[TCP]: Add tcp_dec_pcount_approx int variant

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

include/net/tcp.h

@@ -599,16 +599,21 @@ static inline int tcp_skb_mss(const struct sk_buff *skb)
 	return skb_shinfo(skb)->gso_size;
 }
 
-static inline void tcp_dec_pcount_approx(__u32 *count,
-					 const struct sk_buff *skb)
+static inline void tcp_dec_pcount_approx_int(__u32 *count, const int decr)
 {
 	if (*count) {
-		*count -= tcp_skb_pcount(skb);
+		*count -= decr;
 		if ((int)*count < 0)
 			*count = 0;
 	}
 }
 
+static inline void tcp_dec_pcount_approx(__u32 *count,
+					 const struct sk_buff *skb)
+{
+	tcp_dec_pcount_approx_int(count, tcp_skb_pcount(skb));
+}
+
 static inline void tcp_packets_out_inc(struct sock *sk,
 				       const struct sk_buff *skb)
 {

net/ipv4/tcp_output.c

@@ -740,22 +740,16 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss
 		if (diff > 0) {
 			/* Adjust Reno SACK estimate. */
 			if (!tp->rx_opt.sack_ok) {
-				tp->sacked_out -= diff;
-				if ((int)tp->sacked_out < 0)
-					tp->sacked_out = 0;
+				tcp_dec_pcount_approx_int(&tp->sacked_out, diff);
 				tcp_sync_left_out(tp);
 			}
 
-			tp->fackets_out -= diff;
-			if ((int)tp->fackets_out < 0)
-				tp->fackets_out = 0;
+			tcp_dec_pcount_approx_int(&tp->fackets_out, diff);
 			/* SACK fastpath might overwrite it unless dealt with */
 			if (tp->fastpath_skb_hint != NULL &&
 			    after(TCP_SKB_CB(tp->fastpath_skb_hint)->seq,
 				  TCP_SKB_CB(skb)->seq)) {
-				tp->fastpath_cnt_hint -= diff;
-				if ((int)tp->fastpath_cnt_hint < 0)
-					tp->fastpath_cnt_hint = 0;
+				tcp_dec_pcount_approx_int(&tp->fastpath_cnt_hint, diff);
 			}
 		}
 	}