From: Muchun Song <songmuchun@xxxxxxxxxxxxx> commit 1685bde6b9af55923180a76152036c7fb7176db0 upstream. We use a global percpu int_active_memcg variable to store the remote memcg when we are in the interrupt context. But get_active_memcg always return the current->active_memcg or root_mem_cgroup. The remote memcg (set in the interrupt context) is ignored. This is not what we want. So fix it. Link: https://lkml.kernel.org/r/20210223091101.42150-1-songmuchun@xxxxxxxxxxxxx Fixes: 37d5985c003d ("mm: kmem: prepare remote memcg charging infra for interrupt contexts") Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Reviewed-by: Roman Gushchin <guro@xxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1083,13 +1083,9 @@ static __always_inline struct mem_cgroup rcu_read_lock(); memcg = active_memcg(); - if (memcg) { - /* current->active_memcg must hold a ref. */ - if (WARN_ON_ONCE(!css_tryget(&memcg->css))) - memcg = root_mem_cgroup; - else - memcg = current->active_memcg; - } + /* remote memcg must hold a ref. */ + if (memcg && WARN_ON_ONCE(!css_tryget(&memcg->css))) + memcg = root_mem_cgroup; rcu_read_unlock(); return memcg;
