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linux/fs/btrfs
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Nikolay Borisov dcc3eb9638 btrfs: convert snapshot/nocow exlcusion to drew lock 
This patch removes all haphazard code implementing nocow writers
exclusion from pending snapshot creation and switches to using the drew
lock to ensure this invariant still holds.

'Readers' are snapshot creators from create_snapshot and 'writers' are
nocow writers from buffered write path or btrfs_setsize. This locking
scheme allows for multiple snapshots to happen while any nocow writers
are blocked, since writes to page cache in the nocow path will make
snapshots inconsistent.

So for performance reasons we'd like to have the ability to run multiple
concurrent snapshots and also favors readers in this case. And in case
there aren't pending snapshots (which will be the majority of the cases)
we rely on the percpu's writers counter to avoid cacheline contention.

The main gain from using the drew lock is it's now a lot easier to
reason about the guarantees of the locking scheme and whether there is
some silent breakage lurking.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-03-23 17:01:44 +01:00
..
tests btrfs: rename btrfs_put_fs_root and btrfs_grab_fs_root 2020-03-23 17:01:33 +01:00
acl.c btrfs: cleanup btrfs_setxattr_trans and drop transaction parameter 2019-04-29 19:02:44 +02:00
async-thread.c btrfs: add __pure attribute to functions 2019-11-18 12:46:52 +01:00
async-thread.h btrfs: add __pure attribute to functions 2019-11-18 12:46:52 +01:00
backref.c btrfs: backref, use correct count to resolve normal data refs 2020-03-23 17:01:40 +01:00
backref.h btrfs: fiemap: preallocate ulists for btrfs_check_shared 2019-07-01 13:34:53 +02:00
block-group.c btrfs: switch to per-transaction pinned extents 2020-03-23 17:01:38 +01:00
block-group.h btrfs: Move and unexport btrfs_rmap_block 2020-01-23 17:24:34 +01:00
block-rsv.c btrfs: add a comment describing block reserves 2020-03-23 17:01:26 +01:00
block-rsv.h btrfs: migrate the global_block_rsv helpers to block-rsv.c 2019-07-02 12:30:55 +02:00
btrfs_inode.h btrfs: introduce per-inode file extent tree 2020-03-23 17:01:24 +01:00
check-integrity.c btrfs: remove buffer_heads form super block mirror integrity checking 2020-03-23 17:01:40 +01:00
check-integrity.h btrfs: remove btrfsic_submit_bh() 2020-03-23 17:01:39 +01:00
compression.c btrfs: use larger zlib buffer for s390 hardware compression 2020-01-31 10:30:40 -08:00
compression.h btrfs: compression: remove ops pointer from workspace_manager 2019-11-18 12:46:59 +01:00
ctree.c btrfs: move root node locking helpers to locking.c 2020-03-23 17:01:33 +01:00
ctree.h btrfs: convert snapshot/nocow exlcusion to drew lock 2020-03-23 17:01:44 +01:00
delalloc-space.c btrfs: add a comment describing delalloc space reservation 2020-03-23 17:01:27 +01:00
delalloc-space.h btrfs: migrate the delalloc space stuff to it's own home 2019-07-04 17:26:17 +02:00
delayed-inode.c btrfs: add wrapper for transaction abort predicate 2020-03-23 17:01:34 +01:00
delayed-inode.h Btrfs: delayed-inode: use rb_first_cached for ins_root and del_root 2018-10-15 17:23:33 +02:00
delayed-ref.c Btrfs: fix race between adding and putting tree mod seq elements and nodes 2020-01-31 14:01:20 +01:00
delayed-ref.h btrfs: migrate the delayed refs rsv code 2019-07-04 17:26:17 +02:00
dev-replace.c btrfs: sysfs, rename device_link add/remove functions 2020-03-23 17:01:35 +01:00
dev-replace.h btrfs: add __pure attribute to functions 2019-11-18 12:46:52 +01:00
dir-item.c btrfs: remove unused parameter fs_info from btrfs_extend_item 2019-04-29 19:02:50 +02:00
discard.c btrfs: add correction to handle -1 edge case in async discard 2020-01-20 16:41:01 +01:00
discard.h btrfs: have multiple discard lists 2020-01-20 16:41:00 +01:00
disk-io.c btrfs: convert snapshot/nocow exlcusion to drew lock 2020-03-23 17:01:44 +01:00
disk-io.h btrfs: use the page cache for super block reading 2020-03-23 17:01:39 +01:00
export.c btrfs: export helpers for subvolume name/id resolution 2020-03-23 17:01:42 +01:00
export.h btrfs: export helpers for subvolume name/id resolution 2020-03-23 17:01:42 +01:00
extent-io-tree.h btrfs: switch to per-transaction pinned extents 2020-03-23 17:01:38 +01:00
extent-tree.c btrfs: convert snapshot/nocow exlcusion to drew lock 2020-03-23 17:01:44 +01:00
extent_io.c btrfs: Add missing lock annotation for release_extent_buffer() 2020-03-23 17:01:42 +01:00
extent_io.h btrfs: sink argument tree to extent_read_full_page 2020-03-23 17:01:35 +01:00
extent_map.c Btrfs: fix race between using extent maps and merging them 2020-02-12 17:16:46 +01:00
extent_map.h btrfs: remove extent_map::bdev 2019-11-18 23:43:44 +01:00
file-item.c btrfs: introduce per-inode file extent tree 2020-03-23 17:01:24 +01:00
file.c btrfs: convert snapshot/nocow exlcusion to drew lock 2020-03-23 17:01:44 +01:00
free-space-cache.c btrfs: simplify error handling in __btrfs_write_out_cache() 2020-03-23 17:01:43 +01:00
free-space-cache.h btrfs: have multiple discard lists 2020-01-20 16:41:00 +01:00
free-space-tree.c btrfs: rename btrfs_put_fs_root and btrfs_grab_fs_root 2020-03-23 17:01:33 +01:00
free-space-tree.h btrfs: rename btrfs_block_group_cache 2019-11-18 17:51:51 +01:00
inode-item.c btrfs: Make btrfs_find_name_in_ext_backref return struct btrfs_inode_extref 2019-09-09 14:59:16 +02:00
inode-map.c btrfs: keep track of which extents have been discarded 2020-01-20 16:40:57 +01:00
inode-map.h
inode.c btrfs: convert snapshot/nocow exlcusion to drew lock 2020-03-23 17:01:44 +01:00
ioctl.c btrfs: convert snapshot/nocow exlcusion to drew lock 2020-03-23 17:01:44 +01:00
Kconfig btrfs: add Kconfig dependency for BLAKE2B 2019-12-09 17:56:06 +01:00
locking.c btrfs: Implement DREW lock 2020-03-23 17:01:43 +01:00
locking.h btrfs: Implement DREW lock 2020-03-23 17:01:43 +01:00
lzo.c btrfs: compression: inline free_workspace 2019-11-18 12:46:59 +01:00
Makefile btrfs: add the beginning of async discard, discard workqueue 2020-01-20 16:40:57 +01:00
misc.h btrfs: add 64bit safe helper for power of two checks 2019-11-18 12:46:50 +01:00
ordered-data.c btrfs: drop argument tree from btrfs_lock_and_flush_ordered_range 2020-03-23 17:01:34 +01:00
ordered-data.h btrfs: drop argument tree from btrfs_lock_and_flush_ordered_range 2020-03-23 17:01:34 +01:00
orphan.c
print-tree.c btrfs: Remove unneeded semicolon 2020-01-20 16:40:55 +01:00
print-tree.h
props.c btrfs: props: remove unnecessary hash_init() 2019-11-18 12:46:55 +01:00
props.h btrfs: delete unused function btrfs_set_prop_trans 2019-04-29 19:02:54 +02:00
qgroup.c btrfs: rename btrfs_put_fs_root and btrfs_grab_fs_root 2020-03-23 17:01:33 +01:00
qgroup.h btrfs: destroy qgroup extent records on transaction abort 2020-02-19 00:35:54 +01:00
raid56.c btrfs: raid56: simplify tracking of Q stripe presence 2020-03-23 17:01:41 +01:00
raid56.h btrfs: constify map parameter for nr_parity_stripes and nr_data_stripes 2019-07-01 13:34:58 +02:00
rcu-string.h
reada.c btrfs: rename btrfs_block_group_cache 2019-11-18 17:51:51 +01:00
ref-verify.c btrfs: ref-verify: fix memory leaks 2020-02-12 17:16:31 +01:00
ref-verify.h btrfs: ref-verify: Use btrfs_ref to refactor btrfs_ref_tree_mod() 2019-04-29 19:02:49 +02:00
relocation.c btrfs: relocation: Remove is_cowonly_root() 2020-03-23 17:01:38 +01:00
root-tree.c btrfs: rename btrfs_put_fs_root and btrfs_grab_fs_root 2020-03-23 17:01:33 +01:00
scrub.c btrfs: rename btrfs_put_fs_root and btrfs_grab_fs_root 2020-03-23 17:01:33 +01:00
send.c btrfs: rename btrfs_put_fs_root and btrfs_grab_fs_root 2020-03-23 17:01:33 +01:00
send.h
space-info.c btrfs: describe the space reservation system in general 2020-03-23 17:01:27 +01:00
space-info.h btrfs: take overcommit into account in inc_block_group_ro 2020-01-31 14:02:01 +01:00
struct-funcs.c btrfs: tie extent buffer and it's token together 2019-09-09 14:59:16 +02:00
super.c btrfs: export helpers for subvolume name/id resolution 2020-03-23 17:01:42 +01:00
sysfs.c btrfs: sysfs, unify handler name of devinfo/missing 2020-03-23 17:01:36 +01:00
sysfs.h btrfs: sysfs, rename device_link add/remove functions 2020-03-23 17:01:35 +01:00
transaction.c btrfs: switch to per-transaction pinned extents 2020-03-23 17:01:38 +01:00
transaction.h btrfs: switch to per-transaction pinned extents 2020-03-23 17:01:38 +01:00
tree-checker.c btrfs: tree-checker: Verify location key for DIR_ITEM/DIR_INDEX 2020-01-20 16:40:56 +01:00
tree-checker.h btrfs: get fs_info from eb in btrfs_check_chunk_valid 2019-04-29 19:02:39 +02:00
tree-defrag.c btrfs: open code now trivial btrfs_set_lock_blocking 2019-02-25 14:13:27 +01:00
tree-log.c btrfs: Make btrfs_pin_extent_for_log_replay take transaction handle 2020-03-23 17:01:37 +01:00
tree-log.h btrfs: get fs_info from trans in btrfs_set_log_full_commit 2019-04-29 19:02:41 +02:00
ulist.c
ulist.h
uuid-tree.c btrfs: bail out of uuid tree scanning if we're closing 2020-03-23 17:01:41 +01:00
volumes.c btrfs: bail out of uuid tree scanning if we're closing 2020-03-23 17:01:41 +01:00
volumes.h btrfs: make btrfs_check_uuid_tree private to disk-io.c 2020-03-23 17:01:41 +01:00
xattr.c Btrfs: fix failure to persist compression property xattr deletion on fsync 2019-06-17 16:37:17 +02:00
xattr.h btrfs: cleanup btrfs_setxattr_trans and drop transaction parameter 2019-04-29 19:02:44 +02:00
zlib.c btrfs: use larger zlib buffer for s390 hardware compression 2020-01-31 10:30:40 -08:00
zstd.c btrfs: compression: inline free_workspace 2019-11-18 12:46:59 +01:00