[PATCH] nvme: Implement Enhanced Command Retry

[keith.busch@intel.com (Keith Busch)]

On Tue, Nov 27, 2018@04:46:26PM +0100, Christoph Hellwig wrote:
> On Tue, Nov 27, 2018@08:37:10AM -0700, Keith Busch wrote:
> >  		if (!blk_queue_dying(req->q)) {
> > +			unsigned long delay = 0;
> > +			struct nvme_ns *ns = req->q->queuedata;
> > +			u16 crd = (nvme_req(req)->status & NVME_SC_CRD) >> 11;
> > +
> > +			if (crd && ns)
> > +				delay = ns->ctrl->crdt[crd - 1] * 100;
> 
> Do we need bounce checking for crd here?

I assume you mean bounds, in which case it should not be necessary since
the result of the mask and shift can't be > 3, which is the size of the
crdt array. I can add the check if not having it is visually alarming.

> > +
> >  			nvme_req(req)->retries++;
> > -			blk_mq_requeue_request(req, true);
> > +			blk_mq_requeue_request(req, false);
> > +			blk_mq_delay_kick_requeue_list(req->q, delay);
> >  			return;
> 
> I also think it would be nice to split out this code block into
> a little nvme_retry_req ala nvme_failover_req.

Sounds good, will do.
 
> Otherwise this looks sensible to me.