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,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 C55ECC11F67 for ; Thu, 1 Jul 2021 23:04:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A07996140E for ; Thu, 1 Jul 2021 23:04:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234102AbhGAXGp (ORCPT ); Thu, 1 Jul 2021 19:06:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:32910 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233648AbhGAXGo (ORCPT ); Thu, 1 Jul 2021 19:06:44 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A3DC1613DC; Thu, 1 Jul 2021 23:04:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625180653; bh=+HiBm4y2G/OI/CCrGo4hwCm699FrUDzFzL1HhjQ1s2A=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=YO86vBw446qb7l/fbFDkIStu00xNLetn6+c2vfY1/FQgoSaG/8o988/hOB/fD1eGG GmSD/s9Du7L9qzcSI0PY9EpLbZ2pRP5+0U4+cJwQ1W4Z41PqNoa8SBTLWlJdAvN6ng ZHeEvFoxx3k11PeJkfZh5s1kMHol5+BkIG7M6frKDmw+6WoxCIru51HLl7d2eI8SGG FKtstFrCLRsjIi/bCtYZZVNpgaww61ii2RMSVBKghrAj/RBgLsqfqPPSjJ0nj7FPdu o88gMK0y0dkR5e6Rn+8qC7HUe0qUwAc2hxDQj0h6DxFxEM9UTjqqq1nGfD2aukek8j 3f2UKK0kJ7ZKQ== 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> From: Chao Yu Message-ID: <648a96f7-2c83-e9ed-0cbd-4ee8e4797724@kernel.org> Date: Fri, 2 Jul 2021 07:04:12 +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 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(). 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