Native multipath across multiple subsystem NQNs

[Keith Busch]

On Sat, Feb 12, 2022 at 07:34:22AM +0100, Christoph Hellwig wrote:
> The answer is neither.  The fact that NVMe with ANA required namespaces
> to be be attached to the same subsystem is good and important.
> TPE 4034 is retrograde and completely broken in this respect and should
> have never been ratifier.  Please fix your storage system to export
> virtual subsystems like everyone else and don't break the nice NVMe
> architecture.

If anything, the driver could check for duplicate namespace identifiers
across subsystems so that we could warn about or prevent exposing them.