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

[Keith Busch]

On Tue, Apr 10, 2018 at 04:49:53PM -0400, Mike Snitzer wrote:
> This isn't new since the 4.17 merge or anything, I first noticed this
> issue existed while using a 4.16-rc4 kernel.
> 
> modprobe nvme_core multipath=N

Thanks for the notice.

There is definitely a bug here when CONFIG_NVME_MULTIPATH=y but nvme_core
multipath is disabled in the presence of shared namespaces. I think we'd
need each namespace to get a different "head" out of the subsystem in
this case, but it may take a moment for me to detangle this.