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* [PATCH] mm/memcg: Fix incorrect flushing of lruvec data in obj_stock
@ 2021-08-02  2:28 Waiman Long
  2021-08-02  6:28 ` Michal Hocko
  2021-08-02 14:32 ` Shakeel Butt
  0 siblings, 2 replies; 4+ messages in thread
From: Waiman Long @ 2021-08-02  2:28 UTC (permalink / raw)
  To: Johannes Weiner, Michal Hocko, Vladimir Davydov, Andrew Morton,
	Tejun Heo, Christoph Lameter, Pekka Enberg, David Rientjes,
	Joonsoo Kim, Vlastimil Babka, Roman Gushchin
  Cc: linux-kernel, cgroups, linux-mm, Shakeel Butt, Muchun Song,
	Alex Shi, Chris Down, Yafang Shao, Wei Yang, Masayoshi Mizuma,
	Xing Zhengjun, Matthew Wilcox, Waiman Long

When mod_objcg_state() is called with a pgdat that is different from
that in the obj_stock, the old lruvec data cached in obj_stock are
flushed out. Unfortunately, they were flushed to the new pgdat and
hence the wrong node, not the one cached in obj_stock.

Fix that by flushing the data to the cached pgdat instead.

Fixes: 68ac5b3c8db2 ("mm/memcg: cache vmstat data in percpu memcg_stock_pcp")
Signed-off-by: Waiman Long <longman@redhat.com>
---
 mm/memcontrol.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ae1f5d0cb581..881ec4ddddcd 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3106,17 +3106,19 @@ void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
 		stock->cached_pgdat = pgdat;
 	} else if (stock->cached_pgdat != pgdat) {
 		/* Flush the existing cached vmstat data */
+		struct pglist_data *oldpg = stock->cached_pgdat;
+
+		stock->cached_pgdat = pgdat;
 		if (stock->nr_slab_reclaimable_b) {
-			mod_objcg_mlstate(objcg, pgdat, NR_SLAB_RECLAIMABLE_B,
+			mod_objcg_mlstate(objcg, oldpg, NR_SLAB_RECLAIMABLE_B,
 					  stock->nr_slab_reclaimable_b);
 			stock->nr_slab_reclaimable_b = 0;
 		}
 		if (stock->nr_slab_unreclaimable_b) {
-			mod_objcg_mlstate(objcg, pgdat, NR_SLAB_UNRECLAIMABLE_B,
+			mod_objcg_mlstate(objcg, oldpg, NR_SLAB_UNRECLAIMABLE_B,
 					  stock->nr_slab_unreclaimable_b);
 			stock->nr_slab_unreclaimable_b = 0;
 		}
-		stock->cached_pgdat = pgdat;
 	}
 
 	bytes = (idx == NR_SLAB_RECLAIMABLE_B) ? &stock->nr_slab_reclaimable_b
-- 
2.18.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-08-02 14:32 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2021-08-02  2:28 [PATCH] mm/memcg: Fix incorrect flushing of lruvec data in obj_stock Waiman Long
2021-08-02  6:28 ` Michal Hocko
2021-08-02 13:32   ` Waiman Long
2021-08-02 14:32 ` Shakeel Butt

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