s390/qeth: unregister netdevice only when registered

qeth only registers its netdevice when the qeth device is first set
online. Thus a device that has never been set online will trigger
a WARN ("network todo 'hsi%d' but state 0") in unregister_netdev() when
removed.

Fix this by protecting the unregister step, just like we already protect
against repeated registering of the netdevice.

Fixes: d3d1b20 ("s390/qeth: allocate netdevice early")
Reported-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core.h

@@ -843,6 +843,11 @@ struct qeth_trap_id {
 /*some helper functions*/
 #define QETH_CARD_IFNAME(card) (((card)->dev)? (card)->dev->name : "")
 
+static inline bool qeth_netdev_is_registered(struct net_device *dev)
+{
+	return dev->netdev_ops != NULL;
+}
+
 static inline void qeth_scrub_qdio_buffer(struct qdio_buffer *buf,
 					  unsigned int elements)
 {

drivers/s390/net/qeth_l2_main.c

@@ -826,7 +826,8 @@ static void qeth_l2_remove_device(struct ccwgroup_device *cgdev)
 
 	if (cgdev->state == CCWGROUP_ONLINE)
 		qeth_l2_set_offline(cgdev);
-	unregister_netdev(card->dev);
+	if (qeth_netdev_is_registered(card->dev))
+		unregister_netdev(card->dev);
 }
 
 static const struct ethtool_ops qeth_l2_ethtool_ops = {
@@ -866,7 +867,7 @@ static int qeth_l2_setup_netdev(struct qeth_card *card)
 {
 	int rc;
 
-	if (card->dev->netdev_ops)
+	if (qeth_netdev_is_registered(card->dev))
 		return 0;
 
 	card->dev->priv_flags |= IFF_UNICAST_FLT;

drivers/s390/net/qeth_l3_main.c

@@ -2356,7 +2356,7 @@ static int qeth_l3_setup_netdev(struct qeth_card *card)
 	unsigned int headroom;
 	int rc;
 
-	if (card->dev->netdev_ops)
+	if (qeth_netdev_is_registered(card->dev))
 		return 0;
 
 	if (card->info.type == QETH_CARD_TYPE_OSD ||
@@ -2465,7 +2465,8 @@ static void qeth_l3_remove_device(struct ccwgroup_device *cgdev)
 	if (cgdev->state == CCWGROUP_ONLINE)
 		qeth_l3_set_offline(cgdev);
 
-	unregister_netdev(card->dev);
+	if (qeth_netdev_is_registered(card->dev))
+		unregister_netdev(card->dev);
 	qeth_l3_clear_ip_htable(card, 0);
 	qeth_l3_clear_ipato_list(card);
 }