From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D4A5C76190 for ; Mon, 22 Jul 2019 12:00:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 39E1F20449 for ; Mon, 22 Jul 2019 12:00:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563796822; bh=FSHcNSS7eLlpKjxsa4Y9DUwXY6fDE0VgYbiQq4W8kMo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=kGNq1QhEAQcvf57zoPyeoLhonwM4v2a3WkHMNWxAPiPjX7gwPen/FKYHSBRbAzk6X Kg588iVUCL29lFz6lYwZwFylmn39tgkMESC8AbKFNaJZPhiRUDRG4vmbuGhEzzOQKB N4E4LpZCezg7GllNMyK7xE4CZQP2NLzfLmDSwHWw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729335AbfGVMAV (ORCPT ); Mon, 22 Jul 2019 08:00:21 -0400 Received: from mx2.suse.de ([195.135.220.15]:45998 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728269AbfGVMAV (ORCPT ); Mon, 22 Jul 2019 08:00:21 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 905F2B048; Mon, 22 Jul 2019 12:00:19 +0000 (UTC) Date: Mon, 22 Jul 2019 14:00:18 +0200 From: Michal Hocko To: Yang Shi Cc: shakeelb@google.com, vdavydov.dev@gmail.com, hannes@cmpxchg.org, ktkhai@virtuozzo.com, guro@fb.com, hughd@google.com, cai@lca.pw, kirill.shutemov@linux.intel.com, akpm@linux-foundation.org, stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: vmscan: check if mem cgroup is disabled or not before calling memcg slab shrinker Message-ID: <20190722120018.GZ30461@dhcp22.suse.cz> References: <1563385526-20805-1-git-send-email-yang.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1563385526-20805-1-git-send-email-yang.shi@linux.alibaba.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 18-07-19 01:45:26, 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 Acked-by: Michal Hocko > --- > 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 -- Michal Hocko SUSE Labs