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=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no 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 51C42C433E5 for ; Fri, 24 Jul 2020 04:15:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 255C42065F for ; Fri, 24 Jul 2020 04:15:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595564126; bh=tkfPJBD817kb8WARIKFUNAFEqvVREUeE9Gq32+Ff2UU=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=vgLns2maBe9uitT5tG2BGvvstOkBnfsiefMTHUUKEaR6rt6uKhIYD343jyAMRw/yw xf8N06g91/qs3dX2dwhDePdTqW5JojoMAxhZQmjlvfDj5TOSma7Cbf7y+Fe/4J3VU2 RXGsz/P3J0btdwR6xl+OBhfPB4aafxBB5SSxCK4E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725898AbgGXEPZ (ORCPT ); Fri, 24 Jul 2020 00:15:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:53806 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725860AbgGXEPZ (ORCPT ); Fri, 24 Jul 2020 00:15:25 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C11CC2064B; Fri, 24 Jul 2020 04:15:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595564125; bh=tkfPJBD817kb8WARIKFUNAFEqvVREUeE9Gq32+Ff2UU=; h=Date:From:To:Subject:In-Reply-To:From; b=xFWmV+tBZ2FHeNSd/YQSFjgYf9M68jhmeHQAse3YWum1UWE2ILVnuUZ7JgRVoPQK/ 2enidPIfpiKFrkXBusXibjdfojATlEBV4lLNRIgYTuNtK/pcepJLvhpr6+e2Gex1Ca LrBoIzgJCzxnZ9MXoJpAAbWRQI57/K8n101FCFbk= Date: Thu, 23 Jul 2020 21:15:24 -0700 From: Andrew Morton To: akpm@linux-foundation.org, alex.shi@linux.alibaba.com, hannes@cmpxchg.org, hughd@google.com, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, shakeelb@google.com, stable@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 06/15] mm/memcg: fix refcount error while moving and swapping Message-ID: <20200724041524.eAqB5zPs6%akpm@linux-foundation.org> In-Reply-To: <20200723211432.b31831a0df3bc2cbdae31b40@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: mm-commits-owner@vger.kernel.org Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Hugh Dickins Subject: mm/memcg: fix refcount error while moving and swapping It was hard to keep a test running, moving tasks between memcgs with move_charge_at_immigrate, while swapping: mem_cgroup_id_get_many()'s refcount is discovered to be 0 (supposedly impossible), so it is then forced to REFCOUNT_SATURATED, and after thousands of warnings in quick succession, the test is at last put out of misery by being OOM killed. This is because of the way moved_swap accounting was saved up until the task move gets completed in __mem_cgroup_clear_mc(), deferred from when mem_cgroup_move_swap_account() actually exchanged old and new ids. Concurrent activity can free up swap quicker than the task is scanned, bringing id refcount down 0 (which should only be possible when offlining). Just skip that optimization: do that part of the accounting immediately. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2007071431050.4726@eggly.anvils Fixes: 615d66c37c75 ("mm: memcontrol: fix memcg id ref counter on swap charge move") Signed-off-by: Hugh Dickins Cc: Johannes Weiner Cc: Alex Shi Cc: Shakeel Butt Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton --- mm/memcontrol.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/memcontrol.c~mm-memcg-fix-refcount-error-while-moving-and-swapping +++ a/mm/memcontrol.c @@ -5669,7 +5669,6 @@ static void __mem_cgroup_clear_mc(void) if (!mem_cgroup_is_root(mc.to)) page_counter_uncharge(&mc.to->memory, mc.moved_swap); - mem_cgroup_id_get_many(mc.to, mc.moved_swap); css_put_many(&mc.to->css, mc.moved_swap); mc.moved_swap = 0; @@ -5860,7 +5859,8 @@ put: /* get_mctgt_type() gets the page ent = target.ent; if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to)) { mc.precharge--; - /* we fixup refcnts and charges later. */ + mem_cgroup_id_get_many(mc.to, 1); + /* we fixup other refcnts and charges later. */ mc.moved_swap++; } break; _