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 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 A3D24C11F64 for ; Thu, 1 Jul 2021 17:10:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83C6061409 for ; Thu, 1 Jul 2021 17:10:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233072AbhGARMx (ORCPT ); Thu, 1 Jul 2021 13:12:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:48802 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229987AbhGARMx (ORCPT ); Thu, 1 Jul 2021 13:12:53 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4D70661405; Thu, 1 Jul 2021 17:10:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625159422; bh=xdnAA7baVCohcq+q0n62eDKdetlkpnI4UjNwJ3Ih8CU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M+RhoUajTF1gDgnHS60QrdV574dAeRY/sXEy1jFcWO6rPhV07SByNFM8vKZH/auLT PSINIJLIG8yzSgOA8LTGfMk9heo0H5qbFim6132xUPayb9R7uvBIpgyqLis9Ej4EsF 9FyE4zlnLw8iKeQ1hTPUN+k1IkgUcvtEhesKv3I7Lj8WyHQemeLMz1onksshmlA/jd 0udbOX+Nwau9XcbhVdimeNGmjoeang+5BLX2GU+MHCGhbpYqGsz9dNnrGD+VQGunkF Vasq0rXWNNzqRrXkgsSLuzvyNZA0hlN2fMQ/ZNM331EC2MI+WcJCEAuz86T21tQOwj wD2WPOszA+gKA== Date: Thu, 1 Jul 2021 10:10:20 -0700 From: Jaegeuk Kim To: Chao Yu Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, chao@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210601101024.119356-1-yuchao0@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; > > 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