1 files changed, 38 insertions, 12 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index b2ba5581d2ae..d9b40248b97f 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -146,7 +146,6 @@ static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst);
 static void              ipv4_link_failure(struct sk_buff *skb);
 static void              ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu);
 static int rt_garbage_collect(struct dst_ops *ops);
-static void rt_emergency_hash_rebuild(struct net *net);
 
 
 static struct dst_ops ipv4_dst_ops = {
@@ -780,11 +779,30 @@ static void rt_do_flush(int process_context)
 #define FRACT_BITS 3
 #define ONE (1UL << FRACT_BITS)
 
+/*
+ * Given a hash chain and an item in this hash chain,
+ * find if a previous entry has the same hash_inputs
+ * (but differs on tos, mark or oif)
+ * Returns 0 if an alias is found.
+ * Returns ONE if rth has no alias before itself.
+ */
+static int has_noalias(const struct rtable *head, const struct rtable *rth)
+{
+        const struct rtable *aux = head;
+
+        while (aux != rth) {
+                if (compare_hash_inputs(&aux->fl, &rth->fl))
+                        return 0;
+                aux = aux->u.dst.rt_next;
+        }
+        return ONE;
+}
+
 static void rt_check_expire(void)
 {
         static unsigned int rover;
         unsigned int i = rover, goal;
-        struct rtable *rth, *aux, **rthp;
+        struct rtable *rth, **rthp;
         unsigned long samples = 0;
         unsigned long sum = 0, sum2 = 0;
         unsigned long delta;
@@ -835,15 +853,7 @@ nofree:
                                          * attributes don't unfairly skew
                                          * the length computation
                                          */
-                                        for (aux = rt_hash_table[i].chain;;) {
-                                                if (aux == rth) {
-                                                        length += ONE;
-                                                        break;
-                                                }
-                                                if (compare_hash_inputs(&aux->fl, &rth->fl))
-                                                        break;
-                                                aux = aux->u.dst.rt_next;
-                                        }
+                                        length += has_noalias(rt_hash_table[i].chain, rth);
                                         continue;
                                 }
                         } else if (!rt_may_expire(rth, tmo, ip_rt_gc_timeout))
@@ -1073,6 +1083,21 @@ work_done:
 out:    return 0;
 }
 
+/*
+ * Returns number of entries in a hash chain that have different hash_inputs
+ */
+static int slow_chain_length(const struct rtable *head)
+{
+        int length = 0;
+        const struct rtable *rth = head;
+
+        while (rth) {
+                length += has_noalias(head, rth);
+                rth = rth->u.dst.rt_next;
+        }
+        return length >> FRACT_BITS;
+}
+
 static int rt_intern_hash(unsigned hash, struct rtable *rt,
                           struct rtable **rp, struct sk_buff *skb)
 {
@@ -1185,7 +1210,8 @@ restart:
                         rt_free(cand);
                 }
         } else {
-                if (chain_length > rt_chain_length_max) {
+                if (chain_length > rt_chain_length_max &&
+                    slow_chain_length(rt_hash_table[hash].chain) > rt_chain_length_max) {
                         struct net *net = dev_net(rt->u.dst.dev);
                         int num = ++net->ipv4.current_rt_cache_rebuild_count;
                         if (!rt_caching(dev_net(rt->u.dst.dev))) {