[PATCH V2 09/13] scsi: force unfreezing queue into atomic mode

[Ming Lei]

On Mon, Jan 24, 2022 at 02:15:16PM +0100, Christoph Hellwig wrote:
> On Sat, Jan 22, 2022 at 07:10:50PM +0800, Ming Lei wrote:
> > In scsi_disk_release() request queue is frozen for clearing
> > disk->private_data, and there can't be any FS IO issued to
> > this queue, and only private passthrough request will be handled, so
> > force unfreezing queue into atomic mode.
> > 
> > Signed-off-by: Ming Lei <ming.lei at redhat.com>
> > ---
> >  drivers/scsi/sd.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> > index 0e73c3f2f381..27f04c860f00 100644
> > --- a/drivers/scsi/sd.c
> > +++ b/drivers/scsi/sd.c
> > @@ -3670,7 +3670,7 @@ static void scsi_disk_release(struct device *dev)
> >  	 * in case multiple processes open a /dev/sd... node concurrently.
> >  	 */
> >  	blk_mq_freeze_queue(q);
> > -	blk_mq_unfreeze_queue(q);
> > +	__blk_mq_unfreeze_queue(q, true);
> 
> I think the right thing here is to drop the freeze/unfreeze pair.
> Now that del_gendisk properly freezes the queue, we don't need this
> protection as the issue that Bart fixed with it can't happen any more.

As you see, the last patch removes freeze/unfreeze pair in del_gendisk(),
which looks not very useful: it can't drain IO on bio based driver, and
del_gendisk() is supposed to provide consistent behavior for both request
and bio based driver.


Thanks,
Ming