net: failover: add net device refcount tracker

Signed-off-by: Eric Dumazet <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/failover.h

···
 struct failover {
 	struct list_head list;
 	struct net_device __rcu *failover_dev;
+	netdevice_tracker	dev_tracker;
 	struct failover_ops __rcu *ops;
 };
 

net/core/failover.c

···
 		return ERR_PTR(-ENOMEM);
 
 	rcu_assign_pointer(failover->ops, ops);
-	dev_hold(dev);
+	dev_hold_track(dev, &failover->dev_tracker, GFP_KERNEL);
 	dev->priv_flags |= IFF_FAILOVER;
 	rcu_assign_pointer(failover->failover_dev, dev);
 
···
 		    failover_dev->name);
 
 	failover_dev->priv_flags &= ~IFF_FAILOVER;
-	dev_put(failover_dev);
+	dev_put_track(failover_dev, &failover->dev_tracker);
 
 	spin_lock(&failover_lock);
 	list_del(&failover->list);