures:
*
* L2ARC device header: l2arc_dev_hdr_phys_t
* L2ARC log block: l2arc_log_blk_phys_t
*
* L2ARC reconstruction:
*
* When writing data, we simply write in the standard rotary fashion,
* evicting buffers as we go and simply writing new data over them (writing
* a new log block every now and then). This obviously means that once we
* loop around the end of the device, we will start cutting into an already
* committed log block (and its referenced data buffers), like so:
*
* current write head__ __old tail
* \ /
* V V
* <--|bufs |lb |bufs |lb | |bufs |lb |bufs |lb |-->
* ^ ^^^^^^^^^___________________________________
* | \
* <<nextwrite>> may overwrite this blk and/or its bufs --'
*
* When importing the pool, we detect this situation and use it to stop
* our scanning process (see l2arc_rebuild).
*
* There is one significant caveat to consider when rebuilding ARC contents
* from an L2ARC device: what about invalidated buffers? Given the above
* construction, we cannot update blocks which we've already written to amend
* them to remove buffers which were invalidated. Thus, during reconstruction,
* we might be populating the cache with buffers for data that's not on the
* main pool anymore, or may have been overwritten!
*
* As it turns out, this isn't a problem. Every arc_read request includes
* both the DVA and, crucially, the birth TXG of the BP the caller is
* looking for. So even if the cache were populated by completely rotten
* blocks for data that had been long deleted and/or overwritten, we'll
* never actually return bad data from the cache, since the DVA with the
* birth TXG uniquely identify a block in space and time - once created,
* a block is immutable on disk. The worst thing we have done is wasted
* some time and memory at l2arc rebuild to reconstruct outdated ARC
* entries that will get dropped from the l2arc as it is being updated
* with new blocks.
*
* L2ARC buffers that have been evicted by l2arc_evict() ahead of the write
* hand are not restored. This is done by saving the offset (in bytes)
* l2arc_evict() has evicted to in the L2ARC device header and taking it
* into account when restoring buffers.
*/
static boolean_t
l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
{
/*
* A buffer is *not* eligible for the L2ARC if it:
* 1. belongs to a different spa.
* 2. is already cached on the L2ARC.
* 3. has an I/O in progress (it may be an incomplete read).
* 4. is flagged not eligible (zfs property).
*/
if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr))
return (B_FALSE);
return (B_TRUE);
}
static uint64_t
l2arc_write_size(l2arc_dev_t *dev)
{
uint64_t size;
/*
* Make sure our globals have meaningful values in case the user
* altered them.
*/
size = l2arc_write_max;
if (size == 0) {
cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
"be greater than zero, resetting it to the default (%d)",
L2ARC_WRITE_SIZE);
size = l2arc_write_max = L2ARC_WRITE_SIZE;
}
if (arc_warm == B_FALSE)
size += l2arc_write_boost;
/* We need to add in the worst case scenario of log block overhead. */
size += l2arc_log_blk_overhead(size, dev);
if (dev->l2ad_vdev->vdev_has_trim && l2arc_trim_ahead > 0) {
/*
* Trim ahead of the write size 64MB or (l2arc_trim_ahead/100)
* times the writesize, whichever is greater.
*/
size += MAX(64 * 1024 * 1024,
(size * l2arc_trim_ahead) / 100);
}
/*
* Make sure the write size does not exceed the size of the cache
* device. This is important in l2arc_evict(), otherwise infinite
* iteration can occur.
*/
if (size > dev->l2ad_end - dev->l2ad_start) {
cmn_err(CE_NOTE, "l2arc_write_max or l2arc_write_boost "
"plus the overhead of log blocks (persistent L2ARC, "
"%llu bytes) exceeds the size of the cache device "
"(guid %llu), resetting them to the default (%d)",
(u_longlong_t)l2arc_log_blk_overhead(size, dev),
(u_longlong_t)dev->l2ad_vdev->vdev_guid, L2ARC_WRITE_SIZE);
size = l2arc_write_max = l2arc_write_boost = L2ARC_WRITE_SIZE;
if (l2arc_trim_ahead > 1) {
cmn_err(CE_NOTE, "l2arc_trim_ahead set to 1");
l2arc_trim_ahead = 1;
}
if (arc_warm == B_FALSE)
size += l2arc_write_boost;
size += l2arc_log_blk_overhead(size, dev);
if (dev->l2ad_vdev->vdev_has_trim && l2arc_trim_ahead > 0) {
size += MAX(64 * 1024 * 1024,
(size * l2arc_trim_ahead) / 100);
}
}
return (size);
}
static clock_t
l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
{
clock_t interval, next, now;
/*
* If the ARC lists are busy, increase our write rate; if the
* lists are stale, idle back. This is achieved by checking
* how much we previously wrote - if it was more than half of
* what we wanted, schedule the next write much sooner.
*/
if (l2arc_feed_again && wrote > (wanted / 2))
interval = (hz * l2arc_feed_min_ms) / 1000;
else
interval = hz * l2arc_feed_secs;
now = ddi_get_lbolt();
next = MAX(now, MIN(now + interval, began + interval));
return (next);
}
/*
* Cycle through L2ARC devices. This is how L2ARC load balances.
* If a device is returned, this also returns holding the spa config lock.
*/
static l2arc_dev_t *
l2arc_dev_get_next(void)
{
l2arc_dev_t *first, *next = NULL;
/*
* Lock out the removal of spas (spa_namespace_lock), then removal
* of cache devices (l2arc_dev_mtx). Once a device has been selected,
* both locks will be dropped and a spa config lock held instead.
*/
mutex_enter(&spa_namespace_lock);
mutex_enter(&l2arc_dev_mtx);
/* if there are no vdevs, there is nothing to do */
if (l2arc_ndev == 0)
goto out;
first = NULL;
next = l2arc_dev_last;
do {
/* loop around the list looking for a non-faulted vdev */
if (next == NULL) {
next = list_head(l2arc_dev_list);
} else {
next = list_next(l2arc_dev_list, next);
if (next == NULL)
next = list_head(l2arc_dev_list);
}
/* if we have come back to the start, bail out */
if (first == NULL)
first = next;
else if (next == first)
break;
ASSERT3P(next, !=, NULL);
} while (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild ||
next->l2ad_trim_all);
/* if we were unable to find any usable vdevs, return NULL */
if (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild ||
next->l2ad_trim_all)
next = NULL;
l2arc_dev_last = next;
out:
mutex_exit(&l2arc_dev_mtx);
/*
* Grab the config lock to prevent the 'next' device from being
* removed while we are writing to it.
*/
if (next != NULL)
spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
mutex_exit(&spa_namespace_lock);
return (next);
}
/*
* Free buffers that were tagged for destruction.
*/
static void
l2arc_do_free_on_write(void)
{
l2arc_data_free_t *df;
mutex_enter(&l2arc_free_on_write_mtx);
while ((df = list_remove_head(l2arc_free_on_write)) != NULL) {
ASSERT3P(df->l2df_abd, !=, NULL);
abd_free(df->l2df_abd);
kmem_free(df, sizeof (l2arc_data_free_t));
}
mutex_exit(&l2arc_free_on_write_mtx);
}
/*
* A write to a cache device has completed. Update all headers to allow
* reads from these buffers to begin.
*/
static void
l2arc_write_done(zio_t *zio)
{
l2arc_write_callback_t *cb;
l2arc_lb_abd_buf_t *abd_buf;
l2arc_lb_ptr_buf_t *lb_ptr_buf;
l2arc_dev_t *dev;
l2arc_dev_hdr_phys_t *l2dhdr;
list_t *buflist;
arc_buf_hdr_t *head, *hdr, *hdr_prev;
kmutex_t *hash_lock;
int64_t bytes_dropped = 0;
cb = zio->io_private;
ASSERT3P(cb, !=, NULL);
dev = cb->l2wcb_dev;
l2dhdr = dev->l2ad_dev_hdr;
ASSERT3P(dev, !=, NULL);
head = cb->l2wcb_head;
ASSERT3P(head, !=, NULL);
buflist = &dev->l2ad_buflist;
ASSERT3P(buflist, !=, NULL);
DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
l2arc_write_callback_t *, cb);
/*
* All writes completed, or an error was hit.
*/
top:
mutex_enter(&dev->l2ad_mtx);
for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
hdr_prev = list_prev(buflist, hdr);
hash_lock = HDR_LOCK(hdr);
/*
* We cannot use mutex_enter or else we can deadlock
* with l2arc_write_buffers (due to swapping the order
* the hash lock and l2ad_mtx are taken).
*/
if (!mutex_tryenter(hash_lock)) {
/*
* Missed the hash lock. We must retry so we
* don't leave the ARC_FLAG_L2_WRITING bit set.
*/
ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
/*
* We don't want to rescan the headers we've
* already marked as having been written out, so
* we reinsert the head node so we can pick up
* where we left off.
*/
list_remove(buflist, head);
list_insert_after(buflist, hdr, head);
mutex_exit(&dev->l2ad_mtx);
/*
* We wait for the hash lock to become available
* to try and prevent busy waiting, and increase
* the chance we'll be able to acquire the lock
* the next time around.
*/
mutex_enter(hash_lock);
mutex_exit(hash_lock);
goto top;
}
/*
* We could not have been moved into the arc_l2c_only
* state while in-flight due to our ARC_FLAG_L2_WRITING
* bit being set. Let's just ensure that's being enforced.
*/
ASSERT(HDR_HAS_L1HDR(hdr));
/*
* Skipped - drop L2ARC entry and mark the header as no
* longer L2 eligibile.
*/
if (zio->io_error != 0) {
/*
* Error - drop L2ARC entry.
*/
list_remove(buflist, hdr);
arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
uint64_t psize = HDR_GET_PSIZE(hdr);
l2arc_hdr_arcstats_decrement(hdr);
bytes_dropped +=
vdev_psize_to_asize(dev->l2ad_vdev, psize);
(void) zfs_refcount_remove_many(&dev->l2ad_alloc,
arc_hdr_size(hdr), hdr);
}
/*
* Allow ARC to begin reads and ghost list evictions to
* this L2ARC entry.
*/
arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
mutex_exit(hash_lock);
}
/*
* Free the allocated abd buffers for writing the log blocks.
* If the zio failed reclaim the allocated space and remove the
* pointers to these log blocks from the log block pointer list
* of the L2ARC device.
*/
while ((abd_buf = list_remove_tail(&cb->l2wcb_abd_list)) != NULL) {
abd_free(abd_buf->abd);
zio_buf_free(abd_buf, sizeof (*abd_buf));
if (zio->io_error != 0) {
lb_ptr_buf = list_remove_head(&dev->l2ad_lbptr_list);
/*
* L2BLK_GET_PSIZE returns aligned size for log
* blocks.
*/
uint64_t asize =
L2BLK_GET_PSIZE((lb_ptr_buf->lb_ptr)->lbp_prop);
bytes_dropped += asize;
ARCSTAT_INCR(arcstat_l2_log_blk_asize, -asize);
ARCSTAT_BUMPDOWN(arcstat_l2_log_blk_count);
zfs_refcount_remove_many(&dev->l2ad_lb_asize, asize,
lb_ptr_buf);
zfs_refcount_remove(&dev->l2ad_lb_count, lb_ptr_buf);
kmem_free(lb_ptr_buf->lb_ptr,
sizeof (l2arc_log_blkptr_t));
kmem_free(lb_ptr_buf, sizeof (l2arc_lb_ptr_buf_t));
}
}
list_destroy(&cb->l2wcb_abd_list);
if (zio->io_error != 0) {
ARCSTAT_BUMP(arcstat_l2_writes_error);
/*
* Restore the lbps array in the header to its previous state.
* If the list of log block pointers is empty, zero out the
* log block pointers in the device header.
*/
lb_ptr_buf = list_head(&dev->l2ad_lbptr_list);
for (int i = 0; i < 2; i++) {
if (lb_ptr_buf == NULL) {
/*
* If the list is empty zero out the device
* header. Otherwise zero out the second log
* block pointer in the header.
*/
if (i == 0) {
memset(l2dhdr, 0,
dev->l2ad_dev_hdr_asize);
} else {
memset(&l2dhdr->dh_start_lbps[i], 0,
sizeof (l2arc_log_blkptr_t));
}
break;
}
memcpy(&l2dhdr->dh_start_lbps[i], lb_ptr_buf->lb_ptr,
sizeof (l2arc_log_blkptr_t));
lb_ptr_buf = list_next(&dev->l2ad_lbptr_list,
lb_ptr_buf);
}
}
ARCSTAT_BUMP(arcstat_l2_writes_done);
list_remove(buflist, head);
ASSERT(!HDR_HAS_L1HDR(head));
kmem_cache_free(hdr_l2only_cache, head);
mutex_exit(&dev->l2ad_mtx);
ASSERT(dev->l2ad_vdev != NULL);
vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
l2arc_do_free_on_write();
kmem_free(cb, sizeof (l2arc_write_callback_t));
}
static int
l2arc_untransform(zio_t *zio, l2arc_read_callback_t *cb)
{
int ret;
spa_t *spa = zio->io_spa;
arc_buf_hdr_t *hdr = cb->l2rcb_hdr;
blkptr_t *bp = zio->io_bp;
uint8_t salt[ZIO_DATA_SALT_LEN];
uint8_t iv[ZIO_DATA_IV_LEN];
uint8_t mac[ZIO_DATA_MAC_LEN];
boolean_t no_crypt = B_FALSE;
/*
* ZIL data is never be written to the L2ARC, so we don't need
* special handling for its unique MAC storage.
*/
ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG);
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
/*
* If the data was encrypted, decrypt it now. Note that
* we must check the bp here and not the hdr, since the
* hdr does not have its encryption parameters updated
* until arc_read_done().
*/
if (BP_IS_ENCRYPTED(bp)) {
abd_t *eabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr,
ARC_HDR_USE_RESERVE);
zio_crypt_decode_params_bp(bp, salt, iv);
zio_crypt_decode_mac_bp(bp, mac);
ret = spa_do_crypt_abd(B_FALSE, spa, &cb->l2rcb_zb,
BP_GET_TYPE(bp), BP_GET_DEDUP(bp), BP_SHOULD_BYTESWAP(bp),
salt, iv, mac, HDR_GET_PSIZE(hdr), eabd,
hdr->b_l1hdr.b_pabd, &no_crypt);
if (ret != 0) {
arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr);
goto error;
}
/*
* If we actually performed decryption, replace b_pabd
* with the decrypted data. Otherwise we can just throw
* our decryption buffer away.
*/
if (!no_crypt) {
arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
arc_hdr_size(hdr), hdr);
hdr->b_l1hdr.b_pabd = eabd;
zio->io_abd = eabd;
} else {
arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr);
}
}
/*
* If the L2ARC block was compressed, but ARC compression
* is disabled we decompress the data into a new buffer and
* replace the existing data.
*/
if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
!HDR_COMPRESSION_ENABLED(hdr)) {
abd_t *cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr,
ARC_HDR_USE_RESERVE);
void *tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr));
ret = zio_decompress_data(HDR_GET_COMPRESS(hdr),
hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr),
HDR_GET_LSIZE(hdr), &hdr->b_complevel);
if (ret != 0) {
abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
arc_free_data_abd(hdr, cabd, arc_hdr_size(hdr), hdr);
goto error;
}
abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
arc_hdr_size(hdr), hdr);
hdr->b_l1hdr.b_pabd = cabd;
zio->io_abd = cabd;
zio->io_size = HDR_GET_LSIZE(hdr);
}
return (0);
error:
return (ret);
}
/*
* A read to a cache device completed. Validate buffer contents before
* handing over to the regular ARC routines.
*/
static void
l2arc_read_done(zio_t *zio)
{
int tfm_error = 0;
l2arc_read_callback_t *cb = zio->io_private;
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
boolean_t valid_cksum;
boolean_t using_rdata = (BP_IS_ENCRYPTED(&cb->l2rcb_bp) &&
(cb->l2rcb_flags & ZIO_FLAG_RAW_ENCRYPT));
ASSERT3P(zio->io_vd, !=, NULL);
ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
ASSERT3P(cb, !=, NULL);
hdr = cb->l2rcb_hdr;
ASSERT3P(hdr, !=, NULL);
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
/*
* If the data was read into a temporary buffer,
* move it and free the buffer.
*/
if (cb->l2rcb_abd != NULL) {
ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
if (zio->io_error == 0) {
if (using_rdata) {
abd_copy(hdr->b_crypt_hdr.b_rabd,
cb->l2rcb_abd, arc_hdr_size(hdr));
} else {
abd_copy(hdr->b_l1hdr.b_pabd,
cb->l2rcb_abd, arc_hdr_size(hdr));
}
}
/*
* The following must be done regardless of whether
* there was an error:
* - free the temporary buffer
* - point zio to the real ARC buffer
* - set zio size accordingly
* These are required because zio is either re-used for
* an I/O of the block in the case of the error
* or the zio is passed to arc_read_done() and it
* needs real data.
*/
abd_free(cb->l2rcb_abd);
zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
if (using_rdata) {
ASSERT(HDR_HAS_RABD(hdr));
zio->io_abd = zio->io_orig_abd =
hdr->b_crypt_hdr.b_rabd;
} else {
ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
}
}
ASSERT3P(zio->io_abd, !=, NULL);
/*
* Check this survived the L2ARC journey.
*/
ASSERT(zio->io_abd == hdr->b_l1hdr.b_pabd ||
(HDR_HAS_RABD(hdr) && zio->io_abd == hdr->b_crypt_hdr.b_rabd));
zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
zio->io_prop.zp_complevel = hdr->b_complevel;
valid_cksum = arc_cksum_is_equal(hdr, zio);
/*
* b_rabd will always match the data as it exists on disk if it is
* being used. Therefore if we are reading into b_rabd we do not
* attempt to untransform the data.
*/
if (valid_cksum && !using_rdata)
tfm_error = l2arc_untransform(zio, cb);
if (valid_cksum && tfm_error == 0 && zio->io_error == 0 &&
!HDR_L2_EVICTED(hdr)) {
mutex_exit(hash_lock);
zio->io_private = hdr;
arc_read_done(zio);
} else {
/*
* Buffer didn't survive caching. Increment stats and
* reissue to the original storage device.
*/
if (zio->io_error != 0) {
ARCSTAT_BUMP(arcstat_l2_io_error);
} else {
zio->io_error = SET_ERROR(EIO);
}
if (!valid_cksum || tfm_error != 0)
ARCSTAT_BUMP(arcstat_l2_cksum_bad);
/*
* If there's no waiter, issue an async i/o to the primary
* storage now. If there *is* a waiter, the caller must
* issue the i/o in a context where it's OK to block.
*/
if (zio->io_waiter == NULL) {
zio_t *pio = zio_unique_parent(zio);
void *abd = (using_rdata) ?
hdr->b_crypt_hdr.b_rabd : hdr->b_l1hdr.b_pabd;
ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
zio = zio_read(pio, zio->io_spa, zio->io_bp,
abd, zio->io_size, arc_read_done,
hdr, zio->io_priority, cb->l2rcb_flags,
&cb->l2rcb_zb);
/*
* Original ZIO will be freed, so we need to update
* ARC header with the new ZIO pointer to be used
* by zio_change_priority() in arc_read().
*/
for (struct arc_callback *acb = hdr->b_l1hdr.b_acb;
acb != NULL; acb = acb->acb_next)
acb->acb_zio_head = zio;
mutex_exit(hash_lock);
zio_nowait(zio);
} else {
mutex_exit(hash_lock);
}
}
kmem_free(cb, sizeof (l2arc_read_callback_t));
}
/*
* This is the list priority from which the L2ARC will search for pages to
* cache. This is used within loops (0..3) to cycle through lists in the
* desired order. This order can have a significant effect on cache
* performance.
*
* Currently the metadata lists are hit first, MFU then MRU, followed by
* the data lists. This function returns a locked list, and also returns
* the lock pointer.
*/
static multilist_sublist_t *
l2arc_sublist_lock(int list_num)
{
multilist_t *ml = NULL;
unsigned int idx;
ASSERT(list_num >= 0 && list_num < L2ARC_FEED_TYPES);
switch (list_num) {
case 0:
ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
break;
case 1:
ml = &arc_mru->arcs_list[ARC_BUFC_METADATA];
break;
case 2:
ml = &arc_mfu->arcs_list[ARC_BUFC_DATA];
break;
case 3:
ml = &arc_mru->arcs_list[ARC_BUFC_DATA];
break;
default:
return (NULL);
}
/*
* Return a randomly-selected sublist. This is acceptable
* because the caller feeds only a little bit of data for each
* call (8MB). Subsequent calls will result in different
* sublists being selected.
*/
idx = multilist_get_random_index(ml);
return (multilist_sublist_lock(ml, idx));
}
/*
* Calculates the maximum overhead of L2ARC metadata log blocks for a given
* L2ARC write size. l2arc_evict and l2arc_write_size need to include this
* overhead in processing to make sure there is enough headroom available
* when writing buffers.
*/
static inline uint64_t
l2arc_log_blk_overhead(uint64_t write_sz, l2arc_dev_t *dev)
{
if (dev->l2ad_log_entries == 0) {
return (0);
} else {
uint64_t log_entries = write_sz >> SPA_MINBLOCKSHIFT;
uint64_t log_blocks = (log_entries +
dev->l2ad_log_entries - 1) /
dev->l2ad_log_entries;
return (vdev_psize_to_asize(dev->l2ad_vdev,
sizeof (l2arc_log_blk_phys_t)) * log_blocks);
}
}
/*
* Evict buffers from the device write hand to the distance specified in
* bytes. This distance may span populated buffers, it may span nothing.
* This is clearing a region on the L2ARC device ready for writing.
* If the 'all' boolean is set, every buffer is evicted.
*/
static void
l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
{
list_t *buflist;
arc_buf_hdr_t *hdr, *hdr_prev;
kmutex_t *hash_lock;
uint64_t taddr;
l2arc_lb_ptr_buf_t *lb_ptr_buf, *lb_ptr_buf_prev;
vdev_t *vd = dev->l2ad_vdev;
boolean_t rerun;
buflist = &dev->l2ad_buflist;
top:
rerun = B_FALSE;
if (dev->l2ad_hand + distance > dev->l2ad_end) {
/*
* When there is no space to accommodate upcoming writes,
* evict to the end. Then bump the write and evict hands
* to the start and iterate. This iteration does not
* happen indefinitely as we make sure in
* l2arc_write_size() that when the write hand is reset,
* the write size does not exceed the end of the device.
*/
rerun = B_TRUE;
taddr = dev->l2ad_end;
} else {
taddr = dev->l2ad_hand + distance;
}
DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
uint64_t, taddr, boolean_t, all);
if (!all) {
/*
* This check has to be placed after deciding whether to
* iterate (rerun).
*/
if (dev->l2ad_first) {
/*
* This is the first sweep through the device. There is
* nothing to evict. We have already trimmmed the
* whole device.
*/
goto out;
} else {
/*
* Trim the space to be evicted.
*/
if (vd->vdev_has_trim && dev->l2ad_evict < taddr &&
l2arc_trim_ahead > 0) {
/*
* We have to drop the spa_config lock because
* vdev_trim_range() will acquire it.
* l2ad_evict already accounts for the label
* size. To prevent vdev_trim_ranges() from
* adding it again, we subtract it from
* l2ad_evict.
*/
spa_config_exit(dev->l2ad_spa, SCL_L2ARC, dev);
vdev_trim_simple(vd,
dev->l2ad_evict - VDEV_LABEL_START_SIZE,
taddr - dev->l2ad_evict);
spa_config_enter(dev->l2ad_spa, SCL_L2ARC, dev,
RW_READER);
}
/*
* When rebuilding L2ARC we retrieve the evict hand
* from the header of the device. Of note, l2arc_evict()
* does not actually delete buffers from the cache
* device, but trimming may do so depending on the
* hardware implementation. Thus keeping track of the
* evict hand is useful.
*/
dev->l2ad_evict = MAX(dev->l2ad_evict, taddr);
}
}
retry:
mutex_enter(&dev->l2ad_mtx);
/*
* We have to account for evicted log blocks. Run vdev_space_update()
* on log blocks whose offset (in bytes) is before the evicted offset
* (in bytes) by searching in the list of pointers to log blocks
* present in the L2ARC device.
*/
for (lb_ptr_buf = list_tail(&dev->l2ad_lbptr_list); lb_ptr_buf;
lb_ptr_buf = lb_ptr_buf_prev) {
lb_ptr_buf_prev = list_prev(&dev->l2ad_lbptr_list, lb_ptr_buf);
/* L2BLK_GET_PSIZE returns aligned size for log blocks */
uint64_t asize = L2BLK_GET_PSIZE(
(lb_ptr_buf->lb_ptr)->lbp_prop);
/*
* We don't worry about log blocks left behind (ie
* lbp_payload_start < l2ad_hand) because l2arc_write_buffers()
* will never write more than l2arc_evict() evicts.
*/
if (!all && l2arc_log_blkptr_valid(dev, lb_ptr_buf->lb_ptr)) {
break;
} else {
vdev_space_update(vd, -asize, 0, 0);
ARCSTAT_INCR(arcstat_l2_log_blk_asize, -asize);
ARCSTAT_BUMPDOWN(arcstat_l2_log_blk_count);
zfs_refcount_remove_many(&dev->l2ad_lb_asize, asize,
lb_ptr_buf);
zfs_refcount_remove(&dev->l2ad_lb_count, lb_ptr_buf);
list_remove(&dev->l2ad_lbptr_list, lb_ptr_buf);
kmem_free(lb_ptr_buf->lb_ptr,
sizeof (l2arc_log_blkptr_t));
kmem_free(lb_ptr_buf, sizeof (l2arc_lb_ptr_buf_t));
}
}
for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
hdr_prev = list_prev(buflist, hdr);
ASSERT(!HDR_EMPTY(hdr));
hash_lock = HDR_LOCK(hdr);
/*
* We cannot use mutex_enter or else we can deadlock
* with l2arc_write_buffers (due to swapping the order
* the hash lock and l2ad_mtx are taken).
*/
if (!mutex_tryenter(hash_lock)) {
/*
* Missed the hash lock. Retry.
*/
ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
mutex_exit(&dev->l2ad_mtx);
mutex_enter(hash_lock);
mutex_exit(hash_lock);
goto retry;
}
/*
* A header can't be on this list if it doesn't have L2 header.
*/
ASSERT(HDR_HAS_L2HDR(hdr));
/* Ensure this header has finished being written. */
ASSERT(!HDR_L2_WRITING(hdr));
ASSERT(!HDR_L2_WRITE_HEAD(hdr));
if (!all && (hdr->b_l2hdr.b_daddr >= dev->l2ad_evict ||
hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
/*
* We've evicted to the target address,
* or the end of the device.
*/
mutex_exit(hash_lock);
break;
}
if (!HDR_HAS_L1HDR(hdr)) {
ASSERT(!HDR_L2_READING(hdr));
/*
* This doesn't exist in the ARC. Destroy.
* arc_hdr_destroy() will call list_remove()
* and decrement arcstat_l2_lsize.
*/
arc_change_state(arc_anon, hdr);
arc_hdr_destroy(hdr);
} else {
ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
/*
* Invalidate issued or about to be issued
* reads, since we may be about to write
* over this location.
*/
if (HDR_L2_READING(hdr)) {
ARCSTAT_BUMP(arcstat_l2_evict_reading);
arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
}
arc_hdr_l2hdr_destroy(hdr);
}
mutex_exit(hash_lock);
}
mutex_exit(&dev->l2ad_mtx);
out:
/*
* We need to check if we evict all buffers, otherwise we may iterate
* unnecessarily.
*/
if (!all && rerun) {
/*
* Bump device hand to the device start if it is approaching the
* end. l2arc_evict() has already evicted ahead for this case.
*/
dev->l2ad_hand = dev->l2ad_start;
dev->l2ad_evict = dev->l2ad_start;
dev->l2ad_first = B_FALSE;
goto top;
}
if (!all) {
/*
* In case of cache device removal (all) the following
* assertions may be violated without functional consequences
* as the device is about to be removed.
*/
ASSERT3U(dev->l2ad_hand + distance, <, dev->l2ad_end);
if (!dev->l2ad_first)
ASSERT3U(dev->l2ad_hand, <=, dev->l2ad_evict);
}
}
/*
* Handle any abd transforms that might be required for writing to the L2ARC.
* If successful, this function will always return an abd with the data
* transformed as it is on disk in a new abd of asize bytes.
*/
static int
l2arc_apply_transforms(spa_t *spa, arc_buf_hdr_t *hdr, uint64_t asize,
abd_t **abd_out)
{
int ret;
void *tmp = NULL;
abd_t *cabd = NULL, *eabd = NULL, *to_write = hdr->b_l1hdr.b_pabd;
enum zio_compress compress = HDR_GET_COMPRESS(hdr);
uint64_t psize = HDR_GET_PSIZE(hdr);
uint64_t size = arc_hdr_size(hdr);
boolean_t ismd = HDR_ISTYPE_METADATA(hdr);
boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
dsl_crypto_key_t *dck = NULL;
uint8_t mac[ZIO_DATA_MAC_LEN] = { 0 };
boolean_t no_crypt = B_FALSE;
ASSERT((HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
!HDR_COMPRESSION_ENABLED(hdr)) ||
HDR_ENCRYPTED(hdr) || HDR_SHARED_DATA(hdr) || psize != asize);
ASSERT3U(psize, <=, asize);
/*
* If this data simply needs its own buffer, we simply allocate it
* and copy the data. This may be done to eliminate a dependency on a
* shared buffer or to reallocate the buffer to match asize.
*/
if (HDR_HAS_RABD(hdr) && asize != psize) {
ASSERT3U(asize, >=, psize);
to_write = abd_alloc_for_io(asize, ismd);
abd_copy(to_write, hdr->b_crypt_hdr.b_rabd, psize);
if (psize != asize)
abd_zero_off(to_write, psize, asize - psize);
goto out;
}
if ((compress == ZIO_COMPRESS_OFF || HDR_COMPRESSION_ENABLED(hdr)) &&
!HDR_ENCRYPTED(hdr)) {
ASSERT3U(size, ==, psize);
to_write = abd_alloc_for_io(asize, ismd);
abd_copy(to_write, hdr->b_l1hdr.b_pabd, size);
if (size != asize)
abd_zero_off(to_write, size, asize - size);
goto out;
}
if (compress != ZIO_COMPRESS_OFF && !HDR_COMPRESSION_ENABLED(hdr)) {
/*
* In some cases, we can wind up with size > asize, so
* we need to opt for the larger allocation option here.
*
* (We also need abd_return_buf_copy in all cases because
* it's an ASSERT() to modify the buffer before returning it
* with arc_return_buf(), and all the compressors
* write things before deciding to fail compression in nearly
* every case.)
*/
uint64_t bufsize = MAX(size, asize);
cabd = abd_alloc_for_io(bufsize, ismd);
tmp = abd_borrow_buf(cabd, bufsize);
psize = zio_compress_data(compress, to_write, &tmp, size,
hdr->b_complevel);
if (psize >= asize) {
psize = HDR_GET_PSIZE(hdr);
abd_return_buf_copy(cabd, tmp, bufsize);
HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
to_write = cabd;
abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize);
if (psize != asize)
abd_zero_off(to_write, psize, asize - psize);
goto encrypt;
}
ASSERT3U(psize, <=, HDR_GET_PSIZE(hdr));
if (psize < asize)
memset((char *)tmp + psize, 0, bufsize - psize);
psize = HDR_GET_PSIZE(hdr);
abd_return_buf_copy(cabd, tmp, bufsize);
to_write = cabd;
}
encrypt:
if (HDR_ENCRYPTED(hdr)) {
eabd = abd_alloc_for_io(asize, ismd);
/*
* If the dataset was disowned before the buffer
* made it to this point, the key to re-encrypt
* it won't be available. In this case we simply
* won't write the buffer to the L2ARC.
*/
ret = spa_keystore_lookup_key(spa, hdr->b_crypt_hdr.b_dsobj,
FTAG, &dck);
if (ret != 0)
goto error;
ret = zio_do_crypt_abd(B_TRUE, &dck->dck_key,
hdr->b_crypt_hdr.b_ot, bswap, hdr->b_crypt_hdr.b_salt,
hdr->b_crypt_hdr.b_iv, mac, psize, to_write, eabd,
&no_crypt);
if (ret != 0)
goto error;
if (no_crypt)
abd_copy(eabd, to_write, psize);
if (psize != asize)
abd_zero_off(eabd, psize, asize - psize);
/* assert that the MAC we got here matches the one we saved */
ASSERT0(memcmp(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN));
spa_keystore_dsl_key_rele(spa, dck, FTAG);
if (to_write == cabd)
abd_free(cabd);
to_write = eabd;
}
out:
ASSERT3P(to_write, !=, hdr->b_l1hdr.b_pabd);
*abd_out = to_write;
return (0);
error:
if (dck != NULL)
spa_keystore_dsl_key_rele(spa, dck, FTAG);
if (cabd != NULL)
abd_free(cabd);
if (eabd != NULL)
abd_free(eabd);
*abd_out = NULL;
return (ret);
}
static void
l2arc_blk_fetch_done(zio_t *zio)
{
l2arc_read_callback_t *cb;
cb = zio->io_private;
if (cb->l2rcb_abd != NULL)
abd_free(cb->l2rcb_abd);
kmem_free(cb, sizeof (l2arc_read_callback_t));
}
/*
* Find and write ARC buffers to the L2ARC device.
*
* An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
* for reading until they have completed writing.
* The headroom_boost is an in-out parameter used to maintain headroom boost
* state between calls to this function.
*
* Returns the number of bytes actually written (which may be smaller than
* the delta by which the device hand has changed due to alignment and the
* writing of log blocks).
*/
static uint64_t
l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
{
arc_buf_hdr_t *hdr, *hdr_prev, *head;
uint64_t write_asize, write_psize, write_lsize, headroom;
boolean_t full;
l2arc_write_callback_t *cb = NULL;
zio_t *pio, *wzio;
uint64_t guid = spa_load_guid(spa);
l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
ASSERT3P(dev->l2ad_vdev, !=, NULL);
pio = NULL;
write_lsize = write_asize = write_psize = 0;
full = B_FALSE;
head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
/*
* Copy buffers for L2ARC writing.
*/
for (int pass = 0; pass < L2ARC_FEED_TYPES; pass++) {
/*
* If pass == 1 or 3, we cache MRU metadata and data
* respectively.
*/
if (l2arc_mfuonly) {
if (pass == 1 || pass == 3)
continue;
}
multilist_sublist_t *mls = l2arc_sublist_lock(pass);
uint64_t passed_sz = 0;
VERIFY3P(mls, !=, NULL);
/*
* L2ARC fast warmup.
*
* Until the ARC is warm and starts to evict, read from the
* head of the ARC lists rather than the tail.
*/
if (arc_warm == B_FALSE)
hdr = multilist_sublist_head(mls);
else
hdr = multilist_sublist_tail(mls);
headroom = target_sz * l2arc_headroom;
if (zfs_compressed_arc_enabled)
headroom = (headroom * l2arc_headroom_boost) / 100;
for (; hdr; hdr = hdr_prev) {
kmutex_t *hash_lock;
abd_t *to_write = NULL;
if (arc_warm == B_FALSE)
hdr_prev = multilist_sublist_next(mls, hdr);
else
hdr_prev = multilist_sublist_prev(mls, hdr);
hash_lock = HDR_LOCK(hdr);
if (!mutex_tryenter(hash_lock)) {
/*
* Skip this buffer rather than waiting.
*/
continue;
}
passed_sz += HDR_GET_LSIZE(hdr);
if (l2arc_headroom != 0 && passed_sz > headroom) {
/*
* Searched too far.
*/
mutex_exit(hash_lock);
break;
}
if (!l2arc_write_eligible(guid, hdr)) {
mutex_exit(hash_lock);
continue;
}
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
ASSERT3U(arc_hdr_size(hdr), >, 0);
ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
HDR_HAS_RABD(hdr));
uint64_t psize = HDR_GET_PSIZE(hdr);
uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
psize);
/*
* If the allocated size of this buffer plus the max
* size for the pending log block exceeds the evicted
* target size, terminate writing buffers for this run.
*/
if (write_asize + asize +
sizeof (l2arc_log_blk_phys_t) > target_sz) {
full = B_TRUE;
mutex_exit(hash_lock);
break;
}
/*
* We rely on the L1 portion of the header below, so
* it's invalid for this header to have been evicted out
* of the ghost cache, prior to being written out. The
* ARC_FLAG_L2_WRITING bit ensures this won't happen.
*/
arc_hdr_set_flags(hdr, ARC_FLAG_L2_WRITING);
/*
* If this header has b_rabd, we can use this since it
* must always match the data exactly as it exists on
* disk. Otherwise, the L2ARC can normally use the
* hdr's data, but if we're sharing data between the
* hdr and one of its bufs, L2ARC needs its own copy of
* the data so that the ZIO below can't race with the
* buf consumer. To ensure that this copy will be
* available for the lifetime of the ZIO and be cleaned
* up afterwards, we add it to the l2arc_free_on_write
* queue. If we need to apply any transforms to the
* data (compression, encryption) we will also need the
* extra buffer.
*/
if (HDR_HAS_RABD(hdr) && psize == asize) {
to_write = hdr->b_crypt_hdr.b_rabd;
} else if ((HDR_COMPRESSION_ENABLED(hdr) ||
HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) &&
!HDR_ENCRYPTED(hdr) && !HDR_SHARED_DATA(hdr) &&
psize == asize) {
to_write = hdr->b_l1hdr.b_pabd;
} else {
int ret;
arc_buf_contents_t type = arc_buf_type(hdr);
ret = l2arc_apply_transforms(spa, hdr, asize,
&to_write);
if (ret != 0) {
arc_hdr_clear_flags(hdr,
ARC_FLAG_L2_WRITING);
mutex_exit(hash_lock);
continue;
}
l2arc_free_abd_on_write(to_write, asize, type);
}
if (pio == NULL) {
/*
* Insert a dummy header on the buflist so
* l2arc_write_done() can find where the
* write buffers begin without searching.
*/
mutex_enter(&dev->l2ad_mtx);
list_insert_head(&dev->l2ad_buflist, head);
mutex_exit(&dev->l2ad_mtx);
cb = kmem_alloc(
sizeof (l2arc_write_callback_t), KM_SLEEP);
cb->l2wcb_dev = dev;
cb->l2wcb_head = head;
/*
* Create a list to save allocated abd buffers
* for l2arc_log_blk_commit().
*/
list_create(&cb->l2wcb_abd_list,
sizeof (l2arc_lb_abd_buf_t),
offsetof(l2arc_lb_abd_buf_t, node));
pio = zio_root(spa, l2arc_write_done, cb,
ZIO_FLAG_CANFAIL);
}
hdr->b_l2hdr.b_dev = dev;
hdr->b_l2hdr.b_hits = 0;
hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
hdr->b_l2hdr.b_arcs_state =
hdr->b_l1hdr.b_state->arcs_state;
arc_hdr_set_flags(hdr, ARC_FLAG_HAS_L2HDR);
mutex_enter(&dev->l2ad_mtx);
list_insert_head(&dev->l2ad_buflist, hdr);
mutex_exit(&dev->l2ad_mtx);
(void) zfs_refcount_add_many(&dev->l2ad_alloc,
arc_hdr_size(hdr), hdr);
wzio = zio_write_phys(pio, dev->l2ad_vdev,
hdr->b_l2hdr.b_daddr, asize, to_write,
ZIO_CHECKSUM_OFF, NULL, hdr,
ZIO_PRIORITY_ASYNC_WRITE,
ZIO_FLAG_CANFAIL, B_FALSE);
write_lsize += HDR_GET_LSIZE(hdr);
DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
zio_t *, wzio);
write_psize += psize;
write_asize += asize;
dev->l2ad_hand += asize;
l2arc_hdr_arcstats_increment(hdr);
vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
mutex_exit(hash_lock);
/*
* Append buf info to current log and commit if full.
* arcstat_l2_{size,asize} kstats are updated
* internally.
*/
if (l2arc_log_blk_insert(dev, hdr)) {
/*
* l2ad_hand will be adjusted in
* l2arc_log_blk_commit().
*/
write_asize +=
l2arc_log_blk_commit(dev, pio, cb);
}
zio_nowait(wzio);
}
multilist_sublist_unlock(mls);
if (full == B_TRUE)
break;
}
/* No buffers selected for writing? */
if (pio == NULL) {
ASSERT0(write_lsize);
ASSERT(!HDR_HAS_L1HDR(head));
kmem_cache_free(hdr_l2only_cache, head);
/*
* Although we did not write any buffers l2ad_evict may
* have advanced.
*/
if (dev->l2ad_evict != l2dhdr->dh_evict)
l2arc_dev_hdr_update(dev);
return (0);
}
if (!dev->l2ad_first)
ASSERT3U(dev->l2ad_hand, <=, dev->l2ad_evict);
ASSERT3U(write_asize, <=, target_sz);
ARCSTAT_BUMP(arcstat_l2_writes_sent);
ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize);
dev->l2ad_writing = B_TRUE;
(void) zio_wait(pio);
dev->l2ad_writing = B_FALSE;
/*
* Update the device header after the zio completes as
* l2arc_write_done() may have updated the memory holding the log block
* pointers in the device header.
*/
l2arc_dev_hdr_update(dev);
return (write_asize);
}
static boolean_t
l2arc_hdr_limit_reached(void)
{
int64_t s = aggsum_upper_bound(&arc_sums.arcstat_l2_hdr_size);
return (arc_reclaim_needed() ||
(s > (arc_warm ? arc_c : arc_c_max) * l2arc_meta_percent / 100));
}
/*
* This thread feeds the L2ARC at regular intervals. This is the beating
* heart of the L2ARC.
*/
static __attribute__((noreturn)) void
l2arc_feed_thread(void *unused)
{
(void) unused;
callb_cpr_t cpr;
l2arc_dev_t *dev;
spa_t *spa;
uint64_t size, wrote;
clock_t begin, next = ddi_get_lbolt();
fstrans_cookie_t cookie;
CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
mutex_enter(&l2arc_feed_thr_lock);
cookie = spl_fstrans_mark();
while (l2arc_thread_exit == 0) {
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_idle(&l2arc_feed_thr_cv,
&l2arc_feed_thr_lock, next);
CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
next = ddi_get_lbolt() + hz;
/*
* Quick check for L2ARC devices.
*/
mutex_enter(&l2arc_dev_mtx);
if (l2arc_ndev == 0) {
mutex_exit(&l2arc_dev_mtx);
continue;
}
mutex_exit(&l2arc_dev_mtx);
begin = ddi_get_lbolt();
/*
* This selects the next l2arc device to write to, and in
* doing so the next spa to feed from: dev->l2ad_spa. This
* will return NULL if there are now no l2arc devices or if
* they are all faulted.
*
* If a device is returned, its spa's config lock is also
* held to prevent device removal. l2arc_dev_get_next()
* will grab and release l2arc_dev_mtx.
*/
if ((dev = l2arc_dev_get_next()) == NULL)
continue;
spa = dev->l2ad_spa;
ASSERT3P(spa, !=, NULL);
/*
* If the pool is read-only then force the feed thread to
* sleep a little longer.
*/
if (!spa_writeable(spa)) {
next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
spa_config_exit(spa, SCL_L2ARC, dev);
continue;
}
/*
* Avoid contributing to memory pressure.
*/
if (l2arc_hdr_limit_reached()) {
ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
spa_config_exit(spa, SCL_L2ARC, dev);
continue;
}
ARCSTAT_BUMP(arcstat_l2_feeds);
size = l2arc_write_size(dev);
/*
* Evict L2ARC buffers that will be overwritten.
*/
l2arc_evict(dev, size, B_FALSE);
/*
* Write ARC buffers.
*/
wrote = l2arc_write_buffers(spa, dev, size);
/*
* Calculate interval between writes.
*/
next = l2arc_write_interval(begin, size, wrote);
spa_config_exit(spa, SCL_L2ARC, dev);
}
spl_fstrans_unmark(cookie);
l2arc_thread_exit = 0;
cv_broadcast(&l2arc_feed_thr_cv);
CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
thread_exit();
}
boolean_t
l2arc_vdev_present(vdev_t *vd)
{
return (l2arc_vdev_get(vd) != NULL);
}
/*
* Returns the l2arc_dev_t associated with a particular vdev_t or NULL if
* the vdev_t isn't an L2ARC device.
*/
l2arc_dev_t *
l2arc_vdev_get(vdev_t *vd)
{
l2arc_dev_t *dev;
mutex_enter(&l2arc_dev_mtx);
for (dev = list_head(l2arc_dev_list); dev != NULL;
dev = list_next(l2arc_dev_list, dev)) {
if (dev->l2ad_vdev == vd)
break;
}
mutex_exit(&l2arc_dev_mtx);
return (dev);
}
static void
l2arc_rebuild_dev(l2arc_dev_t *dev, boolean_t reopen)
{
l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize;
spa_t *spa = dev->l2ad_spa;
/*
* The L2ARC has to hold at least the payload of one log block for
* them to be restored (persistent L2ARC). The payload of a log block
* depends on the amount of its log entries. We always write log blocks
* with 1022 entries. How many of them are committed or restored depends
* on the size of the L2ARC device. Thus the maximum payload of
* one log block is 1022 * SPA_MAXBLOCKSIZE = 16GB. If the L2ARC device
* is less than that, we reduce the amount of committed and restored
* log entries per block so as to enable persistence.
*/
if (dev->l2ad_end < l2arc_rebuild_blocks_min_l2size) {
dev->l2ad_log_entries = 0;
} else {
dev->l2ad_log_entries = MIN((dev->l2ad_end -
dev->l2ad_start) >> SPA_MAXBLOCKSHIFT,
L2ARC_LOG_BLK_MAX_ENTRIES);
}
/*
* Read the device header, if an error is returned do not rebuild L2ARC.
*/
if (l2arc_dev_hdr_read(dev) == 0 && dev->l2ad_log_entries > 0) {
/*
* If we are onlining a cache device (vdev_reopen) that was
* still present (l2arc_vdev_present()) and rebuild is enabled,
* we should evict all ARC buffers and pointers to log blocks
* and reclaim their space before restoring its contents to
* L2ARC.
*/
if (reopen) {
if (!l2arc_rebuild_enabled) {
return;
} else {
l2arc_evict(dev, 0, B_TRUE);
/* start a new log block */
dev->l2ad_log_ent_idx = 0;
dev->l2ad_log_blk_payload_asize = 0;
dev->l2ad_log_blk_payload_start = 0;
}
}
/*
* Just mark the device as pending for a rebuild. We won't
* be starting a rebuild in line here as it would block pool
* import. Instead spa_load_impl will hand that off to an
* async task which will call l2arc_spa_rebuild_start.
*/
dev->l2ad_rebuild = B_TRUE;
} else if (spa_writeable(spa)) {
/*
* In this case TRIM the whole device if l2arc_trim_ahead > 0,
* otherwise create a new header. We zero out the memory holding
* the header to reset dh_start_lbps. If we TRIM the whole
* device the new header will be written by
* vdev_trim_l2arc_thread() at the end of the TRIM to update the
* trim_state in the header too. When reading the header, if
* trim_state is not VDEV_TRIM_COMPLETE and l2arc_trim_ahead > 0
* we opt to TRIM the whole device again.
*/
if (l2arc_trim_ahead > 0) {
dev->l2ad_trim_all = B_TRUE;
} else {
memset(l2dhdr, 0, l2dhdr_asize);
l2arc_dev_hdr_update(dev);
}
}
}
/*
* Add a vdev for use by the L2ARC. By this point the spa has already
* validated the vdev and opened it.
*/
void
l2arc_add_vdev(spa_t *spa, vdev_t *vd)
{
l2arc_dev_t *adddev;
uint64_t l2dhdr_asize;
ASSERT(!l2arc_vdev_present(vd));
/*
* Create a new l2arc device entry.
*/
adddev = vmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
adddev->l2ad_spa = spa;
adddev->l2ad_vdev = vd;
/* leave extra size for an l2arc device header */
l2dhdr_asize = adddev->l2ad_dev_hdr_asize =
MAX(sizeof (*adddev->l2ad_dev_hdr), 1 << vd->vdev_ashift);
adddev->l2ad_start = VDEV_LABEL_START_SIZE + l2dhdr_asize;
adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
ASSERT3U(adddev->l2ad_start, <, adddev->l2ad_end);
adddev->l2ad_hand = adddev->l2ad_start;
adddev->l2ad_evict = adddev->l2ad_start;
adddev->l2ad_first = B_TRUE;
adddev->l2ad_writing = B_FALSE;
adddev->l2ad_trim_all = B_FALSE;
list_link_init(&adddev->l2ad_node);
adddev->l2ad_dev_hdr = kmem_zalloc(l2dhdr_asize, KM_SLEEP);
mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
/*
* This is a list of all ARC buffers that are still valid on the
* device.
*/
list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
/*
* This is a list of pointers to log blocks that are still present
* on the device.
*/
list_create(&adddev->l2ad_lbptr_list, sizeof (l2arc_lb_ptr_buf_t),
offsetof(l2arc_lb_ptr_buf_t, node));
vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
zfs_refcount_create(&adddev->l2ad_alloc);
zfs_refcount_create(&adddev->l2ad_lb_asize);
zfs_refcount_create(&adddev->l2ad_lb_count);
/*
* Decide if dev is eligible for L2ARC rebuild or whole device
* trimming. This has to happen before the device is added in the
* cache device list and l2arc_dev_mtx is released. Otherwise
* l2arc_feed_thread() might already start writing on the
* device.
*/
l2arc_rebuild_dev(adddev, B_FALSE);
/*
* Add device to global list
*/
mutex_enter(&l2arc_dev_mtx);
list_insert_head(l2arc_dev_list, adddev);
atomic_inc_64(&l2arc_ndev);
mutex_exit(&l2arc_dev_mtx);
}
/*
* Decide if a vdev is eligible for L2ARC rebuild, called from vdev_reopen()
* in case of onlining a cache device.
*/
void
l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen)
{
l2arc_dev_t *dev = NULL;
dev = l2arc_vdev_get(vd);
ASSERT3P(dev, !=, NULL);
/*
* In contrast to l2arc_add_vdev() we do not have to worry about
* l2arc_feed_thread() invalidating previous content when onlining a
* cache device. The device parameters (l2ad*) are not cleared when
* offlining the device and writing new buffers will not invalidate
* all previous content. In worst case only buffers that have not had
* their log block written to the device will be lost.
* When onlining the cache device (ie offline->online without exporting
* the pool in between) this happens:
* vdev_reopen() -> vdev_open() -> l2arc_rebuild_vdev()
* | |
* vdev_is_dead() = B_FALSE l2ad_rebuild = B_TRUE
* During the time where vdev_is_dead = B_FALSE and until l2ad_rebuild
* is set to B_TRUE we might write additional buffers to the device.
*/
l2arc_rebuild_dev(dev, reopen);
}
/*
* Remove a vdev from the L2ARC.
*/
void
l2arc_remove_vdev(vdev_t *vd)
{
l2arc_dev_t *remdev = NULL;
/*
* Find the device by vdev
*/
remdev = l2arc_vdev_get(vd);
ASSERT3P(remdev, !=, NULL);
/*
* Cancel any ongoing or scheduled rebuild.
*/
mutex_enter(&l2arc_rebuild_thr_lock);
if (remdev->l2ad_rebuild_began == B_TRUE) {
remdev->l2ad_rebuild_cancel = B_TRUE;
while (remdev->l2ad_rebuild == B_TRUE)
cv_wait(&l2arc_rebuild_thr_cv, &l2arc_rebuild_thr_lock);
}
mutex_exit(&l2arc_rebuild_thr_lock);
/*
* Remove device from global list
*/
mutex_enter(&l2arc_dev_mtx);
list_remove(l2arc_dev_list, remdev);
l2arc_dev_last = NULL; /* may have been invalidated */
atomic_dec_64(&l2arc_ndev);
mutex_exit(&l2arc_dev_mtx);
/*
* Clear all buflists and ARC references. L2ARC device flush.
*/
l2arc_evict(remdev, 0, B_TRUE);
list_destroy(&remdev->l2ad_buflist);
ASSERT(list_is_empty(&remdev->l2ad_lbptr_list));
list_destroy(&remdev->l2ad_lbptr_list);
mutex_destroy(&remdev->l2ad_mtx);
zfs_refcount_destroy(&remdev->l2ad_alloc);
zfs_refcount_destroy(&remdev->l2ad_lb_asize);
zfs_refcount_destroy(&remdev->l2ad_lb_count);
kmem_free(remdev->l2ad_dev_hdr, remdev->l2ad_dev_hdr_asize);
vmem_free(remdev, sizeof (l2arc_dev_t));
}
void
l2arc_init(void)
{
l2arc_thread_exit = 0;
l2arc_ndev = 0;
mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&l2arc_rebuild_thr_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&l2arc_rebuild_thr_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
l2arc_dev_list = &L2ARC_dev_list;
l2arc_free_on_write = &L2ARC_free_on_write;
list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
offsetof(l2arc_dev_t, l2ad_node));
list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
offsetof(l2arc_data_free_t, l2df_list_node));
}
void
l2arc_fini(void)
{
mutex_destroy(&l2arc_feed_thr_lock);
cv_destroy(&l2arc_feed_thr_cv);
mutex_destroy(&l2arc_rebuild_thr_lock);
cv_destroy(&l2arc_rebuild_thr_cv);
mutex_destroy(&l2arc_dev_mtx);
mutex_destroy(&l2arc_free_on_write_mtx);
list_destroy(l2arc_dev_list);
list_destroy(l2arc_free_on_write);
}
void
l2arc_start(void)
{
if (!(spa_mode_global & SPA_MODE_WRITE))
return;
(void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
TS_RUN, defclsyspri);
}
void
l2arc_stop(void)
{
if (!(spa_mode_global & SPA_MODE_WRITE))
return;
mutex_enter(&l2arc_feed_thr_lock);
cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
l2arc_thread_exit = 1;
while (l2arc_thread_exit != 0)
cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
mutex_exit(&l2arc_feed_thr_lock);
}
/*
* Punches out rebuild threads for the L2ARC devices in a spa. This should
* be called after pool import from the spa async thread, since starting
* these threads directly from spa_import() will make them part of the
* "zpool import" context and delay process exit (and thus pool import).
*/
void
l2arc_spa_rebuild_start(spa_t *spa)
{
ASSERT(MUTEX_HELD(&spa_namespace_lock));
/*
* Locate the spa's l2arc devices and kick off rebuild threads.
*/
for (int i = 0; i < spa->spa_l2cache.sav_count; i++) {
l2arc_dev_t *dev =
l2arc_vdev_get(spa->spa_l2cache.sav_vdevs[i]);
if (dev == NULL) {
/* Don't attempt a rebuild if the vdev is UNAVAIL */
continue;
}
mutex_enter(&l2arc_rebuild_thr_lock);
if (dev->l2ad_rebuild && !dev->l2ad_rebuild_cancel) {
dev->l2ad_rebuild_began = B_TRUE;
(void) thread_create(NULL, 0, l2arc_dev_rebuild_thread,
dev, 0, &p0, TS_RUN, minclsyspri);
}
mutex_exit(&l2arc_rebuild_thr_lock);
}
}
/*
* Main entry point for L2ARC rebuilding.
*/
static __attribute__((noreturn)) void
l2arc_dev_rebuild_thread(void *arg)
{
l2arc_dev_t *dev = arg;
VERIFY(!dev->l2ad_rebuild_cancel);
VERIFY(dev->l2ad_rebuild);
(void) l2arc_rebuild(dev);
mutex_enter(&l2arc_rebuild_thr_lock);
dev->l2ad_rebuild_began = B_FALSE;
dev->l2ad_rebuild = B_FALSE;
mutex_exit(&l2arc_rebuild_thr_lock);
thread_exit();
}
/*
* This function implements the actual L2ARC metadata rebuild. It:
* starts reading the log block chain and restores each block's contents
* to memory (reconstructing arc_buf_hdr_t's).
*
* Operation stops under any of the following conditions:
*
* 1) We reach the end of the log block chain.
* 2) We encounter *any* error condition (cksum errors, io errors)
*/
static int
l2arc_rebuild(l2arc_dev_t *dev)
{
vdev_t *vd = dev->l2ad_vdev;
spa_t *spa = vd->vdev_spa;
int err = 0;
l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
l2arc_log_blk_phys_t *this_lb, *next_lb;
zio_t *this_io = NULL, *next_io = NULL;
l2arc_log_blkptr_t lbps[2];
l2arc_lb_ptr_buf_t *lb_ptr_buf;
boolean_t lock_held;
this_lb = vmem_zalloc(sizeof (*this_lb), KM_SLEEP);
next_lb = vmem_zalloc(sizeof (*next_lb), KM_SLEEP);
/*
* We prevent device removal while issuing reads to the device,
* then during the rebuilding phases we drop this lock again so
* that a spa_unload or device remove can be initiated - this is
* safe, because the spa will signal us to stop before removing
* our device and wait for us to stop.
*/
spa_config_enter(spa, SCL_L2ARC, vd, RW_READER);
lock_held = B_TRUE;
/*
* Retrieve the persistent L2ARC device state.
* L2BLK_GET_PSIZE returns aligned size for log blocks.
*/
dev->l2ad_evict = MAX(l2dhdr->dh_evict, dev->l2ad_start);
dev->l2ad_hand = MAX(l2dhdr->dh_start_lbps[0].lbp_daddr +
L2BLK_GET_PSIZE((&l2dhdr->dh_start_lbps[0])->lbp_prop),
dev->l2ad_start);
dev->l2ad_first = !!(l2dhdr->dh_flags & L2ARC_DEV_HDR_EVICT_FIRST);
vd->vdev_trim_action_time = l2dhdr->dh_trim_action_time;
vd->vdev_trim_state = l2dhdr->dh_trim_state;
/*
* In case the zfs module parameter l2arc_rebuild_enabled is false
* we do not start the rebuild process.
*/
if (!l2arc_rebuild_enabled)
goto out;
/* Prepare the rebuild process */
memcpy(lbps, l2dhdr->dh_start_lbps, sizeof (lbps));
/* Start the rebuild process */
for (;;) {
if (!l2arc_log_blkptr_valid(dev, &lbps[0]))
break;
if ((err = l2arc_log_blk_read(dev, &lbps[0], &lbps[1],
this_lb, next_lb, this_io, &next_io)) != 0)
goto out;
/*
* Our memory pressure valve. If the system is running low
* on memory, rather than swamping memory with new ARC buf
* hdrs, we opt not to rebuild the L2ARC. At this point,
* however, we have already set up our L2ARC dev to chain in
* new metadata log blocks, so the user may choose to offline/
* online the L2ARC dev at a later time (or re-import the pool)
* to reconstruct it (when there's less memory pressure).
*/
if (l2arc_hdr_limit_reached()) {
ARCSTAT_BUMP(arcstat_l2_rebuild_abort_lowmem);
cmn_err(CE_NOTE, "System running low on memory, "
"aborting L2ARC rebuild.");
err = SET_ERROR(ENOMEM);
goto out;
}
spa_config_exit(spa, SCL_L2ARC, vd);
lock_held = B_FALSE;
/*
* Now that we know that the next_lb checks out alright, we
* can start reconstruction from this log block.
* L2BLK_GET_PSIZE returns aligned size for log blocks.
*/
uint64_t asize = L2BLK_GET_PSIZE((&lbps[0])->lbp_prop);
l2arc_log_blk_restore(dev, this_lb, asize);
/*
* log block restored, include its pointer in the list of
* pointers to log blocks present in the L2ARC device.
*/
lb_ptr_buf = kmem_zalloc(sizeof (l2arc_lb_ptr_buf_t), KM_SLEEP);
lb_ptr_buf->lb_ptr = kmem_zalloc(sizeof (l2arc_log_blkptr_t),
KM_SLEEP);
memcpy(lb_ptr_buf->lb_ptr, &lbps[0],
sizeof (l2arc_log_blkptr_t));
mutex_enter(&dev->l2ad_mtx);
list_insert_tail(&dev->l2ad_lbptr_list, lb_ptr_buf);
ARCSTAT_INCR(arcstat_l2_log_blk_asize, asize);
ARCSTAT_BUMP(arcstat_l2_log_blk_count);
zfs_refcount_add_many(&dev->l2ad_lb_asize, asize, lb_ptr_buf);
zfs_refcount_add(&dev->l2ad_lb_count, lb_ptr_buf);
mutex_exit(&dev->l2ad_mtx);
vdev_space_update(vd, asize, 0, 0);
/*
* Protection against loops of log blocks:
*
* l2ad_hand l2ad_evict
* V V
* l2ad_start |=======================================| l2ad_end
* -----|||----|||---|||----|||
* (3) (2) (1) (0)
* ---|||---|||----|||---|||
* (7) (6) (5) (4)
*
* In this situation the pointer of log block (4) passes
* l2arc_log_blkptr_valid() but the log block should not be
* restored as it is overwritten by the payload of log block
* (0). Only log blocks (0)-(3) should be restored. We check
* whether l2ad_evict lies in between the payload starting
* offset of the next log block (lbps[1].lbp_payload_start)
* and the payload starting offset of the present log block
* (lbps[0].lbp_payload_start). If true and this isn't the
* first pass, we are looping from the beginning and we should
* stop.
*/
if (l2arc_range_check_overlap(lbps[1].lbp_payload_start,
lbps[0].lbp_payload_start, dev->l2ad_evict) &&
!dev->l2ad_first)
goto out;
kpreempt(KPREEMPT_SYNC);
for (;;) {
mutex_enter(&l2arc_rebuild_thr_lock);
if (dev->l2ad_rebuild_cancel) {
dev->l2ad_rebuild = B_FALSE;
cv_signal(&l2arc_rebuild_thr_cv);
mutex_exit(&l2arc_rebuild_thr_lock);
err = SET_ERROR(ECANCELED);
goto out;
}
mutex_exit(&l2arc_rebuild_thr_lock);
if (spa_config_tryenter(spa, SCL_L2ARC, vd,
RW_READER)) {
lock_held = B_TRUE;
break;
}
/*
* L2ARC config lock held by somebody in writer,
* possibly due to them trying to remove us. They'll
* likely to want us to shut down, so after a little
* delay, we check l2ad_rebuild_cancel and retry
* the lock again.
*/
delay(1);
}
/*
* Continue with the next log block.
*/
lbps[0] = lbps[1];
lbps[1] = this_lb->lb_prev_lbp;
PTR_SWAP(this_lb, next_lb);
this_io = next_io;
next_io = NULL;
}
if (this_io != NULL)
l2arc_log_blk_fetch_abort(this_io);
out:
if (next_io != NULL)
l2arc_log_blk_fetch_abort(next_io);
vmem_free(this_lb, sizeof (*this_lb));
vmem_free(next_lb, sizeof (*next_lb));
if (!l2arc_rebuild_enabled) {
spa_history_log_internal(spa, "L2ARC rebuild", NULL,
"disabled");
} else if (err == 0 && zfs_refcount_count(&dev->l2ad_lb_count) > 0) {
ARCSTAT_BUMP(arcstat_l2_rebuild_success);
spa_history_log_internal(spa, "L2ARC rebuild", NULL,
"successful, restored %llu blocks",
(u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count));
} else if (err == 0 && zfs_refcount_count(&dev->l2ad_lb_count) == 0) {
/*
* No error but also nothing restored, meaning the lbps array
* in the device header points to invalid/non-present log
* blocks. Reset the header.
*/
spa_history_log_internal(spa, "L2ARC rebuild", NULL,
"no valid log blocks");
memset(l2dhdr, 0, dev->l2ad_dev_hdr_asize);
l2arc_dev_hdr_update(dev);
} else if (err == ECANCELED) {
/*
* In case the rebuild was canceled do not log to spa history
* log as the pool may be in the process of being removed.
*/
zfs_dbgmsg("L2ARC rebuild aborted, restored %llu blocks",
(u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count));
} else if (err != 0) {
spa_history_log_internal(spa, "L2ARC rebuild", NULL,
"aborted, restored %llu blocks",
(u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count));
}
if (lock_held)
spa_config_exit(spa, SCL_L2ARC, vd);
return (err);
}
/*
* Attempts to read the device header on the provided L2ARC device and writes
* it to `hdr'. On success, this function returns 0, otherwise the appropriate
* error code is returned.
*/
static int
l2arc_dev_hdr_read(l2arc_dev_t *dev)
{
int err;
uint64_t guid;
l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
const uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize;
abd_t *abd;
guid = spa_guid(dev->l2ad_vdev->vdev_spa);
abd = abd_get_from_buf(l2dhdr, l2dhdr_asize);
err = zio_wait(zio_read_phys(NULL, dev->l2ad_vdev,
VDEV_LABEL_START_SIZE, l2dhdr_asize, abd,
ZIO_CHECKSUM_LABEL, NULL, NULL, ZIO_PRIORITY_SYNC_READ,
ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY |
ZIO_FLAG_SPECULATIVE, B_FALSE));
abd_free(abd);
if (err != 0) {
ARCSTAT_BUMP(arcstat_l2_rebuild_abort_dh_errors);
zfs_dbgmsg("L2ARC IO error (%d) while reading device header, "
"vdev guid: %llu", err,
(u_longlong_t)dev->l2ad_vdev->vdev_guid);
return (err);
}
if (l2dhdr->dh_magic == BSWAP_64(L2ARC_DEV_HDR_MAGIC))
byteswap_uint64_array(l2dhdr, sizeof (*l2dhdr));
if (l2dhdr->dh_magic != L2ARC_DEV_HDR_MAGIC ||
l2dhdr->dh_spa_guid != guid ||
l2dhdr->dh_vdev_guid != dev->l2ad_vdev->vdev_guid ||
l2dhdr->dh_version != L2ARC_PERSISTENT_VERSION ||
l2dhdr->dh_log_entries != dev->l2ad_log_entries ||
l2dhdr->dh_end != dev->l2ad_end ||
!l2arc_range_check_overlap(dev->l2ad_start, dev->l2ad_end,
l2dhdr->dh_evict) ||
(l2dhdr->dh_trim_state != VDEV_TRIM_COMPLETE &&
l2arc_trim_ahead > 0)) {
/*
* Attempt to rebuild a device containing no actual dev hdr
* or containing a header from some other pool or from another
* version of persistent L2ARC.
*/
ARCSTAT_BUMP(arcstat_l2_rebuild_abort_unsupported);
return (SET_ERROR(ENOTSUP));
}
return (0);
}
/*
* Reads L2ARC log blocks from storage and validates their contents.
*
* This function implements a simple fetcher to make sure that while
* we're processing one buffer the L2ARC is already fetching the next
* one in the chain.
*
* The arguments this_lp and next_lp point to the current and next log block
* address in the block chain. Similarly, this_lb and next_lb hold the
* l2arc_log_blk_phys_t's of the current and next L2ARC blk.
*
* The `this_io' and `next_io' arguments are used for block fetching.
* When issuing the first blk IO during rebuild, you should pass NULL for
* `this_io'. This function will then issue a sync IO to read the block and
* also issue an async IO to fetch the next block in the block chain. The
* fetched IO is returned in `next_io'. On subsequent calls to this
* function, pass the value returned in `next_io' from the previous call
* as `this_io' and a fresh `next_io' pointer to hold the next fetch IO.
* Prior to the call, you should initialize your `next_io' pointer to be
* NULL. If no fetch IO was issued, the pointer is left set at NULL.
*
* On success, this function returns 0, otherwise it returns an appropriate
* error code. On error the fetching IO is aborted and cleared before
* returning from this function. Therefore, if we return `success', the
* caller can assume that we have taken care of cleanup of fetch IOs.
*/
static int
l2arc_log_blk_read(l2arc_dev_t *dev,
const l2arc_log_blkptr_t *this_lbp, const l2arc_log_blkptr_t *next_lbp,
l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb,
zio_t *this_io, zio_t **next_io)
{
int err = 0;
zio_cksum_t cksum;
abd_t *abd = NULL;
uint64_t asize;
ASSERT(this_lbp != NULL && next_lbp != NULL);
ASSERT(this_lb != NULL && next_lb != NULL);
ASSERT(next_io != NULL && *next_io == NULL);
ASSERT(l2arc_log_blkptr_valid(dev, this_lbp));
/*
* Check to see if we have issued the IO for this log block in a
* previous run. If not, this is the first call, so issue it now.
*/
if (this_io == NULL) {
this_io = l2arc_log_blk_fetch(dev->l2ad_vdev, this_lbp,
this_lb);
}
/*
* Peek to see if we can start issuing the next IO immediately.
*/
if (l2arc_log_blkptr_valid(dev, next_lbp)) {
/*
* Start issuing IO for the next log block early - this
* should help keep the L2ARC device busy while we
* decompress and restore this log block.
*/
*next_io = l2arc_log_blk_fetch(dev->l2ad_vdev, next_lbp,
next_lb);
}
/* Wait for the IO to read this log block to complete */
if ((err = zio_wait(this_io)) != 0) {
ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors);
zfs_dbgmsg("L2ARC IO error (%d) while reading log block, "
"offset: %llu, vdev guid: %llu", err,
(u_longlong_t)this_lbp->lbp_daddr,
(u_longlong_t)dev->l2ad_vdev->vdev_guid);
goto cleanup;
}
/*
* Make sure the buffer checks out.
* L2BLK_GET_PSIZE returns aligned size for log blocks.
*/
asize = L2BLK_GET_PSIZE((this_lbp)->lbp_prop);
fletcher_4_native(this_lb, asize, NULL, &cksum);
if (!ZIO_CHECKSUM_EQUAL(cksum, this_lbp->lbp_cksum)) {
ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_lb_errors);
zfs_dbgmsg("L2ARC log block cksum failed, offset: %llu, "
"vdev guid: %llu, l2ad_hand: %llu, l2ad_evict: %llu",
(u_longlong_t)this_lbp->lbp_daddr,
(u_longlong_t)dev->l2ad_vdev->vdev_guid,
(u_longlong_t)dev->l2ad_hand,
(u_longlong_t)dev->l2ad_evict);
err = SET_ERROR(ECKSUM);
goto cleanup;
}
/* Now we can take our time decoding this buffer */
switch (L2BLK_GET_COMPRESS((this_lbp)->lbp_prop)) {
case ZIO_COMPRESS_OFF:
break;
case ZIO_COMPRESS_LZ4:
abd = abd_alloc_for_io(asize, B_TRUE);
abd_copy_from_buf_off(abd, this_lb, 0, asize);
if ((err = zio_decompress_data(
L2BLK_GET_COMPRESS((this_lbp)->lbp_prop),
abd, this_lb, asize, sizeof (*this_lb), NULL)) != 0) {
err = SET_ERROR(EINVAL);
goto cleanup;
}
break;
default:
err = SET_ERROR(EINVAL);
goto cleanup;
}
if (this_lb->lb_magic == BSWAP_64(L2ARC_LOG_BLK_MAGIC))
byteswap_uint64_array(this_lb, sizeof (*this_lb));
if (this_lb->lb_magic != L2ARC_LOG_BLK_MAGIC) {
err = SET_ERROR(EINVAL);
goto cleanup;
}
cleanup:
/* Abort an in-flight fetch I/O in case of error */
if (err != 0 && *next_io != NULL) {
l2arc_log_blk_fetch_abort(*next_io);
*next_io = NULL;
}
if (abd != NULL)
abd_free(abd);
return (err);
}
/*
* Restores the payload of a log block to ARC. This creates empty ARC hdr
* entries which only contain an l2arc hdr, essentially restoring the
* buffers to their L2ARC evicted state. This function also updates space
* usage on the L2ARC vdev to make sure it tracks restored buffers.
*/
static void
l2arc_log_blk_restore(l2arc_dev_t *dev, const l2arc_log_blk_phys_t *lb,
uint64_t lb_asize)
{
uint64_t size = 0, asize = 0;
uint64_t log_entries = dev->l2ad_log_entries;
/*
* Usually arc_adapt() is called only for data, not headers, but
* since we may allocate significant amount of memory here, let ARC
* grow its arc_c.
*/
arc_adapt(log_entries * HDR_L2ONLY_SIZE);
for (int i = log_entries - 1; i >= 0; i--) {
/*
* Restore goes in the reverse temporal direction to preserve
* correct temporal ordering of buffers in the l2ad_buflist.
* l2arc_hdr_restore also does a list_insert_tail instead of
* list_insert_head on the l2ad_buflist:
*
* LIST l2ad_buflist LIST
* HEAD <------ (time) ------ TAIL
* direction +-----+-----+-----+-----+-----+ direction
* of l2arc <== | buf | buf | buf | buf | buf | ===> of rebuild
* fill +-----+-----+-----+-----+-----+
* ^ ^
* | |
* | |
* l2arc_feed_thread l2arc_rebuild
* will place new bufs here restores bufs here
*
* During l2arc_rebuild() the device is not used by
* l2arc_feed_thread() as dev->l2ad_rebuild is set to true.
*/
size += L2BLK_GET_LSIZE((&lb->lb_entries[i])->le_prop);
asize += vdev_psize_to_asize(dev->l2ad_vdev,
L2BLK_GET_PSIZE((&lb->lb_entries[i])->le_prop));
l2arc_hdr_restore(&lb->lb_entries[i], dev);
}
/*
* Record rebuild stats:
* size Logical size of restored buffers in the L2ARC
* asize Aligned size of restored buffers in the L2ARC
*/
ARCSTAT_INCR(arcstat_l2_rebuild_size, size);
ARCSTAT_INCR(arcstat_l2_rebuild_asize, asize);
ARCSTAT_INCR(arcstat_l2_rebuild_bufs, log_entries);
ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_asize, lb_asize);
ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, asize / lb_asize);
ARCSTAT_BUMP(arcstat_l2_rebuild_log_blks);
}
/*
* Restores a single ARC buf hdr from a log entry. The ARC buffer is put
* into a state indicating that it has been evicted to L2ARC.
*/
static void
l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, l2arc_dev_t *dev)
{
arc_buf_hdr_t *hdr, *exists;
kmutex_t *hash_lock;
arc_buf_contents_t type = L2BLK_GET_TYPE((le)->le_prop);
uint64_t asize;
/*
* Do all the allocation before grabbing any locks, this lets us
* sleep if memory is full and we don't have to deal with failed
* allocations.
*/
hdr = arc_buf_alloc_l2only(L2BLK_GET_LSIZE((le)->le_prop), type,
dev, le->le_dva, le->le_daddr,
L2BLK_GET_PSIZE((le)->le_prop), le->le_birth,
L2BLK_GET_COMPRESS((le)->le_prop), le->le_complevel,
L2BLK_GET_PROTECTED((le)->le_prop),
L2BLK_GET_PREFETCH((le)->le_prop),
L2BLK_GET_STATE((le)->le_prop));
asize = vdev_psize_to_asize(dev->l2ad_vdev,
L2BLK_GET_PSIZE((le)->le_prop));
/*
* vdev_space_update() has to be called before arc_hdr_destroy() to
* avoid underflow since the latter also calls vdev_space_update().
*/
l2arc_hdr_arcstats_increment(hdr);
vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
mutex_enter(&dev->l2ad_mtx);
list_insert_tail(&dev->l2ad_buflist, hdr);
(void) zfs_refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
mutex_exit(&dev->l2ad_mtx);
exists = buf_hash_insert(hdr, &hash_lock);
if (exists) {
/* Buffer was already cached, no need to restore it. */
arc_hdr_destroy(hdr);
/*
* If the buffer is already cached, check whether it has
* L2ARC metadata. If not, enter them and update the flag.
* This is important is case of onlining a cache device, since
* we previously evicted all L2ARC metadata from ARC.
*/
if (!HDR_HAS_L2HDR(exists)) {
arc_hdr_set_flags(exists, ARC_FLAG_HAS_L2HDR);
exists->b_l2hdr.b_dev = dev;
exists->b_l2hdr.b_daddr = le->le_daddr;
exists->b_l2hdr.b_arcs_state =
L2BLK_GET_STATE((le)->le_prop);
mutex_enter(&dev->l2ad_mtx);
list_insert_tail(&dev->l2ad_buflist, exists);
(void) zfs_refcount_add_many(&dev->l2ad_alloc,
arc_hdr_size(exists), exists);
mutex_exit(&dev->l2ad_mtx);
l2arc_hdr_arcstats_increment(exists);
vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
}
ARCSTAT_BUMP(arcstat_l2_rebuild_bufs_precached);
}
mutex_exit(hash_lock);
}
/*
* Starts an asynchronous read IO to read a log block. This is used in log
* block reconstruction to start reading the next block before we are done
* decoding and reconstructing the current block, to keep the l2arc device
* nice and hot with read IO to process.
* The returned zio will contain a newly allocated memory buffers for the IO
* data which should then be freed by the caller once the zio is no longer
* needed (i.e. due to it having completed). If you wish to abort this
* zio, you should do so using l2arc_log_blk_fetch_abort, which takes
* care of disposing of the allocated buffers correctly.
*/
static zio_t *
l2arc_log_blk_fetch(vdev_t *vd, const l2arc_log_blkptr_t *lbp,
l2arc_log_blk_phys_t *lb)
{
uint32_t asize;
zio_t *pio;
l2arc_read_callback_t *cb;
/* L2BLK_GET_PSIZE returns aligned size for log blocks */
asize = L2BLK_GET_PSIZE((lbp)->lbp_prop);
ASSERT(asize <= sizeof (l2arc_log_blk_phys_t));
cb = kmem_zalloc(sizeof (l2arc_read_callback_t), KM_SLEEP);
cb->l2rcb_abd = abd_get_from_buf(lb, asize);
pio = zio_root(vd->vdev_spa, l2arc_blk_fetch_done, cb,
ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY);
(void) zio_nowait(zio_read_phys(pio, vd, lbp->lbp_daddr, asize,
cb->l2rcb_abd, ZIO_CHECKSUM_OFF, NULL, NULL,
ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL |
ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE));
return (pio);
}
/*
* Aborts a zio returned from l2arc_log_blk_fetch and frees the data
* buffers allocated for it.
*/
static void
l2arc_log_blk_fetch_abort(zio_t *zio)
{
(void) zio_wait(zio);
}
/*
* Creates a zio to update the device header on an l2arc device.
*/
void
l2arc_dev_hdr_update(l2arc_dev_t *dev)
{
l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
const uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize;
abd_t *abd;
int err;
VERIFY(spa_config_held(dev->l2ad_spa, SCL_STATE_ALL, RW_READER));
l2dhdr->dh_magic = L2ARC_DEV_HDR_MAGIC;
l2dhdr->dh_version = L2ARC_PERSISTENT_VERSION;
l2dhdr->dh_spa_guid = spa_guid(dev->l2ad_vdev->vdev_spa);
l2dhdr->dh_vdev_guid = dev->l2ad_vdev->vdev_guid;
l2dhdr->dh_log_entries = dev->l2ad_log_entries;
l2dhdr->dh_evict = dev->l2ad_evict;
l2dhdr->dh_start = dev->l2ad_start;
l2dhdr->dh_end = dev->l2ad_end;
l2dhdr->dh_lb_asize = zfs_refcount_count(&dev->l2ad_lb_asize);
l2dhdr->dh_lb_count = zfs_refcount_count(&dev->l2ad_lb_count);
l2dhdr->dh_flags = 0;
l2dhdr->dh_trim_action_time = dev->l2ad_vdev->vdev_trim_action_time;
l2dhdr->dh_trim_state = dev->l2ad_vdev->vdev_trim_state;
if (dev->l2ad_first)
l2dhdr->dh_flags |= L2ARC_DEV_HDR_EVICT_FIRST;
abd = abd_get_from_buf(l2dhdr, l2dhdr_asize);
err = zio_wait(zio_write_phys(NULL, dev->l2ad_vdev,
VDEV_LABEL_START_SIZE, l2dhdr_asize, abd, ZIO_CHECKSUM_LABEL, NULL,
NULL, ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE));
abd_free(abd);
if (err != 0) {
zfs_dbgmsg("L2ARC IO error (%d) while writing device header, "
"vdev guid: %llu", err,
(u_longlong_t)dev->l2ad_vdev->vdev_guid);
}
}
/*
* Commits a log block to the L2ARC device. This routine is invoked from
* l2arc_write_buffers when the log block fills up.
* This function allocates some memory to temporarily hold the serialized
* buffer to be written. This is then released in l2arc_write_done.
*/
static uint64_t
l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, l2arc_write_callback_t *cb)
{
l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
uint64_t psize, asize;
zio_t *wzio;
l2arc_lb_abd_buf_t *abd_buf;
uint8_t *tmpbuf = NULL;
l2arc_lb_ptr_buf_t *lb_ptr_buf;
VERIFY3S(dev->l2ad_log_ent_idx, ==, dev->l2ad_log_entries);
abd_buf = zio_buf_alloc(sizeof (*abd_buf));
abd_buf->abd = abd_get_from_buf(lb, sizeof (*lb));
lb_ptr_buf = kmem_zalloc(sizeof (l2arc_lb_ptr_buf_t), KM_SLEEP);
lb_ptr_buf->lb_ptr = kmem_zalloc(sizeof (l2arc_log_blkptr_t), KM_SLEEP);
/* link the buffer into the block chain */
lb->lb_prev_lbp = l2dhdr->dh_start_lbps[1];
lb->lb_magic = L2ARC_LOG_BLK_MAGIC;
/*
* l2arc_log_blk_commit() may be called multiple times during a single
* l2arc_write_buffers() call. Save the allocated abd buffers in a list
* so we can free them in l2arc_write_done() later on.
*/
list_insert_tail(&cb->l2wcb_abd_list, abd_buf);
/* try to compress the buffer */
psize = zio_compress_data(ZIO_COMPRESS_LZ4,
abd_buf->abd, (void **) &tmpbuf, sizeof (*lb), 0);
/* a log block is never entirely zero */
ASSERT(psize != 0);
asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
ASSERT(asize <= sizeof (*lb));
/*
* Update the start log block pointer in the device header to point
* to the log block we're about to write.
*/
l2dhdr->dh_start_lbps[1] = l2dhdr->dh_start_lbps[0];
l2dhdr->dh_start_lbps[0].lbp_daddr = dev->l2ad_hand;
l2dhdr->dh_start_lbps[0].lbp_payload_asize =
dev->l2ad_log_blk_payload_asize;
l2dhdr->dh_start_lbps[0].lbp_payload_start =
dev->l2ad_log_blk_payload_start;
L2BLK_SET_LSIZE(
(&l2dhdr->dh_start_lbps[0])->lbp_prop, sizeof (*lb));
L2BLK_SET_PSIZE(
(&l2dhdr->dh_start_lbps[0])->lbp_prop, asize);
L2BLK_SET_CHECKSUM(
(&l2dhdr->dh_start_lbps[0])->lbp_prop,
ZIO_CHECKSUM_FLETCHER_4);
if (asize < sizeof (*lb)) {
/* compression succeeded */
memset(tmpbuf + psize, 0, asize - psize);
L2BLK_SET_COMPRESS(
(&l2dhdr->dh_start_lbps[0])->lbp_prop,
ZIO_COMPRESS_LZ4);
} else {
/* compression failed */
memcpy(tmpbuf, lb, sizeof (*lb));
L2BLK_SET_COMPRESS(
(&l2dhdr->dh_start_lbps[0])->lbp_prop,
ZIO_COMPRESS_OFF);
}
/* checksum what we're about to write */
fletcher_4_native(tmpbuf, asize, NULL,
&l2dhdr->dh_start_lbps[0].lbp_cksum);
abd_free(abd_buf->abd);
/* perform the write itself */
abd_buf->abd = abd_get_from_buf(tmpbuf, sizeof (*lb));
abd_take_ownership_of_buf(abd_buf->abd, B_TRUE);
wzio = zio_write_phys(pio, dev->l2ad_vdev, dev->l2ad_hand,
asize, abd_buf->abd, ZIO_CHECKSUM_OFF, NULL, NULL,
ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE);
DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio);
(void) zio_nowait(wzio);
dev->l2ad_hand += asize;
/*
* Include the committed log block's pointer in the list of pointers
* to log blocks present in the L2ARC device.
*/
memcpy(lb_ptr_buf->lb_ptr, &l2dhdr->dh_start_lbps[0],
sizeof (l2arc_log_blkptr_t));
mutex_enter(&dev->l2ad_mtx);
list_insert_head(&dev->l2ad_lbptr_list, lb_ptr_buf);
ARCSTAT_INCR(arcstat_l2_log_blk_asize, asize);
ARCSTAT_BUMP(arcstat_l2_log_blk_count);
zfs_refcount_add_many(&dev->l2ad_lb_asize, asize, lb_ptr_buf);
zfs_refcount_add(&dev->l2ad_lb_count, lb_ptr_buf);
mutex_exit(&dev->l2ad_mtx);
vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
/* bump the kstats */
ARCSTAT_INCR(arcstat_l2_write_bytes, asize);
ARCSTAT_BUMP(arcstat_l2_log_blk_writes);
ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_asize, asize);
ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio,
dev->l2ad_log_blk_payload_asize / asize);
/* start a new log block */
dev->l2ad_log_ent_idx = 0;
dev->l2ad_log_blk_payload_asize = 0;
dev->l2ad_log_blk_payload_start = 0;
return (asize);
}
/*
* Validates an L2ARC log block address to make sure that it can be read
* from the provided L2ARC device.
*/
boolean_t
l2arc_log_blkptr_valid(l2arc_dev_t *dev, const l2arc_log_blkptr_t *lbp)
{
/* L2BLK_GET_PSIZE returns aligned size for log blocks */
uint64_t asize = L2BLK_GET_PSIZE((lbp)->lbp_prop);
uint64_t end = lbp->lbp_daddr + asize - 1;
uint64_t start = lbp->lbp_payload_start;
boolean_t evicted = B_FALSE;
/*
* A log block is valid if all of the following conditions are true:
* - it fits entirely (including its payload) between l2ad_start and
* l2ad_end
* - it has a valid size
* - neither the log block itself nor part of its payload was evicted
* by l2arc_evict():
*
* l2ad_hand l2ad_evict
* | | lbp_daddr
* | start | | end
* | | | | |
* V V V V V
* l2ad_start ============================================ l2ad_end
* --------------------------||||
* ^ ^
* | log block
* payload
*/
evicted =
l2arc_range_check_overlap(start, end, dev->l2ad_hand) ||
l2arc_range_check_overlap(start, end, dev->l2ad_evict) ||
l2arc_range_check_overlap(dev->l2ad_hand, dev->l2ad_evict, start) ||
l2arc_range_check_overlap(dev->l2ad_hand, dev->l2ad_evict, end);
return (start >= dev->l2ad_start && end <= dev->l2ad_end &&
asize > 0 && asize <= sizeof (l2arc_log_blk_phys_t) &&
(!evicted || dev->l2ad_first));
}
/*
* Inserts ARC buffer header `hdr' into the current L2ARC log block on
* the device. The buffer being inserted must be present in L2ARC.
* Returns B_TRUE if the L2ARC log block is full and needs to be committed
* to L2ARC, or B_FALSE if it still has room for more ARC buffers.
*/
static boolean_t
l2arc_log_blk_insert(l2arc_dev_t *dev, const arc_buf_hdr_t *hdr)
{
l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
l2arc_log_ent_phys_t *le;
if (dev->l2ad_log_entries == 0)
return (B_FALSE);
int index = dev->l2ad_log_ent_idx++;
ASSERT3S(index, <, dev->l2ad_log_entries);
ASSERT(HDR_HAS_L2HDR(hdr));
le = &lb->lb_entries[index];
memset(le, 0, sizeof (*le));
le->le_dva = hdr->b_dva;
le->le_birth = hdr->b_birth;
le->le_daddr = hdr->b_l2hdr.b_daddr;
if (index == 0)
dev->l2ad_log_blk_payload_start = le->le_daddr;
L2BLK_SET_LSIZE((le)->le_prop, HDR_GET_LSIZE(hdr));
L2BLK_SET_PSIZE((le)->le_prop, HDR_GET_PSIZE(hdr));
L2BLK_SET_COMPRESS((le)->le_prop, HDR_GET_COMPRESS(hdr));
le->le_complevel = hdr->b_complevel;
L2BLK_SET_TYPE((le)->le_prop, hdr->b_type);
L2BLK_SET_PROTECTED((le)->le_prop, !!(HDR_PROTECTED(hdr)));
L2BLK_SET_PREFETCH((le)->le_prop, !!(HDR_PREFETCH(hdr)));
L2BLK_SET_STATE((le)->le_prop, hdr->b_l1hdr.b_state->arcs_state);
dev->l2ad_log_blk_payload_asize += vdev_psize_to_asize(dev->l2ad_vdev,
HDR_GET_PSIZE(hdr));
return (dev->l2ad_log_ent_idx == dev->l2ad_log_entries);
}
/*
* Checks whether a given L2ARC device address sits in a time-sequential
* range. The trick here is that the L2ARC is a rotary buffer, so we can't
* just do a range comparison, we need to handle the situation in which the
* range wraps around the end of the L2ARC device. Arguments:
* bottom -- Lower end of the range to check (written to earlier).
* top -- Upper end of the range to check (written to later).
* check -- The address for which we want to determine if it sits in
* between the top and bottom.
*
* The 3-way conditional below represents the following cases:
*
* bottom < top : Sequentially ordered case:
* <check>--------+-------------------+
* | (overlap here?) |
* L2ARC dev V V
* |---------------<bottom>============<top>--------------|
*
* bottom > top: Looped-around case:
* <check>--------+------------------+
* | (overlap here?) |
* L2ARC dev V V
* |===============<top>---------------<bottom>===========|
* ^ ^
* | (or here?) |
* +---------------+---------<check>
*
* top == bottom : Just a single address comparison.
*/
boolean_t
l2arc_range_check_overlap(uint64_t bottom, uint64_t top, uint64_t check)
{
if (bottom < top)
return (bottom <= check && check <= top);
else if (bottom > top)
return (check <= top || bottom <= check);
else
return (check == top);
}
EXPORT_SYMBOL(arc_buf_size);
EXPORT_SYMBOL(arc_write);
EXPORT_SYMBOL(arc_read);
EXPORT_SYMBOL(arc_buf_info);
EXPORT_SYMBOL(arc_getbuf_func);
EXPORT_SYMBOL(arc_add_prune_callback);
EXPORT_SYMBOL(arc_remove_prune_callback);
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min, param_set_arc_min,
spl_param_get_u64, ZMOD_RW, "Minimum ARC size in bytes");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, max, param_set_arc_max,
spl_param_get_u64, ZMOD_RW, "Maximum ARC size in bytes");
ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_balance, UINT, ZMOD_RW,
"Balance between metadata and data on ghost hits.");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, grow_retry, param_set_arc_int,
param_get_uint, ZMOD_RW, "Seconds before growing ARC size");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, shrink_shift, param_set_arc_int,
param_get_uint, ZMOD_RW, "log2(fraction of ARC to reclaim)");
ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, pc_percent, UINT, ZMOD_RW,
"Percent of pagecache to reclaim ARC to");
ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, average_blocksize, UINT, ZMOD_RD,
"Target average block size");
ZFS_MODULE_PARAM(zfs, zfs_, compressed_arc_enabled, INT, ZMOD_RW,
"Disable compressed ARC buffers");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min_prefetch_ms, param_set_arc_int,
param_get_uint, ZMOD_RW, "Min life of prefetch block in ms");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min_prescient_prefetch_ms,
param_set_arc_int, param_get_uint, ZMOD_RW,
"Min life of prescient prefetched block in ms");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, write_max, U64, ZMOD_RW,
"Max write bytes per interval");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, write_boost, U64, ZMOD_RW,
"Extra write bytes during device warmup");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, headroom, U64, ZMOD_RW,
"Number of max device writes to precache");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, headroom_boost, U64, ZMOD_RW,
"Compressed l2arc_headroom multiplier");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, trim_ahead, U64, ZMOD_RW,
"TRIM ahead L2ARC write size multiplier");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, feed_secs, U64, ZMOD_RW,
"Seconds between L2ARC writing");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, feed_min_ms, U64, ZMOD_RW,
"Min feed interval in milliseconds");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, noprefetch, INT, ZMOD_RW,
"Skip caching prefetched buffers");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, feed_again, INT, ZMOD_RW,
"Turbo L2ARC warmup");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, norw, INT, ZMOD_RW,
"No reads during writes");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, meta_percent, UINT, ZMOD_RW,
"Percent of ARC size allowed for L2ARC-only headers");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, rebuild_enabled, INT, ZMOD_RW,
"Rebuild the L2ARC when importing a pool");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, rebuild_blocks_min_l2size, U64, ZMOD_RW,
"Min size in bytes to write rebuild log blocks in L2ARC");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, mfuonly, INT, ZMOD_RW,
"Cache only MFU data from ARC into L2ARC");
ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, exclude_special, INT, ZMOD_RW,
"Exclude dbufs on special vdevs from being cached to L2ARC if set.");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, lotsfree_percent, param_set_arc_int,
param_get_uint, ZMOD_RW, "System free memory I/O throttle in bytes");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, sys_free, param_set_arc_u64,
spl_param_get_u64, ZMOD_RW, "System free memory target size in bytes");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, dnode_limit, param_set_arc_u64,
spl_param_get_u64, ZMOD_RW, "Minimum bytes of dnodes in ARC");
ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, dnode_limit_percent,
param_set_arc_int, param_get_uint, ZMOD_RW,
"Percent of ARC meta buffers for dnodes");
ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, dnode_reduce_percent, UINT, ZMOD_RW,
"Percentage of excess dnodes to try to unpin");
ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, eviction_pct, UINT, ZMOD_RW,
"When full, ARC allocation waits for eviction of this % of alloc size");
ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, evict_batch_limit, UINT, ZMOD_RW,
"The number of headers to evict per sublist before moving to the next");
ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, prune_task_threads, INT, ZMOD_RW,
"Number of arc_prune threads");
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