[PATCH 3/4] mm/memcg: retrieve parent memcg from css.parent

[Wei Yang <richard.weiyang@xxxxxxxxx>]

The parent we get from page_counter is correct, while this is two
different hierarchy.

Let's retrieve the parent memcg from css.parent just like parent_cs(),
blkcg_parent(), etc.

Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
---
 include/linux/memcontrol.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 0c5c403f4be6..12bf443f7b14 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -886,9 +886,7 @@ static inline struct mem_cgroup *lruvec_memcg(struct lruvec *lruvec)
  */
 static inline struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
 {
-	if (!memcg->memory.parent)
-		return NULL;
-	return mem_cgroup_from_counter(memcg->memory.parent, memory);
+	return mem_cgroup_from_css(memcg->css.parent);
 }
 
 static inline bool mem_cgroup_is_descendant(struct mem_cgroup *memcg,
-- 
2.33.1