diff --git a/mm/swap_cgroup.c b/mm/swap_cgroup.c
index fcd2740..45affae 100644
--- a/mm/swap_cgroup.c
+++ b/mm/swap_cgroup.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 #include <linux/swap_cgroup.h>
 #include <linux/vmalloc.h>
 #include <linux/mm.h>