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From:   Matteo Croce <mcroce@linux.microsoft.com>
Date:   Wed, 26 May 2021 16:13:23 +0200
Message-ID: <CAFnufp0V7X_nvN3RGK-C0AXappQ+qjMS_rb7iQhcjT8E0OVpzA@mail.gmail.com>
Subject: Re: [PATCH] nbd: provide a way for userspace processes to identify
 device backends
To:     Prasanna Kalever <pkalever@redhat.com>
Cc:     Ming Lei <ming.lei@redhat.com>,
        Prasanna Kumar Kalever <prasanna.kalever@redhat.com>,
        linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
        nbd@other.debian.org, Josef Bacik <josef@toxicpanda.com>,
        Jens Axboe <axboe@kernel.dk>,
        Ilya Dryomov <idryomov@redhat.com>,
        Xiubo Li <xiubli@redhat.com>,
        Lennart Poettering <lennart@poettering.net>,
        Luca Boccassi <bluca@debian.org>
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On Wed, May 19, 2021 at 4:33 PM Matteo Croce <mcroce@linux.microsoft.com> wrote:
>
> On Tue, May 18, 2021 at 9:52 AM Prasanna Kalever <pkalever@redhat.com> wrote:
> > > BTW, loop has similar issue, and patch of 'block: add a sequence number to disks'
> > > is added for addressing this issue, what do you think of that generic
> > > approach wrt. this nbd's issue? such as used the exposed sysfs sequence number
> > > for addressing this issue?
> > >
> > > https://lore.kernel.org/linux-block/YH81n34d2G3C4Re+@gardel-login/#r
> >
> > If I understand the changes and the background of the fix correctly, I
> > think with that fix author is trying to monotonically increase the seq
> > number and add it to the disk on every single device map/attach and
> > expose it through the sysfs, which will help the userspace processes
> > further to correlate events for particular and specific devices that
> > reuse the same loop device.
> >
>
> Yes, but nothing prevents to use diskseq in nbd, and increase it on reconfigure.
> That would allow to detect if the device has been reconfigured.
>
> Regards,
> --
> per aspera ad upstream

FYI: I just sent a v2 of the diskseq change

https://lore.kernel.org/linux-block/20210520135622.44625-1-mcroce@linux.microsoft.com/

-- 
per aspera ad upstream