Commit 1685bde6 authored by Muchun Song's avatar Muchun Song Committed by Linus Torvalds
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mm: memcontrol: fix get_active_memcg return value 

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@bytedance.com


Fixes: 37d5985c ("mm: kmem: prepare remote memcg charging infra for interrupt contexts")
Signed-off-by: default avatarMuchun Song <songmuchun@bytedance.com>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Reviewed-by: default avatarRoman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cae3af62

mm/memcontrol.c

+3 −7
Original line number Diff line number Diff line
@@ -1061,13 +1061,9 @@ static __always_inline struct mem_cgroup *get_active_memcg(void) 


	rcu_read_lock();

	memcg = active_memcg();

	if (memcg) {

		/* current->active_memcg must hold a ref. */

		if (WARN_ON_ONCE(!css_tryget(&memcg->css)))

	/* remote memcg must hold a ref. */

	if (memcg && WARN_ON_ONCE(!css_tryget(&memcg->css)))

		memcg = root_mem_cgroup;

		else

			memcg = current->active_memcg;

	}

	rcu_read_unlock();



	return memcg;