nvmf: Refactor nvmf_add_namespaces to be more generic

[jhb]

Summary

Rename to nvmf_scan_active_namespaces and accept an additional
callback function and callback argument. The callback is invoked on
each active namespace enumerated by the active namespace list from the
IDENTIFY command.

Sponsored by: Chelsio Communications

[imp]

This is definitely better as it is. And I'm not 100% sure about the rescan stuff... it was my takeaway before I had to remove the 1 NVMe card I had that supported namespace management from my active system... I played around with several different combos, and I think I saw the repeat in a sloop of delete ns ; add ns... But that's been a couple of years.

sys/dev/nvmf/host/nvmf.c

299

part of me thinks this will eventually live in some .h file.

342

I think the fail-safe thing here is to tell the SIM to rescan the existing namespace. If nothing changed, there's no harm.

417

(eg, apropos of earlier comment):

I think this should instead just skip the nvmf_init_ns() below (or just call the rescan here. I recall messing around with this in nvmE land, and coming to the conclusion we needed it sometimes.

or maybe scan the active namespace and then call the sim thing.

[jhb]

sys/dev/nvmf/host/nvmf.c

417

This is only used during the initial walk of the active NS list during attach (post-attach rescans use a different callback that ignores an already-active ID). The assumption here is that it would be a bug to list an active namespace twice. Note that the namespace list is required to be sorted by ID as well. Generally speaking this is also acting on a snapshot of the list read from the controller, not something that can change while it is being iterated.