'modprobe nvme_core multipath=N' crashes in face of multipath fabric

[Keith Busch]

On Thu, Apr 12, 2018 at 11:12:12AM +0300, Sagi Grimberg wrote:
> On 04/12/2018 12:46 AM, Mike Snitzer wrote:
> > This patch fixed the issue for me.  Verified that modprobe nvme_core
> > multipath=N and multipath=Y works with the mptest case I shared in my
> > original report.
> > 
> > If you do go with this patch, please feel free to add:
> > 
> > Tested-by: Mike Snitzer <snitzer at redhat.com>
> 
> This looks good to me too, you can add my
> 
> Reviewed-by: Sagi Grimberg <sagi at grimberg.me>

I'm going to have to make one minor change here since this will still
break if you've a multi-path subsystem with multiple namespaces. I'll
just need to move the IDA up to the subsystem level instead of on the
subsystem heads, but otherwise much the same.