mm/memcontrol: fix warning in mem_cgroup_page_lruvec()

Boot a CONFIG_MEMCG=y kernel with "cgroup_disabled=memory" and you are
met by a series of warnings from the VM_WARN_ON_ONCE_PAGE(!memcg, page)
recently added to the inline mem_cgroup_page_lruvec().

An earlier attempt to place that warning, in mem_cgroup_lruvec(), had
been careful to do so after weeding out the mem_cgroup_disabled() case;
but was itself invalid because of the mem_cgroup_lruvec(NULL, pgdat) in
clear_pgdat_congested() and age_active_anon().

Warning in mem_cgroup_page_lruvec() was once useful in detecting a KSM
charge bug, so may be worth keeping: but skip if mem_cgroup_disabled().

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()")
Signed-off-by: Hugh Dickins <[email protected]>
Reviewed-by: Alex Shi <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Acked-by: Chris Down <[email protected]>
Reviewed-by: Baoquan He <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Hui Su <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Shakeel Butt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d827bd7f3bfe..eeb0b52203e9 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -665,7 +665,7 @@ static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page,
 {
 	struct mem_cgroup *memcg = page_memcg(page);
 
-	VM_WARN_ON_ONCE_PAGE(!memcg, page);
+	VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page);
 	return mem_cgroup_lruvec(memcg, pgdat);
 }