Linux Virtualization - May 2018 - [PATCH net-next v11 2/5] netvsc: refactor notifier/event handling code to use the failover framework

On Tue, May 22, 2018 at 05:36:14PM +0200, Jiri Pirko
wrote:
> Tue, May 22, 2018 at 05:28:42PM CEST, sridhar.samudrala at intel.com wrote:
> >
> >On 5/22/2018 2:08 AM, Jiri Pirko wrote:
> >> Tue, May 22, 2018 at 11:06:37AM CEST, jiri at resnulli.us wrote:
> >> > Tue, May 22, 2018 at 04:06:18AM CEST, sridhar.samudrala at
intel.com wrote:
> >> > > Use the registration/notification framework supported by
the generic
> >> > > failover infrastructure.
> >> > > 
> >> > > Signed-off-by: Sridhar Samudrala <sridhar.samudrala
at intel.com>
> >> > In previous patchset versions, the common code did
> >> > netdev_rx_handler_register() and netdev_upper_dev_link() etc
> >> > (netvsc_vf_join()). Now, this is still done in netvsc. Why?
> >> > 
> >> > This should be part of the common "failover" code.
> >
> >Based on Stephen's feedback on earlier patches, i tried to minimize
the changes to
> >netvsc and only commonize the notifier and the main event handler
routine.
> >Another complication is that netvsc does part of registration in a
delayed workqueue.
> 
> :( This kind of degrades the whole efford of having single solution
> in "failover" module. I think that common parts, as
> netdev_rx_handler_register() and others certainly is should be inside
> the common module. This is not a good time to minimize changes. Let's
do
> the thing properly and fix the netvsc mess now.
> 
> 
> >
> >It should be possible to move some of the code from net_failover.c to
generic
> >failover.c in future if Stephen is ok with it.
> >
> >
> >> > 
> >> Also note that in the current patchset you use IFF_FAILOVER flag
for
> >> master, yet for the slave you use IFF_SLAVE. That is wrong.
> >> IFF_FAILOVER_SLAVE should be used.
> >
> >Not sure which code you are referring to.? I only set
IFF_FAILOVER_SLAVE
> >in patch 3.
> 
> The existing netvsc driver.
We really can't change netvsc's flags now, even if it's interface is
messy, it's being used in the field. We can add a flag that makes netvsc
behave differently, and if this flag also allows enhanced functionality
userspace will gradually switch.

Anything breaking userspace I fully expect Stephen to nack and
IMO with good reason.

-- 
MST

Fixing the subj, sorry about that.

Tue, May 22, 2018 at 05:46:21PM CEST, mst at redhat.com
wrote:
>On Tue, May 22, 2018 at 05:36:14PM +0200, Jiri Pirko wrote:
>> Tue, May 22, 2018 at 05:28:42PM CEST, sridhar.samudrala at intel.com
wrote:
>> >
>> >On 5/22/2018 2:08 AM, Jiri Pirko wrote:
>> >> Tue, May 22, 2018 at 11:06:37AM CEST, jiri at resnulli.us
wrote:
>> >> > Tue, May 22, 2018 at 04:06:18AM CEST, sridhar.samudrala
at intel.com wrote:
>> >> > > Use the registration/notification framework
supported by the generic
>> >> > > failover infrastructure.
>> >> > > 
>> >> > > Signed-off-by: Sridhar Samudrala
<sridhar.samudrala at intel.com>
>> >> > In previous patchset versions, the common code did
>> >> > netdev_rx_handler_register() and netdev_upper_dev_link()
etc
>> >> > (netvsc_vf_join()). Now, this is still done in netvsc.
Why?
>> >> > 
>> >> > This should be part of the common "failover"
code.
>> >
>> >Based on Stephen's feedback on earlier patches, i tried to
minimize the changes to
>> >netvsc and only commonize the notifier and the main event handler
routine.
>> >Another complication is that netvsc does part of registration in a
delayed workqueue.
>> 
>> :( This kind of degrades the whole efford of having single solution
>> in "failover" module. I think that common parts, as
>> netdev_rx_handler_register() and others certainly is should be inside
>> the common module. This is not a good time to minimize changes.
Let's do
>> the thing properly and fix the netvsc mess now.
>> 
>> 
>> >
>> >It should be possible to move some of the code from net_failover.c
to generic
>> >failover.c in future if Stephen is ok with it.
>> >
>> >
>> >> > 
>> >> Also note that in the current patchset you use IFF_FAILOVER
flag for
>> >> master, yet for the slave you use IFF_SLAVE. That is wrong.
>> >> IFF_FAILOVER_SLAVE should be used.
>> >
>> >Not sure which code you are referring to.? I only set
IFF_FAILOVER_SLAVE
>> >in patch 3.
>> 
>> The existing netvsc driver.
>
>We really can't change netvsc's flags now, even if it's
interface is
>messy, it's being used in the field. We can add a flag that makes netvsc
>behave differently, and if this flag also allows enhanced functionality
>userspace will gradually switch.
Okay, although in this case, it really does not make much sense, so be
it. Leave the netvsc set the ->priv flag to IFF_SLAVE as it is doing
now. (This once-wrong-forever-wrong policy is flustrating me).

But since this patchset introduces private flag IFF_FAILOVER and
IFF_FAILOVER_SLAVE, and we set IFF_FAILOVER to the netvsc netdev
instance, we should also set IFF_FAILOVER_SLAVE to the enslaved VF
netdevice to get at least some consistency between virtio_net and
netvsc.

>
>Anything breaking userspace I fully expect Stephen to nack and
>IMO with good reason.
>
>-- 
>MST

On 5/22/2018 9:12 AM, Jiri Pirko wrote:
> Fixing the subj, sorry about that.
>
> Tue, May 22, 2018 at 05:46:21PM CEST, mst at redhat.com wrote:
>> On Tue, May 22, 2018 at 05:36:14PM +0200, Jiri Pirko wrote:
>>> Tue, May 22, 2018 at 05:28:42PM CEST, sridhar.samudrala at
intel.com wrote:
>>>> On 5/22/2018 2:08 AM, Jiri Pirko wrote:
>>>>> Tue, May 22, 2018 at 11:06:37AM CEST, jiri at resnulli.us
wrote:
>>>>>> Tue, May 22, 2018 at 04:06:18AM CEST, sridhar.samudrala
at intel.com wrote:
>>>>>>> Use the registration/notification framework
supported by the generic
>>>>>>> failover infrastructure.
>>>>>>>
>>>>>>> Signed-off-by: Sridhar Samudrala
<sridhar.samudrala at intel.com>
>>>>>> In previous patchset versions, the common code did
>>>>>> netdev_rx_handler_register() and
netdev_upper_dev_link() etc
>>>>>> (netvsc_vf_join()). Now, this is still done in netvsc.
Why?
>>>>>>
>>>>>> This should be part of the common "failover"
code.
>>>> Based on Stephen's feedback on earlier patches, i tried to
minimize the changes to
>>>> netvsc and only commonize the notifier and the main event
handler routine.
>>>> Another complication is that netvsc does part of registration
in a delayed workqueue.
>>> :( This kind of degrades the whole efford of having single solution
>>> in "failover" module. I think that common parts, as
>>> netdev_rx_handler_register() and others certainly is should be
inside
>>> the common module. This is not a good time to minimize changes.
Let's do
>>> the thing properly and fix the netvsc mess now.
>>>
>>>
>>>> It should be possible to move some of the code from
net_failover.c to generic
>>>> failover.c in future if Stephen is ok with it.
>>>>
>>>>
>>>>> Also note that in the current patchset you use IFF_FAILOVER
flag for
>>>>> master, yet for the slave you use IFF_SLAVE. That is wrong.
>>>>> IFF_FAILOVER_SLAVE should be used.
>>>> Not sure which code you are referring to.? I only set
IFF_FAILOVER_SLAVE
>>>> in patch 3.
>>> The existing netvsc driver.
>> We really can't change netvsc's flags now, even if it's
interface is
>> messy, it's being used in the field. We can add a flag that makes
netvsc
>> behave differently, and if this flag also allows enhanced functionality
>> userspace will gradually switch.
> Okay, although in this case, it really does not make much sense, so be
> it. Leave the netvsc set the ->priv flag to IFF_SLAVE as it is doing
> now. (This once-wrong-forever-wrong policy is flustrating me).
>
> But since this patchset introduces private flag IFF_FAILOVER and
> IFF_FAILOVER_SLAVE, and we set IFF_FAILOVER to the netvsc netdev
> instance, we should also set IFF_FAILOVER_SLAVE to the enslaved VF
> netdevice to get at least some consistency between virtio_net and
> netvsc.
OK. I can make this change to set/unset IFF_FAILOVER_SLAVE in the netvsc
register/unregister routines so that it is consistent with virtio_net.

Based on your discussion with mst, i think we can even remove IFF_SLAVE
setting on netvsc as it should not impact userspace.  If Stephen is OK
we can make this change too.

Do you see any other items that need to be resolved for this series to go in
this merge window?


>
>> Anything breaking userspace I fully expect Stephen to nack and
>> IMO with good reason.
>>
>> -- 
>> MST