[PATCH] nvme: allow to re-attach namespaces after all paths are down

[Keith Busch]

On Mon, May 10, 2021 at 03:25:04PM -0700, Sagi Grimberg wrote:
> Hannes, you sent a patch like this before, my comment was that a nshead
> should be removed before the final reference (which who knows when it
> will ever arrive) as if a nsid were to be reused by the controller for
> a different namespace then we'd reject it so I'm not sure how this helps?

Hm, you're considering something like if a user does namespace
management commands to delete one that is in-use (mounted, raid, etc),
then creates and attaches a new namespace that happens to be assigned
the same NSID.

The new one may get different EUI/NGUID values, so this approach here
would prevent the namespace from being usable without additional user
intervention. I think we'd want the driver to allocate an entirely new
head in that case if we could detect that's what happened. There is also
a possibility that the controller recycles the same NGUID for the new
namespace, and that could be confusing for the application holding the
open reference on the old namespace.