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

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Date:   Fri, 18 Mar 2022 07:02:12 +0000
From:   "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>
To:     "Kohada.Tetsuhiro@...MitsubishiElectric.co.jp" 
        <Kohada.Tetsuhiro@...MitsubishiElectric.co.jp>,
        Namjae Jeon <linkinjeon@...nel.org>
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 T.Kohada,

> > 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.
> 
> REQ_FUA and REQ_PREFLUSH may not make much sense on SD cards or USB
> sticks.
> However, the behavior of SCSI/ATAPI type devices with lazy write cache is
>  - Issue the SYNCHRONIZE_CACHE command to write all the data to the
> medium.
>  - Issue a WRITE command with FORCE_UNIT_ACCESS (device does not use
> write cache) for the boot sector.
> This guarantees a strict write order.

Thank you for your detailed explanation.
I will update my patch.

Best Regards,
Yuezhang Mo