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.
Fixes: ec9f02384f60 ("mm: workingset: fix vmstat counters for shadow nodes")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
---
v1->v2:
- Just resend the patch.
mm/memcontrol.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2dde734df7d1..bbd40c5af61e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -875,8 +875,13 @@ void __mod_lruvec_kmem_state(void *p, enum node_stat_item idx, int val)
rcu_read_lock();
memcg = mem_cgroup_from_obj(p);
- /* 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(memcg, pgdat);
--
2.20.1
