gre: used time_before for comparing jiffies

The functions time_before is more robust for comparing
jiffies against other values.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -491,7 +491,7 @@ static void ipgre_err(struct sk_buff *skb, u32 info)
 	if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
 		goto out;
 
-	if (jiffies - t->err_time < IPTUNNEL_ERR_TIMEO)
+	if (time_before(jiffies, t->err_time + IPTUNNEL_ERR_TIMEO))
 		t->err_count++;
 	else
 		t->err_count = 1;
@@ -803,7 +803,8 @@ static int ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 #endif
 
 	if (tunnel->err_count > 0) {
-		if (jiffies - tunnel->err_time < IPTUNNEL_ERR_TIMEO) {
+		if (time_before(jiffies,
+				tunnel->err_time + IPTUNNEL_ERR_TIMEO)) {
 			tunnel->err_count--;
 
 			dst_link_failure(skb);