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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BA8BAC11F67 for ; Fri, 2 Jul 2021 01:32:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9668D61411 for ; Fri, 2 Jul 2021 01:32:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234743AbhGBBfB (ORCPT ); Thu, 1 Jul 2021 21:35:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:52166 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234708AbhGBBfA (ORCPT ); Thu, 1 Jul 2021 21:35:00 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7E1AA613BC; Fri, 2 Jul 2021 01:32:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625189549; bh=x/cZLU8gLdFXi9n2Y5IATFQF9pEIi5JCiI99YW3rBRE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VfMcQoeK3ZoEMkwoJqws8BVhZSz4DxiT6HAGhBVmKqaAb6IiHe1b5epTXAtdDqHu+ nDICz5+SGgFnKFT5rUk6ZhNnPoamJ1SRBNNPnmt7nCTv33T+UE8BHEAqb1hTdFVNIQ wF84i5f1Y0KO4H0mJCTibirBqDCk1G+4jg44w8izkKP/oeYuvNWhQr08QgSOf4EDTp gUbjeS9dM2p0HNPYD39d6z7jKHbCZW5MJr8rK0babaX/wSbTTGo4r4F2NUl26k3cUb OAF4NgUnO9wvyuWtnxO0MUMhM+n+klNroU7rjZAPXreinZx+R+QZig3c7KFytBJ9R8 pVUhk6XvGICHg== Date: Thu, 1 Jul 2021 18:32:28 -0700 From: Jaegeuk Kim To: Chao Yu Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 RFC] f2fs: fix to force keeping write barrier for strict fsync mode Message-ID: References: <20210601101024.119356-1-yuchao0@huawei.com> <648a96f7-2c83-e9ed-0cbd-4ee8e4797724@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <648a96f7-2c83-e9ed-0cbd-4ee8e4797724@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? > > 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