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From: Prasanna Kalever <pkalever@redhat.com>
To: Matteo Croce <mcroce@linux.microsoft.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>
Subject: Re: [PATCH] nbd: provide a way for userspace processes to identify device backends
Date: Thu, 27 May 2021 10:52:50 +0530	[thread overview]
Message-ID: <CANwsLLEtOws-+X=3CCGzO88poP9NF8uNN8aW9wHOJ+QA=SFH3A@mail.gmail.com> (raw)
In-Reply-To: <CAFnufp0V7X_nvN3RGK-C0AXappQ+qjMS_rb7iQhcjT8E0OVpzA@mail.gmail.com>

On Wed, May 26, 2021 at 7:44 PM Matteo Croce <mcroce@linux.microsoft.com> wrote:
>
> 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/

Thanks, Matteo, I will take a look.

Just to set the expectation here, I don't have any thoughts on
leverage the diskseq number for nbd as part of this patch. This patch
is trying to solve a different problem which is more severe for us
than helping to identify the reconfigured events.

That all said, once diskseq patches are merged, I will surely open a
new patch with the required changes in nbd, to leverage diskseq
number.

Best Regards,
--
Prasanna

>
> --
> per aspera ad upstream
>


  reply	other threads:[~2021-05-27  5:23 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-29 10:28 Prasanna Kumar Kalever
2021-04-30  2:14 ` Xiubo Li
2021-05-17 14:42   ` Prasanna Kalever
2021-05-18  0:29 ` Ming Lei
2021-05-18  7:52   ` Prasanna Kalever
2021-05-18  9:24     ` Ming Lei
2021-05-18  9:49       ` Prasanna Kalever
2021-05-19  7:54         ` Ming Lei
2021-05-19 14:17           ` Prasanna Kalever
2021-05-19 14:33     ` Matteo Croce
2021-05-26 14:13       ` Matteo Croce
2021-05-27  5:22         ` Prasanna Kalever [this message]
2021-06-16  8:42 ` Prasanna Kalever
2021-06-16 12:59 ` Jens Axboe

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