netdev - [PATCH net-next] tcp: use 2-arg optimal variant of kfree

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Date:   Fri,  2 Dec 2022 05:28:47 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>,
        Dmitry Safonov <dima@...sta.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH net-next] tcp: use 2-arg optimal variant of kfree_rcu()

kfree_rcu(1-arg) should be avoided as much as possible,
since this is only possible from sleepable contexts,
and incurr extra rcu barriers.

I wish the 1-arg variant of kfree_rcu() would
get a distinct name, like kfree_rcu_slow()
to avoid it being abused.

Fixes: 459837b522f7 ("net/tcp: Disable TCP-MD5 static key on tcp_md5sig_info destruction")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Dmitry Safonov <dima@...sta.com>
Cc: Paul E. McKenney <paulmck@...nel.org>
---
 net/ipv4/tcp_ipv4.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 7fae586405cfb10011a0674289280bf400dfa8d8..8320d0ecb13ae1e3e259f3c13a4c2797fbd984a5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1245,7 +1245,7 @@ int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
 
 			md5sig = rcu_dereference_protected(tp->md5sig_info, lockdep_sock_is_held(sk));
 			rcu_assign_pointer(tp->md5sig_info, NULL);
-			kfree_rcu(md5sig);
+			kfree_rcu(md5sig, rcu);
 			return -EUSERS;
 		}
 	}
@@ -1271,7 +1271,7 @@ int tcp_md5_key_copy(struct sock *sk, const union tcp_md5_addr *addr,
 			md5sig = rcu_dereference_protected(tp->md5sig_info, lockdep_sock_is_held(sk));
 			net_warn_ratelimited("Too many TCP-MD5 keys in the system\n");
 			rcu_assign_pointer(tp->md5sig_info, NULL);
-			kfree_rcu(md5sig);
+			kfree_rcu(md5sig, rcu);
 			return -EUSERS;
 		}
 	}
-- 
2.39.0.rc0.267.gcb52ba06e7-goog