[PATCH net-next] tcp: minor optimization in tcp ack fast path processing

[Yafang Shao]

Bitwise operation is a little faster.
So I replace after() with (flag & FLAG_SND_UNA_ADVANCED) as this flag is
already set before.

Cc: Joe Perches <joe@xxxxxxxxxxx>
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
 net/ipv4/tcp_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2868ef2..0167015 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3610,7 +3610,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	if (flag & FLAG_UPDATE_TS_RECENT)
 		tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
 
-	if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
+	if (!(flag & FLAG_SLOWPATH) && (flag & FLAG_SND_UNA_ADVANCED)) {
 		/* Window is constant, pure forward advance.
 		 * No more checks are required.
 		 * Note, we use the fact that SND.UNA>=SND.WL2.
-- 
1.8.3.1