[TCP]: Make fackets_out accurate

Substraction for fackets_out is unconditional when snd_una
advances, thus there's no need to do it inside the loop. Just
make sure correct bounds are honored.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 7 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f9e4d7ad68b7..46aedd6ca020 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2299,8 +2299,8 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
          * 1. Reno does not count dupacks (sacked_out) automatically. */
         if (!tp->packets_out)
                 tp->sacked_out = 0;
-        /* 2. SACK counts snd_fack in packets inaccurately. */
-        if (tp->sacked_out == 0)
+
+        if (WARN_ON(!tp->sacked_out && tp->fackets_out))
                 tp->fackets_out = 0;
 
         /* Now state machine starts.
@@ -2568,10 +2568,6 @@ static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
                 } else if (*seq_rtt < 0)
                         *seq_rtt = now - scb->when;
 
-                if (tp->fackets_out) {
-                        __u32 dval = min(tp->fackets_out, packets_acked);
-                        tp->fackets_out -= dval;
-                }
                 /* hint's skb might be NULL but we don't need to care */
                 tp->fastpath_cnt_hint -= min_t(u32, packets_acked,
                                                tp->fastpath_cnt_hint);
@@ -2657,7 +2653,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
                         seq_rtt = now - scb->when;
                         last_ackt = skb->tstamp;
                 }
-                tcp_dec_pcount_approx(&tp->fackets_out, skb);
                 tp->packets_out -= tcp_skb_pcount(skb);
                 tcp_unlink_write_queue(skb, sk);
                 sk_stream_free_skb(sk, skb);
@@ -2672,6 +2667,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
                 tcp_ack_update_rtt(sk, acked, seq_rtt);
                 tcp_rearm_rto(sk);
 
+                tp->fackets_out -= min(pkts_acked, tp->fackets_out);
                 if (tcp_is_reno(tp))
                         tcp_remove_reno_sacks(sk, pkts_acked);