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=-17.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 D2BA4C11F68 for ; Fri, 2 Jul 2021 15:49:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B078E613F7 for ; Fri, 2 Jul 2021 15:49:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232100AbhGBPv7 (ORCPT ); Fri, 2 Jul 2021 11:51:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:38518 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230098AbhGBPv7 (ORCPT ); Fri, 2 Jul 2021 11:51:59 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3CCA4613E0; Fri, 2 Jul 2021 15:49:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625240966; bh=umoakCnWsBbcM3DyAF7EavSSv/WZSVC1e7aQOhrCIFc=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=P5KEmgILEO054nKjMe9lfPYurTgRfuQzNEfFD6CZNOvXdi++vYwSnSVbdQhmefEUv f33BoAyzU77fyTBgIdD+wWFd8vT67z5bTxl1wO9d56p8eTrxaoXIgHFLJ30zzmzw7R 6XNEi2W8XZyoYvXnmzhqdvCPPVXSnXoqaC87brr9TnJJQfdwlE57yHmIB54Nxd8w6D 2OkN50SwWrIsjJCZT2N3N8Hpo4FRLC23iXS7uLPrioFlBA8XOOIkcdI3T3yWndG2Z1 o3pzXl2oOupDMNVAYUIqsrNn2t9BPKltmL1kiBxwta7gLdFnADJUvFW0W+rkqn+3yz a5mEHmhS6LVig== Subject: Re: [PATCH v2 RFC] f2fs: fix to force keeping write barrier for strict fsync mode To: Jaegeuk Kim Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <20210601101024.119356-1-yuchao0@huawei.com> <648a96f7-2c83-e9ed-0cbd-4ee8e4797724@kernel.org> From: Chao Yu Message-ID: Date: Fri, 2 Jul 2021 23:49:25 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/7/2 9:32, Jaegeuk Kim wrote: > On 07/02, Chao Yu wrote: >> On 2021/7/2 1:10, Jaegeuk Kim wrote: >>> On 06/01, Chao Yu wrote: >>>> [1] https://www.mail-archive.com/linux-f2fs-devel@lists.sourceforge.net/msg15126.html >>>> >>>> As [1] reported, if lower device doesn't support write barrier, in below >>>> case: >>>> >>>> - write page #0; persist >>>> - overwrite page #0 >>>> - fsync >>>> - write data page #0 OPU into device's cache >>>> - write inode page into device's cache >>>> - issue flush >>> >>> Well, we have preflush for node writes, so I don't think this is the case. >>> >>> fio.op_flags |= REQ_PREFLUSH | REQ_FUA; >> >> This is only used for atomic write case, right? >> >> I mean the common case which is called from f2fs_issue_flush() in >> f2fs_do_sync_file(). > > How about adding PREFLUSH when writing node blocks aligned to the above set? You mean implementation like v1 as below? https://lore.kernel.org/linux-f2fs-devel/20200120100045.70210-1-yuchao0@huawei.com/ Thanks, > >> >> And please see do_checkpoint(), we call f2fs_flush_device_cache() and >> commit_checkpoint() separately to keep persistence order of CP datas. >> >> See commit 46706d5917f4 ("f2fs: flush cp pack except cp pack 2 page at first") >> for details. >> >> Thanks, >> >>> >>>> >>>> If SPO is triggered during flush command, inode page can be persisted >>>> before data page #0, so that after recovery, inode page can be recovered >>>> with new physical block address of data page #0, however there may >>>> contains dummy data in new physical block address. >>>> >>>> Then what user will see is: after overwrite & fsync + SPO, old data in >>>> file was corrupted, if any user do care about such case, we can suggest >>>> user to use STRICT fsync mode, in this mode, we will force to trigger >>>> preflush command to persist data in device cache in prior to node >>>> writeback, it avoids potential data corruption during fsync(). >>>> >>>> Signed-off-by: Chao Yu >>>> --- >>>> v2: >>>> - fix this by adding additional preflush command rather than using >>>> atomic write flow. >>>> fs/f2fs/file.c | 14 ++++++++++++++ >>>> 1 file changed, 14 insertions(+) >>>> >>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>> index 7d5311d54f63..238ca2a733ac 100644 >>>> --- a/fs/f2fs/file.c >>>> +++ b/fs/f2fs/file.c >>>> @@ -301,6 +301,20 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end, >>>> f2fs_exist_written_data(sbi, ino, UPDATE_INO)) >>>> goto flush_out; >>>> goto out; >>>> + } else { >>>> + /* >>>> + * for OPU case, during fsync(), node can be persisted before >>>> + * data when lower device doesn't support write barrier, result >>>> + * in data corruption after SPO. >>>> + * So for strict fsync mode, force to trigger preflush to keep >>>> + * data/node write order to avoid potential data corruption. >>>> + */ >>>> + if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT && >>>> + !atomic) { >>>> + ret = f2fs_issue_flush(sbi, inode->i_ino); >>>> + if (ret) >>>> + goto out; >>>> + } >>>> } >>>> go_write: >>>> /* >>>> -- >>>> 2.29.2