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>

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index a88da72..860f4f2 100644 (file)
--- 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.