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Wed, 6 Jan 2021 06:49:38 +0000 (UTC) Received: from localhost (ovpn-12-186.pek2.redhat.com [10.72.12.186]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E46805D9CD; Wed, 6 Jan 2021 06:49:37 +0000 (UTC) Date: Wed, 6 Jan 2021 14:49:35 +0800 From: Baoquan He To: Hugh Dickins Cc: Andrew Morton , Hui Su , Alex Shi , Lorenzo Stoakes , Michal Hocko , Johannes Weiner , Shakeel Butt , Roman Gushchin , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/memcontrol: fix warning in mem_cgroup_page_lruvec() Message-ID: <20210106064935.GA3338@MiWiFi-R3L-srv> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 01/03/21 at 09:03pm, Hugh Dickins wrote: > 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 > --- > > 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); Thanks for fixing this. We also encountered this issue in kdump kernel with the mainline 5.10 kernel since 'cgroup_disable=memory' is added. Reviewed-by: Baoquan He