netdev - Re: [PATCH net-next v11 2/5] netvsc: refactor notifier/event handling code to use the failover framework

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Date:   Tue, 22 May 2018 18:12:46 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        stephen@...workplumber.org, davem@...emloft.net,
        netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, jesse.brandeburg@...el.com,
        alexander.h.duyck@...el.com, kubakici@...pl, jasowang@...hat.com,
        loseweigh@...il.com, aaron.f.brown@...el.com,
        anjali.singhai@...el.com
Subject: Re: [PATCH net-next v11 2/5] netvsc: refactor notifier/event
 handling code to use the failover framework

Fixing the subj, sorry about that.

Tue, May 22, 2018 at 05:46:21PM CEST, mst@...hat.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@...el.com wrote:
>> >
>> >On 5/22/2018 2:08 AM, Jiri Pirko wrote:
>> >> Tue, May 22, 2018 at 11:06:37AM CEST, jiri@...nulli.us wrote:
>> >> > Tue, May 22, 2018 at 04:06:18AM CEST, sridhar.samudrala@...el.com wrote:
>> >> > > Use the registration/notification framework supported by the generic
>> >> > > failover infrastructure.
>> >> > > 
>> >> > > Signed-off-by: Sridhar Samudrala <sridhar.samudrala@...el.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