diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 6985015..2e348fb 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>