Btrfs: skip locking when searching commit root

We won't change commit root, skip locking dance with commit root
when walking backrefs, this can speed up btrfs send operations.

Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index a88da721dfc5..860f4f22b9b0 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -873,8 +873,10 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
         path = btrfs_alloc_path();
         if (!path)
                 return -ENOMEM;
-        if (!trans)
+        if (!trans) {
                 path->search_commit_root = 1;
+                path->skip_locking = 1;
+        }
 
         /*
          * grab both a lock on the path and a lock on the delayed ref head.