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Message-ID: <2c1083cb-53d6-1cd6-9e1b-14a501db6f9a@linux.alibaba.com>
Date: Mon, 4 Jan 2021 16:11:12 +0800
From: Alex Shi <alex.shi@...ux.alibaba.com>
To: Hugh Dickins <hughd@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Hui Su <sh_def@....com>, Lorenzo Stoakes <lstoakes@...il.com>,
Michal Hocko <mhocko@...e.com>,
Johannes Weiner <hannes@...xchg.org>,
Shakeel Butt <shakeelb@...gle.com>,
Roman Gushchin <guro@...org>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [PATCH] mm/memcontrol: fix warning in mem_cgroup_page_lruvec()
Reviewed-by: Alex Shi <alex.shi@...ux.alibaba.com>
在 2021/1/4 下午1:03, Hugh Dickins 写道:
> 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().
>
> Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()")
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> ---
>
> include/linux/memcontrol.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- 5.11-rc2/include/linux/memcontrol.h 2020-12-27 20:39:36.751923135 -0800
> +++ linux/include/linux/memcontrol.h 2021-01-03 19:38:24.822978559 -0800
> @@ -665,7 +665,7 @@ static inline struct lruvec *mem_cgroup_
> {
> 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);
> }
>
>
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