Re: [PATCH 1/3] radix-tree: add radix_tree_prev_hole()

Andrew Morton
2009-04-12T17:31:54Z

On Sun, 12 Apr 2009 15:19:51 +0800 Wu Fengguang <fengguang.wu@intel.com> wrote:

> +unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
> + unsigned long index, unsigned long max_scan)
> +{
> + unsigned long i;
> +
> + for (i = 0; i < max_scan; i++) {
> + if (!radix_tree_lookup(root, index))
> + break;
> + index--;
> + if (index == LONG_MAX)
> + break;
> + }
> +
> + return index;
> +}

argh. This is about as inefficient as we could possibly make it :(

Really, this function should dive into radix-tree internals and walk
individual radix_tree_node.slots[] arrays. And heck, it can peek at
radix_tree_node.count and _bypass_ entire nodes, too.