btrfs: only unlock block in verify_parent_transid if we locked it

This is a regression from my patch a26e8c9f75b0bfd8cccc9e8f110737b136eb5994, we
need to only unlock the block if we were the one who locked it.  Otherwise this
will trip BUG_ON()'s in locking.c  Thanks,

cc: stable@vger.kernel.org
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8bb4aa19898f..f00165de6fbf 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -369,7 +369,8 @@ static int verify_parent_transid(struct extent_io_tree *io_tree,
 out:
         unlock_extent_cached(io_tree, eb->start, eb->start + eb->len - 1,
                              &cached_state, GFP_NOFS);
-        btrfs_tree_read_unlock_blocking(eb);
+        if (need_lock)
+                btrfs_tree_read_unlock_blocking(eb);
         return ret;
 }