macvtap: Rewrite macvtap_newlink so the error handling works.

Place macvlan_common_newlink at the end of macvtap_newlink because
failing in newlink after registering your network device is not
supported.

Move device_create into a netdevice creation notifier.   The network device
notifier is the only hook that is called after the network device has been
registered with the device layer and before register_network_device returns
success.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 49 insertions, 24 deletions

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 515aa873929e..25689e9df3b7 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -280,34 +280,16 @@ static int macvtap_newlink(struct net *src_net,
                            struct nlattr *tb[],
                            struct nlattr *data[])
 {
-        struct device *classdev;
-        dev_t devt;
-        int err;
-
-        err = macvlan_common_newlink(src_net, dev, tb, data,
-                                     macvtap_receive, macvtap_forward);
-        if (err)
-                goto out;
-
-        devt = MKDEV(MAJOR(macvtap_major), dev->ifindex);
-
-        classdev = device_create(macvtap_class, &dev->dev, devt,
-                                 dev, "tap%d", dev->ifindex);
-        if (IS_ERR(classdev)) {
-                err = PTR_ERR(classdev);
-                macvtap_del_queues(dev);
-        }
-
-out:
-        return err;
+        /* Don't put anything that may fail after macvlan_common_newlink
+         * because we can't undo what it does.
+         */
+        return macvlan_common_newlink(src_net, dev, tb, data,
+                                      macvtap_receive, macvtap_forward);
 }
 
 static void macvtap_dellink(struct net_device *dev,
                             struct list_head *head)
 {
-        device_destroy(macvtap_class,
-                       MKDEV(MAJOR(macvtap_major), dev->ifindex));
-
         macvtap_del_queues(dev);
         macvlan_dellink(dev, head);
 }
@@ -975,6 +957,42 @@ struct socket *macvtap_get_socket(struct file *file)
 }
 EXPORT_SYMBOL_GPL(macvtap_get_socket);
 
+static int macvtap_device_event(struct notifier_block *unused,
+                                unsigned long event, void *ptr)
+{
+        struct net_device *dev = ptr;
+        struct device *classdev;
+        dev_t devt;
+
+        if (dev->rtnl_link_ops != &macvtap_link_ops)
+                return NOTIFY_DONE;
+
+
+        switch (event) {
+        case NETDEV_REGISTER:
+                /* Create the device node here after the network device has
+                 * been registered but before register_netdevice has
+                 * finished running.
+                 */
+                devt = MKDEV(MAJOR(macvtap_major), dev->ifindex);
+                classdev = device_create(macvtap_class, &dev->dev, devt,
+                                         dev, "tap%d", dev->ifindex);
+                if (IS_ERR(classdev))
+                        return notifier_from_errno(PTR_ERR(classdev));
+                break;
+        case NETDEV_UNREGISTER:
+                devt = MKDEV(MAJOR(macvtap_major), dev->ifindex);
+                device_destroy(macvtap_class, devt);
+                break;
+        }
+
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block macvtap_notifier_block __read_mostly = {
+        .notifier_call  = macvtap_device_event,
+};
+
 static int macvtap_init(void)
 {
         int err;
@@ -995,12 +1013,18 @@ static int macvtap_init(void)
                 goto out3;
         }
 
-        err = macvlan_link_register(&macvtap_link_ops);
+        err = register_netdevice_notifier(&macvtap_notifier_block);
         if (err)
                 goto out4;
 
+        err = macvlan_link_register(&macvtap_link_ops);
+        if (err)
+                goto out5;
+
         return 0;
 
+out5:
+        unregister_netdevice_notifier(&macvtap_notifier_block);
 out4:
         class_unregister(macvtap_class);
 out3:
@@ -1015,6 +1039,7 @@ module_init(macvtap_init);
 static void macvtap_exit(void)
 {
         rtnl_link_unregister(&macvtap_link_ops);
+        unregister_netdevice_notifier(&macvtap_notifier_block);
         class_unregister(macvtap_class);
         cdev_del(&macvtap_cdev);
         unregister_chrdev_region(macvtap_major, MACVTAP_NUM_DEVS);