Re: [PATCH V4 1/7] block: introduce blk_quiesce_timeout() and blk_unquiesce_timeout()

[Ming Lei <ming.lei@redhat.com>]

On Thu, May 10, 2018 at 03:01:04PM +0000, Bart Van Assche wrote:
> On Sat, 2018-05-05 at 21:58 +0800, Ming Lei wrote:
> > Turns out the current way can't drain timout completely because mod_timer()
> > can be triggered in the work func, which can be just run inside the synced
> > timeout work:
> > 
> >         del_timer_sync(&q->timeout);
> >         cancel_work_sync(&q->timeout_work);
> > 
> > This patch introduces one flag of 'timeout_off' for fixing this issue, turns
> > out this simple way does work.
> > 
> > Also blk_quiesce_timeout() and blk_unquiesce_timeout() are introduced for
> > draining timeout, which is needed by NVMe.
> 
> Hello Ming,
> 
> The description of the above patch does not motivate sufficiently why you think
> that this change is necessary. As you know it is already possible to wait until
> timeout handling has finished by calling blk_mq_freeze_queue() +
> blk_mq_unfreeze_queue(). An explanation is needed of why you think that calling

blk_mq_freeze_queue() +  blk_mq_unfreeze_queue() can't work, you have to
call blk_mq_freeze_queue_wait() between the two, but blk_mq_freeze_queue_wait
is a big trouble for NVMe, and can't be used inside nvme_dev_disable().

You can find the usage in the last patch of this series.

Thanks,
Ming