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

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Message-ID: <20180523062748.GA3155@nanopsycho>
Date:   Wed, 23 May 2018 08:27:48 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.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

Tue, May 22, 2018 at 10:54:29PM CEST, sridhar.samudrala@...el.com wrote:
>
>
>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@...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.
>
>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?

As I wrote previously, the common code including rx_handler registration
and setting of flags and master link should be done in a common code,
moved away from netvsc code.

Thanks.


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