Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: make shrinker not depend on memcg kmem"), shrinkers' idr is protected by CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to protect shrinker idr replace with CONFIG_MEMCG_KMEM.

And, in CONFIG_MEMCG && CONFIG_SLOB case, shrinker_idr contains only shrinker, and it is deferred_split_shrinker. But it is never actually called, since idr_replace() is never compiled due to the wrong #ifdef. The deferred_split_shrinker all the time is staying in half-registered state, and it's never called for subordinate mem cgroups.

Fixes: 0a432dcbeb32 ("mm: shrinker: make shrinker not depend on memcg kmem") Reviewed-by: Kirill Tkhai ktkhai@virtuozzo.com Acked-by: Michal Hocko mhocko@suse.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Shakeel Butt shakeelb@google.com Cc: Roman Gushchin guro@fb.com Cc: stable@vger.kernel.org 5.4+ Signed-off-by: Yang Shi yang.shi@linux.alibaba.com --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c index ee4eecc..e7f10c4 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) { down_write(&shrinker_rwsem); list_add_tail(&shrinker->list, &shrinker_list); -#ifdef CONFIG_MEMCG_KMEM +#ifdef CONFIG_MEMCG if (shrinker->flags & SHRINKER_MEMCG_AWARE) idr_replace(&shrinker_idr, shrinker, shrinker->id); #endif