linux-kernel - RE: [PATCH 1/6] Drivers: hv: kvp: fix IP Failover

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Message-ID: <CY1PR03MB21372546187CA26E8734EF7BA09A0@CY1PR03MB2137.namprd03.prod.outlook.com>
Date:	Fri, 1 Apr 2016 21:03:20 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Greg KH <gregkh@...uxfoundation.org>,
	Vitaly Kuznetsov <vkuznets@...hat.com>
CC:	"olaf@...fle.de" <olaf@...fle.de>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>
Subject: RE: [PATCH 1/6] Drivers: hv: kvp: fix IP Failover



> -----Original Message-----
> From: Greg KH [mailto:gregkh@...uxfoundation.org]
> Sent: Thursday, March 31, 2016 1:19 PM
> To: Vitaly Kuznetsov <vkuznets@...hat.com>
> Cc: KY Srinivasan <kys@...rosoft.com>; olaf@...fle.de;
> jasowang@...hat.com; linux-kernel@...r.kernel.org; apw@...onical.com;
> devel@...uxdriverproject.org
> Subject: Re: [PATCH 1/6] Drivers: hv: kvp: fix IP Failover
> 
> On Tue, Mar 29, 2016 at 02:27:16PM +0200, Vitaly Kuznetsov wrote:
> > "K. Y. Srinivasan" <kys@...rosoft.com> writes:
> >
> > > From: Vitaly Kuznetsov <vkuznets@...hat.com>
> > >
> > > Hyper-V VMs can be replicated to another hosts and there is a feature to
> > > set different IP for replicas, it is called 'Failover TCP/IP'. When
> > > such guest starts Hyper-V host sends it KVP_OP_SET_IP_INFO message
> as soon
> > > as we finish negotiation procedure. The problem is that it can happen
> (and
> > > it actually happens) before userspace daemon connects and we reply
> with
> > > HV_E_FAIL to the message. As there are no repetitions we fail to set the
> > > requested IP.
> > >
> > > Solve the issue by postponing our reply to the negotiation message till
> > > userspace daemon is connected. We can't wait too long as there is a
> > > host-side timeout (cca. 75 seconds) and if we fail to reply in this time
> > > frame the whole KVP service will become inactive. The solution is not
> > > ideal - if it takes userspace daemon more than 60 seconds to connect
> > > IP Failover will still fail but I don't see a solution with our current
> > > separation between kernel and userspace parts.
> > >
> > > Other two modules (VSS and FCOPY) don't require such delay, leave
> them
> > > untouched.
> > >
> > > Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> > > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> >
> > An issue was found with this patch: we don't cancel
> > kvp_host_handshake_work on module unload and if the work is still
> > pending we end up crashing. As far as I can see this series didn't make
> > it to char-misc tree so instead of sending a patch to this patch I'll
> > send v2 for the original issue.
> >
> > Sorry for the inconvenience.
> 
> Ok, I'll drop this whole series.  K.Y., can you resend this series after
> fixing this up?

Will do.

Thanks,

K. Y
> 
> thanks,
> 
> greg k-h