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Btrfs: make btrfs_search_forward return with nodes unlocked

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None of the uses of btrfs_search_forward() need to have the path
nodes (level >= 1) read locked, only the leaf needs to be locked
while the caller processes it. Therefore make it return a path
with all nodes unlocked, except for the leaf.

This change is motivated by the observation that during a file
fsync we repeatdly call btrfs_search_forward() and process the
returned leaf while upper nodes of the returned path (level >= 1)
are read locked, which unnecessarily blocks other tasks that want
to write to the same fs/subvol btree.
Therefore instead of modifying the fsync code to unlock all nodes
with level >= 1 immediately after calling btrfs_search_forward(),
change btrfs_search_forward() to do it, so that it benefits all
callers.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Filipe Manana
2014-08-04 19:37:21 +01:00
committed by Chris Mason
parent 79aec2b80d
commit f98de9b9c0
5 changed files with 7 additions and 15 deletions
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2
fs/btrfs/volumes.c
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@@ -3625,8 +3625,6 @@ static int btrfs_uuid_scan_kthread(void *data)
max_key.type = BTRFS_ROOT_ITEM_KEY;
max_key.offset = (u64)-1;
path->keep_locks = 1;
while (1) {
ret = btrfs_search_forward(root, &key, path, 0);
if (ret) {