linux-kernel - RE: [PATCH v2] exfat: do not clear VolumeDirty in writeback

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Message-ID: <HK2PR04MB389107EDB293B91E9750CEEE81119@HK2PR04MB3891.apcprd04.prod.outlook.com>
Date:   Wed, 16 Mar 2022 09:17:42 +0000
From:   "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>
To:     Namjae Jeon <linkinjeon@...nel.org>,
        "Kohada.Tetsuhiro@...MitsubishiElectric.co.jp" 
        <Kohada.Tetsuhiro@...mitsubishielectric.co.jp>
CC:     "sj1557.seo@...sung.com" <sj1557.seo@...sung.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Andy.Wu@...y.com" <Andy.Wu@...y.com>,
        "Wataru.Aoyama@...y.com" <Wataru.Aoyama@...y.com>
Subject: RE: [PATCH v2] exfat: do not clear VolumeDirty in writeback

Hi Namjae, Kohada.Tetsuhiro,

> >> -       if (sync)
> >> -               sync_dirty_buffer(sbi->boot_bh);
> >> +       sync_dirty_buffer(sbi->boot_bh);
> >> +
> >
> > Use __sync_dirty_buffer() with REQ_FUA/REQ_PREFLUSH instead to
> > guarantee a strict write order (including devices).
> Yuezhang, It seems to make sense. Can you check this ?
> 

When call exfat_clear_volume_dirty(sb), all dirty buffers had synced by sync_blockdev(), so I think REQ_FUA/REQ_PREFLUSH is not needed.

```
        sync_blockdev(sb->s_bdev);                                                                                                                            
        if (exfat_clear_volume_dirty(sb))
```

exfat_clear_volume_dirty() is only called in sync or umount context.
In sync or umount context, all requests will be issued with REQ_SYNC regardless of whether REQ_SYNC is
set when submitting buffer.

And since the request of set VolumeDirty is issued with REQ_SYNC. So for simplicity, call sync_dirty_buffer()
unconditionally.

Best Regards,
Yuezhang Mo