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

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Date:   Tue, 28 Nov 2023 09:21:45 +0100
From:   Daniel Wagner <dwagner@...e.de>
To:     Keith Busch <kbusch@...nel.org>
Cc:     Christoph Hellwig <hch@....de>, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Sagi Grimberg <sagi@...mberg.me>,
        Hannes Reinecke <hare@...e.de>
Subject: Re: [RFC v1] nvme: add cse, ds, ms, nsze and nuse to sysfs

On Mon, Nov 27, 2023 at 09:46:43AM -0700, Keith Busch wrote:
> On Mon, Nov 27, 2023 at 05:33:33PM +0100, Christoph Hellwig wrote:
> > On Mon, Nov 27, 2023 at 09:30:14AM -0700, Keith Busch wrote:
> > > > > Should this even be an nvme specific attribute? I thought we should have
> > > > > blk-integrity.c report its 'tuple_size' attribute instead. That should
> > > > > work as long as we're not dealing with extended metadata at least, but
> > > > > that's kind of a special format that doesn't have block layer support.
> > > > 
> > > > Reporting the tuple size is a good idea.  But is that enough for
> > > > the existing nvme-cli use case?

'nvme list' is just listening the block size and the meta size in the
'Format' field. So nothing really crazy going on:

  Usage                      Format
  -------------------------- ----------------
  343.33  GB / 512.11  GB    512   B +  0 B

nvme-cli commands like 'nmve ns-id' etc will always issue a command so
that is not a concern. It's just the libnvme nvme_scan_topology() call
which should stop issuing any commands.

I'll add the missing tuple_size to the integrity sysfs dir in this case.

> > > nvme-cli currently queries with admin passthrough identify command, so
> > > adding a new attribute won't break that. I assume Daniel would have it
> > > fallback to that same command for backward compatibilty if a desired
> > > sysfs attribute doesn't exist.

Yes, a fallback will exist. There is no need to break existing users.

In summary, the only missing entries are

 - csi
 - tuple_size
 - nuse