bonding: check return value of nofitier when changing type

This patch adds the possibility to refuse the bonding type change for
other subsystems (such as for example bridge, vlan, etc.)
Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -1480,8 +1480,15 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 				 bond_dev->name,
 				 bond_dev->type, slave_dev->type);
 
-			netdev_bonding_change(bond_dev,
-					      NETDEV_PRE_TYPE_CHANGE);
+			res = netdev_bonding_change(bond_dev,
+						    NETDEV_PRE_TYPE_CHANGE);
+			res = notifier_to_errno(res);
+			if (res) {
+				pr_err("%s: refused to change device type\n",
+				       bond_dev->name);
+				res = -EBUSY;
+				goto err_undo_flags;
+			}
 
 			if (slave_dev->type != ARPHRD_ETHER)
 				bond_setup_by_slave(bond_dev, slave_dev);

include/linux/netdevice.h

@@ -2005,7 +2005,7 @@ extern void		__dev_addr_unsync(struct dev_addr_list **to, int *to_count, struct
 extern int		dev_set_promiscuity(struct net_device *dev, int inc);
 extern int		dev_set_allmulti(struct net_device *dev, int inc);
 extern void		netdev_state_change(struct net_device *dev);
-extern void		netdev_bonding_change(struct net_device *dev,
+extern int		netdev_bonding_change(struct net_device *dev,
 					      unsigned long event);
 extern void		netdev_features_change(struct net_device *dev);
 /* Load a device via the kmod */

net/core/dev.c

@@ -1084,9 +1084,9 @@ void netdev_state_change(struct net_device *dev)
 }
 EXPORT_SYMBOL(netdev_state_change);
 
-void netdev_bonding_change(struct net_device *dev, unsigned long event)
+int netdev_bonding_change(struct net_device *dev, unsigned long event)
 {
-	call_netdevice_notifiers(event, dev);
+	return call_netdevice_notifiers(event, dev);
 }
 EXPORT_SYMBOL(netdev_bonding_change);