Btrfs: Properly release lock in pin_down_bytes

When buffer isn't uptodate, pin_down_bytes may leave the tree locked
after it returns.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e6a3ba9..cdfb4ff 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1485,8 +1485,8 @@
 		struct extent_buffer *buf;
 		buf = btrfs_find_tree_block(root, bytenr, num_bytes);
 		if (buf) {
-			if (btrfs_try_tree_lock(buf) &&
-			    btrfs_buffer_uptodate(buf, 0)) {
+			if (btrfs_buffer_uptodate(buf, 0) &&
+			    btrfs_try_tree_lock(buf)) {
 				u64 transid =
 				    root->fs_info->running_transaction->transid;
 				u64 header_transid =