tcp: Check hlist_empty(&tb->bhash2) instead of hlist_empty(&tb->owners).

We use hlist_empty(&tb->owners) to check if the bhash bucket has a socket.
We can check the child bhash2 buckets instead.

For this to work, the bhash2 bucket must be freed before the bhash bucket.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: q2ven

net/ipv4/inet_connection_sock.c

@@ -474,7 +474,7 @@ void inet_csk_update_fastreuse(struct inet_bind_bucket *tb,
 	kuid_t uid = sock_i_uid(sk);
 	bool reuse = sk->sk_reuse && sk->sk_state != TCP_LISTEN;
 
-	if (hlist_empty(&tb->owners)) {
+	if (hlist_empty(&tb->bhash2)) {
 		tb->fastreuse = reuse;
 		if (sk->sk_reuseport) {
 			tb->fastreuseport = FASTREUSEPORT_ANY;
@@ -566,7 +566,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 	}
 
 	if (!found_port) {
-		if (!hlist_empty(&tb->owners)) {
+		if (!hlist_empty(&tb->bhash2)) {
 			if (sk->sk_reuse == SK_FORCE_REUSE ||
 			    (tb->fastreuse > 0 && reuse) ||
 			    sk_reuseport_match(tb, sk))
@@ -608,11 +608,10 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 
 fail_unlock:
 	if (ret) {
+		if (bhash2_created)
+			inet_bind2_bucket_destroy(hinfo->bind2_bucket_cachep, tb2);
 		if (bhash_created)
 			inet_bind_bucket_destroy(hinfo->bind_bucket_cachep, tb);
-		if (bhash2_created)
-			inet_bind2_bucket_destroy(hinfo->bind2_bucket_cachep,
-						  tb2);
 	}
 	if (head2_lock_acquired)
 		spin_unlock(&head2->lock);

net/ipv4/inet_hashtables.c

@@ -88,7 +88,7 @@ struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
  */
 void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket *tb)
 {
-	if (hlist_empty(&tb->owners)) {
+	if (hlist_empty(&tb->bhash2)) {
 		__hlist_del(&tb->node);
 		kmem_cache_free(cachep, tb);
 	}
@@ -195,7 +195,6 @@ static void __inet_put_port(struct sock *sk)
 	__sk_del_bind_node(sk);
 	inet_csk(sk)->icsk_bind_hash = NULL;
 	inet_sk(sk)->inet_num = 0;
-	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
 
 	spin_lock(&head2->lock);
 	if (inet_csk(sk)->icsk_bind2_hash) {
@@ -207,6 +206,7 @@ static void __inet_put_port(struct sock *sk)
 	}
 	spin_unlock(&head2->lock);
 
+	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
 	spin_unlock(&head->lock);
 }
 
@@ -1062,7 +1062,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 				if (tb->fastreuse >= 0 ||
 				    tb->fastreuseport >= 0)
 					goto next_port;
-				WARN_ON(hlist_empty(&tb->owners));
+				WARN_ON(hlist_empty(&tb->bhash2));
 				if (!check_established(death_row, sk,
 						       port, &tw))
 					goto ok;

net/ipv4/inet_timewait_sock.c

@@ -37,11 +37,11 @@ void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
 
 	__hlist_del(&tw->tw_bind_node);
 	tw->tw_tb = NULL;
-	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
 
 	__hlist_del(&tw->tw_bind2_node);
 	tw->tw_tb2 = NULL;
 	inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2);
+	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
 
 	__sock_put((struct sock *)tw);
 }