diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index faad98e..4f71219 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1149,17 +1149,23 @@
  * Checks whether given mem is same or in the root_mem_cgroup's
  * hierarchy subtree
  */
-static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
-		struct mem_cgroup *memcg)
+bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
+				  struct mem_cgroup *memcg)
 {
-	bool ret;
-
 	if (root_memcg == memcg)
 		return true;
 	if (!root_memcg->use_hierarchy)
 		return false;
+	return css_is_ancestor(&memcg->css, &root_memcg->css);
+}
+
+static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
+				       struct mem_cgroup *memcg)
+{
+	bool ret;
+
 	rcu_read_lock();
-	ret = css_is_ancestor(&memcg->css, &root_memcg->css);
+	ret = __mem_cgroup_same_or_subtree(root_memcg, memcg);
 	rcu_read_unlock();
 	return ret;
 }