tcp: refactor pkts acked accounting

A small refactoring that gets number of packets cumulatively acked
from tcp_clean_rtx_queue() directly.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2d690b3..40824b3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3104,7 +3104,7 @@
  * arrived at the other end.
  */
 static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
-			       u32 prior_snd_una,
+			       u32 prior_snd_una, int *acked,
 			       struct tcp_sacktag_state *sack)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
@@ -3277,6 +3277,7 @@
 		}
 	}
 #endif
+	*acked = pkts_acked;
 	return flag;
 }
 
@@ -3642,10 +3643,8 @@
 		goto no_queue;
 
 	/* See if we can take anything off of the retransmit queue. */
-	acked = tp->packets_out;
-	flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una,
+	flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una, &acked,
 				    &sack_state);
-	acked -= tp->packets_out;
 
 	if (tcp_ack_is_dubious(sk, flag)) {
 		is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));