tcp: move tcp_rate_check_app_limited() to tcp.c

tcp_rate_check_app_limited() is used from tcp_sendmsg_locked()
fast path and from other callers.

Move it to tcp.c so that it can be inlined in tcp_sendmsg_locked().

Small increase of code, for better TCP performance.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 0/0 grow/shrink: 1/0 up/down: 87/0 (87)
Function                                     old     new   delta
tcp_sendmsg_locked                          4217    4304     +87
Total: Before=22566462, After=22566549, chg +0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20260121095923.3134639-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 20 insertions, 23 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 9345f1757169..efff433de9a4 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -809,6 +809,7 @@ static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
 
 /* tcp.c */
 void tcp_get_info(struct sock *, struct tcp_info *);
+void tcp_rate_check_app_limited(struct sock *sk);
 
 /* Read 'sendfile()'-style from a TCP socket */
 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
@@ -1355,8 +1356,6 @@ static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
 /* From tcp_cong.c */
 void tcp_set_ca_state(struct sock *sk, const u8 ca_state);
 
-/* From tcp_rate.c */
-void tcp_rate_check_app_limited(struct sock *sk);
 
 static inline bool tcp_skb_sent_after(u64 t1, u64 t2, u32 seq1, u32 seq2)
 {
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index ec36d2ec059e..18108a6f0499 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -9,7 +9,7 @@ obj-y     := route.o inetpeer.o protocol.o \
 	     inet_timewait_sock.o inet_connection_sock.o \
 	     tcp.o tcp_input.o tcp_output.o tcp_timer.o tcp_ipv4.o \
 	     tcp_minisocks.o tcp_cong.o tcp_metrics.o tcp_fastopen.o \
-	     tcp_rate.o tcp_recovery.o tcp_ulp.o \
+	     tcp_recovery.o tcp_ulp.o \
 	     tcp_offload.o tcp_plb.o datagram.o raw.o udp.o udplite.o \
 	     udp_offload.o arp.o icmp.o devinet.o af_inet.o igmp.o \
 	     fib_frontend.o fib_semantics.o fib_trie.o fib_notifier.o \
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index d5319ebe2452..148cdf3cd623 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1074,6 +1074,24 @@ int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied,
 	return err;
 }
 
+/* If a gap is detected between sends, mark the socket application-limited. */
+void tcp_rate_check_app_limited(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (/* We have less than one packet to send. */
+	    tp->write_seq - tp->snd_nxt < tp->mss_cache &&
+	    /* Nothing in sending host's qdisc queues or NIC tx queue. */
+	    sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1) &&
+	    /* We are not limited by CWND. */
+	    tcp_packets_in_flight(tp) < tcp_snd_cwnd(tp) &&
+	    /* All lost packets have been retransmitted. */
+	    tp->lost_out <= tp->retrans_out)
+		tp->app_limited =
+			(tp->delivered + tcp_packets_in_flight(tp)) ? : 1;
+}
+EXPORT_SYMBOL_GPL(tcp_rate_check_app_limited);
+
 int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 {
 	struct net_devmem_dmabuf_binding *binding = NULL;
diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c
deleted file mode 100644
index 272806ba3b4e..000000000000
--- a/net/ipv4/tcp_rate.c
+++ /dev/null
@@ -1,20 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-#include <net/tcp.h>
-
-/* If a gap is detected between sends, mark the socket application-limited. */
-void tcp_rate_check_app_limited(struct sock *sk)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-
-	if (/* We have less than one packet to send. */
-	    tp->write_seq - tp->snd_nxt < tp->mss_cache &&
-	    /* Nothing in sending host's qdisc queues or NIC tx queue. */
-	    sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1) &&
-	    /* We are not limited by CWND. */
-	    tcp_packets_in_flight(tp) < tcp_snd_cwnd(tp) &&
-	    /* All lost packets have been retransmitted. */
-	    tp->lost_out <= tp->retrans_out)
-		tp->app_limited =
-			(tp->delivered + tcp_packets_in_flight(tp)) ? : 1;
-}
-EXPORT_SYMBOL_GPL(tcp_rate_check_app_limited);