From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: mm/list_lru.c: revert "mm/list_lru: optimize memcg_reparent_list_lru_node()"
405cc51fc1049c73 ("mm/list_lru: optimize memcg_reparent_list_lru_node()")
has subtle races which are proving ugly to fix. Revert the original
optimization. If quantitative testing indicates that we have a
significant problem here then other implementations can be looked at.
Fixes: 405cc51fc1049c73 ("mm/list_lru: optimize memcg_reparent_list_lru_node()")
Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/list_lru.c | 6 ------
1 file changed, 6 deletions(-)
--- a/mm/list_lru.c~mm-list_lruc-revert-mm-list_lru-optimize-memcg_reparent_list_lru_node
+++ a/mm/list_lru.c
@@ -395,12 +395,6 @@ static void memcg_reparent_list_lru_node
struct list_lru_one *src, *dst;
/*
- * If there is no lru entry in this nlru, we can skip it immediately.
- */
- if (!READ_ONCE(nlru->nr_items))
- return;
-
- /*
* Since list_lru_{add,del} may be called under an IRQ-safe lock,
* we have to use IRQ-safe primitives here to avoid deadlock.
*/
_
