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mirror_zfs/include/sys/space_map.h
Serapheim Dimitropoulos 425d3237ee Get rid of space_map_update() for ms_synced_length 
Initially, metaslabs and space maps used to be the same thing
in ZFS. Later, we started differentiating them by referring
to the space map as the on-disk state of the metaslab, making
the metaslab a higher-level concept that is metadata that deals
with space accounting. Today we've managed to split that code
furthermore, with the space map being its own on-disk data
structure used in areas of ZFS besides metaslabs (e.g. the
vdev-wide space maps used for zpool checkpoint or vdev removal
features).

This patch refactors the space map code to further split the
space map code from the metaslab code. It does so by getting
rid of the idea that the space map can have a different in-core
and on-disk length (sm_length vs smp_length) which is something
that is only used for the metaslab code, and other consumers
of space maps just have to deal with. Instead, this patch
introduces changes that move the old in-core length of the
metaslab's space map to the metaslab structure itself (see
ms_synced_length field) while making the space map code only
care about the actual space map's length on-disk.

The result of this is that space map consumers no longer have
to deal with syncing two different lengths for the same
structure (e.g. space_map_update() goes away) while metaslab
specific behavior stays within the metaslab code. Specifically,
the ms_synced_length field keeps track of the amount of data
metaslab_load() can read from the metaslab's space map while
working concurrently with metaslab_sync() that may be
appending to that same space map.

As a side note, the patch also adds a few comments around
the metaslab code documenting some assumptions and expected
behavior.

Reviewed-by: Matt Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Closes #8328
2019-02-12 10:38:11 -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 http://www.opensolaris.org/os/licensing.
* 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 2009 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
* Copyright (c) 2012, 2018 by Delphix. All rights reserved.
*/
#ifndef _SYS_SPACE_MAP_H
#define _SYS_SPACE_MAP_H
#include <sys/avl.h>
#include <sys/range_tree.h>
#include <sys/dmu.h>
#ifdef __cplusplus
extern "C" {
#endif
/*
* The size of the space map object has increased to include a histogram.
* The SPACE_MAP_SIZE_V0 designates the original size and is used to
* maintain backward compatibility.
*/
#define SPACE_MAP_SIZE_V0 (3 * sizeof (uint64_t))
#define SPACE_MAP_HISTOGRAM_SIZE 32
/*
* The space_map_phys is the on-disk representation of the space map.
* Consumers of space maps should never reference any of the members of this
* structure directly. These members may only be updated in syncing context.
*
* Note the smp_object is no longer used but remains in the structure
* for backward compatibility.
*/
typedef struct space_map_phys {
/* object number: not needed but kept for backwards compatibility */
uint64_t smp_object;
/* length of the object in bytes */
uint64_t smp_length;
/* space allocated from the map */
int64_t smp_alloc;
/* reserved */
uint64_t smp_pad[5];
/*
* The smp_histogram maintains a histogram of free regions. Each
* bucket, smp_histogram[i], contains the number of free regions
* whose size is:
* 2^(i+sm_shift) <= size of free region in bytes < 2^(i+sm_shift+1)
*/
uint64_t smp_histogram[SPACE_MAP_HISTOGRAM_SIZE];
} space_map_phys_t;
/*
* The space map object defines a region of space, its size, how much is
* allocated, and the on-disk object that stores this information.
* Consumers of space maps may only access the members of this structure.
*
* Note: the space_map may not be accessed concurrently; consumers
* must provide external locking if required.
*/
typedef struct space_map {
uint64_t sm_start; /* start of map */
uint64_t sm_size; /* size of map */
uint8_t sm_shift; /* unit shift */
objset_t *sm_os; /* objset for this map */
uint64_t sm_object; /* object id for this map */
uint32_t sm_blksz; /* block size for space map */
dmu_buf_t *sm_dbuf; /* space_map_phys_t dbuf */
space_map_phys_t *sm_phys; /* on-disk space map */
} space_map_t;
/*
* debug entry
*
* 2 2 10 50
* +-----+-----+------------+----------------------------------+
* | 1 0 | act | syncpass | txg (lower bits) |
* +-----+-----+------------+----------------------------------+
* 63 62 61 60 59 50 49 0
*
*
* one-word entry
*
* 1 47 1 15
* +-----------------------------------------------------------+
* | 0 | offset (sm_shift units) | type | run |
* +-----------------------------------------------------------+
* 63 62 16 15 14 0
*
*
* two-word entry
*
* 2 2 36 24
* +-----+-----+---------------------------+-------------------+
* | 1 1 | pad | run | vdev |
* +-----+-----+---------------------------+-------------------+
* 63 62 61 60 59 24 23 0
*
* 1 63
* +------+----------------------------------------------------+
* | type | offset |
* +------+----------------------------------------------------+
* 63 62 0
*
* Note that a two-word entry will not straddle a block boundary.
* If necessary, the last word of a block will be padded with a
* debug entry (with act = syncpass = txg = 0).
*/
typedef enum {
SM_ALLOC,
SM_FREE
} maptype_t;
typedef struct space_map_entry {
maptype_t sme_type;
uint32_t sme_vdev; /* max is 2^24-1; SM_NO_VDEVID if not present */
uint64_t sme_offset; /* max is 2^63-1; units of sm_shift */
uint64_t sme_run; /* max is 2^36; units of sm_shift */
} space_map_entry_t;
#define SM_NO_VDEVID (1 << SPA_VDEVBITS)
/* one-word entry constants */
#define SM_DEBUG_PREFIX 2
#define SM_OFFSET_BITS 47
#define SM_RUN_BITS 15
/* two-word entry constants */
#define SM2_PREFIX 3
#define SM2_OFFSET_BITS 63
#define SM2_RUN_BITS 36
#define SM_PREFIX_DECODE(x) BF64_DECODE(x, 62, 2)
#define SM_PREFIX_ENCODE(x) BF64_ENCODE(x, 62, 2)
#define SM_DEBUG_ACTION_DECODE(x) BF64_DECODE(x, 60, 2)
#define SM_DEBUG_ACTION_ENCODE(x) BF64_ENCODE(x, 60, 2)
#define SM_DEBUG_SYNCPASS_DECODE(x) BF64_DECODE(x, 50, 10)
#define SM_DEBUG_SYNCPASS_ENCODE(x) BF64_ENCODE(x, 50, 10)
#define SM_DEBUG_TXG_DECODE(x) BF64_DECODE(x, 0, 50)
#define SM_DEBUG_TXG_ENCODE(x) BF64_ENCODE(x, 0, 50)
#define SM_OFFSET_DECODE(x) BF64_DECODE(x, 16, SM_OFFSET_BITS)
#define SM_OFFSET_ENCODE(x) BF64_ENCODE(x, 16, SM_OFFSET_BITS)
#define SM_TYPE_DECODE(x) BF64_DECODE(x, 15, 1)
#define SM_TYPE_ENCODE(x) BF64_ENCODE(x, 15, 1)
#define SM_RUN_DECODE(x) (BF64_DECODE(x, 0, SM_RUN_BITS) + 1)
#define SM_RUN_ENCODE(x) BF64_ENCODE((x) - 1, 0, SM_RUN_BITS)
#define SM_RUN_MAX SM_RUN_DECODE(~0ULL)
#define SM_OFFSET_MAX SM_OFFSET_DECODE(~0ULL)
#define SM2_RUN_DECODE(x) (BF64_DECODE(x, SPA_VDEVBITS, SM2_RUN_BITS) + 1)
#define SM2_RUN_ENCODE(x) BF64_ENCODE((x) - 1, SPA_VDEVBITS, SM2_RUN_BITS)
#define SM2_VDEV_DECODE(x) BF64_DECODE(x, 0, SPA_VDEVBITS)
#define SM2_VDEV_ENCODE(x) BF64_ENCODE(x, 0, SPA_VDEVBITS)
#define SM2_TYPE_DECODE(x) BF64_DECODE(x, SM2_OFFSET_BITS, 1)
#define SM2_TYPE_ENCODE(x) BF64_ENCODE(x, SM2_OFFSET_BITS, 1)
#define SM2_OFFSET_DECODE(x) BF64_DECODE(x, 0, SM2_OFFSET_BITS)
#define SM2_OFFSET_ENCODE(x) BF64_ENCODE(x, 0, SM2_OFFSET_BITS)
#define SM2_RUN_MAX SM2_RUN_DECODE(~0ULL)
#define SM2_OFFSET_MAX SM2_OFFSET_DECODE(~0ULL)
boolean_t sm_entry_is_debug(uint64_t e);
boolean_t sm_entry_is_single_word(uint64_t e);
boolean_t sm_entry_is_double_word(uint64_t e);
typedef int (*sm_cb_t)(space_map_entry_t *sme, void *arg);
int space_map_load(space_map_t *sm, range_tree_t *rt, maptype_t maptype);
int space_map_load_length(space_map_t *sm, range_tree_t *rt, maptype_t maptype,
uint64_t length);
int space_map_iterate(space_map_t *sm, uint64_t length,
sm_cb_t callback, void *arg);
int space_map_incremental_destroy(space_map_t *sm, sm_cb_t callback, void *arg,
dmu_tx_t *tx);
void space_map_histogram_clear(space_map_t *sm);
void space_map_histogram_add(space_map_t *sm, range_tree_t *rt,
dmu_tx_t *tx);
uint64_t space_map_object(space_map_t *sm);
int64_t space_map_allocated(space_map_t *sm);
uint64_t space_map_length(space_map_t *sm);
void space_map_write(space_map_t *sm, range_tree_t *rt, maptype_t maptype,
uint64_t vdev_id, dmu_tx_t *tx);
uint64_t space_map_estimate_optimal_size(space_map_t *sm, range_tree_t *rt,
uint64_t vdev_id);
void space_map_truncate(space_map_t *sm, int blocksize, dmu_tx_t *tx);
uint64_t space_map_alloc(objset_t *os, int blocksize, dmu_tx_t *tx);
void space_map_free(space_map_t *sm, dmu_tx_t *tx);
void space_map_free_obj(objset_t *os, uint64_t smobj, dmu_tx_t *tx);
int space_map_open(space_map_t **smp, objset_t *os, uint64_t object,
uint64_t start, uint64_t size, uint8_t shift);
void space_map_close(space_map_t *sm);
#ifdef __cplusplus
}
#endif
#endif /* _SYS_SPACE_MAP_H */
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