diff --git a/lib/radix-tree.c b/lib/radix-tree.c
new file mode 100644
index 0000000..04d6643
--- /dev/null
+++ b/lib/radix-tree.c
@@ -0,0 +1,807 @@
+/*
+ * Copyright (C) 2001 Momchil Velikov
+ * Portions Copyright (C) 2001 Christoph Hellwig
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/radix-tree.h>
+#include <linux/percpu.h>
+#include <linux/slab.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/gfp.h>
+#include <linux/string.h>
+#include <linux/bitops.h>
+
+
+#ifdef __KERNEL__
+#define RADIX_TREE_MAP_SHIFT	6
+#else
+#define RADIX_TREE_MAP_SHIFT	3	/* For more stressful testing */
+#endif
+#define RADIX_TREE_TAGS		2
+
+#define RADIX_TREE_MAP_SIZE	(1UL << RADIX_TREE_MAP_SHIFT)
+#define RADIX_TREE_MAP_MASK	(RADIX_TREE_MAP_SIZE-1)
+
+#define RADIX_TREE_TAG_LONGS	\
+	((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
+
+struct radix_tree_node {
+	unsigned int	count;
+	void		*slots[RADIX_TREE_MAP_SIZE];
+	unsigned long	tags[RADIX_TREE_TAGS][RADIX_TREE_TAG_LONGS];
+};
+
+struct radix_tree_path {
+	struct radix_tree_node *node, **slot;
+	int offset;
+};
+
+#define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
+#define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
+
+static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH];
+
+/*
+ * Radix tree node cache.
+ */
+static kmem_cache_t *radix_tree_node_cachep;
+
+/*
+ * Per-cpu pool of preloaded nodes
+ */
+struct radix_tree_preload {
+	int nr;
+	struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
+};
+DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
+
+/*
+ * This assumes that the caller has performed appropriate preallocation, and
+ * that the caller has pinned this thread of control to the current CPU.
+ */
+static struct radix_tree_node *
+radix_tree_node_alloc(struct radix_tree_root *root)
+{
+	struct radix_tree_node *ret;
+
+	ret = kmem_cache_alloc(radix_tree_node_cachep, root->gfp_mask);
+	if (ret == NULL && !(root->gfp_mask & __GFP_WAIT)) {
+		struct radix_tree_preload *rtp;
+
+		rtp = &__get_cpu_var(radix_tree_preloads);
+		if (rtp->nr) {
+			ret = rtp->nodes[rtp->nr - 1];
+			rtp->nodes[rtp->nr - 1] = NULL;
+			rtp->nr--;
+		}
+	}
+	return ret;
+}
+
+static inline void
+radix_tree_node_free(struct radix_tree_node *node)
+{
+	kmem_cache_free(radix_tree_node_cachep, node);
+}
+
+/*
+ * Load up this CPU's radix_tree_node buffer with sufficient objects to
+ * ensure that the addition of a single element in the tree cannot fail.  On
+ * success, return zero, with preemption disabled.  On error, return -ENOMEM
+ * with preemption not disabled.
+ */
+int radix_tree_preload(int gfp_mask)
+{
+	struct radix_tree_preload *rtp;
+	struct radix_tree_node *node;
+	int ret = -ENOMEM;
+
+	preempt_disable();
+	rtp = &__get_cpu_var(radix_tree_preloads);
+	while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
+		preempt_enable();
+		node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
+		if (node == NULL)
+			goto out;
+		preempt_disable();
+		rtp = &__get_cpu_var(radix_tree_preloads);
+		if (rtp->nr < ARRAY_SIZE(rtp->nodes))
+			rtp->nodes[rtp->nr++] = node;
+		else
+			kmem_cache_free(radix_tree_node_cachep, node);
+	}
+	ret = 0;
+out:
+	return ret;
+}
+
+static inline void tag_set(struct radix_tree_node *node, int tag, int offset)
+{
+	if (!test_bit(offset, &node->tags[tag][0]))
+		__set_bit(offset, &node->tags[tag][0]);
+}
+
+static inline void tag_clear(struct radix_tree_node *node, int tag, int offset)
+{
+	__clear_bit(offset, &node->tags[tag][0]);
+}
+
+static inline int tag_get(struct radix_tree_node *node, int tag, int offset)
+{
+	return test_bit(offset, &node->tags[tag][0]);
+}
+
+/*
+ *	Return the maximum key which can be store into a
+ *	radix tree with height HEIGHT.
+ */
+static inline unsigned long radix_tree_maxindex(unsigned int height)
+{
+	return height_to_maxindex[height];
+}
+
+/*
+ *	Extend a radix tree so it can store key @index.
+ */
+static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
+{
+	struct radix_tree_node *node;
+	unsigned int height;
+	char tags[RADIX_TREE_TAGS];
+	int tag;
+
+	/* Figure out what the height should be.  */
+	height = root->height + 1;
+	while (index > radix_tree_maxindex(height))
+		height++;
+
+	if (root->rnode == NULL) {
+		root->height = height;
+		goto out;
+	}
+
+	/*
+	 * Prepare the tag status of the top-level node for propagation
+	 * into the newly-pushed top-level node(s)
+	 */
+	for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
+		int idx;
+
+		tags[tag] = 0;
+		for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
+			if (root->rnode->tags[tag][idx]) {
+				tags[tag] = 1;
+				break;
+			}
+		}
+	}
+
+	do {
+		if (!(node = radix_tree_node_alloc(root)))
+			return -ENOMEM;
+
+		/* Increase the height.  */
+		node->slots[0] = root->rnode;
+
+		/* Propagate the aggregated tag info into the new root */
+		for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
+			if (tags[tag])
+				tag_set(node, tag, 0);
+		}
+
+		node->count = 1;
+		root->rnode = node;
+		root->height++;
+	} while (height > root->height);
+out:
+	return 0;
+}
+
+/**
+ *	radix_tree_insert    -    insert into a radix tree
+ *	@root:		radix tree root
+ *	@index:		index key
+ *	@item:		item to insert
+ *
+ *	Insert an item into the radix tree at position @index.
+ */
+int radix_tree_insert(struct radix_tree_root *root,
+			unsigned long index, void *item)
+{
+	struct radix_tree_node *node = NULL, *tmp, **slot;
+	unsigned int height, shift;
+	int offset;
+	int error;
+
+	/* Make sure the tree is high enough.  */
+	if ((!index && !root->rnode) ||
+			index > radix_tree_maxindex(root->height)) {
+		error = radix_tree_extend(root, index);
+		if (error)
+			return error;
+	}
+
+	slot = &root->rnode;
+	height = root->height;
+	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
+
+	offset = 0;			/* uninitialised var warning */
+	while (height > 0) {
+		if (*slot == NULL) {
+			/* Have to add a child node.  */
+			if (!(tmp = radix_tree_node_alloc(root)))
+				return -ENOMEM;
+			*slot = tmp;
+			if (node)
+				node->count++;
+		}
+
+		/* Go a level down */
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		node = *slot;
+		slot = (struct radix_tree_node **)(node->slots + offset);
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	if (*slot != NULL)
+		return -EEXIST;
+	if (node) {
+		node->count++;
+		BUG_ON(tag_get(node, 0, offset));
+		BUG_ON(tag_get(node, 1, offset));
+	}
+
+	*slot = item;
+	return 0;
+}
+EXPORT_SYMBOL(radix_tree_insert);
+
+/**
+ *	radix_tree_lookup    -    perform lookup operation on a radix tree
+ *	@root:		radix tree root
+ *	@index:		index key
+ *
+ *	Lookup the item at the position @index in the radix tree @root.
+ */
+void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
+{
+	unsigned int height, shift;
+	struct radix_tree_node **slot;
+
+	height = root->height;
+	if (index > radix_tree_maxindex(height))
+		return NULL;
+
+	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
+	slot = &root->rnode;
+
+	while (height > 0) {
+		if (*slot == NULL)
+			return NULL;
+
+		slot = (struct radix_tree_node **)
+			((*slot)->slots +
+				((index >> shift) & RADIX_TREE_MAP_MASK));
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	return *slot;
+}
+EXPORT_SYMBOL(radix_tree_lookup);
+
+/**
+ *	radix_tree_tag_set - set a tag on a radix tree node
+ *	@root:		radix tree root
+ *	@index:		index key
+ *	@tag: 		tag index
+ *
+ *	Set the search tag corresponging to @index in the radix tree.  From
+ *	the root all the way down to the leaf node.
+ *
+ *	Returns the address of the tagged item.   Setting a tag on a not-present
+ *	item is a bug.
+ */
+void *radix_tree_tag_set(struct radix_tree_root *root,
+			unsigned long index, int tag)
+{
+	unsigned int height, shift;
+	struct radix_tree_node **slot;
+
+	height = root->height;
+	if (index > radix_tree_maxindex(height))
+		return NULL;
+
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+	slot = &root->rnode;
+
+	while (height > 0) {
+		int offset;
+
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		tag_set(*slot, tag, offset);
+		slot = (struct radix_tree_node **)((*slot)->slots + offset);
+		BUG_ON(*slot == NULL);
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	return *slot;
+}
+EXPORT_SYMBOL(radix_tree_tag_set);
+
+/**
+ *	radix_tree_tag_clear - clear a tag on a radix tree node
+ *	@root:		radix tree root
+ *	@index:		index key
+ *	@tag: 		tag index
+ *
+ *	Clear the search tag corresponging to @index in the radix tree.  If
+ *	this causes the leaf node to have no tags set then clear the tag in the
+ *	next-to-leaf node, etc.
+ *
+ *	Returns the address of the tagged item on success, else NULL.  ie:
+ *	has the same return value and semantics as radix_tree_lookup().
+ */
+void *radix_tree_tag_clear(struct radix_tree_root *root,
+			unsigned long index, int tag)
+{
+	struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
+	unsigned int height, shift;
+	void *ret = NULL;
+
+	height = root->height;
+	if (index > radix_tree_maxindex(height))
+		goto out;
+
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+	pathp->node = NULL;
+	pathp->slot = &root->rnode;
+
+	while (height > 0) {
+		int offset;
+
+		if (*pathp->slot == NULL)
+			goto out;
+
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		pathp[1].offset = offset;
+		pathp[1].node = *pathp[0].slot;
+		pathp[1].slot = (struct radix_tree_node **)
+				(pathp[1].node->slots + offset);
+		pathp++;
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	ret = *pathp[0].slot;
+	if (ret == NULL)
+		goto out;
+
+	do {
+		int idx;
+
+		tag_clear(pathp[0].node, tag, pathp[0].offset);
+		for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
+			if (pathp[0].node->tags[tag][idx])
+				goto out;
+		}
+		pathp--;
+	} while (pathp[0].node);
+out:
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_tag_clear);
+
+#ifndef __KERNEL__	/* Only the test harness uses this at present */
+/**
+ *	radix_tree_tag_get - get a tag on a radix tree node
+ *	@root:		radix tree root
+ *	@index:		index key
+ *	@tag: 		tag index
+ *
+ *	Return the search tag corresponging to @index in the radix tree.
+ *
+ *	Returns zero if the tag is unset, or if there is no corresponding item
+ *	in the tree.
+ */
+int radix_tree_tag_get(struct radix_tree_root *root,
+			unsigned long index, int tag)
+{
+	unsigned int height, shift;
+	struct radix_tree_node **slot;
+	int saw_unset_tag = 0;
+
+	height = root->height;
+	if (index > radix_tree_maxindex(height))
+		return 0;
+
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+	slot = &root->rnode;
+
+	for ( ; ; ) {
+		int offset;
+
+		if (*slot == NULL)
+			return 0;
+
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+
+		/*
+		 * This is just a debug check.  Later, we can bale as soon as
+		 * we see an unset tag.
+		 */
+		if (!tag_get(*slot, tag, offset))
+			saw_unset_tag = 1;
+		if (height == 1) {
+			int ret = tag_get(*slot, tag, offset);
+
+			BUG_ON(ret && saw_unset_tag);
+			return ret;
+		}
+		slot = (struct radix_tree_node **)((*slot)->slots + offset);
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+}
+EXPORT_SYMBOL(radix_tree_tag_get);
+#endif
+
+static unsigned int
+__lookup(struct radix_tree_root *root, void **results, unsigned long index,
+	unsigned int max_items, unsigned long *next_index)
+{
+	unsigned int nr_found = 0;
+	unsigned int shift;
+	unsigned int height = root->height;
+	struct radix_tree_node *slot;
+
+	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
+	slot = root->rnode;
+
+	while (height > 0) {
+		unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
+
+		for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
+			if (slot->slots[i] != NULL)
+				break;
+			index &= ~((1UL << shift) - 1);
+			index += 1UL << shift;
+			if (index == 0)
+				goto out;	/* 32-bit wraparound */
+		}
+		if (i == RADIX_TREE_MAP_SIZE)
+			goto out;
+		height--;
+		if (height == 0) {	/* Bottom level: grab some items */
+			unsigned long j = index & RADIX_TREE_MAP_MASK;
+
+			for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
+				index++;
+				if (slot->slots[j]) {
+					results[nr_found++] = slot->slots[j];
+					if (nr_found == max_items)
+						goto out;
+				}
+			}
+		}
+		shift -= RADIX_TREE_MAP_SHIFT;
+		slot = slot->slots[i];
+	}
+out:
+	*next_index = index;
+	return nr_found;
+}
+
+/**
+ *	radix_tree_gang_lookup - perform multiple lookup on a radix tree
+ *	@root:		radix tree root
+ *	@results:	where the results of the lookup are placed
+ *	@first_index:	start the lookup from this key
+ *	@max_items:	place up to this many items at *results
+ *
+ *	Performs an index-ascending scan of the tree for present items.  Places
+ *	them at *@results and returns the number of items which were placed at
+ *	*@results.
+ *
+ *	The implementation is naive.
+ */
+unsigned int
+radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
+			unsigned long first_index, unsigned int max_items)
+{
+	const unsigned long max_index = radix_tree_maxindex(root->height);
+	unsigned long cur_index = first_index;
+	unsigned int ret = 0;
+
+	while (ret < max_items) {
+		unsigned int nr_found;
+		unsigned long next_index;	/* Index of next search */
+
+		if (cur_index > max_index)
+			break;
+		nr_found = __lookup(root, results + ret, cur_index,
+					max_items - ret, &next_index);
+		ret += nr_found;
+		if (next_index == 0)
+			break;
+		cur_index = next_index;
+	}
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup);
+
+/*
+ * FIXME: the two tag_get()s here should use find_next_bit() instead of
+ * open-coding the search.
+ */
+static unsigned int
+__lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
+	unsigned int max_items, unsigned long *next_index, int tag)
+{
+	unsigned int nr_found = 0;
+	unsigned int shift;
+	unsigned int height = root->height;
+	struct radix_tree_node *slot;
+
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+	slot = root->rnode;
+
+	while (height > 0) {
+		unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
+
+		for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
+			if (tag_get(slot, tag, i)) {
+				BUG_ON(slot->slots[i] == NULL);
+				break;
+			}
+			index &= ~((1UL << shift) - 1);
+			index += 1UL << shift;
+			if (index == 0)
+				goto out;	/* 32-bit wraparound */
+		}
+		if (i == RADIX_TREE_MAP_SIZE)
+			goto out;
+		height--;
+		if (height == 0) {	/* Bottom level: grab some items */
+			unsigned long j = index & RADIX_TREE_MAP_MASK;
+
+			for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
+				index++;
+				if (tag_get(slot, tag, j)) {
+					BUG_ON(slot->slots[j] == NULL);
+					results[nr_found++] = slot->slots[j];
+					if (nr_found == max_items)
+						goto out;
+				}
+			}
+		}
+		shift -= RADIX_TREE_MAP_SHIFT;
+		slot = slot->slots[i];
+	}
+out:
+	*next_index = index;
+	return nr_found;
+}
+
+/**
+ *	radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
+ *	                             based on a tag
+ *	@root:		radix tree root
+ *	@results:	where the results of the lookup are placed
+ *	@first_index:	start the lookup from this key
+ *	@max_items:	place up to this many items at *results
+ *	@tag:		the tag index
+ *
+ *	Performs an index-ascending scan of the tree for present items which
+ *	have the tag indexed by @tag set.  Places the items at *@results and
+ *	returns the number of items which were placed at *@results.
+ */
+unsigned int
+radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
+		unsigned long first_index, unsigned int max_items, int tag)
+{
+	const unsigned long max_index = radix_tree_maxindex(root->height);
+	unsigned long cur_index = first_index;
+	unsigned int ret = 0;
+
+	while (ret < max_items) {
+		unsigned int nr_found;
+		unsigned long next_index;	/* Index of next search */
+
+		if (cur_index > max_index)
+			break;
+		nr_found = __lookup_tag(root, results + ret, cur_index,
+					max_items - ret, &next_index, tag);
+		ret += nr_found;
+		if (next_index == 0)
+			break;
+		cur_index = next_index;
+	}
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
+
+/**
+ *	radix_tree_delete    -    delete an item from a radix tree
+ *	@root:		radix tree root
+ *	@index:		index key
+ *
+ *	Remove the item at @index from the radix tree rooted at @root.
+ *
+ *	Returns the address of the deleted item, or NULL if it was not present.
+ */
+void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
+{
+	struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
+	struct radix_tree_path *orig_pathp;
+	unsigned int height, shift;
+	void *ret = NULL;
+	char tags[RADIX_TREE_TAGS];
+	int nr_cleared_tags;
+
+	height = root->height;
+	if (index > radix_tree_maxindex(height))
+		goto out;
+
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+	pathp->node = NULL;
+	pathp->slot = &root->rnode;
+
+	while (height > 0) {
+		int offset;
+
+		if (*pathp->slot == NULL)
+			goto out;
+
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		pathp[1].offset = offset;
+		pathp[1].node = *pathp[0].slot;
+		pathp[1].slot = (struct radix_tree_node **)
+				(pathp[1].node->slots + offset);
+		pathp++;
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	ret = *pathp[0].slot;
+	if (ret == NULL)
+		goto out;
+
+	orig_pathp = pathp;
+
+	/*
+	 * Clear all tags associated with the just-deleted item
+	 */
+	memset(tags, 0, sizeof(tags));
+	do {
+		int tag;
+
+		nr_cleared_tags = RADIX_TREE_TAGS;
+		for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
+			int idx;
+
+			if (tags[tag])
+				continue;
+
+			tag_clear(pathp[0].node, tag, pathp[0].offset);
+
+			for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
+				if (pathp[0].node->tags[tag][idx]) {
+					tags[tag] = 1;
+					nr_cleared_tags--;
+					break;
+				}
+			}
+		}
+		pathp--;
+	} while (pathp[0].node && nr_cleared_tags);
+
+	pathp = orig_pathp;
+	*pathp[0].slot = NULL;
+	while (pathp[0].node && --pathp[0].node->count == 0) {
+		pathp--;
+		BUG_ON(*pathp[0].slot == NULL);
+		*pathp[0].slot = NULL;
+		radix_tree_node_free(pathp[1].node);
+	}
+	if (root->rnode == NULL)
+		root->height = 0;
+out:
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_delete);
+
+/**
+ *	radix_tree_tagged - test whether any items in the tree are tagged
+ *	@root:		radix tree root
+ *	@tag:		tag to test
+ */
+int radix_tree_tagged(struct radix_tree_root *root, int tag)
+{
+	int idx;
+
+	if (!root->rnode)
+		return 0;
+	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
+		if (root->rnode->tags[tag][idx])
+			return 1;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(radix_tree_tagged);
+
+static void
+radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
+{
+	memset(node, 0, sizeof(struct radix_tree_node));
+}
+
+static __init unsigned long __maxindex(unsigned int height)
+{
+	unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
+	unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
+
+	if (tmp >= RADIX_TREE_INDEX_BITS)
+		index = ~0UL;
+	return index;
+}
+
+static __init void radix_tree_init_maxindex(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
+		height_to_maxindex[i] = __maxindex(i);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int radix_tree_callback(struct notifier_block *nfb,
+                            unsigned long action,
+                            void *hcpu)
+{
+       int cpu = (long)hcpu;
+       struct radix_tree_preload *rtp;
+
+       /* Free per-cpu pool of perloaded nodes */
+       if (action == CPU_DEAD) {
+               rtp = &per_cpu(radix_tree_preloads, cpu);
+               while (rtp->nr) {
+                       kmem_cache_free(radix_tree_node_cachep,
+                                       rtp->nodes[rtp->nr-1]);
+                       rtp->nodes[rtp->nr-1] = NULL;
+                       rtp->nr--;
+               }
+       }
+       return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+void __init radix_tree_init(void)
+{
+	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
+			sizeof(struct radix_tree_node), 0,
+			SLAB_PANIC, radix_tree_node_ctor, NULL);
+	radix_tree_init_maxindex();
+	hotcpu_notifier(radix_tree_callback, 0);
+}