tcp: bind() optimize port allocation

Port autoselection finds a port and then drop the lock,
then right after that, gets the hash bucket again and lock it.

Fix it to go direct.
Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/inet_connection_sock.c

@@ -123,15 +123,13 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 						smallest_size = tb->num_owners;
 						smallest_rover = rover;
 						if (atomic_read(&hashinfo->bsockets) > (high - low) + 1) {
-							spin_unlock(&head->lock);
 							snum = smallest_rover;
-							goto have_snum;
+							goto tb_found;
 						}
 					}
 					if (!inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb)) {
-						spin_unlock(&head->lock);
 						snum = rover;
-						goto have_snum;
+						goto tb_found;
 					}
 					goto next;
 				}