[PATCH] mm/memcg: bail out early when !memcg in mem_cgroup_lruvec

[Alex Shi]

In some scenarios, we call NULL memcg in mem_cgroup_lruvec(NULL, pgdat)
so we could get out early to skip unnecessary check.

Also warning if both parameter are NULL.

Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
---
 include/linux/memcontrol.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3a995bb3157f..5e4da83eb9ce 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -613,7 +613,9 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
 	struct mem_cgroup_per_node *mz;
 	struct lruvec *lruvec;
 
-	if (mem_cgroup_disabled()) {
+	VM_WARN_ON_ONCE(!memcg && !pgdat);
+
+	if (mem_cgroup_disabled() || !memcg) {
 		lruvec = &pgdat->__lruvec;
 		goto out;
 	}
-- 
2.29.GIT