lkml.org 
[lkml]   [2021]   [Jul]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [f2fs-dev] [PATCH v3] f2fs: fix to force keeping write barrier for strict fsync mode
From
Date
Ping,

On 2021/7/20 9:19, Chao Yu wrote:
> On 2021/7/20 9:15, Jaegeuk Kim wrote:
>> Wasn't it supposed to be v1?
>
> I skip IPU case for v1, and resend it as v3, is it fine to you?
>
> Thanks,
>
>>
>> On 07/20, 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
>>>
>>> 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 use atomic
>>> write sematics to keep write order in between data/node and last node,
>>> so that it avoids potential data corruption during fsync().
>>>
>>> Signed-off-by: Chao Yu <chao@kernel.org>
>>> ---
>>> fs/f2fs/file.c | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>>
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index 6afd4562335f..00b45876eaa1 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -301,6 +301,18 @@ 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 use atomic write sematics
>>> + * to keep write order in between data/node and last node to
>>> + * avoid potential data corruption.
>>> + */
>>> + if (F2FS_OPTION(sbi).fsync_mode ==
>>> + FSYNC_MODE_STRICT && !atomic)
>>> + atomic = true;
>>> }
>>> go_write:
>>> /*
>>> --
>>> 2.22.1
>
>
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>

\
 
 \ /
  Last update: 2021-07-29 03:42    [W:0.097 / U:0.228 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site