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

From: Jiri Pirko <jiri@resnulli.us>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Sridhar Samudrala <sridhar.samudrala@intel.com>,
	stephen@networkplumber.org, davem@davemloft.net,
	netdev@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	virtio-dev@lists.oasis-open.org, jesse.brandeburg@intel.com,
	alexander.h.duyck@intel.com, kubakici@wp.pl, jasowang@redhat.com,
	loseweigh@gmail.com, aaron.f.brown@intel.com,
	anjali.singhai@intel.com
Subject: Re: [PATCH net-next v11 2/5] netvsc: refactor notifier/event handling code to use the failover framework
Date: Tue, 22 May 2018 17:13:43 +0200	[thread overview]
Message-ID: <20180522151343.GJ2149@nanopsycho> (raw)
In-Reply-To: <20180522163502-mutt-send-email-mst@kernel.org>

Tue, May 22, 2018 at 03:39:33PM CEST, mst@redhat.com wrote:
>On Tue, May 22, 2018 at 03:26:26PM +0200, Jiri Pirko wrote:
>> Tue, May 22, 2018 at 03:17:37PM CEST, mst@redhat.com wrote:
>> >On Tue, May 22, 2018 at 03:14:22PM +0200, Jiri Pirko wrote:
>> >> Tue, May 22, 2018 at 03:12:40PM CEST, mst@redhat.com wrote:
>> >> >On Tue, May 22, 2018 at 11:08:53AM +0200, Jiri Pirko wrote:
>> >> >> Tue, May 22, 2018 at 11:06:37AM CEST, jiri@resnulli.us wrote:
>> >> >> >Tue, May 22, 2018 at 04:06:18AM CEST, sridhar.samudrala@intel.com wrote:
>> >> >> >>Use the registration/notification framework supported by the generic
>> >> >> >>failover infrastructure.
>> >> >> >>
>> >> >> >>Signed-off-by: Sridhar Samudrala <sridhar.samudrala@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.
>> >> >> >
>> >> >> 
>> >> >> 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.
>> >> >
>> >> >Or drop IFF_FAILOVER_SLAVE and set both IFF_FAILOVER and IFF_SLAVE?
>> >> 
>> >> No. IFF_SLAVE is for bonding.
>> >
>> >What breaks if we reuse it for failover?
>> 
>> This is exposed to userspace. IFF_SLAVE is expected for bonding slaves.
>> And failover slave is not a bonding slave.
>
>That does not really answer the question.  I'd claim it's sufficiently
>like a bond slave for IFF_SLAVE to make sense.
>
>In fact you will find that netvsc already sets IFF_SLAVE, and so

netvsc does the whole failover thing in a wrong way. This patchset is
trying to fix it.

>does e.g. the eql driver.
>
>The advantage of using IFF_SLAVE is that userspace knows to skip it.  If

The userspace should know how to skip other types of slaves - team,
bridge, ovs, etc. The "master link" should be the one to look at.

>we don't set IFF_SLAVE existing userspace tries to use the lowerdev.

Each master type has a IFF_ master flag and IFF_ slave flag. In private
flag. I don't see no reason to break this pattern here.