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,URIBL_BLOCKED,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 62584C433ED for ; Thu, 15 Apr 2021 03:19:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D6D2611B0 for ; Thu, 15 Apr 2021 03:19:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229696AbhDODUC (ORCPT ); Wed, 14 Apr 2021 23:20:02 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:16590 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229467AbhDODUB (ORCPT ); Wed, 14 Apr 2021 23:20:01 -0400 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FLPf84wj3z17Qhk; Thu, 15 Apr 2021 11:17:20 +0800 (CST) Received: from [10.174.176.162] (10.174.176.162) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.498.0; Thu, 15 Apr 2021 11:19:34 +0800 Subject: Re: [PATCH 2/5] swap: fix do_swap_page() race with swapoff To: Tim Chen , "Huang, Ying" CC: , , , , , , , , , , , References: <20210408130820.48233-1-linmiaohe@huawei.com> <20210408130820.48233-3-linmiaohe@huawei.com> <87o8ejug76.fsf@yhuang6-desk1.ccr.corp.intel.com> <878s5lu16i.fsf@yhuang6-desk1.ccr.corp.intel.com> <7ce9d6a2-6a9a-1203-0566-8a3bf478876f@linux.intel.com> From: Miaohe Lin Message-ID: Date: Thu, 15 Apr 2021 11:19:34 +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: <7ce9d6a2-6a9a-1203-0566-8a3bf478876f@linux.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.176.162] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/4/15 0:13, Tim Chen wrote: > > > On 4/13/21 6:04 PM, Huang, Ying wrote: >> Tim Chen writes: >> >>> On 4/12/21 6:27 PM, Huang, Ying wrote: >>> >>>> >>>> This isn't the commit that introduces the race. You can use `git blame` >>>> find out the correct commit. For this it's commit 0bcac06f27d7 "mm, >>>> swap: skip swapcache for swapin of synchronous device". >>>> >>>> And I suggest to merge 1/5 and 2/5 to make it easy to get the full >>>> picture. >>> >>> I'll suggest make fix to do_swap_page race with get/put_swap_device >>> as a first patch. Then the per_cpu_ref stuff in patch 1 and patch 2 can >>> be combined together. >> >> The original get/put_swap_device() use rcu_read_lock/unlock(). I don't >> think it's good to wrap swap_read_page() with it. After all, some >> complex operations are done in swap_read_page(), including >> blk_io_schedule(). >> > > In that case then have the patches to make get/put_swap_device to use > percpu_ref first. And the patch to to fix the race in do_swap_page > later in another patch. > > Patch 2 is mixing the two. > Looks like a good way to organize this patch series. Many thanks! > Tim > . >