From: Eric Dumazet <edumazet@google.com>
Date: Wed, 17 Aug 2016 14:48:36 +0000 (-0700)
Subject: tcp: defer sacked assignment
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=dca0aaf8472f15836a68bbed8a0ef9ea39e783aa;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

tcp: defer sacked assignment

While chasing tcp_xmit_retransmit_queue() kasan issue, I found
that we could avoid reading sacked field of skb that we wont send,
possibly removing one cache line miss.

Very minor change in slow path, but why not ? ;)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index bdaef7fd6e47..8b45794eb6b2 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2776,7 +2776,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
 
 	max_segs = tcp_tso_autosize(sk, tcp_current_mss(sk));
 	tcp_for_write_queue_from(skb, sk) {
-		__u8 sacked = TCP_SKB_CB(skb)->sacked;
+		__u8 sacked;
 		int segs;
 
 		if (skb == tcp_send_head(sk))
@@ -2788,6 +2788,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
 		segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
 		if (segs <= 0)
 			return;
+		sacked = TCP_SKB_CB(skb)->sacked;
 		/* In case tcp_shift_skb_data() have aggregated large skbs,
 		 * we need to make sure not sending too bigs TSO packets
 		 */