diff --git a/ap/os/linux/linux-3.4.x/lib/radix-tree.c b/ap/os/linux/linux-3.4.x/lib/radix-tree.c
new file mode 100644
index 0000000..52ebdb1
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/lib/radix-tree.c
@@ -0,0 +1,1445 @@
+/*
+ * Copyright (C) 2001 Momchil Velikov
+ * Portions Copyright (C) 2001 Christoph Hellwig
+ * Copyright (C) 2005 SGI, Christoph Lameter
+ * Copyright (C) 2006 Nick Piggin
+ * Copyright (C) 2012 Konstantin Khlebnikov
+ *
+ * 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/export.h>
+#include <linux/radix-tree.h>
+#include <linux/percpu.h>
+#include <linux/slab.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/string.h>
+#include <linux/bitops.h>
+#include <linux/rcupdate.h>
+
+
+#ifdef __KERNEL__
+#define RADIX_TREE_MAP_SHIFT	(CONFIG_BASE_SMALL ? 4 : 6)
+#else
+#define RADIX_TREE_MAP_SHIFT	3	/* For more stressful testing */
+#endif
+
+#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	height;		/* Height from the bottom */
+	unsigned int	count;
+	union {
+		struct radix_tree_node *parent;	/* Used when ascending tree */
+		struct rcu_head	rcu_head;	/* Used when freeing node */
+	};
+	void __rcu	*slots[RADIX_TREE_MAP_SIZE];
+	unsigned long	tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
+};
+
+#define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
+#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
+					  RADIX_TREE_MAP_SHIFT))
+
+/*
+ * The height_to_maxindex array needs to be one deeper than the maximum
+ * path as height 0 holds only 1 entry.
+ */
+static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
+
+/*
+ * Radix tree node cache.
+ */
+static struct kmem_cache *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];
+};
+static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
+
+static inline void *ptr_to_indirect(void *ptr)
+{
+	return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
+}
+
+static inline void *indirect_to_ptr(void *ptr)
+{
+	return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
+}
+
+static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
+{
+	return root->gfp_mask & __GFP_BITS_MASK;
+}
+
+static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
+		int offset)
+{
+	__set_bit(offset, node->tags[tag]);
+}
+
+static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
+		int offset)
+{
+	__clear_bit(offset, node->tags[tag]);
+}
+
+static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
+		int offset)
+{
+	return test_bit(offset, node->tags[tag]);
+}
+
+static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
+{
+	root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
+}
+
+static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
+{
+	root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
+}
+
+static inline void root_tag_clear_all(struct radix_tree_root *root)
+{
+	root->gfp_mask &= __GFP_BITS_MASK;
+}
+
+static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
+{
+	return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
+}
+
+/*
+ * Returns 1 if any slot in the node has this tag set.
+ * Otherwise returns 0.
+ */
+static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
+{
+	int idx;
+	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
+		if (node->tags[tag][idx])
+			return 1;
+	}
+	return 0;
+}
+
+/**
+ * radix_tree_find_next_bit - find the next set bit in a memory region
+ *
+ * @addr: The address to base the search on
+ * @size: The bitmap size in bits
+ * @offset: The bitnumber to start searching at
+ *
+ * Unrollable variant of find_next_bit() for constant size arrays.
+ * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
+ * Returns next bit offset, or size if nothing found.
+ */
+static __always_inline unsigned long
+radix_tree_find_next_bit(const unsigned long *addr,
+			 unsigned long size, unsigned long offset)
+{
+	if (!__builtin_constant_p(size))
+		return find_next_bit(addr, size, offset);
+
+	if (offset < size) {
+		unsigned long tmp;
+
+		addr += offset / BITS_PER_LONG;
+		tmp = *addr >> (offset % BITS_PER_LONG);
+		if (tmp)
+			return __ffs(tmp) + offset;
+		offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
+		while (offset < size) {
+			tmp = *++addr;
+			if (tmp)
+				return __ffs(tmp) + offset;
+			offset += BITS_PER_LONG;
+		}
+	}
+	return size;
+}
+
+/*
+ * 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 = NULL;
+	gfp_t gfp_mask = root_gfp_mask(root);
+
+	if (!(gfp_mask & __GFP_WAIT)) {
+		struct radix_tree_preload *rtp;
+
+		/*
+		 * Provided the caller has preloaded here, we will always
+		 * succeed in getting a node here (and never reach
+		 * kmem_cache_alloc)
+		 */
+		rtp = &get_cpu_var(radix_tree_preloads);
+		if (rtp->nr) {
+			ret = rtp->nodes[rtp->nr - 1];
+			rtp->nodes[rtp->nr - 1] = NULL;
+			rtp->nr--;
+		}
+		put_cpu_var(radix_tree_preloads);
+	}
+	if (ret == NULL)
+		ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
+
+	BUG_ON(radix_tree_is_indirect_ptr(ret));
+	return ret;
+}
+
+static void radix_tree_node_rcu_free(struct rcu_head *head)
+{
+	struct radix_tree_node *node =
+			container_of(head, struct radix_tree_node, rcu_head);
+	int i;
+
+	/*
+	 * must only free zeroed nodes into the slab. radix_tree_shrink
+	 * can leave us with a non-NULL entry in the first slot, so clear
+	 * that here to make sure.
+	 */
+	for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
+		tag_clear(node, i, 0);
+
+	node->slots[0] = NULL;
+	node->count = 0;
+
+	kmem_cache_free(radix_tree_node_cachep, node);
+}
+
+static inline void
+radix_tree_node_free(struct radix_tree_node *node)
+{
+	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
+}
+
+#ifndef CONFIG_PREEMPT_RT_FULL
+/*
+ * 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.
+ *
+ * To make use of this facility, the radix tree must be initialised without
+ * __GFP_WAIT being passed to INIT_RADIX_TREE().
+ */
+int radix_tree_preload(gfp_t 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;
+}
+EXPORT_SYMBOL(radix_tree_preload);
+#endif
+
+/*
+ *	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;
+	struct radix_tree_node *slot;
+	unsigned int height;
+	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;
+	}
+
+	do {
+		unsigned int newheight;
+		if (!(node = radix_tree_node_alloc(root)))
+			return -ENOMEM;
+
+		/* Propagate the aggregated tag info into the new root */
+		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
+			if (root_tag_get(root, tag))
+				tag_set(node, tag, 0);
+		}
+
+		/* Increase the height.  */
+		newheight = root->height+1;
+		node->height = newheight;
+		node->count = 1;
+		node->parent = NULL;
+		slot = root->rnode;
+		if (newheight > 1) {
+			slot = indirect_to_ptr(slot);
+			slot->parent = node;
+		}
+		node->slots[0] = slot;
+		node = ptr_to_indirect(node);
+		rcu_assign_pointer(root->rnode, node);
+		root->height = newheight;
+	} 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, *slot;
+	unsigned int height, shift;
+	int offset;
+	int error;
+
+	BUG_ON(radix_tree_is_indirect_ptr(item));
+
+	/* Make sure the tree is high enough.  */
+	if (index > radix_tree_maxindex(root->height)) {
+		error = radix_tree_extend(root, index);
+		if (error)
+			return error;
+	}
+
+	slot = indirect_to_ptr(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 (!(slot = radix_tree_node_alloc(root)))
+				return -ENOMEM;
+			slot->height = height;
+			slot->parent = node;
+			if (node) {
+				rcu_assign_pointer(node->slots[offset], slot);
+				node->count++;
+			} else
+				rcu_assign_pointer(root->rnode, ptr_to_indirect(slot));
+		}
+
+		/* Go a level down */
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		node = slot;
+		slot = node->slots[offset];
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	if (slot != NULL)
+		return -EEXIST;
+
+	if (node) {
+		node->count++;
+		rcu_assign_pointer(node->slots[offset], item);
+		BUG_ON(tag_get(node, 0, offset));
+		BUG_ON(tag_get(node, 1, offset));
+	} else {
+		rcu_assign_pointer(root->rnode, item);
+		BUG_ON(root_tag_get(root, 0));
+		BUG_ON(root_tag_get(root, 1));
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(radix_tree_insert);
+
+/*
+ * is_slot == 1 : search for the slot.
+ * is_slot == 0 : search for the node.
+ */
+static void *radix_tree_lookup_element(struct radix_tree_root *root,
+				unsigned long index, int is_slot)
+{
+	unsigned int height, shift;
+	struct radix_tree_node *node, **slot;
+
+	node = rcu_dereference_raw(root->rnode);
+	if (node == NULL)
+		return NULL;
+
+	if (!radix_tree_is_indirect_ptr(node)) {
+		if (index > 0)
+			return NULL;
+		return is_slot ? (void *)&root->rnode : node;
+	}
+	node = indirect_to_ptr(node);
+
+	height = node->height;
+	if (index > radix_tree_maxindex(height))
+		return NULL;
+
+	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
+
+	do {
+		slot = (struct radix_tree_node **)
+			(node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
+		node = rcu_dereference_raw(*slot);
+		if (node == NULL)
+			return NULL;
+
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	} while (height > 0);
+
+	return is_slot ? (void *)slot : indirect_to_ptr(node);
+}
+
+/**
+ *	radix_tree_lookup_slot    -    lookup a slot in a radix tree
+ *	@root:		radix tree root
+ *	@index:		index key
+ *
+ *	Returns:  the slot corresponding to the position @index in the
+ *	radix tree @root. This is useful for update-if-exists operations.
+ *
+ *	This function can be called under rcu_read_lock iff the slot is not
+ *	modified by radix_tree_replace_slot, otherwise it must be called
+ *	exclusive from other writers. Any dereference of the slot must be done
+ *	using radix_tree_deref_slot.
+ */
+void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
+{
+	return (void **)radix_tree_lookup_element(root, index, 1);
+}
+EXPORT_SYMBOL(radix_tree_lookup_slot);
+
+/**
+ *	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.
+ *
+ *	This function can be called under rcu_read_lock, however the caller
+ *	must manage lifetimes of leaf nodes (eg. RCU may also be used to free
+ *	them safely). No RCU barriers are required to access or modify the
+ *	returned item, however.
+ */
+void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
+{
+	return radix_tree_lookup_element(root, index, 0);
+}
+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 (which must be < RADIX_TREE_MAX_TAGS)
+ *	corresponding 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, unsigned int tag)
+{
+	unsigned int height, shift;
+	struct radix_tree_node *slot;
+
+	height = root->height;
+	BUG_ON(index > radix_tree_maxindex(height));
+
+	slot = indirect_to_ptr(root->rnode);
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+
+	while (height > 0) {
+		int offset;
+
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		if (!tag_get(slot, tag, offset))
+			tag_set(slot, tag, offset);
+		slot = slot->slots[offset];
+		BUG_ON(slot == NULL);
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	/* set the root's tag bit */
+	if (slot && !root_tag_get(root, tag))
+		root_tag_set(root, tag);
+
+	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 (which must be < RADIX_TREE_MAX_TAGS)
+ *	corresponding 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, unsigned int tag)
+{
+	struct radix_tree_node *node = NULL;
+	struct radix_tree_node *slot = NULL;
+	unsigned int height, shift;
+	int uninitialized_var(offset);
+
+	height = root->height;
+	if (index > radix_tree_maxindex(height))
+		goto out;
+
+	shift = height * RADIX_TREE_MAP_SHIFT;
+	slot = indirect_to_ptr(root->rnode);
+
+	while (shift) {
+		if (slot == NULL)
+			goto out;
+
+		shift -= RADIX_TREE_MAP_SHIFT;
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		node = slot;
+		slot = slot->slots[offset];
+	}
+
+	if (slot == NULL)
+		goto out;
+
+	while (node) {
+		if (!tag_get(node, tag, offset))
+			goto out;
+		tag_clear(node, tag, offset);
+		if (any_tag_set(node, tag))
+			goto out;
+
+		index >>= RADIX_TREE_MAP_SHIFT;
+		offset = index & RADIX_TREE_MAP_MASK;
+		node = node->parent;
+	}
+
+	/* clear the root's tag bit */
+	if (root_tag_get(root, tag))
+		root_tag_clear(root, tag);
+
+out:
+	return slot;
+}
+EXPORT_SYMBOL(radix_tree_tag_clear);
+
+/**
+ * radix_tree_tag_get - get a tag on a radix tree node
+ * @root:		radix tree root
+ * @index:		index key
+ * @tag: 		tag index (< RADIX_TREE_MAX_TAGS)
+ *
+ * Return values:
+ *
+ *  0: tag not present or not set
+ *  1: tag set
+ *
+ * Note that the return value of this function may not be relied on, even if
+ * the RCU lock is held, unless tag modification and node deletion are excluded
+ * from concurrency.
+ */
+int radix_tree_tag_get(struct radix_tree_root *root,
+			unsigned long index, unsigned int tag)
+{
+	unsigned int height, shift;
+	struct radix_tree_node *node;
+
+	/* check the root's tag bit */
+	if (!root_tag_get(root, tag))
+		return 0;
+
+	node = rcu_dereference_raw(root->rnode);
+	if (node == NULL)
+		return 0;
+
+	if (!radix_tree_is_indirect_ptr(node))
+		return (index == 0);
+	node = indirect_to_ptr(node);
+
+	height = node->height;
+	if (index > radix_tree_maxindex(height))
+		return 0;
+
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+
+	for ( ; ; ) {
+		int offset;
+
+		if (node == NULL)
+			return 0;
+
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		if (!tag_get(node, tag, offset))
+			return 0;
+		if (height == 1)
+			return 1;
+		node = rcu_dereference_raw(node->slots[offset]);
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+}
+EXPORT_SYMBOL(radix_tree_tag_get);
+
+/**
+ * radix_tree_next_chunk - find next chunk of slots for iteration
+ *
+ * @root:	radix tree root
+ * @iter:	iterator state
+ * @flags:	RADIX_TREE_ITER_* flags and tag index
+ * Returns:	pointer to chunk first slot, or NULL if iteration is over
+ */
+void **radix_tree_next_chunk(struct radix_tree_root *root,
+			     struct radix_tree_iter *iter, unsigned flags)
+{
+	unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
+	struct radix_tree_node *rnode, *node;
+	unsigned long index, offset;
+
+	if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
+		return NULL;
+
+	/*
+	 * Catch next_index overflow after ~0UL. iter->index never overflows
+	 * during iterating; it can be zero only at the beginning.
+	 * And we cannot overflow iter->next_index in a single step,
+	 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
+	 *
+	 * This condition also used by radix_tree_next_slot() to stop
+	 * contiguous iterating, and forbid swithing to the next chunk.
+	 */
+	index = iter->next_index;
+	if (!index && iter->index)
+		return NULL;
+
+	rnode = rcu_dereference_raw(root->rnode);
+	if (radix_tree_is_indirect_ptr(rnode)) {
+		rnode = indirect_to_ptr(rnode);
+	} else if (rnode && !index) {
+		/* Single-slot tree */
+		iter->index = 0;
+		iter->next_index = 1;
+		iter->tags = 1;
+		return (void **)&root->rnode;
+	} else
+		return NULL;
+
+restart:
+	shift = (rnode->height - 1) * RADIX_TREE_MAP_SHIFT;
+	offset = index >> shift;
+
+	/* Index outside of the tree */
+	if (offset >= RADIX_TREE_MAP_SIZE)
+		return NULL;
+
+	node = rnode;
+	while (1) {
+		if ((flags & RADIX_TREE_ITER_TAGGED) ?
+				!test_bit(offset, node->tags[tag]) :
+				!node->slots[offset]) {
+			/* Hole detected */
+			if (flags & RADIX_TREE_ITER_CONTIG)
+				return NULL;
+
+			if (flags & RADIX_TREE_ITER_TAGGED)
+				offset = radix_tree_find_next_bit(
+						node->tags[tag],
+						RADIX_TREE_MAP_SIZE,
+						offset + 1);
+			else
+				while (++offset	< RADIX_TREE_MAP_SIZE) {
+					if (node->slots[offset])
+						break;
+				}
+			index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
+			index += offset << shift;
+			/* Overflow after ~0UL */
+			if (!index)
+				return NULL;
+			if (offset == RADIX_TREE_MAP_SIZE)
+				goto restart;
+		}
+
+		/* This is leaf-node */
+		if (!shift)
+			break;
+
+		node = rcu_dereference_raw(node->slots[offset]);
+		if (node == NULL)
+			goto restart;
+		shift -= RADIX_TREE_MAP_SHIFT;
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+	}
+
+	/* Update the iterator state */
+	iter->index = index;
+	iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
+
+	/* Construct iter->tags bit-mask from node->tags[tag] array */
+	if (flags & RADIX_TREE_ITER_TAGGED) {
+		unsigned tag_long, tag_bit;
+
+		tag_long = offset / BITS_PER_LONG;
+		tag_bit  = offset % BITS_PER_LONG;
+		iter->tags = node->tags[tag][tag_long] >> tag_bit;
+		/* This never happens if RADIX_TREE_TAG_LONGS == 1 */
+		if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
+			/* Pick tags from next element */
+			if (tag_bit)
+				iter->tags |= node->tags[tag][tag_long + 1] <<
+						(BITS_PER_LONG - tag_bit);
+			/* Clip chunk size, here only BITS_PER_LONG tags */
+			iter->next_index = index + BITS_PER_LONG;
+		}
+	}
+
+	return node->slots + offset;
+}
+EXPORT_SYMBOL(radix_tree_next_chunk);
+
+/**
+ * radix_tree_range_tag_if_tagged - for each item in given range set given
+ *				   tag if item has another tag set
+ * @root:		radix tree root
+ * @first_indexp:	pointer to a starting index of a range to scan
+ * @last_index:		last index of a range to scan
+ * @nr_to_tag:		maximum number items to tag
+ * @iftag:		tag index to test
+ * @settag:		tag index to set if tested tag is set
+ *
+ * This function scans range of radix tree from first_index to last_index
+ * (inclusive).  For each item in the range if iftag is set, the function sets
+ * also settag. The function stops either after tagging nr_to_tag items or
+ * after reaching last_index.
+ *
+ * The tags must be set from the leaf level only and propagated back up the
+ * path to the root. We must do this so that we resolve the full path before
+ * setting any tags on intermediate nodes. If we set tags as we descend, then
+ * we can get to the leaf node and find that the index that has the iftag
+ * set is outside the range we are scanning. This reults in dangling tags and
+ * can lead to problems with later tag operations (e.g. livelocks on lookups).
+ *
+ * The function returns number of leaves where the tag was set and sets
+ * *first_indexp to the first unscanned index.
+ * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
+ * be prepared to handle that.
+ */
+unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
+		unsigned long *first_indexp, unsigned long last_index,
+		unsigned long nr_to_tag,
+		unsigned int iftag, unsigned int settag)
+{
+	unsigned int height = root->height;
+	struct radix_tree_node *node = NULL;
+	struct radix_tree_node *slot;
+	unsigned int shift;
+	unsigned long tagged = 0;
+	unsigned long index = *first_indexp;
+
+	last_index = min(last_index, radix_tree_maxindex(height));
+	if (index > last_index)
+		return 0;
+	if (!nr_to_tag)
+		return 0;
+	if (!root_tag_get(root, iftag)) {
+		*first_indexp = last_index + 1;
+		return 0;
+	}
+	if (height == 0) {
+		*first_indexp = last_index + 1;
+		root_tag_set(root, settag);
+		return 1;
+	}
+
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+	slot = indirect_to_ptr(root->rnode);
+
+	for (;;) {
+		unsigned long upindex;
+		int offset;
+
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		if (!slot->slots[offset])
+			goto next;
+		if (!tag_get(slot, iftag, offset))
+			goto next;
+		if (shift) {
+			/* Go down one level */
+			shift -= RADIX_TREE_MAP_SHIFT;
+			node = slot;
+			slot = slot->slots[offset];
+			continue;
+		}
+
+		/* tag the leaf */
+		tagged++;
+		tag_set(slot, settag, offset);
+
+		/* walk back up the path tagging interior nodes */
+		upindex = index;
+		while (node) {
+			upindex >>= RADIX_TREE_MAP_SHIFT;
+			offset = upindex & RADIX_TREE_MAP_MASK;
+
+			/* stop if we find a node with the tag already set */
+			if (tag_get(node, settag, offset))
+				break;
+			tag_set(node, settag, offset);
+			node = node->parent;
+		}
+
+		/*
+		 * Small optimization: now clear that node pointer.
+		 * Since all of this slot's ancestors now have the tag set
+		 * from setting it above, we have no further need to walk
+		 * back up the tree setting tags, until we update slot to
+		 * point to another radix_tree_node.
+		 */
+		node = NULL;
+
+next:
+		/* Go to next item at level determined by 'shift' */
+		index = ((index >> shift) + 1) << shift;
+		/* Overflow can happen when last_index is ~0UL... */
+		if (index > last_index || !index)
+			break;
+		if (tagged >= nr_to_tag)
+			break;
+		while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) {
+			/*
+			 * We've fully scanned this node. Go up. Because
+			 * last_index is guaranteed to be in the tree, what
+			 * we do below cannot wander astray.
+			 */
+			slot = slot->parent;
+			shift += RADIX_TREE_MAP_SHIFT;
+		}
+	}
+	/*
+	 * We need not to tag the root tag if there is no tag which is set with
+	 * settag within the range from *first_indexp to last_index.
+	 */
+	if (tagged > 0)
+		root_tag_set(root, settag);
+	*first_indexp = index;
+
+	return tagged;
+}
+EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
+
+
+/**
+ *	radix_tree_next_hole    -    find the next hole (not-present entry)
+ *	@root:		tree root
+ *	@index:		index key
+ *	@max_scan:	maximum range to search
+ *
+ *	Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
+ *	indexed hole.
+ *
+ *	Returns: the index of the hole if found, otherwise returns an index
+ *	outside of the set specified (in which case 'return - index >= max_scan'
+ *	will be true). In rare cases of index wrap-around, 0 will be returned.
+ *
+ *	radix_tree_next_hole may be called under rcu_read_lock. However, like
+ *	radix_tree_gang_lookup, this will not atomically search a snapshot of
+ *	the tree at a single point in time. For example, if a hole is created
+ *	at index 5, then subsequently a hole is created at index 10,
+ *	radix_tree_next_hole covering both indexes may return 10 if called
+ *	under rcu_read_lock.
+ */
+unsigned long radix_tree_next_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 == 0)
+			break;
+	}
+
+	return index;
+}
+EXPORT_SYMBOL(radix_tree_next_hole);
+
+/**
+ *	radix_tree_prev_hole    -    find the prev hole (not-present entry)
+ *	@root:		tree root
+ *	@index:		index key
+ *	@max_scan:	maximum range to search
+ *
+ *	Search backwards in the range [max(index-max_scan+1, 0), index]
+ *	for the first hole.
+ *
+ *	Returns: the index of the hole if found, otherwise returns an index
+ *	outside of the set specified (in which case 'index - return >= max_scan'
+ *	will be true). In rare cases of wrap-around, ULONG_MAX will be returned.
+ *
+ *	radix_tree_next_hole may be called under rcu_read_lock. However, like
+ *	radix_tree_gang_lookup, this will not atomically search a snapshot of
+ *	the tree at a single point in time. For example, if a hole is created
+ *	at index 10, then subsequently a hole is created at index 5,
+ *	radix_tree_prev_hole covering both indexes may return 5 if called under
+ *	rcu_read_lock.
+ */
+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 == ULONG_MAX)
+			break;
+	}
+
+	return index;
+}
+EXPORT_SYMBOL(radix_tree_prev_hole);
+
+/**
+ *	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.
+ *
+ *	Like radix_tree_lookup, radix_tree_gang_lookup may be called under
+ *	rcu_read_lock. In this case, rather than the returned results being
+ *	an atomic snapshot of the tree at a single point in time, the semantics
+ *	of an RCU protected gang lookup are as though multiple radix_tree_lookups
+ *	have been issued in individual locks, and results stored in 'results'.
+ */
+unsigned int
+radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
+			unsigned long first_index, unsigned int max_items)
+{
+	struct radix_tree_iter iter;
+	void **slot;
+	unsigned int ret = 0;
+
+	if (unlikely(!max_items))
+		return 0;
+
+	radix_tree_for_each_slot(slot, root, &iter, first_index) {
+		results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
+		if (!results[ret])
+			continue;
+		if (++ret == max_items)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup);
+
+/**
+ *	radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
+ *	@root:		radix tree root
+ *	@results:	where the results of the lookup are placed
+ *	@indices:	where their indices should be placed (but usually NULL)
+ *	@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
+ *	their slots at *@results and returns the number of items which were
+ *	placed at *@results.
+ *
+ *	The implementation is naive.
+ *
+ *	Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
+ *	be dereferenced with radix_tree_deref_slot, and if using only RCU
+ *	protection, radix_tree_deref_slot may fail requiring a retry.
+ */
+unsigned int
+radix_tree_gang_lookup_slot(struct radix_tree_root *root,
+			void ***results, unsigned long *indices,
+			unsigned long first_index, unsigned int max_items)
+{
+	struct radix_tree_iter iter;
+	void **slot;
+	unsigned int ret = 0;
+
+	if (unlikely(!max_items))
+		return 0;
+
+	radix_tree_for_each_slot(slot, root, &iter, first_index) {
+		results[ret] = slot;
+		if (indices)
+			indices[ret] = iter.index;
+		if (++ret == max_items)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
+
+/**
+ *	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 (< RADIX_TREE_MAX_TAGS)
+ *
+ *	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,
+		unsigned int tag)
+{
+	struct radix_tree_iter iter;
+	void **slot;
+	unsigned int ret = 0;
+
+	if (unlikely(!max_items))
+		return 0;
+
+	radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
+		results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
+		if (!results[ret])
+			continue;
+		if (++ret == max_items)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
+
+/**
+ *	radix_tree_gang_lookup_tag_slot - perform multiple slot 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 (< RADIX_TREE_MAX_TAGS)
+ *
+ *	Performs an index-ascending scan of the tree for present items which
+ *	have the tag indexed by @tag set.  Places the slots at *@results and
+ *	returns the number of slots which were placed at *@results.
+ */
+unsigned int
+radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
+		unsigned long first_index, unsigned int max_items,
+		unsigned int tag)
+{
+	struct radix_tree_iter iter;
+	void **slot;
+	unsigned int ret = 0;
+
+	if (unlikely(!max_items))
+		return 0;
+
+	radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
+		results[ret] = slot;
+		if (++ret == max_items)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
+
+#if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
+#include <linux/sched.h> /* for cond_resched() */
+
+/*
+ * This linear search is at present only useful to shmem_unuse_inode().
+ */
+static unsigned long __locate(struct radix_tree_node *slot, void *item,
+			      unsigned long index, unsigned long *found_index)
+{
+	unsigned int shift, height;
+	unsigned long i;
+
+	height = slot->height;
+	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
+
+	for ( ; height > 1; height--) {
+		i = (index >> shift) & RADIX_TREE_MAP_MASK;
+		for (;;) {
+			if (slot->slots[i] != NULL)
+				break;
+			index &= ~((1UL << shift) - 1);
+			index += 1UL << shift;
+			if (index == 0)
+				goto out;	/* 32-bit wraparound */
+			i++;
+			if (i == RADIX_TREE_MAP_SIZE)
+				goto out;
+		}
+
+		shift -= RADIX_TREE_MAP_SHIFT;
+		slot = rcu_dereference_raw(slot->slots[i]);
+		if (slot == NULL)
+			goto out;
+	}
+
+	/* Bottom level: check items */
+	for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
+		if (slot->slots[i] == item) {
+			*found_index = index + i;
+			index = 0;
+			goto out;
+		}
+	}
+	index += RADIX_TREE_MAP_SIZE;
+out:
+	return index;
+}
+
+/**
+ *	radix_tree_locate_item - search through radix tree for item
+ *	@root:		radix tree root
+ *	@item:		item to be found
+ *
+ *	Returns index where item was found, or -1 if not found.
+ *	Caller must hold no lock (since this time-consuming function needs
+ *	to be preemptible), and must check afterwards if item is still there.
+ */
+unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
+{
+	struct radix_tree_node *node;
+	unsigned long max_index;
+	unsigned long cur_index = 0;
+	unsigned long found_index = -1;
+
+	do {
+		rcu_read_lock();
+		node = rcu_dereference_raw(root->rnode);
+		if (!radix_tree_is_indirect_ptr(node)) {
+			rcu_read_unlock();
+			if (node == item)
+				found_index = 0;
+			break;
+		}
+
+		node = indirect_to_ptr(node);
+		max_index = radix_tree_maxindex(node->height);
+		if (cur_index > max_index)
+			break;
+
+		cur_index = __locate(node, item, cur_index, &found_index);
+		rcu_read_unlock();
+		cond_resched();
+	} while (cur_index != 0 && cur_index <= max_index);
+
+	return found_index;
+}
+#else
+unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
+{
+	return -1;
+}
+#endif /* CONFIG_SHMEM && CONFIG_SWAP */
+
+/**
+ *	radix_tree_shrink    -    shrink height of a radix tree to minimal
+ *	@root		radix tree root
+ */
+static inline void radix_tree_shrink(struct radix_tree_root *root)
+{
+	/* try to shrink tree height */
+	while (root->height > 0) {
+		struct radix_tree_node *to_free = root->rnode;
+		struct radix_tree_node *slot;
+
+		BUG_ON(!radix_tree_is_indirect_ptr(to_free));
+		to_free = indirect_to_ptr(to_free);
+
+		/*
+		 * The candidate node has more than one child, or its child
+		 * is not at the leftmost slot, we cannot shrink.
+		 */
+		if (to_free->count != 1)
+			break;
+		if (!to_free->slots[0])
+			break;
+
+		/*
+		 * We don't need rcu_assign_pointer(), since we are simply
+		 * moving the node from one part of the tree to another: if it
+		 * was safe to dereference the old pointer to it
+		 * (to_free->slots[0]), it will be safe to dereference the new
+		 * one (root->rnode) as far as dependent read barriers go.
+		 */
+		slot = to_free->slots[0];
+		if (root->height > 1) {
+			slot->parent = NULL;
+			slot = ptr_to_indirect(slot);
+		}
+		root->rnode = slot;
+		root->height--;
+
+		/*
+		 * We have a dilemma here. The node's slot[0] must not be
+		 * NULLed in case there are concurrent lookups expecting to
+		 * find the item. However if this was a bottom-level node,
+		 * then it may be subject to the slot pointer being visible
+		 * to callers dereferencing it. If item corresponding to
+		 * slot[0] is subsequently deleted, these callers would expect
+		 * their slot to become empty sooner or later.
+		 *
+		 * For example, lockless pagecache will look up a slot, deref
+		 * the page pointer, and if the page is 0 refcount it means it
+		 * was concurrently deleted from pagecache so try the deref
+		 * again. Fortunately there is already a requirement for logic
+		 * to retry the entire slot lookup -- the indirect pointer
+		 * problem (replacing direct root node with an indirect pointer
+		 * also results in a stale slot). So tag the slot as indirect
+		 * to force callers to retry.
+		 */
+		if (root->height == 0)
+			*((unsigned long *)&to_free->slots[0]) |=
+						RADIX_TREE_INDIRECT_PTR;
+
+		radix_tree_node_free(to_free);
+	}
+}
+
+/**
+ *	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_node *node = NULL;
+	struct radix_tree_node *slot = NULL;
+	struct radix_tree_node *to_free;
+	unsigned int height, shift;
+	int tag;
+	int uninitialized_var(offset);
+
+	height = root->height;
+	if (index > radix_tree_maxindex(height))
+		goto out;
+
+	slot = root->rnode;
+	if (height == 0) {
+		root_tag_clear_all(root);
+		root->rnode = NULL;
+		goto out;
+	}
+	slot = indirect_to_ptr(slot);
+	shift = height * RADIX_TREE_MAP_SHIFT;
+
+	do {
+		if (slot == NULL)
+			goto out;
+
+		shift -= RADIX_TREE_MAP_SHIFT;
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		node = slot;
+		slot = slot->slots[offset];
+	} while (shift);
+
+	if (slot == NULL)
+		goto out;
+
+	/*
+	 * Clear all tags associated with the item to be deleted.
+	 * This way of doing it would be inefficient, but seldom is any set.
+	 */
+	for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
+		if (tag_get(node, tag, offset))
+			radix_tree_tag_clear(root, index, tag);
+	}
+
+	to_free = NULL;
+	/* Now free the nodes we do not need anymore */
+	while (node) {
+		node->slots[offset] = NULL;
+		node->count--;
+		/*
+		 * Queue the node for deferred freeing after the
+		 * last reference to it disappears (set NULL, above).
+		 */
+		if (to_free)
+			radix_tree_node_free(to_free);
+
+		if (node->count) {
+			if (node == indirect_to_ptr(root->rnode))
+				radix_tree_shrink(root);
+			goto out;
+		}
+
+		/* Node with zero slots in use so free it */
+		to_free = node;
+
+		index >>= RADIX_TREE_MAP_SHIFT;
+		offset = index & RADIX_TREE_MAP_MASK;
+		node = node->parent;
+	}
+
+	root_tag_clear_all(root);
+	root->height = 0;
+	root->rnode = NULL;
+	if (to_free)
+		radix_tree_node_free(to_free);
+
+out:
+	return slot;
+}
+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, unsigned int tag)
+{
+	return root_tag_get(root, tag);
+}
+EXPORT_SYMBOL(radix_tree_tagged);
+
+static void
+radix_tree_node_ctor(void *node)
+{
+	memset(node, 0, sizeof(struct radix_tree_node));
+}
+
+static __init unsigned long __maxindex(unsigned int height)
+{
+	unsigned int width = height * RADIX_TREE_MAP_SHIFT;
+	int shift = RADIX_TREE_INDEX_BITS - width;
+
+	if (shift < 0)
+		return ~0UL;
+	if (shift >= BITS_PER_LONG)
+		return 0UL;
+	return ~0UL >> shift;
+}
+
+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);
+}
+
+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 || action == CPU_DEAD_FROZEN) {
+               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;
+}
+
+void __init radix_tree_init(void)
+{
+	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
+			sizeof(struct radix_tree_node), 0,
+			SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
+			radix_tree_node_ctor);
+	radix_tree_init_maxindex();
+	hotcpu_notifier(radix_tree_callback, 0);
+}