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a10e552b99
Adding O_DIRECT support to ZFS to bypass the ARC for writes/reads.
O_DIRECT support in ZFS will always ensure there is coherency between
buffered and O_DIRECT IO requests. This ensures that all IO requests,
whether buffered or direct, will see the same file contents at all
times. Just as in other FS's , O_DIRECT does not imply O_SYNC. While
data is written directly to VDEV disks, metadata will not be synced
until the associated TXG is synced.
For both O_DIRECT read and write request the offset and request sizes,
at a minimum, must be PAGE_SIZE aligned. In the event they are not,
then EINVAL is returned unless the direct property is set to always (see
below).
For O_DIRECT writes:
The request also must be block aligned (recordsize) or the write
request will take the normal (buffered) write path. In the event that
request is block aligned and a cached copy of the buffer in the ARC,
then it will be discarded from the ARC forcing all further reads to
retrieve the data from disk.
For O_DIRECT reads:
The only alignment restrictions are PAGE_SIZE alignment. In the event
that the requested data is in buffered (in the ARC) it will just be
copied from the ARC into the user buffer.
For both O_DIRECT writes and reads the O_DIRECT flag will be ignored in
the event that file contents are mmap'ed. In this case, all requests
that are at least PAGE_SIZE aligned will just fall back to the buffered
paths. If the request however is not PAGE_SIZE aligned, EINVAL will
be returned as always regardless if the file's contents are mmap'ed.
Since O_DIRECT writes go through the normal ZIO pipeline, the
following operations are supported just as with normal buffered writes:
Checksum
Compression
Encryption
Erasure Coding
There is one caveat for the data integrity of O_DIRECT writes that is
distinct for each of the OS's supported by ZFS.
FreeBSD - FreeBSD is able to place user pages under write protection so
any data in the user buffers and written directly down to the
VDEV disks is guaranteed to not change. There is no concern
with data integrity and O_DIRECT writes.
Linux - Linux is not able to place anonymous user pages under write
protection. Because of this, if the user decides to manipulate
the page contents while the write operation is occurring, data
integrity can not be guaranteed. However, there is a module
parameter `zfs_vdev_direct_write_verify` that controls the
if a O_DIRECT writes that can occur to a top-level VDEV before
a checksum verify is run before the contents of the I/O buffer
are committed to disk. In the event of a checksum verification
failure the write will return EIO. The number of O_DIRECT write
checksum verification errors can be observed by doing
`zpool status -d`, which will list all verification errors that
have occurred on a top-level VDEV. Along with `zpool status`, a
ZED event will be issues as `dio_verify` when a checksum
verification error occurs.
ZVOLs and dedup is not currently supported with Direct I/O.
A new dataset property `direct` has been added with the following 3
allowable values:
disabled - Accepts O_DIRECT flag, but silently ignores it and treats
the request as a buffered IO request.
standard - Follows the alignment restrictions outlined above for
write/read IO requests when the O_DIRECT flag is used.
always - Treats every write/read IO request as though it passed
O_DIRECT and will do O_DIRECT if the alignment restrictions
are met otherwise will redirect through the ARC. This
property will not allow a request to fail.
There is also a module parameter zfs_dio_enabled that can be used to
force all reads and writes through the ARC. By setting this module
parameter to 0, it mimics as if the direct dataset property is set to
disabled.
Reviewed-by: Brian Behlendorf <behlendorf@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Co-authored-by: Mark Maybee <mark.maybee@delphix.com>
Co-authored-by: Matt Macy <mmacy@FreeBSD.org>
Co-authored-by: Brian Behlendorf <behlendorf@llnl.gov>
Closes #10018
284 lines
7.7 KiB
C
284 lines
7.7 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or https://opensource.org/licenses/CDDL-1.0.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2010 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/*
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* Copyright (c) 2012, Joyent, Inc. All rights reserved.
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* Copyright (c) 2013, 2018 by Delphix. All rights reserved.
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*/
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#ifndef _SYS_DMU_IMPL_H
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#define _SYS_DMU_IMPL_H
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#include <sys/txg_impl.h>
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#include <sys/zio.h>
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#include <sys/dnode.h>
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#include <sys/zfs_context.h>
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#include <sys/zfs_ioctl.h>
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#include <sys/uio.h>
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#include <sys/abd.h>
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#include <sys/arc.h>
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#include <sys/dbuf.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* This is the locking strategy for the DMU. Numbers in parenthesis are
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* cases that use that lock order, referenced below:
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*
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* ARC is self-contained
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* bplist is self-contained
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* refcount is self-contained
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* txg is self-contained (hopefully!)
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* zst_lock
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* zf_rwlock
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*
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* XXX try to improve evicting path?
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*
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* dp_config_rwlock > os_obj_lock > dn_struct_rwlock >
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* dn_dbufs_mtx > hash_mutexes > db_mtx > dd_lock > leafs
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*
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* dp_config_rwlock
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* must be held before: everything
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* protects dd namespace changes
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* protects property changes globally
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* held from:
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* dsl_dir_open/r:
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* dsl_dir_create_sync/w:
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* dsl_dir_sync_destroy/w:
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* dsl_dir_rename_sync/w:
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* dsl_prop_changed_notify/r:
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*
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* os_obj_lock
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* must be held before:
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* everything except dp_config_rwlock
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* protects os_obj_next
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* held from:
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* dmu_object_alloc: dn_dbufs_mtx, db_mtx, hash_mutexes, dn_struct_rwlock
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*
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* dn_struct_rwlock
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* must be held before:
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* everything except dp_config_rwlock and os_obj_lock
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* protects structure of dnode (eg. nlevels)
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* db_blkptr can change when syncing out change to nlevels
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* dn_maxblkid
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* dn_nlevels
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* dn_*blksz*
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* phys nlevels, maxblkid, physical blkptr_t's (?)
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* held from:
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* callers of dbuf_read_impl, dbuf_hold[_impl], dbuf_prefetch
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* dmu_object_info_from_dnode: dn_dirty_mtx (dn_datablksz)
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* dbuf_read_impl: db_mtx, dmu_zfetch()
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* dmu_zfetch: zf_rwlock/r, zst_lock, dbuf_prefetch()
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* dbuf_new_size: db_mtx
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* dbuf_dirty: db_mtx
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* dbuf_findbp: (callers, phys? - the real need)
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* dbuf_create: dn_dbufs_mtx, hash_mutexes, db_mtx (phys?)
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* dbuf_prefetch: dn_dirty_mtx, hash_mutexes, db_mtx, dn_dbufs_mtx
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* dbuf_hold_impl: hash_mutexes, db_mtx, dn_dbufs_mtx, dbuf_findbp()
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* dnode_sync/w (increase_indirection): db_mtx (phys)
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* dnode_set_blksz/w: dn_dbufs_mtx (dn_*blksz*)
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* dnode_new_blkid/w: (dn_maxblkid)
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* dnode_free_range/w: dn_dirty_mtx (dn_maxblkid)
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* dnode_next_offset: (phys)
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*
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* dn_dbufs_mtx
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* must be held before:
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* db_mtx, hash_mutexes
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* protects:
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* dn_dbufs
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* dn_evicted
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* held from:
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* dmu_evict_user: db_mtx (dn_dbufs)
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* dbuf_free_range: db_mtx (dn_dbufs)
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* dbuf_remove_ref: db_mtx, callees:
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* dbuf_hash_remove: hash_mutexes, db_mtx
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* dbuf_create: hash_mutexes, db_mtx (dn_dbufs)
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* dnode_set_blksz: (dn_dbufs)
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*
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* hash_mutexes (global)
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* must be held before:
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* db_mtx
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* protects dbuf_hash_table (global) and db_hash_next
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* held from:
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* dbuf_find: db_mtx
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* dbuf_hash_insert: db_mtx
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* dbuf_hash_remove: db_mtx
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*
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* db_mtx (meta-leaf)
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* must be held before:
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* dn_mtx, dn_dirty_mtx, dd_lock (leaf mutexes)
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* protects:
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* db_state
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* db_holds
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* db_buf
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* db_changed
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* db_data_pending
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* db_dirtied
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* db_link
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* db_dirty_records
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* db_dirtycnt
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* db_d.*
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* db.*
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* held from:
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* dbuf_dirty: dn_mtx, dn_dirty_mtx
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* dbuf_dirty->dsl_dir_willuse_space: dd_lock
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* dbuf_dirty->dbuf_new_block->dsl_dataset_block_freeable: dd_lock
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* dbuf_undirty: dn_dirty_mtx (db_d)
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* dbuf_write_done: dn_dirty_mtx (db_state)
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* dbuf_*
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* dmu_buf_update_user: none (db_d)
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* dmu_evict_user: none (db_d) (maybe can eliminate)
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* dbuf_find: none (db_holds)
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* dbuf_hash_insert: none (db_holds)
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* dmu_buf_read_array_impl: none (db_state, db_changed)
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* dmu_sync: none (db_dirty_records, db_d)
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* dnode_reallocate: none (db)
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* dmu_write_direct: none (db_dirty_records, db_d)
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* dmu_write_direct_done: none (db_dirty_records, db_d)
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*
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* dn_mtx (leaf)
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* protects:
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* dn_dirty_dbufs
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* dn_ranges
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* phys accounting
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* dn_allocated_txg
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* dn_free_txg
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* dn_assigned_txg
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* dn_dirty_txg
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* dd_assigned_tx
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* dn_notxholds
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* dn_nodnholds
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* dn_dirtyctx
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* dn_dirtyctx_firstset
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* (dn_phys copy fields?)
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* (dn_phys contents?)
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* held from:
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* dnode_*
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* dbuf_dirty: none
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* dbuf_sync: none (phys accounting)
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* dbuf_undirty: none (dn_ranges, dn_dirty_dbufs)
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* dbuf_write_done: none (phys accounting)
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* dmu_object_info_from_dnode: none (accounting)
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* dmu_tx_commit: none
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* dmu_tx_hold_object_impl: none
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* dmu_tx_try_assign: dn_notxholds(cv)
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* dmu_tx_unassign: none
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*
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* dd_lock
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* must be held before:
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* ds_lock
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* ancestors' dd_lock
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* protects:
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* dd_prop_cbs
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* dd_sync_*
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* dd_used_bytes
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* dd_tempreserved
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* dd_space_towrite
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* dd_myname
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* dd_phys accounting?
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* held from:
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* dsl_dir_*
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* dsl_prop_changed_notify: none (dd_prop_cbs)
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* dsl_prop_register: none (dd_prop_cbs)
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* dsl_prop_unregister: none (dd_prop_cbs)
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*
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* os_lock (leaf)
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* protects:
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* os_dirty_dnodes
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* os_free_dnodes
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* os_dnodes
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* os_downgraded_dbufs
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* dn_dirtyblksz
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* dn_dirty_link
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* held from:
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* dnode_create: none (os_dnodes)
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* dnode_destroy: none (os_dnodes)
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* dnode_setdirty: none (dn_dirtyblksz, os_*_dnodes)
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* dnode_free: none (dn_dirtyblksz, os_*_dnodes)
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*
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* ds_lock
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* protects:
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* ds_objset
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* ds_open_refcount
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* ds_snapname
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* ds_phys accounting
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* ds_phys userrefs zapobj
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* ds_reserved
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* held from:
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* dsl_dataset_*
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*
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* dr_mtx (leaf)
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* protects:
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* dr_children
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* held from:
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* dbuf_dirty
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* dbuf_undirty
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* dbuf_sync_indirect
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* dnode_new_blkid
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*/
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struct dmu_pool;
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struct dmu_buf;
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struct zgd;
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typedef struct dmu_sendstatus {
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list_node_t dss_link;
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int dss_outfd;
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proc_t *dss_proc;
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offset_t *dss_off;
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uint64_t dss_blocks; /* blocks visited during the sending process */
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} dmu_sendstatus_t;
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/*
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* dmu_sync_{ready/done} args
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*/
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typedef struct {
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dbuf_dirty_record_t *dsa_dr;
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void (*dsa_done)(struct zgd *, int);
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struct zgd *dsa_zgd;
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dmu_tx_t *dsa_tx;
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} dmu_sync_arg_t;
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void dmu_sync_done(zio_t *, arc_buf_t *buf, void *varg);
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void dmu_sync_ready(zio_t *, arc_buf_t *buf, void *varg);
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void dmu_object_zapify(objset_t *, uint64_t, dmu_object_type_t, dmu_tx_t *);
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void dmu_object_free_zapified(objset_t *, uint64_t, dmu_tx_t *);
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int dmu_write_direct(zio_t *, dmu_buf_impl_t *, abd_t *, dmu_tx_t *);
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int dmu_read_abd(dnode_t *, uint64_t, uint64_t, abd_t *, uint32_t flags);
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int dmu_write_abd(dnode_t *, uint64_t, uint64_t, abd_t *, uint32_t, dmu_tx_t *);
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#if defined(_KERNEL)
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int dmu_read_uio_direct(dnode_t *, zfs_uio_t *, uint64_t);
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int dmu_write_uio_direct(dnode_t *, zfs_uio_t *, uint64_t, dmu_tx_t *);
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#endif
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#ifdef __cplusplus
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}
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#endif
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#endif /* _SYS_DMU_IMPL_H */
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