tcp: lockless TCP_MAXSEG option

setsockopt(TCP_MAXSEG) writes over a field that does not need
socket lock protection anymore.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20250821141901.18839-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/tcp.c

@@ -3890,15 +3890,13 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 		WRITE_ONCE(inet_csk(sk)->icsk_delack_max, delack_max);
 		return 0;
 	}
+	case TCP_MAXSEG:
+		return tcp_sock_set_maxseg(sk, val);
 	}
 
 	sockopt_lock_sock(sk);
 
 	switch (optname) {
-	case TCP_MAXSEG:
-		err = tcp_sock_set_maxseg(sk, val);
-		break;
-
 	case TCP_NODELAY:
 		__tcp_sock_set_nodelay(sk, val);
 		break;