Btrfs: make btrfs_search_forward return with nodes unlocked

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>

1 files changed, 0 insertions, 5 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 4492e01..85ca3cc 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -936,12 +936,9 @@ static int find_new_extents(struct btrfs_root *root,
 	min_key.offset = *off;
 
 	while (1) {
-		path->keep_locks = 1;
 		ret = btrfs_search_forward(root, &min_key, path, newer_than);
 		if (ret != 0)
 			goto none;
-		path->keep_locks = 0;
-		btrfs_unlock_up_safe(path, 1);
 process_slot:
 		if (min_key.objectid != ino)
 			goto none;
@@ -2088,8 +2085,6 @@ static noinline int search_ioctl(struct inode *inode,
 	key.type = sk->min_type;
 	key.offset = sk->min_offset;
 
-	path->keep_locks = 1;
-
 	while (1) {
 		ret = btrfs_search_forward(root, &key, path, sk->min_transid);
 		if (ret != 0) {