fib_trie: Only resize tnodes once instead of on each leaf removal in fib_table_flush

This change makes it so that we only call resize on the tnodes, instead of
from each of the leaves.  By doing this we can significantly reduce the
amount of time spent resizing as we can update all of the leaves in the
tnode first before we make any determinations about resizing.  As a result
we can simply free the tnode in the case that all of the leaves from a
given tnode are flushed instead of resizing with each leaf removed.
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_trie.c

@@ -1399,25 +1399,6 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp,
 }
 EXPORT_SYMBOL_GPL(fib_table_lookup);
 
-/*
- * Remove the leaf and return parent.
- */
-static void trie_leaf_remove(struct trie *t, struct tnode *l)
-{
-	struct tnode *tp = node_parent(l);
-
-	pr_debug("entering trie_leaf_remove(%p)\n", l);
-
-	if (tp) {
-		put_child(tp, get_index(l->key, tp), NULL);
-		trie_rebalance(t, tp);
-	} else {
-		RCU_INIT_POINTER(t->trie, NULL);
-	}
-
-	node_free(l);
-}
-
 /*
  * Caller must hold RTNL.
  */
@@ -1483,8 +1464,18 @@ int fib_table_delete(struct fib_table *tb, struct fib_config *cfg)
 	if (!plen)
 		tb->tb_num_default--;
 
-	if (hlist_empty(&l->leaf))
-		trie_leaf_remove(t, l);
+	if (hlist_empty(&l->leaf)) {
+		struct tnode *tp = node_parent(l);
+
+		if (tp) {
+			put_child(tp, get_index(l->key, tp), NULL);
+			trie_rebalance(t, tp);
+		} else {
+			RCU_INIT_POINTER(t->trie, NULL);
+		}
+
+		node_free(l);
+	}
 
 	if (fa->fa_state & FA_S_ACCESSED)
 		rt_cache_flush(cfg->fc_nlinfo.nl_net);
@@ -1494,33 +1485,6 @@ int fib_table_delete(struct fib_table *tb, struct fib_config *cfg)
 	return 0;
 }
 
-static int trie_flush_leaf(struct tnode *l)
-{
-	struct hlist_node *tmp;
-	unsigned char slen = 0;
-	struct fib_alias *fa;
-	int found = 0;
-
-	hlist_for_each_entry_safe(fa, tmp, &l->leaf, fa_list) {
-		struct fib_info *fi = fa->fa_info;
-
-		if (fi && (fi->fib_flags & RTNH_F_DEAD)) {
-			hlist_del_rcu(&fa->fa_list);
-			fib_release_info(fa->fa_info);
-			alias_free_mem_rcu(fa);
-			found++;
-
-			continue;
-		}
-
-		slen = fa->fa_slen;
-	}
-
-	l->slen = slen;
-
-	return found;
-}
-
 /* Scan for the next right leaf starting at node p->child[idx]
  * Since we have back pointer, no recursion necessary.
  */
@@ -1588,30 +1552,81 @@ static struct tnode *trie_leafindex(struct trie *t, int index)
  */
 int fib_table_flush(struct fib_table *tb)
 {
-	struct trie *t = (struct trie *) tb->tb_data;
-	struct tnode *l, *ll = NULL;
+	struct trie *t = (struct trie *)tb->tb_data;
+	struct hlist_node *tmp;
+	struct fib_alias *fa;
+	struct tnode *n, *pn;
+	unsigned long cindex;
+	unsigned char slen;
 	int found = 0;
 
-	for (l = trie_firstleaf(t); l; l = trie_nextleaf(l)) {
-		found += trie_flush_leaf(l);
+	n = rcu_dereference(t->trie);
+	if (!n)
+		goto flush_complete;
 
-		if (ll) {
-			if (hlist_empty(&ll->leaf))
-				trie_leaf_remove(t, ll);
-			else
-				leaf_pull_suffix(ll);
+	pn = NULL;
+	cindex = 0;
+
+	while (IS_TNODE(n)) {
+		/* record pn and cindex for leaf walking */
+		pn = n;
+		cindex = 1ul << n->bits;
+backtrace:
+		/* walk trie in reverse order */
+		do {
+			while (!(cindex--)) {
+				t_key pkey = pn->key;
+
+				n = pn;
+				pn = node_parent(n);
+
+				/* resize completed node */
+				resize(t, n);
+
+				/* if we got the root we are done */
+				if (!pn)
+					goto flush_complete;
+
+				cindex = get_index(pkey, pn);
 			}
 
-		ll = l;
+			/* grab the next available node */
+			n = tnode_get_child(pn, cindex);
+		} while (!n);
 	}
 
-	if (ll) {
-		if (hlist_empty(&ll->leaf))
-			trie_leaf_remove(t, ll);
-		else
-			leaf_pull_suffix(ll);
+	/* track slen in case any prefixes survive */
+	slen = 0;
+
+	hlist_for_each_entry_safe(fa, tmp, &n->leaf, fa_list) {
+		struct fib_info *fi = fa->fa_info;
+
+		if (fi && (fi->fib_flags & RTNH_F_DEAD)) {
+			hlist_del_rcu(&fa->fa_list);
+			fib_release_info(fa->fa_info);
+			alias_free_mem_rcu(fa);
+			found++;
+
+			continue;
+		}
+
+		slen = fa->fa_slen;
 	}
 
+	/* update leaf slen */
+	n->slen = slen;
+
+	if (hlist_empty(&n->leaf)) {
+		put_child_root(pn, t, n->key, NULL);
+		node_free(n);
+	} else {
+		leaf_pull_suffix(n);
+	}
+
+	/* if trie is leaf only loop is completed */
+	if (pn)
+		goto backtrace;
+flush_complete:
 	pr_debug("trie_flush found=%d\n", found);
 	return found;
 }