netdev - Re: [PATCH net-next v10 2/4] net: Introduce generic failover module

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Date:   Fri, 11 May 2018 20:15:58 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
Cc:     Stephen Hemminger <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, jiri@...nulli.us, aaron.f.brown@...el.com
Subject: Re: [PATCH net-next v10 2/4] net: Introduce generic failover module

On Mon, May 07, 2018 at 05:24:27PM -0700, Samudrala, Sridhar wrote:
> 
> 
> On 5/7/2018 4:53 PM, Stephen Hemminger wrote:
> > On Mon,  7 May 2018 15:10:44 -0700
> > Sridhar Samudrala <sridhar.samudrala@...el.com> wrote:
> > 
> > > +static struct net_device *net_failover_get_bymac(u8 *mac,
> > > +						 struct net_failover_ops **ops)
> > > +{
> > > +	struct net_device *failover_dev;
> > > +	struct net_failover *failover;
> > > +
> > > +	spin_lock(&net_failover_lock);
> > > +	list_for_each_entry(failover, &net_failover_list, list) {
> > > +		failover_dev = rtnl_dereference(failover->failover_dev);
> > > +		if (ether_addr_equal(failover_dev->perm_addr, mac)) {
> > > +			*ops = rtnl_dereference(failover->ops);
> > > +			spin_unlock(&net_failover_lock);
> > > +			return failover_dev;
> > > +		}
> > > +	}
> > > +	spin_unlock(&net_failover_lock);
> > > +	return NULL;
> > > +}
> > This is broken if non-ethernet devices such as Infiniband are present.
> 
> There is check to make sure that a slave and failover devices are of the same type in
> net_failover_slave_register()
> 
> 	failover_dev = net_failover_get_bymac(slave_dev->perm_addr, &nfo_ops);
>         if (!failover_dev)
>                 goto done;
> 
>         if (failover_dev->type != slave_dev->type)
>                 goto done;
> 
> Do you think this is not good enough? I had an explicit check for ARPHRD_ETHER in
> earlier patchsets, but removed it based on Jiri's comment.

Right but how is ether_addr_equal supposed to work if types are
identical but not ethernet?

This can also benefit from a comment referring to the check in
net_failover_slave_register.

-- 
MST