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=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 7F970C76192 for ; Wed, 17 Jul 2019 17:45:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F8F2217F4 for ; Wed, 17 Jul 2019 17:45:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388394AbfGQRpj (ORCPT ); Wed, 17 Jul 2019 13:45:39 -0400 Received: from out30-54.freemail.mail.aliyun.com ([115.124.30.54]:45366 "EHLO out30-54.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727255AbfGQRpj (ORCPT ); Wed, 17 Jul 2019 13:45:39 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=14;SR=0;TI=SMTPD_---0TX8wp0U_1563385527; Received: from e19h19392.et15sqa.tbsite.net(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TX8wp0U_1563385527) by smtp.aliyun-inc.com(127.0.0.1); Thu, 18 Jul 2019 01:45:33 +0800 From: Yang Shi To: shakeelb@google.com, vdavydov.dev@gmail.com, hannes@cmpxchg.org, mhocko@suse.com, ktkhai@virtuozzo.com, guro@fb.com, hughd@google.com, cai@lca.pw, kirill.shutemov@linux.intel.com, akpm@linux-foundation.org Cc: yang.shi@linux.alibaba.com, stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] mm: vmscan: check if mem cgroup is disabled or not before calling memcg slab shrinker Date: Thu, 18 Jul 2019 01:45:26 +0800 Message-Id: <1563385526-20805-1-git-send-email-yang.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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