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>

1 files changed, 21 insertions, 15 deletions

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 3fe4dd917ce1..ac04f31a632e 100644
--- 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)