From 93afcfd1db35882921b2521a637c78755c27b02c Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 15 Nov 2021 11:02:40 -0800
Subject: [PATCH] tcp: small optimization in tcp recvmsg()
Git-commit: 93afcfd1db35882921b2521a637c78755c27b02c
Patch-mainline: v5.15
References: bsc#1195400

When reading large chunks of data, incoming packets might
be added to the backlog from BH.

tcp recvmsg() detects the backlog queue is not empty, and uses
a release_sock()/lock_sock() pair to process this backlog.

We now have __sk_flush_backlog() to perform this
a bit faster.

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 862e8cb8dda5..24d77a32c9cb 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2409,8 +2409,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
 
 		if (copied >= target) {
 			/* Do not sleep, just process backlog. */
-			release_sock(sk);
-			lock_sock(sk);
+			__sk_flush_backlog(sk);
 		} else {
 			sk_wait_data(sk, &timeo, last);
 		}
-- 
2.26.2