[PATCHv2 2/2] nvme: add support multipath passthrough iostats

[Keith Busch]

On Wed, May 27, 2026 at 03:16:57PM +0200, Christoph Hellwig wrote:
> On Tue, May 26, 2026 at 08:39:21AM -0700, Keith Busch wrote:
> > +	struct nvme_ns *ns = q->queuedata;
> >  	struct request *req;
> >  
> > +	if (ns && nvme_ns_head_multipath(ns->head))
> > +		rq_flags |= REQ_NVME_MPATH;
> 
> I just wanted to come with reasons why it this is wrong, but it actually
> seems already - we only have a ns for multipath nodes if multipathing
> is enabled.  Maybe throw a little comment in on that?

Yes. An added subtlety here is that we unconditionally set
REQ_FAILFAST_DRIVER for passthrough requests, so it does not get
failover consideration. You can't steal bio's from a REQ_DRV_IN/OUT
request because all the necessary driver info is attached to the
original request, which doesn't follow the bio.