From 29fbc26e6dfc7be351c23261938de3f93f5cde57 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 15 Nov 2021 11:02:48 -0800
Subject: [PATCH] tcp: do not call tcp_cleanup_rbuf() if we have a backlog
Git-commit: 29fbc26e6dfc7be351c23261938de3f93f5cde57
Patch-mainline: v5.15
References: bsc#1195400

Under pressure, tcp recvmsg() has logic to process the socket backlog,
but calls tcp_cleanup_rbuf() right before.

Avoiding sending ACK right before processing new segments makes
a lot of sense, as this decrease the number of ACK packets,
with no impact on effective ACK clocking.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Wiesner <jwiesner@suse.de>
---
 net/ipv4/tcp.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7b1886103556..d1949fdb1462 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2436,12 +2436,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
 			}
 		}
 
-		tcp_cleanup_rbuf(sk, copied);
-
 		if (copied >= target) {
 			/* Do not sleep, just process backlog. */
 			__sk_flush_backlog(sk);
 		} else {
+			tcp_cleanup_rbuf(sk, copied);
 			sk_defer_free_flush(sk);
 			sk_wait_data(sk, &timeo, last);
 		}
-- 
2.26.2