[RFC v1] nvme: add cse, ds, ms, nsze and nuse to sysfs

[Christoph Hellwig]

On Mon, Nov 27, 2023 at 01:07:32PM +0100, Daniel Wagner wrote:
> libnvme itself is also cashing this value and exposes it via the
> nvme_ns_get_lba_util() getter. I'd say libnvme shouldn't cache it
> either. Instead the function should just issue the ns command to report
> the current nuse value.
> 
> I'll drop the nuse sysfs entry.
> 
> Unfortunately, 'nvme list' is using the 'nuse' field for showing the
> currently used space. I was hoping to get 'nvme list' working without
> issuing any commands.

I'd be ok with implementing nuse in a way where we issue an identify
command to read it, but rate limit the calls to something reasonable.
I think the kernel can do that much better than userspace because it
can keep that state a lot better.