From: Muchun Song <[email protected]>
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 <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Shakeel Butt <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Christopher Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Yafang Shao <[email protected]>
Cc: Chris Down <[email protected]>
Cc: <[email protected]> [5.3+]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
mm/memcontrol.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -776,8 +776,13 @@ void __mod_lruvec_slab_state(void *p, en
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);
