lkml.org 
[lkml]   [2021]   [Jul]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH v2 RFC] f2fs: fix to force keeping write barrier for strict fsync mode
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 <yuchao0@huawei.com>
> ---
> 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

\
 
 \ /
  Last update: 2021-07-01 19:11    [W:0.088 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site