RE: [PATCH] exfat: remove EXFAT_SB_DIRTY flag

Sungjong Seo
2020-06-12T08:34:55Z

> remove EXFAT_SB_DIRTY flag and related codes.
>
> This flag is set/reset in exfat_put_super()/exfat_sync_fs() to avoid
> sync_blockdev().
> However ...
> - exfat_put_super():
> Before calling this, the VFS has already called sync_filesystem(), so sync
> is never performed here.
> - exfat_sync_fs():
> After calling this, the VFS calls sync_blockdev(), so, it is meaningless
> to check EXFAT_SB_DIRTY or to bypass sync_blockdev() here.
> Not only that, but in some cases can't clear VOL_DIRTY.
> ex:
> VOL_DIRTY is set when rmdir starts, but when non-empty-dir is detected,
> return error without setting EXFAT_SB_DIRTY.
> If performe 'sync' in this state, VOL_DIRTY will not be cleared.
>
> Remove the EXFAT_SB_DIRTY check to ensure synchronization.
> And, remove the code related to the flag.
>
> Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>
> ---
> fs/exfat/balloc.c | 4 ++--
> fs/exfat/dir.c | 16 ++++++++--------
> fs/exfat/exfat_fs.h | 5 +----
> fs/exfat/fatent.c | 7 ++-----
> fs/exfat/misc.c | 3 +--
> fs/exfat/namei.c | 12 ++++++------
> fs/exfat/super.c | 11 +++--------
> 7 files changed, 23 insertions(+), 35 deletions(-)
>
[snip]
>
> @@ -62,11 +59,9 @@ static int exfat_sync_fs(struct super_block *sb, int
> wait)
>
> /* If there are some dirty buffers in the bdev inode */
> mutex_lock(&sbi->s_lock);
> - if (test_and_clear_bit(EXFAT_SB_DIRTY, &sbi->s_state)) {
> - sync_blockdev(sb->s_bdev);
> - if (exfat_set_vol_flags(sb, VOL_CLEAN))
> - err = -EIO;
> - }

I looked through most codes related to EXFAT_SB_DIRTY and VOL_DIRTY.
And your approach looks good because all of them seem to be protected by
s_lock.

BTW, as you know, sync_filesystem() calls sync_fs() with 'nowait' first,
and then calls it again with 'wait' twice. No need to sync with lock twice.
If so, isn't it okay to do nothing when wait is 0?

> + sync_blockdev(sb->s_bdev);
> + if (exfat_set_vol_flags(sb, VOL_CLEAN))
> + err = -EIO;
> mutex_unlock(&sbi->s_lock);
> return err;
> }
> --
> 2.25.1