[6/7] mm/memcg: fix incorrect flushing of lruvec data in obj_stock

Commit Message

Andrew Morton Aug. 13, 2021, 11:54 p.m. UTC

From: Waiman Long <[e-mail]>
Subject: mm/memcg: fix incorrect flushing of lruvec data in obj_stock

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 so the data go to
the wrong node.  This will screw up the slab data reported in
/sys/devices/system/node/node*/meminfo.

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

Link: https://lkml.kernel.org/r/[e-mail]
Fixes: 68ac5b3c8db2 ("mm/memcg: cache vmstat data in percpu memcg_stock_pcp")
Signed-off-by: Waiman Long <[e-mail]>
Acked-by: Michal Hocko <[e-mail]>
Reviewed-by: Shakeel Butt <[e-mail]>
Acked-by: Roman Gushchin <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Vladimir Davydov <[e-mail]>
Cc: Tejun Heo <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Muchun Song <[e-mail]>
Cc: Alex Shi <[e-mail]>
Cc: Chris Down <[e-mail]>
Cc: Yafang Shao <[e-mail]>
Cc: Wei Yang <[e-mail]>
Cc: Masayoshi Mizuma <[e-mail]>
Cc: Xing Zhengjun <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Waiman Long <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/memcontrol.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Patch

--- a/mm/memcontrol.c~mm-memcg-fix-incorrect-flushing-of-lruvec-data-in-obj_stock
+++ a/mm/memcontrol.c
@@ -3106,13 +3106,15 @@  void mod_objcg_state(struct obj_cgroup *
 		stock->cached_pgdat = pgdat;
 	} else if (stock->cached_pgdat != pgdat) {
 		/* Flush the existing cached vmstat data */
+		struct pglist_data *oldpg = stock->cached_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;
 		}