diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 7f30da5822d92bba37534a1f0fe0a681e5226bad..3a895c9ab69c913c9a71b585a9ed813bb545a35f 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -417,7 +417,7 @@ struct memcg_blkcg_link {
 };
 
 static RADIX_TREE(memcg_blkcg_tree, GFP_ATOMIC);
-DEFINE_SPINLOCK(memcg_blkcg_tree_lock);
+static DEFINE_SPINLOCK(memcg_blkcg_tree_lock);
 
 static int memcg_blkcg_link_show(struct seq_file *m, void *v)
 {