[INET]: Generalise tcp_v4_hash & tcp_unhash

It really just makes the existing code be a helper function that
tcp_v4_hash and tcp_unhash uses, specifying the right inet_hashinfo,
tcp_hashinfo.

One thing I'll investigate at some point is to have the inet_hashinfo
pointer in sk_prot, so that we get all the hashtable information from
the sk pointer, this can lead to some extra indirections that may well
hurt performance/code size, we'll see. Ultimate idea would be that
sk_prot would provide _all_ the information about a protocol
implementation.
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet_hashtables.h

@@ -240,4 +240,38 @@ static inline void __inet_hash(struct inet_hashinfo *hashinfo,
 	if (listen_possible && sk->sk_state == TCP_LISTEN)
 		wake_up(&hashinfo->lhash_wait);
 }
+
+static inline void inet_hash(struct inet_hashinfo *hashinfo, struct sock *sk)
+{
+	if (sk->sk_state != TCP_CLOSE) {
+		local_bh_disable();
+		__inet_hash(hashinfo, sk, 1);
+		local_bh_enable();
+	}
+}
+
+static inline void inet_unhash(struct inet_hashinfo *hashinfo, struct sock *sk)
+{
+	rwlock_t *lock;
+
+	if (sk_unhashed(sk))
+		goto out;
+
+	if (sk->sk_state == TCP_LISTEN) {
+		local_bh_disable();
+		inet_listen_wlock(hashinfo);
+		lock = &hashinfo->lhash_lock;
+	} else {
+		struct inet_ehash_bucket *head = &hashinfo->ehash[sk->sk_hashent];
+		lock = &head->lock;
+		write_lock_bh(&head->lock);
+	}
+
+	if (__sk_del_node_init(sk))
+		sock_prot_dec_use(sk->sk_prot);
+	write_unlock_bh(lock);
+out:
+	if (sk->sk_state == TCP_LISTEN)
+		wake_up(&hashinfo->lhash_wait);
+}
 #endif /* _INET_HASHTABLES_H */

net/ipv4/tcp_ipv4.c

@@ -230,37 +230,12 @@ fail:
 
 static void tcp_v4_hash(struct sock *sk)
 {
-	if (sk->sk_state != TCP_CLOSE) {
-		local_bh_disable();
-		__inet_hash(&tcp_hashinfo, sk, 1);
-		local_bh_enable();
-	}
+	inet_hash(&tcp_hashinfo, sk);
 }
 
 void tcp_unhash(struct sock *sk)
 {
-	rwlock_t *lock;
-
-	if (sk_unhashed(sk))
-		goto ende;
-
-	if (sk->sk_state == TCP_LISTEN) {
-		local_bh_disable();
-		inet_listen_wlock(&tcp_hashinfo);
-		lock = &tcp_hashinfo.lhash_lock;
-	} else {
-		struct inet_ehash_bucket *head = &tcp_hashinfo.ehash[sk->sk_hashent];
-		lock = &head->lock;
-		write_lock_bh(&head->lock);
-	}
-
-	if (__sk_del_node_init(sk))
-		sock_prot_dec_use(sk->sk_prot);
-	write_unlock_bh(lock);
-
- ende:
-	if (sk->sk_state == TCP_LISTEN)
-		wake_up(&tcp_hashinfo.lhash_wait);
+	inet_unhash(&tcp_hashinfo, sk);
 }
 
 /* Don't inline this cruft.  Here are some nice properties to