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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 4F227C07E9D for ; Mon, 19 Jul 2021 11:50:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 305F86113A for ; Mon, 19 Jul 2021 11:50:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231290AbhGSLJa (ORCPT ); Mon, 19 Jul 2021 07:09:30 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:11344 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230493AbhGSLJa (ORCPT ); Mon, 19 Jul 2021 07:09:30 -0400 Received: from dggeme703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4GT0Qk0cnTz7tG1; Mon, 19 Jul 2021 19:45:34 +0800 (CST) Received: from [10.174.177.180] (10.174.177.180) by dggeme703-chm.china.huawei.com (10.1.199.99) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Mon, 19 Jul 2021 19:50:07 +0800 Subject: Re: linux-5.13.2: warning from kernel/rcu/tree_plugin.h:359 To: Matthew Wilcox CC: Boqun Feng , Zhouyi Zhou , , Oleksandr Natalenko , linux-kernel , , Chris Clayton , Chris Rankin , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , rcu , Andrew Morton , Linux-MM , "Huang, Ying" , References: <2245518.LNIG0phfVR@natalenko.name> <6698965.kvI7vG0SvZ@natalenko.name> <20210718215914.GQ4397@paulmck-ThinkPad-P17-Gen-1> <20210719015313.GS4397@paulmck-ThinkPad-P17-Gen-1> <08803f78-3e99-6b3f-e809-5828fe47cf06@huawei.com> From: Miaohe Lin Message-ID: <8058e175-cec5-c243-6499-c1cd4e3c8605@huawei.com> Date: Mon, 19 Jul 2021 19:50:07 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.180] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggeme703-chm.china.huawei.com (10.1.199.99) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On 2021/7/19 19:22, Matthew Wilcox wrote: > On Mon, Jul 19, 2021 at 07:12:58PM +0800, Miaohe Lin wrote: >> When in the commit 2799e77529c2a, we're using the percpu_ref to serialize against >> concurrent swapoff, i.e. there's percpu_ref inside get_swap_device() instead of >> rcu_read_lock(). Please see commit 63d8620ecf93 ("mm/swapfile: use percpu_ref to >> serialize against concurrent swapoff") for detail. > > Oh, so this is a backport problem. 2799e77529c2 was backported without > its prerequisite 63d8620ecf93. Greg, probably best to just drop Yes, they're posted as a patch set: https://lkml.kernel.org/r/20210426123316.806267-1-linmiaohe@huawei.com > 2799e77529c2 from all stable trees; the race described is not very > important (swapoff vs reading a page back from that swap device). > . > The swapoff races with reading a page back from that swap device should be really uncommon as most users only do swapoff when the system is going to shutdown. Sorry for the trouble!