o net: module refcounting for sk_alloc/sk_free

I had to move the rtnetlink_init and init_netlink calls to af_netlink init time, so that
the sk_alloc called down the rtnetlink_init callchain is done after the PF_NETLINK
net_proto_family is sock_registered, and because of that the af_netlink init function
call had to be moved to earlier by means of subsys_initcall (DaveM's suggestion).

include/linux/net.h

@@ -140,6 +140,9 @@ struct net_proto_family {
 	struct module	*owner;
 };
 
+extern int	     net_family_get(int family);
+extern void	     net_family_put(int family);
+
 struct iovec;
 
 extern int	     sock_wake_async(struct socket *sk, int how, int band);

net/core/sock.c

@@ -589,8 +589,10 @@ static kmem_cache_t *sk_cachep;
  */
 struct sock *sk_alloc(int family, int priority, int zero_it, kmem_cache_t *slab)
 {
-	struct sock *sk;
+	struct sock *sk = NULL;
 
+	if (!net_family_get(family))
+		goto out;
 	if (!slab)
 		slab = sk_cachep;
 	sk = kmem_cache_alloc(slab, priority);
@@ -602,14 +604,16 @@ struct sock *sk_alloc(int family, int priority, int zero_it, kmem_cache_t *slab)
 			sock_lock_init(sk);
 		}
 		sk->slab = slab;
-	}
-
+	} else
+		net_family_put(family);
+out:
 	return sk;
 }
 
 void sk_free(struct sock *sk)
 {
 	struct sk_filter *filter;
+	const int family = sk->family;
 
 	if (sk->destruct)
 		sk->destruct(sk);
@@ -624,6 +628,7 @@ void sk_free(struct sock *sk)
 		printk(KERN_DEBUG "sk_free: optmem leakage (%d bytes) detected.\n", atomic_read(&sk->omem_alloc));
 
 	kmem_cache_free(sk->slab, sk);
+	net_family_put(family);
 }
 
 void __init sk_init(void)

net/netlink/af_netlink.c

@@ -1052,6 +1052,7 @@ struct proto_ops netlink_ops = {
 struct net_proto_family netlink_family_ops = {
 	.family = PF_NETLINK,
 	.create = netlink_create,
+	.owner	= THIS_MODULE,	/* for consistency 8) */
 };
 
 static int __init netlink_proto_init(void)
@@ -1065,6 +1066,11 @@ static int __init netlink_proto_init(void)
 	sock_register(&netlink_family_ops);
 #ifdef CONFIG_PROC_FS
 	create_proc_read_entry("net/netlink", 0, 0, netlink_read_proc, NULL);
+#endif
+	/* The netlink device handler may be needed early. */ 
+	rtnetlink_init();
+#ifdef CONFIG_NETLINK_DEV
+	init_netlink();
 #endif
 	return 0;
 }
@@ -1075,7 +1081,7 @@ static void __exit netlink_proto_exit(void)
        remove_proc_entry("net/netlink", NULL);
 }
 
-module_init(netlink_proto_init);
+subsys_initcall(netlink_proto_init);
 module_exit(netlink_proto_exit);
 
 MODULE_LICENSE("GPL");

net/socket.c

@@ -69,8 +69,6 @@
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <linux/wanrouter.h>
-#include <linux/netlink.h>
-#include <linux/rtnetlink.h>
 #include <linux/if_bridge.h>
 #include <linux/init.h>
 #include <linux/poll.h>
@@ -143,6 +141,31 @@ static struct file_operations socket_file_ops = {
 
 static struct net_proto_family *net_families[NPROTO];
 
+static __inline__ void net_family_bug(int family)
+{
+	printk(KERN_ERR "%d is not yet sock_registered!\n", family);
+	BUG();
+}
+
+int net_family_get(int family)
+{
+	int rc = 1;
+
+	if (likely(net_families[family] != NULL))
+		rc = try_module_get(net_families[family]->owner);
+	else
+		net_family_bug(family);
+	return rc;
+}
+
+void net_family_put(int family)
+{
+	if (likely(net_families[family] != NULL))
+		module_put(net_families[family]->owner);
+	else
+		net_family_bug(family);
+}
+
 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
 static atomic_t net_family_lockct = ATOMIC_INIT(0);
 static spinlock_t net_family_lock = SPIN_LOCK_UNLOCKED;
@@ -511,7 +534,7 @@ void sock_release(struct socket *sock)
 
 		sock->ops->release(sock);
 		sock->ops = NULL;
-		module_put(net_families[family]->owner);
+		net_family_put(family);
 	}
 
 	if (sock->fasync_list)
@@ -1064,7 +1087,7 @@ int sock_create(int family, int type, int protocol, struct socket **res)
 	sock->type  = type;
 
 	i = -EBUSY;
-	if (!try_module_get(net_families[family]->owner))
+	if (!net_family_get(family))
 		goto out_release;
 
 	if ((i = net_families[family]->create(sock, protocol)) < 0) 
@@ -1953,17 +1976,6 @@ void __init sock_init(void)
 	 *  do_initcalls is run.  
 	 */
 
-
-	/*
-	 * The netlink device handler may be needed early.
-	 */
-
-#ifdef CONFIG_NET
-	rtnetlink_init();
-#endif
-#ifdef CONFIG_NETLINK_DEV
-	init_netlink();
-#endif
 #ifdef CONFIG_NETFILTER
 	netfilter_init();
 #endif