net: Slim down setup_net().

Most initialisations in setup_net() do not require pernet_ops_rwsem
and can be moved to preinit_net().
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/net_namespace.c

@@ -310,16 +310,26 @@ struct net *get_net_ns_by_id(const struct net *net, int id)
 EXPORT_SYMBOL_GPL(get_net_ns_by_id);
 
 /* init code that must occur even if setup_net() is not called. */
-static __net_init void preinit_net(struct net *net)
+static __net_init void preinit_net(struct net *net, struct user_namespace *user_ns)
 {
 	refcount_set(&net->passive, 1);
+	refcount_set(&net->ns.count, 1);
+	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net refcnt");
 	ref_tracker_dir_init(&net->notrefcnt_tracker, 128, "net notrefcnt");
+
+	get_random_bytes(&net->hash_mix, sizeof(u32));
+	net->dev_base_seq = 1;
+	net->user_ns = user_ns;
+
+	idr_init(&net->netns_ids);
+	spin_lock_init(&net->nsid_lock);
+	mutex_init(&net->ipv4.ra_mutex);
 }
 
 /*
  * setup_net runs the initializers for the network namespace object.
  */
-static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
+static __net_init int setup_net(struct net *net)
 {
 	/* Must be called with pernet_ops_rwsem held */
 	const struct pernet_operations *ops, *saved_ops;
@@ -327,18 +337,9 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 	LIST_HEAD(dev_kill_list);
 	int error = 0;
 
-	refcount_set(&net->ns.count, 1);
-	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net refcnt");
-
-	get_random_bytes(&net->hash_mix, sizeof(u32));
 	preempt_disable();
 	net->net_cookie = gen_cookie_next(&net_cookie);
 	preempt_enable();
-	net->dev_base_seq = 1;
-	net->user_ns = user_ns;
-	idr_init(&net->netns_ids);
-	spin_lock_init(&net->nsid_lock);
-	mutex_init(&net->ipv4.ra_mutex);
 
 	list_for_each_entry(ops, &pernet_list, list) {
 		error = ops_init(ops, net);
@@ -497,7 +498,7 @@ struct net *copy_net_ns(unsigned long flags,
 		goto dec_ucounts;
 	}
 
-	preinit_net(net);
+	preinit_net(net, user_ns);
 	net->ucounts = ucounts;
 	get_user_ns(user_ns);
 
@@ -505,7 +506,7 @@ struct net *copy_net_ns(unsigned long flags,
 	if (rv < 0)
 		goto put_userns;
 
-	rv = setup_net(net, user_ns);
+	rv = setup_net(net);
 
 	up_read(&pernet_ops_rwsem);
 
@@ -1199,10 +1200,10 @@ void __init net_ns_init(void)
 #ifdef CONFIG_KEYS
 	init_net.key_domain = &init_net_key_domain;
 #endif
-	preinit_net(&init_net);
+	preinit_net(&init_net, &init_user_ns);
 
 	down_write(&pernet_ops_rwsem);
-	if (setup_net(&init_net, &init_user_ns))
+	if (setup_net(&init_net))
 		panic("Could not setup the initial network namespace");
 
 	init_net_initialized = true;