fib_trie: Optimize fib_find_node

This patch makes use of the same features I made use of for
fib_table_lookup to streamline fib_find_node.  The resultant code should be
smaller and run faster than the original.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 3fe4dd9..ac04f31 100644 (file)
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -892,28 +892,34 @@ static void insert_leaf_info(struct hlist_head *head, struct leaf_info *new)
 }
 
 /* rcu_read_lock needs to be hold by caller from readside */
-
 static struct tnode *fib_find_node(struct trie *t, u32 key)
 {
        struct tnode *n = rcu_dereference_rtnl(t->trie);
-       int pos = 0;
 
-       while (n && IS_TNODE(n)) {
-               if (tkey_sub_equals(n->key, pos, n->pos-pos, key)) {
-                       pos = n->pos + n->bits;
-                       n = tnode_get_child_rcu(n,
-                                               tkey_extract_bits(key,
-                                                                 n->pos,
-                                                                 n->bits));
-               } else
+       while (n) {
+               unsigned long index = get_index(key, n);
+
+               /* This bit of code is a bit tricky but it combines multiple
+                * checks into a single check.  The prefix consists of the
+                * prefix plus zeros for the bits in the cindex. The index
+                * is the difference between the key and this value.  From
+                * this we can actually derive several pieces of data.
+                *   if !(index >> bits)
+                *     we know the value is cindex
+                *   else
+                *     we have a mismatch in skip bits and failed
+                */
+               if (index >> n->bits)
+                       return NULL;
+
+               /* we have found a leaf. Prefixes have already been compared */
+               if (IS_LEAF(n))
                        break;
-       }
-       /* Case we have found a leaf. Compare prefixes */
 
-       if (n != NULL && IS_LEAF(n) && tkey_equals(key, n->key))
-               return n;
+               n = rcu_dereference_rtnl(n->child[index]);
+       }
 
-       return NULL;
+       return n;
 }
 
 static void trie_rebalance(struct trie *t, struct tnode *tn)