Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2;
Message-ID: <e8ae84bf-2cd8-4eea-8523-62de6e493dfc@grimberg.me>
Date:   Tue, 28 Nov 2023 12:06:59 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [RFC v1] nvme: add cse, ds, ms, nsze and nuse to sysfs
Content-Language: en-US
To:     Daniel Wagner <dwagner@suse.de>, Keith Busch <kbusch@kernel.org>
Cc:     Christoph Hellwig <hch@lst.de>, linux-nvme@lists.infradead.org,
        linux-kernel@vger.kernel.org, Hannes Reinecke <hare@suse.de>
References: <20231127103208.25748-1-dwagner@suse.de>
 <20231127141857.GA25833@lst.de>
 <ZWS5dM5FzTMr5ftO@kbusch-mbp.dhcp.thefacebook.com>
 <20231127155649.GA1403@lst.de>
 <ZWTEFvYbI1bFTXyZ@kbusch-mbp.dhcp.thefacebook.com>
 <20231127163333.GA2273@lst.de>
 <ZWTH85bmw0cdePXf@kbusch-mbp.dhcp.thefacebook.com>
 <n57gxockmm4iqt53olerr52rgxg3mvgdp4wfshyci2r7dohxfg@22mqtj3ya3g3>
From:   Sagi Grimberg <sagi@grimberg.me>
In-Reply-To: <n57gxockmm4iqt53olerr52rgxg3mvgdp4wfshyci2r7dohxfg@22mqtj3ya3g3>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk


>>>>>> 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.