diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 7edf9c9..2a6b994 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -26,7 +26,7 @@
 
 struct list_lru_one {
 	struct list_head	list;
-	/* kept as signed so we can catch imbalance bugs */
+	/* may become negative during memcg reparenting */
 	long			nr_items;
 };
 
@@ -62,6 +62,7 @@
 #define list_lru_init_memcg(lru)	__list_lru_init((lru), true, NULL)
 
 int memcg_update_all_list_lrus(int num_memcgs);
+void memcg_drain_all_list_lrus(int src_idx, int dst_idx);
 
 /**
  * list_lru_add: add an element to the lru list's tail