[IPV4] fib_trie: iterator recode

Remove the complex loop structure of nextleaf() and replace it with a
simpler tree walker. This improves the performance and is much
cleaner.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.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 4126469..dab439b 100644 (file)
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1711,64 +1711,65 @@ static int trie_flush_leaf(struct trie *t, struct leaf *l)
        return found;
 }
 
-/* rcu_read_lock needs to be hold by caller from readside */
-
-static struct leaf *nextleaf(struct trie *t, struct leaf *thisleaf)
+/*
+ * Scan for the next right leaf starting at node p->child[idx]
+ * Since we have back pointer, no recursion necessary.
+ */
+static struct leaf *leaf_walk_rcu(struct tnode *p, struct node *c)
 {
-       struct node *c = (struct node *) thisleaf;
-       struct tnode *p;
-       int idx;
-       struct node *trie = rcu_dereference(t->trie);
+       do {
+               t_key idx;
 
-       if (c == NULL) {
-               if (trie == NULL)
-                       return NULL;
-
-               if (IS_LEAF(trie))          /* trie w. just a leaf */
-                       return (struct leaf *) trie;
-
-               p = (struct tnode *)trie;  /* Start */
-       } else
-               p = node_parent_rcu(c);
-
-       while (p) {
-               int pos, last;
-
-               /*  Find the next child of the parent */
                if (c)
-                       pos = 1 + tkey_extract_bits(c->key, p->pos, p->bits);
+                       idx = tkey_extract_bits(c->key, p->pos, p->bits) + 1;
                else
-                       pos = 0;
-
-               last = 1 << p->bits;
-               for (idx = pos; idx < last ; idx++) {
-                       c = rcu_dereference(p->child[idx]);
+                       idx = 0;
 
+               while (idx < 1u << p->bits) {
+                       c = tnode_get_child_rcu(p, idx++);
                        if (!c)
                                continue;
 
-                       /* Decend if tnode */
-                       while (IS_TNODE(c)) {
-                               p = (struct tnode *) c;
-                               idx = 0;
-
-                               /* Rightmost non-NULL branch */
-                               if (p && IS_TNODE(p))
-                                       while (!(c = rcu_dereference(p->child[idx]))
-                                              && idx < (1<<p->bits)) idx++;
-
-                               /* Done with this tnode? */
-                               if (idx >= (1 << p->bits) || !c)
-                                       goto up;
+                       if (IS_LEAF(c)) {
+                               prefetch(p->child[idx]);
+                               return (struct leaf *) c;
                        }
-                       return (struct leaf *) c;
+
+                       /* Rescan start scanning in new node */
+                       p = (struct tnode *) c;
+                       idx = 0;
                }
-up:
-               /* No more children go up one step  */
+
+               /* Node empty, walk back up to parent */
                c = (struct node *) p;
-               p = node_parent_rcu(c);
-       }
-       return NULL; /* Ready. Root of trie */
+       } while ( (p = node_parent_rcu(c)) != NULL);
+
+       return NULL; /* Root of trie */
+}
+
+
+static struct leaf *trie_firstleaf(struct trie *t)
+{
+       struct tnode *n = (struct tnode *) rcu_dereference(t->trie);
+
+       if (!n)
+               return NULL;
+
+       if (IS_LEAF(n))          /* trie is just a leaf */
+               return (struct leaf *) n;
+
+       return leaf_walk_rcu(n, NULL);
+}
+
+static struct leaf *trie_nextleaf(struct leaf *l)
+{
+       struct node *c = (struct node *) l;
+       struct tnode *p = node_parent(c);
+
+       if (!p)
+               return NULL;    /* trie with just one leaf */
+
+       return leaf_walk_rcu(p, c);
 }
 
 /*
@@ -1778,9 +1779,9 @@ static int fn_trie_flush(struct fib_table *tb)
 {
        struct trie *t = (struct trie *) tb->tb_data;
        struct leaf *ll = NULL, *l = NULL;
-       int found = 0, h;
+       int found = 0;
 
-       for (h = 0; (l = nextleaf(t, l)) != NULL; h++) {
+       for (l = trie_firstleaf(t); l; l = trie_nextleaf(l)) {
                found += trie_flush_leaf(t, l);
 
                if (ll && hlist_empty(&ll->list))
@@ -1887,7 +1888,6 @@ static int fn_trie_dump_fa(t_key key, int plen, struct list_head *fah,
                        i++;
                        continue;
                }
-               BUG_ON(!fa->fa_info);
 
                if (fib_dump_info(skb, NETLINK_CB(cb->skb).pid,
                                  cb->nlh->nlmsg_seq,
@@ -1916,8 +1916,9 @@ static int fn_trie_dump_plen(struct trie *t, int plen, struct fib_table *tb,
        struct leaf *l = NULL;
 
        s_h = cb->args[3];
+       h = 0;
 
-       for (h = 0; (l = nextleaf(t, l)) != NULL; h++) {
+       for (l = trie_firstleaf(t); l != NULL; h++, l = trie_nextleaf(l)) {
                if (h < s_h)
                        continue;
                if (h > s_h)