net: Abstract default MTU metric calculation behind an accessor.

Like RTAX_ADVMSS, make the default calculation go through a dst_ops
method rather than caching the computation in the routing cache
entries.

Now dst metrics are pretty much left as-is when new entries are
created, thus optimizing metric sharing becomes a real possibility.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 2 deletions

diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index b8a5c0515be8..5e636365d33c 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -111,6 +111,7 @@ static unsigned long dn_rt_deadline;
 static int dn_dst_gc(struct dst_ops *ops);
 static struct dst_entry *dn_dst_check(struct dst_entry *, __u32);
 static unsigned int dn_dst_default_advmss(const struct dst_entry *dst);
+static unsigned int dn_dst_default_mtu(const struct dst_entry *dst);
 static struct dst_entry *dn_dst_negative_advice(struct dst_entry *);
 static void dn_dst_link_failure(struct sk_buff *);
 static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu);
@@ -131,6 +132,7 @@ static struct dst_ops dn_dst_ops = {
         .gc =                   dn_dst_gc,
         .check =                dn_dst_check,
         .default_advmss =       dn_dst_default_advmss,
+        .default_mtu =          dn_dst_default_mtu,
         .negative_advice =      dn_dst_negative_advice,
         .link_failure =         dn_dst_link_failure,
         .update_pmtu =          dn_dst_update_pmtu,
@@ -803,6 +805,11 @@ static unsigned int dn_dst_default_advmss(const struct dst_entry *dst)
         return dn_mss_from_pmtu(dst->dev, dst_mtu(dst));
 }
 
+static unsigned int dn_dst_default_mtu(const struct dst_entry *dst)
+{
+        return dst->dev->mtu;
+}
+
 static int dn_rt_set_next_hop(struct dn_route *rt, struct dn_fib_res *res)
 {
         struct dn_fib_info *fi = res->fi;
@@ -825,8 +832,7 @@ static int dn_rt_set_next_hop(struct dn_route *rt, struct dn_fib_res *res)
                 rt->dst.neighbour = n;
         }
 
-        if (dst_metric(&rt->dst, RTAX_MTU) == 0 ||
-            dst_metric(&rt->dst, RTAX_MTU) > rt->dst.dev->mtu)
+        if (dst_metric(&rt->dst, RTAX_MTU) > rt->dst.dev->mtu)
                 dst_metric_set(&rt->dst, RTAX_MTU, rt->dst.dev->mtu);
         metric = dst_metric_raw(&rt->dst, RTAX_ADVMSS);
         if (metric) {