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4bb59055bc
linux/fs/btrfs
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Filipe Manana 4bb59055bc btrfs: avoid unnecessary btree search restarts when reading node 
When reading a btree node, at read_block_for_search(), if we don't find
the node's (or leaf) extent buffer in the cache, we will read it from
disk. Since that requires waiting on IO, we release all upper level nodes
from our path before reading the target node/leaf, and then return -EAGAIN
to the caller, which will make the caller restart the while btree search.

However we are causing the restart of btree search even for cases where
it is not necessary:

1) We have a path with ->skip_locking set to true, typically when doing
   a search on a commit root, so we are never holding locks on any node;

2) We are doing a read search (the "ins_len" argument passed to
   btrfs_search_slot() is 0), or we are doing a search to modify an
   existing key (the "cow" argument passed to btrfs_search_slot() has
   a value of 1 and "ins_len" is 0), in which case we never hold locks
   for upper level nodes;

3) We are doing a search to insert or delete a key, in which case we may
   or may not have upper level nodes locked. That depends on the current
   minimum write lock levels at btrfs_search_slot(), if we had to split
   or merge parent nodes, if we had to COW upper level nodes and if
   we ever visited slot 0 of an upper level node. It's still common to
   not have upper level nodes locked, but our current node must be at
   least at level 1, for insertions, or at least at level 2 for deletions.
   In these cases when we have locks on upper level nodes, they are always
   write locks.

These cases where we are not holding locks on upper level nodes far
outweigh the cases where we are holding locks, so it's completely wasteful
to retry the whole search when we have no upper nodes locked.

So change the logic to not return -EAGAIN, and make the caller retry the
search, when we don't have the parent node locked - when it's not locked
it means no other upper level nodes are locked as well.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2022-05-16 17:03:06 +02:00
..
tests btrfs: assert we have a write lock when removing and replacing extent maps 2022-03-14 13:13:50 +01:00
acl.c btrfs: remove unused mnt_userns parameter from __btrfs_set_acl 2022-05-16 17:03:06 +02:00
async-thread.c btrfs: fix memory ordering between normal and ordered work functions 2021-11-16 16:50:23 +01:00
async-thread.h
backref.c btrfs: unify the error handling pattern for read_tree_block() 2022-03-14 13:13:53 +01:00
backref.h btrfs: remove ignore_offset argument from btrfs_find_all_roots() 2021-08-23 13:19:01 +02:00
block-group.c btrfs: zoned: activate block group only for extent allocation 2022-04-06 00:50:41 +02:00
block-group.h btrfs: zoned: activate block group only for extent allocation 2022-04-06 00:50:41 +02:00
block-rsv.c btrfs: reserve extra space for the free space tree 2022-01-07 14:18:25 +01:00
block-rsv.h btrfs: init root block_rsv at init root time 2022-01-03 15:09:48 +01:00
btrfs_inode.h btrfs: export a helper for compression hard check 2022-04-27 22:15:40 +02:00
check-integrity.c block: remove genhd.h 2022-02-02 07:49:59 -07:00
check-integrity.h
compression.c btrfs: fix btrfs_submit_compressed_write cgroup attribution 2022-04-06 00:50:51 +02:00
compression.h btrfs: track compressed bio errors as blk_status_t 2022-03-14 13:13:51 +01:00
ctree.c btrfs: avoid unnecessary btree search restarts when reading node 2022-05-16 17:03:06 +02:00
ctree.h for-5.18-rc4-tag 2022-04-26 11:10:42 -07:00
delalloc-space.c btrfs: support different disk extent size for delalloc 2022-03-14 13:13:51 +01:00
delalloc-space.h
delayed-inode.c btrfs: add an inode-item.h 2022-01-07 14:18:23 +01:00
delayed-inode.h
delayed-ref.c btrfs: reserve extra space for the free space tree 2022-01-07 14:18:25 +01:00
delayed-ref.h btrfs: make btrfs_ref::real_root optional 2021-10-26 19:08:06 +02:00
dev-replace.c btrfs: fix assertion failure during scrub due to block group reallocation 2022-04-21 16:06:19 +02:00
dev-replace.h
dir-item.c btrfs: drop the _nr from the item helpers 2022-01-03 15:09:43 +01:00
discard.c btrfs: fix typos in comments 2021-06-22 14:11:57 +02:00
discard.h
disk-io.c for-5.18-rc5-tag 2022-05-06 14:32:16 -07:00
disk-io.h btrfs: add code to support the block group root 2022-03-14 13:13:48 +01:00
export.c
export.h
extent_io.c for-5.18-rc4-tag 2022-04-26 11:10:42 -07:00
extent_io.h btrfs: fix qgroup reserve overflow the qgroup limit 2022-03-23 23:34:15 +01:00
extent_map.c btrfs: assert we have a write lock when removing and replacing extent maps 2022-03-14 13:13:50 +01:00
extent_map.h btrfs: defrag: don't use merged extent map for their generation check 2022-02-23 17:43:13 +01:00
extent-io-tree.h btrfs: Convert from invalidatepage to invalidate_folio 2022-03-15 08:23:29 -04:00
extent-tree.c btrfs: zoned: activate block group only for extent allocation 2022-04-06 00:50:41 +02:00
file-item.c btrfs: handle csum lookup errors properly on reads 2022-03-14 13:13:51 +01:00
file.c btrfs: fix fallocate to use file_modified to update permissions consistently 2022-03-24 17:48:02 +01:00
free-space-cache.c btrfs: add inode to truncate control 2022-01-07 14:18:24 +01:00
free-space-cache.h btrfs: change name and type of private member of btrfs_free_space_ctl 2022-01-03 15:09:50 +01:00
free-space-tree.c btrfs: add support for multiple global roots 2022-03-14 13:13:49 +01:00
free-space-tree.h
inode-item.c btrfs: make should_throttle loop local in btrfs_truncate_inode_items 2022-01-07 14:18:25 +01:00
inode-item.h btrfs: add inode to truncate control 2022-01-07 14:18:24 +01:00
inode.c btrfs: set inode flags earlier in btrfs_new_inode() 2022-05-16 17:03:06 +02:00
ioctl.c btrfs: remove redundant name and name_len parameters to create_subvol 2022-05-16 17:03:06 +02:00
Kconfig btrfs: use generic Kconfig option for 256kB page size limit 2022-01-20 08:52:55 +02:00
locking.c btrfs: fix typos in comments 2021-06-22 14:11:57 +02:00
locking.h btrfs: assert that extent buffers are write locked instead of only locked 2021-10-26 19:08:02 +02:00
lzo.c btrfs: add lzo workspace buffer length constants 2022-03-14 13:13:50 +01:00
Makefile Kbuild: add -Wno-shift-negative-value where -Wextra is used 2022-03-13 17:30:31 +09:00
misc.h btrfs: use correct header for div_u64 in misc.h 2021-09-07 14:29:50 +02:00
ordered-data.c btrfs: add BTRFS_IOC_ENCODED_WRITE 2022-03-14 13:13:51 +01:00
ordered-data.h btrfs: add BTRFS_IOC_ENCODED_WRITE 2022-03-14 13:13:51 +01:00
orphan.c
print-tree.c btrfs: unify the error handling pattern for read_tree_block() 2022-03-14 13:13:53 +01:00
print-tree.h
props.c btrfs: skip compression property for anything other than files and dirs 2022-04-27 22:20:21 +02:00
props.h btrfs: skip compression property for anything other than files and dirs 2022-04-27 22:20:21 +02:00
qgroup.c btrfs: qgroup: remove outdated TODO comments 2022-03-14 13:13:50 +01:00
qgroup.h btrfs: fix lock inversion problem when doing qgroup extent tracing 2021-07-22 15:50:07 +02:00
raid56.c btrfs: remove btrfs_raid_bio::fs_info member 2021-10-26 19:08:03 +02:00
raid56.h btrfs: remove btrfs_raid_bio::fs_info member 2021-10-26 19:08:03 +02:00
rcu-string.h
ref-verify.c btrfs: stop accessing ->extent_root directly 2022-01-03 15:09:49 +01:00
ref-verify.h
reflink.c fs: Remove ->readpages address space operation 2022-04-01 13:45:33 -04:00
reflink.h
relocation.c btrfs: unify the error handling pattern for read_tree_block() 2022-03-14 13:13:53 +01:00
root-tree.c btrfs: do not start relocation until in progress drops are done 2022-03-02 16:52:39 +01:00
scrub.c btrfs: fix assertion failure during scrub due to block group reallocation 2022-04-21 16:06:19 +02:00
send.c btrfs: send: remove redundant ret variable in fs_path_copy 2022-03-14 13:13:47 +01:00
send.h btrfs: reuse existing inode from btrfs_ioctl 2022-03-14 13:13:46 +01:00
space-info.c btrfs: add lockdep_assert_held to need_preemptive_reclaim 2022-03-14 13:13:53 +01:00
space-info.h btrfs: change root to fs_info for btrfs_reserve_metadata_bytes 2022-01-03 15:09:45 +01:00
struct-funcs.c btrfs: add special case to setget helpers for 64k pages 2021-08-23 13:18:58 +02:00
subpage.c btrfs: subpage: fix a wrong check on subpage->writers 2022-03-02 16:51:39 +01:00
subpage.h btrfs: rework page locking in __extent_writepage() 2021-10-26 19:08:05 +02:00
super.c btrfs: add filesystems state details to error messages 2022-03-14 13:13:52 +01:00
sysfs.c btrfs: sysfs: export the balance paused state of exclusive operation 2022-05-05 21:05:56 +02:00
sysfs.h
transaction.c btrfs: pass btrfs_fs_info for deleting snapshots and cleaner 2022-03-14 13:13:52 +01:00
transaction.h btrfs: pass btrfs_fs_info for deleting snapshots and cleaner 2022-03-14 13:13:52 +01:00
tree-checker.c btrfs: add support for multiple global roots 2022-03-14 13:13:49 +01:00
tree-checker.h
tree-defrag.c btrfs: remove unnecessary extent root check in btrfs_defrag_leaves 2022-01-03 15:09:48 +01:00
tree-log.c btrfs: fix assertion failure when logging directory key range item 2022-05-05 21:05:56 +02:00
tree-log.h btrfs: avoid inode logging during rename and link when possible 2022-03-14 13:13:48 +01:00
tree-mod-log.c btrfs: fix race when picking most recent mod log operation for an old root 2021-04-20 19:27:17 +02:00
tree-mod-log.h btrfs: add and use helper to get lowest sequence number for the tree mod log 2021-04-19 17:25:17 +02:00
ulist.c
ulist.h
uuid-tree.c btrfs: drop the _nr from the item helpers 2022-01-03 15:09:43 +01:00
verity.c btrfs: drop the _nr from the item helpers 2022-01-03 15:09:43 +01:00
volumes.c btrfs: mark resumed async balance as writing 2022-04-06 00:49:50 +02:00
volumes.h btrfs: fix direct I/O read repair for split bios 2022-04-19 15:44:56 +02:00
xattr.c btrfs: skip compression property for anything other than files and dirs 2022-04-27 22:20:21 +02:00
xattr.h
zlib.c Revert "btrfs: compression: drop kmap/kunmap from zlib" 2021-10-29 13:03:05 +02:00
zoned.c btrfs: zoned: activate block group properly on unlimited active zone device 2022-05-05 21:05:56 +02:00
zoned.h btrfs: zoned: use dedicated lock for data relocation 2022-04-21 16:06:24 +02:00
zstd.c lib: zstd: Add kernel-specific API 2021-11-08 16:55:21 -08:00