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

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Message-ID: <20231127135755.GB23928@lst.de>
Date:   Mon, 27 Nov 2023 14:57:55 +0100
From:   Christoph Hellwig <hch@....de>
To:     Daniel Wagner <dwagner@...e.de>
Cc:     Keith Busch <kbusch@...nel.org>, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
        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 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.