ip: speedup /proc/net/rt_cache handling

When scanning route cache hash table, we can avoid taking locks for
empty buckets.  Both /proc/net/rt_cache and NETLINK RTM_GETROUTE
interface are taken into account.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 4 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index cca921ea8550..71598f64c113 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -282,6 +282,8 @@ static struct rtable *rt_cache_get_first(struct seq_file *seq)
         struct rtable *r = NULL;
 
         for (st->bucket = rt_hash_mask; st->bucket >= 0; --st->bucket) {
+                if (!rt_hash_table[st->bucket].chain)
+                        continue;
                 rcu_read_lock_bh();
                 r = rcu_dereference(rt_hash_table[st->bucket].chain);
                 while (r) {
@@ -299,11 +301,14 @@ static struct rtable *__rt_cache_get_next(struct seq_file *seq,
                                           struct rtable *r)
 {
         struct rt_cache_iter_state *st = seq->private;
+
         r = r->u.dst.rt_next;
         while (!r) {
                 rcu_read_unlock_bh();
-                if (--st->bucket < 0)
-                        break;
+                do {
+                        if (--st->bucket < 0)
+                                return NULL;
+                } while (!rt_hash_table[st->bucket].chain);
                 rcu_read_lock_bh();
                 r = rt_hash_table[st->bucket].chain;
         }
@@ -2840,7 +2845,9 @@ int ip_rt_dump(struct sk_buff *skb,  struct netlink_callback *cb)
         if (s_h < 0)
                 s_h = 0;
         s_idx = idx = cb->args[1];
-        for (h = s_h; h <= rt_hash_mask; h++) {
+        for (h = s_h; h <= rt_hash_mask; h++, s_idx = 0) {
+                if (!rt_hash_table[h].chain)
+                        continue;
                 rcu_read_lock_bh();
                 for (rt = rcu_dereference(rt_hash_table[h].chain), idx = 0; rt;
                      rt = rcu_dereference(rt->u.dst.rt_next), idx++) {
@@ -2859,7 +2866,6 @@ int ip_rt_dump(struct sk_buff *skb,  struct netlink_callback *cb)
                         dst_release(xchg(&skb->dst, NULL));
                 }
                 rcu_read_unlock_bh();
-                s_idx = 0;
         }
 
 done: