Re: [PATCH 1/2] nvme: pci: simplify timeout handling

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

On Thu, Apr 26, 2018 at 11:57:22PM +0800, Ming Lei wrote:
> Hi Jianchao,
> 
> On Thu, Apr 26, 2018 at 11:07:56PM +0800, jianchao.wang wrote:
> > Hi Ming
> > 
> > Thanks for your wonderful solution. :)
> > 
> > On 04/26/2018 08:39 PM, Ming Lei wrote:
> > > +/*
> > > + * This one is called after queues are quiesced, and no in-fligh timeout
> > > + * and nvme interrupt handling.
> > > + */
> > > +static void nvme_pci_cancel_request(struct request *req, void *data,
> > > +		bool reserved)
> > > +{
> > > +	/* make sure timed-out requests are covered too */
> > > +	if (req->rq_flags & RQF_MQ_TIMEOUT_EXPIRED) {
> > > +		req->aborted_gstate = 0;
> > > +		req->rq_flags &= ~RQF_MQ_TIMEOUT_EXPIRED;
> > > +	}
> > > +
> > > +	nvme_cancel_request(req, data, reserved);
> > > +}
> > > +
> > >  static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
> > >  {
> > >  	int i;
> > > @@ -2223,10 +2316,17 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
> > >  	for (i = dev->ctrl.queue_count - 1; i >= 0; i--)
> > >  		nvme_suspend_queue(&dev->queues[i]);
> > >  
> > > +	/*
> > > +	 * safe to sync timeout after queues are quiesced, then all
> > > +	 * requests(include the time-out ones) will be canceled.
> > > +	 */
> > > +	nvme_sync_queues(&dev->ctrl);
> > > +	blk_sync_queue(dev->ctrl.admin_q);
> > > +
> > Looks like blk_sync_queue cannot drain all the timeout work.
> > 
> > blk_sync_queue
> >   -> del_timer_sync          
> >                           blk_mq_timeout_work
> >                             -> mod_timer
> >   -> cancel_work_sync
> > the timeout work may come back again.
> > we may need to force all the in-flight requests to be timed out with blk_abort_request
> > 
> 
> blk_abort_request() seems over-kill, we could avoid this race simply by
> returning EH_NOT_HANDLED if the controller is in-recovery.
> 
> > >  	nvme_pci_disable(dev);
> > 
> > the interrupt will not come, but there maybe running one.
> > a synchronize_sched() here ?
> 
> We may cover this case by moving nvme_suspend_queue() before
> nvme_stop_queues().

Looks not need the above change, because pci_free_irq() called
from nvme_suspend_queue() won't return until any executing interrupts
for this IRQ have completed.

Thanks,
Ming