tcp: uninline tcp_stream_memory_free()

Both IPv4 and IPv6 needs it via a function pointer.
Following patch will avoid the indirect call.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

include/net/tcp.h

@@ -1965,18 +1965,7 @@ static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
 	return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
 }
 
-/* @wake is one when sk_stream_write_space() calls us.
- * This sends EPOLLOUT only if notsent_bytes is half the limit.
- * This mimics the strategy used in sock_def_write_space().
- */
-static inline bool tcp_stream_memory_free(const struct sock *sk, int wake)
-{
-	const struct tcp_sock *tp = tcp_sk(sk);
-	u32 notsent_bytes = READ_ONCE(tp->write_seq) -
-			    READ_ONCE(tp->snd_nxt);
-
-	return (notsent_bytes << wake) < tcp_notsent_lowat(tp);
-}
+bool tcp_stream_memory_free(const struct sock *sk, int wake);
 
 #ifdef CONFIG_PROC_FS
 int tcp4_proc_init(void);

net/ipv4/tcp_ipv4.c

@@ -2740,6 +2740,20 @@ void tcp4_proc_exit(void)
 }
 #endif /* CONFIG_PROC_FS */
 
+/* @wake is one when sk_stream_write_space() calls us.
+ * This sends EPOLLOUT only if notsent_bytes is half the limit.
+ * This mimics the strategy used in sock_def_write_space().
+ */
+bool tcp_stream_memory_free(const struct sock *sk, int wake)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	u32 notsent_bytes = READ_ONCE(tp->write_seq) -
+			    READ_ONCE(tp->snd_nxt);
+
+	return (notsent_bytes << wake) < tcp_notsent_lowat(tp);
+}
+EXPORT_SYMBOL(tcp_stream_memory_free);
+
 struct proto tcp_prot = {
 	.name			= "TCP",
 	.owner			= THIS_MODULE,