vlan: add net device refcount tracker

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/if_vlan.h

@@ -162,6 +162,7 @@ struct netpoll;
  *	@vlan_id: VLAN identifier
  *	@flags: device flags
  *	@real_dev: underlying netdevice
+ *	@dev_tracker: refcount tracker for @real_dev reference
  *	@real_dev_addr: address of underlying netdevice
  *	@dent: proc dir entry
  *	@vlan_pcpu_stats: ptr to percpu rx stats
@@ -177,6 +178,8 @@ struct vlan_dev_priv {
 	u16					flags;
 
 	struct net_device			*real_dev;
+	netdevice_tracker			dev_tracker;
+
 	unsigned char				real_dev_addr[ETH_ALEN];
 
 	struct proc_dir_entry			*dent;

net/8021q/vlan_dev.c

@@ -616,7 +616,7 @@ static int vlan_dev_init(struct net_device *dev)
 		return -ENOMEM;
 
 	/* Get vlan's reference to real_dev */
-	dev_hold(real_dev);
+	dev_hold_track(real_dev, &vlan->dev_tracker, GFP_KERNEL);
 
 	return 0;
 }
@@ -848,7 +848,7 @@ static void vlan_dev_free(struct net_device *dev)
 	vlan->vlan_pcpu_stats = NULL;
 
 	/* Get rid of the vlan's reference to real_dev */
-	dev_put(vlan->real_dev);
+	dev_put_track(vlan->real_dev, &vlan->dev_tracker);
 }
 
 void vlan_setup(struct net_device *dev)