Merge branch 'tcp-avoid-indirect-call-in-__sk_stream_memory_free'

Eric Dumazet says:

====================
tcp: avoid indirect call in __sk_stream_memory_free()

Small improvement for CONFIG_RETPOLINE=y, when dealing with TCP sockets.
====================

Link: https://lore.kernel.org/r/20201113150809.3443527-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/sock.h

@@ -60,7 +60,7 @@
 #include <linux/rculist_nulls.h>
 #include <linux/poll.h>
 #include <linux/sockptr.h>
-
+#include <linux/indirect_call_wrapper.h>
 #include <linux/atomic.h>
 #include <linux/refcount.h>
 #include <net/dst.h>
@@ -1264,13 +1264,17 @@ static inline void sk_refcnt_debug_release(const struct sock *sk)
 #define sk_refcnt_debug_release(sk) do { } while (0)
 #endif /* SOCK_REFCNT_DEBUG */
 
+INDIRECT_CALLABLE_DECLARE(bool tcp_stream_memory_free(const struct sock *sk, int wake));
+
 static inline bool __sk_stream_memory_free(const struct sock *sk, int wake)
 {
 	if (READ_ONCE(sk->sk_wmem_queued) >= READ_ONCE(sk->sk_sndbuf))
 		return false;
 
 	return sk->sk_prot->stream_memory_free ?
-		sk->sk_prot->stream_memory_free(sk, wake) : true;
+		INDIRECT_CALL_1(sk->sk_prot->stream_memory_free,
+			        tcp_stream_memory_free,
+				sk, wake) : true;
 }
 
 static inline bool sk_stream_memory_free(const struct sock *sk)

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,