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=-10.0 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,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 14452C433FC for ; Mon, 27 Jul 2020 14:27:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E20842083B for ; Mon, 27 Jul 2020 14:27:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595860055; bh=kxqUQb49SOv6aFV5YU78vQgw0KFWI/YswWv7rMQ+cRw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=md8j+5R7Uy/cmq5JE0+H1sake6qBp/y/18rUU6SsBZPbewl2K2xjqBuFPX9XKYcBw HTOrfPQ5/RpBUb6bJS8qqyKJoJxw08LnJDJu6PHmRFdmk1cVwQ+xh0FLZSbz2lL0+k 2Opj9N/MZEfbyuHi2qciVdTlmQS64F1aZ+K7reOI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729241AbgG0OZc (ORCPT ); Mon, 27 Jul 2020 10:25:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:55502 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732449AbgG0OZb (ORCPT ); Mon, 27 Jul 2020 10:25:31 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 8BBD82075A; Mon, 27 Jul 2020 14:25:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595859931; bh=kxqUQb49SOv6aFV5YU78vQgw0KFWI/YswWv7rMQ+cRw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yCDGDpR5IN/5t3rxSlKCao+CYLQwjFyNKNQJKndaSTRHl5K/j2u8UbAwk6JOSZ4An lB146onXMmc/NR2k1D8GipFDmUz1m8fNb2rOqF8qTDUVLer1A+rx2N7315raUcEw3D 6DeTGg5eZ+8VR2OhyGTMZAzypYXO0eolOiaTlln0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hugh Dickins , Andrew Morton , Alex Shi , Johannes Weiner , Shakeel Butt , Michal Hocko , Linus Torvalds Subject: [PATCH 5.7 161/179] mm/memcg: fix refcount error while moving and swapping Date: Mon, 27 Jul 2020 16:05:36 +0200 Message-Id: <20200727134940.518638857@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200727134932.659499757@linuxfoundation.org> References: <20200727134932.659499757@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Hugh Dickins commit 8d22a9351035ef2ff12ef163a1091b8b8cf1e49c upstream. 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. Fixes: 615d66c37c75 ("mm: memcontrol: fix memcg id ref counter on swap charge move") Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Reviewed-by: Alex Shi Cc: Johannes Weiner Cc: Alex Shi Cc: Shakeel Butt Cc: Michal Hocko Cc: Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2007071431050.4726@eggly.anvils Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memcontrol.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5658,7 +5658,6 @@ 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; @@ -5849,7 +5848,8 @@ 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;