[PATCH V2] nvme: report capacity 0 for non supported ZNS SSDs

[hch at lst.de]

On Mon, Nov 02, 2020 at 04:15:01PM +0000, Javier Gonzalez wrote:
> That said, I don't mind the concept, though I recall Christoph had
> concerns about the existing 0-capacity namespace used for invalid
> formats, so I'd like to hear more on that if he has some spare time to
> comment.

Yes, I really don't think 0 sized block devices are the right interface
for namespaces we can't access.  I think the proper fix is to ensure that
we have a character device that allows submitting I/O commands for each
namespaces including those where we don't understand the I/O command set
or parts of it.  That should also really help to have a proper access
model for the KV command set.  Initially we only need NVME_IOCTL_IO64_CMD,
but eventually we'll need some support for async submissions, be
that through io_uring or other ways.