Re: [PATCH v2] exfat: do not clear VolumeDirty in writeback

[Kohada.Tetsuhiro@xxxxxxxxxxxxxxxxxxxxxxxxxxx]

Hi Yuezhang.Mo

> 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.

BR
T.Kohada