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References: <20210802143834.30578-1-longman@redhat.com>
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From:   Shakeel Butt <shakeelb@google.com>
Date:   Mon, 2 Aug 2021 07:39:41 -0700
Message-ID: <CALvZod51JYXv0Vzo-JhsFF1K9SsSXqJCGtEedXtfQAYQAN_5jQ@mail.gmail.com>
Subject: Re: [PATCH v2] mm/memcg: Fix incorrect flushing of lruvec data in obj_stock
To:     Waiman Long <longman@redhat.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Cgroups <cgroups@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
        Muchun Song <songmuchun@bytedance.com>,
        Alex Shi <alex.shi@linux.alibaba.com>,
        Chris Down <chris@chrisdown.name>,
        Yafang Shao <laoar.shao@gmail.com>,
        Wei Yang <richard.weiyang@gmail.com>,
        Masayoshi Mizuma <msys.mizuma@gmail.com>,
        Xing Zhengjun <zhengjun.xing@linux.intel.com>,
        Matthew Wilcox <willy@infradead.org>
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On Mon, Aug 2, 2021 at 7:38 AM Waiman Long <longman@redhat.com> wrote:
>
> When mod_objcg_state() is called with a pgdat that is different from
> that in the obj_stock, the old lruvec data cached in obj_stock are
> flushed out. Unfortunately, they were flushed to the new pgdat and
> so the data go to the wrong node. This will screw up the slab data
> reported in /sys/devices/system/node/node*/meminfo.
>
> Fix that by flushing the data to the cached pgdat instead.
>
> Fixes: 68ac5b3c8db2 ("mm/memcg: cache vmstat data in percpu memcg_stock_pcp")
> Signed-off-by: Waiman Long <longman@redhat.com>
> Acked-by: Michal Hocko <mhocko@suse.com>

Reviewed-by: Shakeel Butt <shakeelb@google.com>