netdev - [PATCH v1 net-next 2/7] tcp: Save __module_get() for TIME

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Message-ID: <20250821061540.2876953-3-kuniyu@google.com>
Date: Thu, 21 Aug 2025 06:15:13 +0000
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Neal Cardwell <ncardwell@...gle.com>, David Ahern <dsahern@...nel.org>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org, 
	Kuniyuki Iwashima <kuniyu@...zon.com>
Subject: [PATCH v1 net-next 2/7] tcp: Save __module_get() for TIME_WAIT sockets.

From: Kuniyuki Iwashima <kuniyu@...zon.com>

__module_get() in inet_twsk_alloc() was necessary to prevent
unloading tw->tw_prot, which is used in inet_twsk_free().

DCCP has gone, and TCP is built-in, so the pair is no longer needed.

ULPs also do not need it because

 * kTLS and XFRM_ESPINTCP restore sk_prot before close()
 * MPTCP is built-in
 * SMC uses TCP as is

, but using tw_prot without module_get() would be error prone to
future ULP addition.

Now we can use kfree() without the slab cache pointer thanks to SLUB.

Let's use kfree() in inet_twsk_free() and remove 2 atomic ops
for each connection.

Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
 include/net/inet_timewait_sock.h | 1 -
 net/ipv4/inet_timewait_sock.c    | 7 +------
 2 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index 67a313575780..500a0478370f 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -48,7 +48,6 @@ struct inet_timewait_sock {
 #define tw_tx_queue_mapping	__tw_common.skc_tx_queue_mapping
 #define tw_rx_queue_mapping	__tw_common.skc_rx_queue_mapping
 #define tw_hash			__tw_common.skc_hash
-#define tw_prot			__tw_common.skc_prot
 #define tw_net			__tw_common.skc_net
 #define tw_daddr        	__tw_common.skc_daddr
 #define tw_v6_daddr		__tw_common.skc_v6_daddr
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 875ff923a8ed..024463a3e696 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -73,10 +73,8 @@ static void inet_twsk_kill(struct inet_timewait_sock *tw)
 
 void inet_twsk_free(struct inet_timewait_sock *tw)
 {
-	struct module *owner = tw->tw_prot->owner;
 	twsk_destructor((struct sock *)tw);
-	kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
-	module_put(owner);
+	kfree(tw);
 }
 
 void inet_twsk_put(struct inet_timewait_sock *tw)
@@ -206,7 +204,6 @@ struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
 		tw->tw_hash	    = sk->sk_hash;
 		tw->tw_ipv6only	    = 0;
 		tw->tw_transparent  = inet_test_bit(TRANSPARENT, sk);
-		tw->tw_prot	    = sk->sk_prot_creator;
 		atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
 		twsk_net_set(tw, sock_net(sk));
 		timer_setup(&tw->tw_timer, tw_timer_handler, 0);
@@ -216,8 +213,6 @@ struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
 		 * timewait socket.
 		 */
 		refcount_set(&tw->tw_refcnt, 0);
-
-		__module_get(tw->tw_prot->owner);
 	}
 
 	return tw;
-- 
2.51.0.rc1.193.gad69d77794-goog