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[209.85.220.65]) by mx.google.com with SMTPS id i66sor2555390ywb.134.2019.07.17.11.02.36 for (Google Transport Security); Wed, 17 Jul 2019 11:02:36 -0700 (PDT) Received-SPF: pass (google.com: domain of shakeelb@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=KV6HAxQG; spf=pass (google.com: domain of shakeelb@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=shakeelb@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=yDzRsEyxIuuSai2DRMs+IGwIO+YipV0U+XFpyiaB7ek=; b=KV6HAxQGdn6bho66u6GdESZdwwdD5tjW0fDv1ZWRFWmhV9jQO5H7q5tBN4YlahuMN8 xHlxAttU7druDTETF9Oi1KMdYnaRSqBOoIn64k5cuiuYGQ4v+oGTISwXQraV6l5MxKnI /pXA0Z9KuUVxOjF1INofKw1JWFWI5GKL38xdnoah2mPGzZqrDlZuiPgsshkxn9SkE9RD 4/C90o3L6ZPqIEBmWavIP7H2Mp3oautWncUe1weerJg8VfUv4DDUnoCeZp8rfQMjLfkU gDyKAi9AdYmM2rxLhZ3O2qlqNqvnSp+ODNOPhS3edwqcT+5bAxOtHefqfQAih6cPsWOx zMog== X-Google-Smtp-Source: APXvYqx8Dv3M/w0Y+tfgf5v5o8BgqNuNH2nvV6nFlb9tCRft8Hoq2fYaYtrbULzBbF+h70b2g7Pn/ZHWVRQWxxJXD1U= X-Received: by 2002:a0d:c345:: with SMTP id f66mr23890145ywd.10.1563386555880; Wed, 17 Jul 2019 11:02:35 -0700 (PDT) MIME-Version: 1.0 References: <1563385526-20805-1-git-send-email-yang.shi@linux.alibaba.com> In-Reply-To: <1563385526-20805-1-git-send-email-yang.shi@linux.alibaba.com> From: Shakeel Butt Date: Wed, 17 Jul 2019 11:02:24 -0700 Message-ID: Subject: Re: [PATCH] mm: vmscan: check if mem cgroup is disabled or not before calling memcg slab shrinker To: Yang Shi Cc: Vladimir Davydov , Johannes Weiner , Michal Hocko , Kirill Tkhai , Roman Gushchin , Hugh Dickins , Qian Cai , "Kirill A. Shutemov" , Andrew Morton , stable@vger.kernel.org, Linux MM , LKML Content-Type: text/plain; charset="UTF-8" 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 Wed, Jul 17, 2019 at 10:45 AM Yang Shi wrote: > > Shakeel Butt reported premature oom on kernel with > "cgroup_disable=memory" since mem_cgroup_is_root() returns false even > though memcg is actually NULL. The drop_caches is also broken. > > It is because commit aeed1d325d42 ("mm/vmscan.c: generalize shrink_slab() > calls in shrink_node()") removed the !memcg check before > !mem_cgroup_is_root(). And, surprisingly root memcg is allocated even > though memory cgroup is disabled by kernel boot parameter. > > Add mem_cgroup_disabled() check to make reclaimer work as expected. > > Fixes: aeed1d325d42 ("mm/vmscan.c: generalize shrink_slab() calls in shrink_node()") > Reported-by: Shakeel Butt > Cc: Vladimir Davydov > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Kirill Tkhai > Cc: Roman Gushchin > Cc: Hugh Dickins > Cc: Qian Cai > Cc: Kirill A. Shutemov > Cc: stable@vger.kernel.org 4.19+ > Signed-off-by: Yang Shi Reviewed-by: Shakeel Butt > --- > mm/vmscan.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index f8e3dcd..c10dc02 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -684,7 +684,14 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, > unsigned long ret, freed = 0; > struct shrinker *shrinker; > > - if (!mem_cgroup_is_root(memcg)) > + /* > + * The root memcg might be allocated even though memcg is disabled > + * via "cgroup_disable=memory" boot parameter. This could make > + * mem_cgroup_is_root() return false, then just run memcg slab > + * shrink, but skip global shrink. This may result in premature > + * oom. > + */ > + if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg)) > return shrink_slab_memcg(gfp_mask, nid, memcg, priority); > > if (!down_read_trylock(&shrinker_rwsem)) > -- > 1.8.3.1 >