tcp: add RCU management to inet_bind_bucket

mainline inclusion
from mainline-v6.15-rc1
category: performance

Add RCU protection to inet_bind_bucket structure.

- Add rcu_head field to the structure definition.

- Use kfree_rcu() at destroy time, and remove inet_bind_bucket_destroy()
  first argument.

- Use hlist_del_rcu() and hlist_add_head_rcu() methods.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250302124237.3913746-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
(cherry picked from commit d186f40)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
Change-Id: I57a0c27b179838e46c3d861bbc862dd90298fb22

Author: edumazet

include/net/inet_hashtables.h

@@ -89,6 +89,7 @@ struct inet_bind_bucket {
 	bool			fast_ipv6_only;
 	struct hlist_node	node;
 	struct hlist_head	bhash2;
+	struct rcu_head		rcu;
 };
 
 struct inet_bind2_bucket {
@@ -226,8 +227,7 @@ struct inet_bind_bucket *
 inet_bind_bucket_create(struct kmem_cache *cachep, struct net *net,
 			struct inet_bind_hashbucket *head,
 			const unsigned short snum, int l3mdev);
-void inet_bind_bucket_destroy(struct kmem_cache *cachep,
-			      struct inet_bind_bucket *tb);
+void inet_bind_bucket_destroy(struct inet_bind_bucket *tb);
 
 bool inet_bind_bucket_match(const struct inet_bind_bucket *tb,
 			    const struct net *net, unsigned short port,

net/ipv4/inet_connection_sock.c

@@ -589,7 +589,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 		if (bhash2_created)
 			inet_bind2_bucket_destroy(hinfo->bind2_bucket_cachep, tb2);
 		if (bhash_created)
-			inet_bind_bucket_destroy(hinfo->bind_bucket_cachep, tb);
+			inet_bind_bucket_destroy(tb);
 	}
 	if (head2_lock_acquired)
 		spin_unlock(&head2->lock);

net/ipv4/inet_hashtables.c

@@ -77,19 +77,19 @@ struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
 		tb->fastreuse = 0;
 		tb->fastreuseport = 0;
 		INIT_HLIST_HEAD(&tb->bhash2);
-		hlist_add_head(&tb->node, &head->chain);
+		hlist_add_head_rcu(&tb->node, &head->chain);
 	}
 	return tb;
 }
 
 /*
  * Caller must hold hashbucket lock for this tb with local BH disabled
  */
-void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket *tb)
+void inet_bind_bucket_destroy(struct inet_bind_bucket *tb)
 {
 	if (hlist_empty(&tb->bhash2)) {
-		__hlist_del(&tb->node);
-		kmem_cache_free(cachep, tb);
+		hlist_del_rcu(&tb->node);
+		kfree_rcu(tb, rcu);
 	}
 }
 
@@ -202,7 +202,7 @@ static void __inet_put_port(struct sock *sk)
 	}
 	spin_unlock(&head2->lock);
 
-	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
+	inet_bind_bucket_destroy(tb);
 	spin_unlock(&head->lock);
 }
 
@@ -286,7 +286,7 @@ int __inet_inherit_port(const struct sock *sk, struct sock *child)
 
 error:
 	if (created_inet_bind_bucket)
-		inet_bind_bucket_destroy(table->bind_bucket_cachep, tb);
+		inet_bind_bucket_destroy(tb);
 	spin_unlock(&head2->lock);
 	spin_unlock(&head->lock);
 	return -ENOMEM;
@@ -1157,7 +1157,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 
 	spin_unlock(&head2->lock);
 	if (tb_created)
-		inet_bind_bucket_destroy(hinfo->bind_bucket_cachep, tb);
+		inet_bind_bucket_destroy(tb);
 	spin_unlock(&head->lock);
 
 	if (tw)

net/ipv4/inet_timewait_sock.c

@@ -39,7 +39,7 @@ void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
 	tw->tw_tb = NULL;
 	tw->tw_tb2 = NULL;
 	inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2);
-	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
+	inet_bind_bucket_destroy(tb);
 
 	__sock_put((struct sock *)tw);
 }