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=-5.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,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 B765FC3A5A7 for ; Wed, 4 Sep 2019 14:29:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7AAD1206B8 for ; Wed, 4 Sep 2019 14:29:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7AAD1206B8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2893B6B0003; Wed, 4 Sep 2019 10:29:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 23A546B0006; Wed, 4 Sep 2019 10:29:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1295E6B0007; Wed, 4 Sep 2019 10:29:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0210.hostedemail.com [216.40.44.210]) by kanga.kvack.org (Postfix) with ESMTP id E75506B0003 for ; Wed, 4 Sep 2019 10:29:04 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 8AC6B82437D2 for ; Wed, 4 Sep 2019 14:29:04 +0000 (UTC) X-FDA: 75897470208.08.art80_3215c4a2d2562 X-HE-Tag: art80_3215c4a2d2562 X-Filterd-Recvd-Size: 3005 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Sep 2019 14:29:04 +0000 (UTC) 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 B16A0AEF6; Wed, 4 Sep 2019 14:29:02 +0000 (UTC) Date: Wed, 4 Sep 2019 16:29:02 +0200 From: Michal Hocko To: Tetsuo Handa Cc: Andrey Ryabinin , Thomas Lindroth , linux-mm@kvack.org Subject: Re: [BUG] kmemcg limit defeats __GFP_NOFAIL allocation Message-ID: <20190904142902.GZ3838@dhcp22.suse.cz> References: <31131c2d-a936-8bbf-e58d-a3baaa457340@gmail.com> <666dbcde-1b8a-9e2d-7d1f-48a117c78ae1@I-love.SAKURA.ne.jp> <4d0eda9a-319d-1a7d-1eed-71da90902367@i-love.sakura.ne.jp> <20190904112500.GO3838@dhcp22.suse.cz> <0056063b-46ff-0ebd-ff0d-c96a1f9ae6b1@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0056063b-46ff-0ebd-ff0d-c96a1f9ae6b1@i-love.sakura.ne.jp> User-Agent: Mutt/1.10.1 (2018-07-13) 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 04-09-19 23:19:31, Tetsuo Handa wrote: > On 2019/09/04 20:25, Michal Hocko wrote: > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 9ec5e12486a7..05a4828edf9d 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2820,7 +2820,8 @@ int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order, > > return ret; > > > > if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && > > - !page_counter_try_charge(&memcg->kmem, nr_pages, &counter)) { > > + !page_counter_try_charge(&memcg->kmem, nr_pages, &counter) && > > + !(gfp_mask & __GFP_NOFAIL)) { > > cancel_charge(memcg, nr_pages); > > return -ENOMEM; > > } > > > > With s/gfp_mask/gfp/ applied, I get no crash but got below warning. > I don't know relevance with the patch. Ohh, right. We are trying to uncharge something that hasn't been charged because page_counter_try_charge has failed. So the fix needs to be more involved. Sorry, I should have realized that. --- diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9ec5e12486a7..e18108b2b786 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2821,6 +2821,16 @@ int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order, if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !page_counter_try_charge(&memcg->kmem, nr_pages, &counter)) { + + /* + * Enforce __GFP_NOFAIL allocation because callers are not + * prepared to see failures and likely do not have any failure + * handling code. + */ + if (gfp & __GFP_NOFAIL) { + page_counter_charge(&memcg->kmem, nr_pages); + return 0; + } cancel_charge(memcg, nr_pages); return -ENOMEM; } -- Michal Hocko SUSE Labs