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

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Message-ID: <e8ae84bf-2cd8-4eea-8523-62de6e493dfc@grimberg.me>
Date:   Tue, 28 Nov 2023 12:06:59 +0200
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Daniel Wagner <dwagner@...e.de>, Keith Busch <kbusch@...nel.org>
Cc:     Christoph Hellwig <hch@....de>, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Hannes Reinecke <hare@...e.de>
Subject: Re: [RFC v1] nvme: add cse, ds, ms, nsze and nuse to sysfs


>>>>>> 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

I agree with the comments made, especially the one made by Christoph
that these values should be added to the nshead.