btrfs: fix locking issues in find_parent_nodes()

- We might unlock head->mutex while it was not locked
- We might leave the function without unlocking delayed_refs->lock

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 98f6bf10bbd4..0436c12da8c2 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -583,7 +583,7 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
         struct btrfs_path *path;
         struct btrfs_key info_key = { 0 };
         struct btrfs_delayed_ref_root *delayed_refs = NULL;
-        struct btrfs_delayed_ref_head *head = NULL;
+        struct btrfs_delayed_ref_head *head;
         int info_level = 0;
         int ret;
         struct list_head prefs_delayed;
@@ -607,6 +607,8 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
          * at a specified point in time
          */
 again:
+        head = NULL;
+
         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
         if (ret < 0)
                 goto out;
@@ -635,8 +637,10 @@ again:
                         goto again;
                 }
                 ret = __add_delayed_refs(head, seq, &info_key, &prefs_delayed);
-                if (ret)
+                if (ret) {
+                        spin_unlock(&delayed_refs->lock);
                         goto out;
+                }
         }
         spin_unlock(&delayed_refs->lock);