net: move net_set_todo inside rollback_registered()

Commit 93ee31f1 ("[NET]: Fix free_netdev on register_netdev
failure.") moved net_set_todo() outside of rollback_registered()
so that rollback_registered() can be used in the failure path of
register_netdevice() but without risking a double free.

Since commit cf124db5 ("net: Fix inconsistent teardown and
release of private netdev state."), however, we have a better
way of handling that condition, since destructors don't call
free_netdev() directly.

After the change in commit c269a24c ("net: make free_netdev()
more lenient with unregistering devices") we can now move
net_set_todo() back.
Reviewed-by: NEdwin Peer <edwin.peer@broadcom.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

net/core/dev.c

@@ -9546,8 +9546,10 @@ static void rollback_registered_many(struct list_head *head)
 
 	synchronize_net();
 
-	list_for_each_entry(dev, head, unreg_list)
+	list_for_each_entry(dev, head, unreg_list) {
 		dev_put(dev);
+		net_set_todo(dev);
+	}
 }
 
 static void rollback_registered(struct net_device *dev)
@@ -10109,7 +10111,6 @@ int register_netdevice(struct net_device *dev)
 		/* Expect explicit free_netdev() on failure */
 		dev->needs_free_netdev = false;
 		rollback_registered(dev);
-		net_set_todo(dev);
 		goto out;
 	}
 	/*
@@ -10732,8 +10733,6 @@ void unregister_netdevice_queue(struct net_device *dev, struct list_head *head)
 		list_move_tail(&dev->unreg_list, head);
 	} else {
 		rollback_registered(dev);
-		/* Finish processing unregister after unlock */
-		net_set_todo(dev);
 	}
 }
 EXPORT_SYMBOL(unregister_netdevice_queue);
@@ -10747,12 +10746,8 @@ EXPORT_SYMBOL(unregister_netdevice_queue);
  */
 void unregister_netdevice_many(struct list_head *head)
 {
-	struct net_device *dev;
-
 	if (!list_empty(head)) {
 		rollback_registered_many(head);
-		list_for_each_entry(dev, head, unreg_list)
-			net_set_todo(dev);
 		list_del(head);
 	}
 }