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Tue, 13 Jul 2021 09:23:47 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id A4142600D1; Tue, 13 Jul 2021 09:23:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626168215; bh=p6qo3HQ0SqxP6PWdKWsMC3NKbvO928431ScHS8VOYJ0=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=Ddt3yDkYY3spoxhgXUQm3yswJpIu859ZBYzp1O6faxARk3Hs8PfywxiUebWwFD/3m hWUqX2TqftP0BHhRH2ZkgnTDEdp+kykEgtsfsT0j6Lktskte303okQuja0Up6ddC4H D2AgB1BSArWKNdf9QHDIs//ubf6pPIafpV9mWoT9fdbrL7U67Dsp9uLMlLBmHLgd0Q STSMLinJ3IOoDvgDHMkUVvkRtUNNEl32jqMMR9EDSnXFdjIv82OHL16mOaR5w1E0h8 xVeAR14PHN2JVqlUTVR2kDlq+8Y/ML8q9wxbShyjQB+aQDek6bUPTOOuZlLj5/x3iP drvm0ZE2ZmXNg== To: Jaegeuk Kim References: <20210601101024.119356-1-yuchao0@huawei.com> <648a96f7-2c83-e9ed-0cbd-4ee8e4797724@kernel.org> From: Chao Yu Message-ID: <55e069f7-662d-630c-1201-d0163b38bc17@kernel.org> Date: Tue, 13 Jul 2021 17:23:32 +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-Language: en-US X-Headers-End: 1m3Edl-006lOP-Gf Subject: Re: [f2fs-dev] [PATCH v2 RFC] f2fs: fix to force keeping write barrier for strict fsync mode X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2021/7/8 1:48, Jaegeuk Kim wrote: > On 07/02, Chao Yu wrote: >> 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/ > > Yea, I think so. :P I prefer v2, we may have several schemes to improve performance with v2, e.g. - use inplace IO to avoid newly added preflush - use flush_merge option to avoid redundant preflush - if lower device supports barrier IO, we can avoid newly added preflush Thanks, > >> >> 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 _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel