can: bcm: registration process optimization in bcm_module_init()

Now, register_netdevice_notifier() and register_pernet_subsys() are both
after can_proto_register(). It can create CAN_BCM socket and process socket
once can_proto_register() successfully, so it is possible missing notifier
event or proc node creation because notifier or bcm proc directory is not
registered or created yet. Although this is a low probability scenario, it
is not impossible.

Move register_pernet_subsys() and register_netdevice_notifier() to the
front of can_proto_register(). In addition, register_pernet_subsys() and
register_netdevice_notifier() may fail, check their results are necessary.
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Link: https://lore.kernel.org/all/823cff0ebec33fa9389eeaf8b8ded3217c32cb38.1663206163.git.william.xuanziyang@huawei.comAcked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/bcm.c

@@ -1749,15 +1749,27 @@ static int __init bcm_module_init(void)
 
 	pr_info("can: broadcast manager protocol\n");
 
+	err = register_pernet_subsys(&canbcm_pernet_ops);
+	if (err)
+		return err;
+
+	err = register_netdevice_notifier(&canbcm_notifier);
+	if (err)
+		goto register_notifier_failed;
+
 	err = can_proto_register(&bcm_can_proto);
 	if (err < 0) {
 		printk(KERN_ERR "can: registration of bcm protocol failed\n");
-		return err;
+		goto register_proto_failed;
 	}
 
-	register_pernet_subsys(&canbcm_pernet_ops);
-	register_netdevice_notifier(&canbcm_notifier);
 	return 0;
+
+register_proto_failed:
+	unregister_netdevice_notifier(&canbcm_notifier);
+register_notifier_failed:
+	unregister_pernet_subsys(&canbcm_pernet_ops);
+	return err;
 }
 
 static void __exit bcm_module_exit(void)