linux-kernel - Re: [Xen-devel] [PATCH 1/2] xen-blkfront: don't call talk_to_blkback when already connected to blkback

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Message-ID: <20160615140849.GE9254@char.us.oracle.com>
Date:	Wed, 15 Jun 2016 10:08:49 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Ross Lagerwall <ross.lagerwall@...rix.com>
Cc:	Bob Liu <bob.liu@...cle.com>, xen-devel@...ts.xenproject.org,
	linux-kernel@...r.kernel.org, roger.pau@...rix.com
Subject: Re: [Xen-devel] [PATCH 1/2] xen-blkfront: don't call talk_to_blkback
 when already connected to blkback

On Wed, Jun 15, 2016 at 09:39:00AM +0100, Ross Lagerwall wrote:
> On 06/08/2016 03:47 PM, Konrad Rzeszutek Wilk wrote:
> >On Wed, Jun 08, 2016 at 02:46:38PM +0800, Bob Liu wrote:
> >>
> >>On 06/07/2016 11:25 PM, Konrad Rzeszutek Wilk wrote:
> >>>On Wed, Jun 01, 2016 at 01:49:23PM +0800, Bob Liu wrote:
> >>>>
> >>>>On 06/01/2016 04:33 AM, Konrad Rzeszutek Wilk wrote:
> >>>>>On Tue, May 31, 2016 at 04:59:16PM +0800, Bob Liu wrote:
> >>>>>>Sometimes blkfont may receive twice blkback_changed() notification after
> >>>>>>migration, then talk_to_blkback() will be called twice too and confused
> >>>>>>xen-blkback.
> >>>>>
> ... snip
> >>>>But sometimes blkfront receives
> >>>>blkback_changed() event more than once!
> >>>
> >>>I think I know why. The udev scripts that get invoked when when
> >>>we attach a disk are a bit custom. As such I think they just
> >>>revalidate the size leading to this.
> >>>
> >>>And this 'poke-at-XenbusStateConnected' state multiple times
> >>>is allowed. It is used to signal disk changes (or just to revalidate).
> >>>Hence it does not matter why really - we need to deal with this.
> >>>
> >>>I modified your patch a bit and are testing it:
> >>>
> >>
> >>Looks much better, thank you very much!
> >
> >Great! I also had it tested overnight and there was no hitch will send it
> >out soon.
> >
> 
> I'd like to request that this patch is backported to Linux 4.5 and both of
> the patches in this series are backported to Linux 4.6. This is affecting
> Debian Testing (using Linux 4.6). It fails to recover its disk when resuming
> or migrating.

Good idea. Done.
> 
> Thanks,
> -- 
> Ross Lagerwall