[NET]: Make helper to get dst entry and "use" it

There are many places that get the dst entry, increase the
__use counter and set the "lastuse" time stamp.

Make a helper for this.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index 97eee5e..66663e5 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -293,9 +293,7 @@
 					   dn_rt_hash_table[hash].chain);
 			rcu_assign_pointer(dn_rt_hash_table[hash].chain, rth);
 
-			rth->u.dst.__use++;
-			dst_hold(&rth->u.dst);
-			rth->u.dst.lastuse = now;
+			dst_use(&rth->u.dst, now);
 			spin_unlock_bh(&dn_rt_hash_table[hash].lock);
 
 			dnrt_drop(rt);
@@ -308,9 +306,7 @@
 	rcu_assign_pointer(rt->u.dst.dn_next, dn_rt_hash_table[hash].chain);
 	rcu_assign_pointer(dn_rt_hash_table[hash].chain, rt);
 
-	dst_hold(&rt->u.dst);
-	rt->u.dst.__use++;
-	rt->u.dst.lastuse = now;
+	dst_use(&rt->u.dst, now);
 	spin_unlock_bh(&dn_rt_hash_table[hash].lock);
 	*rp = rt;
 	return 0;
@@ -1182,9 +1178,7 @@
 			    (flp->mark == rt->fl.mark) &&
 			    (rt->fl.iif == 0) &&
 			    (rt->fl.oif == flp->oif)) {
-				rt->u.dst.lastuse = jiffies;
-				dst_hold(&rt->u.dst);
-				rt->u.dst.__use++;
+				dst_use(&rt->u.dst, jiffies);
 				rcu_read_unlock_bh();
 				*pprt = &rt->u.dst;
 				return 0;
@@ -1456,9 +1450,7 @@
 		    (rt->fl.oif == 0) &&
 		    (rt->fl.mark == skb->mark) &&
 		    (rt->fl.iif == cb->iif)) {
-			rt->u.dst.lastuse = jiffies;
-			dst_hold(&rt->u.dst);
-			rt->u.dst.__use++;
+			dst_use(&rt->u.dst, jiffies);
 			rcu_read_unlock();
 			skb->dst = (struct dst_entry *)rt;
 			return 0;