don't try to reconfig a inactive/destroyed namespace

[kin-cho]

In namespace_reconfig, quit early if input namespace is of size 0 (inactive/destroyed), specifically setup_namespace should not be called.

[stellarhopper]

Hm, I'm wondering if we shouldn't go the other way and /alllow/ reconfiguring an inactive namespace. Seems like a reasonable thing one might expect to do. @djbw Thoughts?

[djbw]

@stellarhopper agree. A reconfig on a namespace with p.size == 0 should reconfigure to a maximally sized namespace with create-namespace defaults. This would seem to need some other pending fixups:

https://lore.kernel.org/linux-nvdimm/156479006271.707590.298793474092813749.stgit@dwillia2-desk3.amr.corp.intel.com/

In particular:

https://lore.kernel.org/linux-nvdimm/156426367330.531577.13173216611909512565.stgit@dwillia2-desk3.amr.corp.intel.com/

[hramrach]

Those pending fixups have been applied.

Is there any remaining issue?