From 173e3732230779437e07348ddc58bd7ca27ac0ba Mon Sep 17 00:00:00 2001 From: Muchun Song Date: Sat, 21 Nov 2020 22:17:12 -0800 Subject: [PATCH] mm: memcg/slab: fix root memcg vmstats commit 8faeb1ffd79593c9cd8a2a80ecdda371e3b826cb upstream. If we reparent the slab objects to the root memcg, when we free the slab object, we need to update the per-memcg vmstats to keep it correct for the root memcg. Now this at least affects the vmstat of NR_KERNEL_STACK_KB for !CONFIG_VMAP_STACK when the thread stack size is smaller than the PAGE_SIZE. David said: "I assume that without this fix that the root memcg's vmstat would always be inflated if we reparented" Fixes: ec9f02384f60 ("mm: workingset: fix vmstat counters for shadow nodes") Signed-off-by: Muchun Song Signed-off-by: Andrew Morton Reviewed-by: Shakeel Butt Acked-by: Roman Gushchin Acked-by: Johannes Weiner Acked-by: David Rientjes Cc: Michal Hocko Cc: Vladimir Davydov Cc: Christopher Lameter Cc: Pekka Enberg Cc: Joonsoo Kim Cc: Roman Gushchin Cc: Vlastimil Babka Cc: Yafang Shao Cc: Chris Down Cc: [5.3+] Link: https://lkml.kernel.org/r/20201110031015.15715-1-songmuchun@bytedance.com Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memcontrol.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index edf98f8588ee..2701497edda5 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -776,8 +776,13 @@ void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, int val) rcu_read_lock(); memcg = memcg_from_slab_page(page); - /* Untracked pages have no memcg, no lruvec. Update only the node */ - if (!memcg || memcg == root_mem_cgroup) { + /* + * Untracked pages have no memcg, no lruvec. Update only the + * node. If we reparent the slab objects to the root memcg, + * when we free the slab object, we need to update the per-memcg + * vmstats to keep it correct for the root memcg. + */ + if (!memcg) { __mod_node_page_state(pgdat, idx, val); } else { lruvec = mem_cgroup_lruvec(pgdat, memcg);