Btrfs: fix unreleased path in btrfs_orphan_cleanup()

When we did stress test for the space relocation, the deadlock happened. By debugging, We found it was caused by the carelessness that we forgot to unlock the read lock of the extent buffers in btrfs_orphan_cleanup() before we end the transaction handle, so the transaction commit task waited the task, which called btrfs_orphan_cleanup(), to unlock the extent buffer, but that task waited the commit task to end the transaction commit, and the deadlock happened. Fix it.

---
 fs/btrfs/inode.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

index c5dd958..d7cd558 100644
@@ -2203,6 +2203,9 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
 		if (ret)
 			goto out;
 	}
+	/* release the path since we're done with it */
+	btrfs_release_path(path);
+
 	root->orphan_cleanup_state = ORPHAN_CLEANUP_DONE;
 
 	if (root->orphan_block_rsv)

1.7.6.4