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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99493C7618D for ; Thu, 6 Apr 2023 12:55:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237928AbjDFMzW (ORCPT ); Thu, 6 Apr 2023 08:55:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52942 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237514AbjDFMzV (ORCPT ); Thu, 6 Apr 2023 08:55:21 -0400 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 469694C21; Thu, 6 Apr 2023 05:55:19 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=rongwei.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VfTAMRc_1680785713; Received: from 30.221.129.255(mailfrom:rongwei.wang@linux.alibaba.com fp:SMTPD_---0VfTAMRc_1680785713) by smtp.aliyun-inc.com; Thu, 06 Apr 2023 20:55:14 +0800 Message-ID: Date: Thu, 6 Apr 2023 20:55:12 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [PATCH v2] mm/swap: fix swap_info_struct race between swapoff and get_swap_pages() Content-Language: en-US To: Aaron Lu Cc: akpm@linux-foundation.org, bagasdotme@gmail.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20230401221920.57986-1-rongwei.wang@linux.alibaba.com> <20230404154716.23058-1-rongwei.wang@linux.alibaba.com> <6dad8c2f-b896-3cc0-26c1-37f5fff406bd@linux.alibaba.com> <20230406121245.GA376058@ziqianlu-desk2> From: Rongwei Wang In-Reply-To: <20230406121245.GA376058@ziqianlu-desk2> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Oh, sorry, I miss this email just now, that because of I'm also replying your previous email. On 2023/4/6 20:12, Aaron Lu wrote: > On Wed, Apr 05, 2023 at 12:08:47AM +0800, Rongwei Wang wrote: >> Hello >> >> I have fix up some stuff base on Patch v1. And in order to help all readers >> and reviewers to >> >> reproduce this bug, share a reproducer here: > I reproduced this problem under a VM this way: > > $ sudo ./stress-ng --swap 1 > // on another terminal > $ for i in `seq 8`; do ./swap & done > Looks simpler than yours :-) Cool, indeed become simpler. > (Didn't realize you have posted your reproducer here since I'm not CCed > and just found it after invented mine) > Then the warning message normally appear within a few seconds. > > Here is the code for the above swap prog: > > #include > #include > #include > > #define SIZE 0x100000 > > int main(void) > { > int i, ret; > void *p; > > p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); > if (p == MAP_FAILED) { > perror("mmap"); > return -1; > } > > ret = 0; > while (1) { > for (i = 0; i < SIZE; i += 0x1000) > ((char *)p)[i] = 1; > ret = madvise(p, SIZE, MADV_PAGEOUT); > if (ret != 0) { > perror("madvise"); > break; > } > } > > return ret; > } > > Unfortunately, this test prog did not work on kernels before v5.4 because > MADV_PAGEOUT is introduced in v5.4. I tested on v5.4 and the problem is > also there. Maybe that is this bug can not be found since now. And we found this is triggered by stress-ng-swap and stress-ng-madvise (PAGEOUT) firstly. It seems this is that reason. It seems MADV_COLD is also introduced together with MADV_PAGEOUT. I have no idea and have to depend on you.:-) > > Haven't found a way to trigger swap with swap device come and go on > kernels before v5.4; tried putting the test prog in a memcg with memory > limit but then the prog is easily killed due to nowhere to swap out. > Personally, I do not intend to continuing searching for the method to reproduce before v5.4. Of course, if you have idea, I can try. Thanks:-)