macvtap: introduce macvtap_get_vlan()

Factor out the device holding logic to a macvtap_get_vlan(), this will be also
used by multiqueue API.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macvtap.c

@@ -893,6 +893,24 @@ static ssize_t macvtap_aio_read(struct kiocb *iocb, const struct iovec *iv,
 	return ret;
 }
 
+static struct macvlan_dev *macvtap_get_vlan(struct macvtap_queue *q)
+{
+	struct macvlan_dev *vlan;
+
+	rcu_read_lock_bh();
+	vlan = rcu_dereference_bh(q->vlan);
+	if (vlan)
+		dev_hold(vlan->dev);
+	rcu_read_unlock_bh();
+
+	return vlan;
+}
+
+static void macvtap_put_vlan(struct macvlan_dev *vlan)
+{
+	dev_put(vlan->dev);
+}
+
 /*
  * provide compatibility with generic tun/tap interface
  */
@@ -924,12 +942,7 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
 		return ret;
 
 	case TUNGETIFF:
-		rcu_read_lock_bh();
-		vlan = rcu_dereference_bh(q->vlan);
-		if (vlan)
-			dev_hold(vlan->dev);
-		rcu_read_unlock_bh();
-
+		vlan = macvtap_get_vlan(q);
 		if (!vlan)
 			return -ENOLINK;
 
@@ -937,7 +950,7 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
 		if (copy_to_user(&ifr->ifr_name, vlan->dev->name, IFNAMSIZ) ||
 		    put_user(q->flags, &ifr->ifr_flags))
 			ret = -EFAULT;
-		dev_put(vlan->dev);
+		macvtap_put_vlan(vlan);
 		return ret;
 
 	case TUNGETFEATURES: