tcp: move __reqsk_free() out of line

Inlining __reqsk_free() is overkill, let's reclaim 2 Kbytes of text.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 2/4 grow/shrink: 2/14 up/down: 225/-2338 (-2113)
Function                                     old     new   delta
__reqsk_free                                   -     114    +114
sock_edemux                                   18      82     +64
inet_csk_listen_start                        233     264     +31
__pfx___reqsk_free                             -      16     +16
__pfx_reqsk_queue_alloc                       16       -     -16
__pfx_reqsk_free                              16       -     -16
reqsk_queue_alloc                             46       -     -46
tcp_req_err                                  272     177     -95
reqsk_fastopen_remove                        348     253     -95
cookie_bpf_check                             157      62     -95
cookie_tcp_reqsk_alloc                       387     290     -97
cookie_v4_check                             1568    1465    -103
reqsk_free                                   105       -    -105
cookie_v6_check                             1519    1412    -107
sock_gen_put                                 187      78    -109
sock_pfree                                   212      82    -130
tcp_try_fastopen                            1818    1683    -135
tcp_v4_rcv                                  3478    3294    -184
reqsk_put                                    306      90    -216
tcp_get_cookie_sock                          551     318    -233
tcp_v6_rcv                                  3404    3141    -263
tcp_conn_request                            2677    2384    -293
Total: Before=24887415, After=24885302, chg -0.01%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260204055147.1682705-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: edumazet

include/net/request_sock.h

@@ -123,14 +123,7 @@ static inline struct sock *skb_steal_sock(struct sk_buff *skb,
 	return sk;
 }
 
-static inline void __reqsk_free(struct request_sock *req)
-{
-	req->rsk_ops->destructor(req);
-	if (req->rsk_listener)
-		sock_put(req->rsk_listener);
-	kfree(req->saved_syn);
-	kmem_cache_free(req->rsk_ops->slab, req);
-}
+void __reqsk_free(struct request_sock *req);
 
 static inline void reqsk_free(struct request_sock *req)
 {

net/ipv4/inet_connection_sock.c

@@ -919,6 +919,16 @@ struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
 }
 EXPORT_SYMBOL(inet_reqsk_alloc);
 
+void __reqsk_free(struct request_sock *req)
+{
+	req->rsk_ops->destructor(req);
+	if (req->rsk_listener)
+		sock_put(req->rsk_listener);
+	kfree(req->saved_syn);
+	kmem_cache_free(req->rsk_ops->slab, req);
+}
+EXPORT_SYMBOL_GPL(__reqsk_free);
+
 static struct request_sock *inet_reqsk_clone(struct request_sock *req,
 					     struct sock *sk)
 {