Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1605 insertions, 0 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
new file mode 100644
index 000000000..cbc691525
--- /dev/null
+++ b/lib/radix-tree.c
@@ -0,0 +1,1605 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * 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
+ * Copyright (C) 2016 Intel, Matthew Wilcox
+ * Copyright (C) 2016 Intel, Ross Zwisler
+ */
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/bug.h>
+#include <linux/cpu.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/kmemleak.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>		/* in_interrupt() */
+#include <linux/radix-tree.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/xarray.h>
+
+/*
+ * Radix tree node cache.
+ */
+struct kmem_cache *radix_tree_node_cachep;
+
+/*
+ * The radix tree is variable-height, so an insert operation not only has
+ * to build the branch to its corresponding item, it also has to build the
+ * branch to existing items if the size has to be increased (by
+ * radix_tree_extend).
+ *
+ * The worst case is a zero height tree with just a single item at index 0,
+ * and then inserting an item at index ULONG_MAX. This requires 2 new branches
+ * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
+ * Hence:
+ */
+#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
+
+/*
+ * The IDR does not have to be as high as the radix tree since it uses
+ * signed integers, not unsigned longs.
+ */
+#define IDR_INDEX_BITS		(8 /* CHAR_BIT */ * sizeof(int) - 1)
+#define IDR_MAX_PATH		(DIV_ROUND_UP(IDR_INDEX_BITS, \
+						RADIX_TREE_MAP_SHIFT))
+#define IDR_PRELOAD_SIZE	(IDR_MAX_PATH * 2 - 1)
+
+/*
+ * Per-cpu pool of preloaded nodes
+ */
+DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = {
+	.lock = INIT_LOCAL_LOCK(lock),
+};
+EXPORT_PER_CPU_SYMBOL_GPL(radix_tree_preloads);
+
+static inline struct radix_tree_node *entry_to_node(void *ptr)
+{
+	return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
+}
+
+static inline void *node_to_entry(void *ptr)
+{
+	return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
+}
+
+#define RADIX_TREE_RETRY	XA_RETRY_ENTRY
+
+static inline unsigned long
+get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
+{
+	return parent ? slot - parent->slots : 0;
+}
+
+static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
+			struct radix_tree_node **nodep, unsigned long index)
+{
+	unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
+	void __rcu **entry = rcu_dereference_raw(parent->slots[offset]);
+
+	*nodep = (void *)entry;
+	return offset;
+}
+
+static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
+{
+	return root->xa_flags & (__GFP_BITS_MASK & ~GFP_ZONEMASK);
+}
+
+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(const 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 tag)
+{
+	root->xa_flags |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT));
+}
+
+static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
+{
+	root->xa_flags &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT));
+}
+
+static inline void root_tag_clear_all(struct radix_tree_root *root)
+{
+	root->xa_flags &= (__force gfp_t)((1 << ROOT_TAG_SHIFT) - 1);
+}
+
+static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag)
+{
+	return (__force int)root->xa_flags & (1 << (tag + ROOT_TAG_SHIFT));
+}
+
+static inline unsigned root_tags_get(const struct radix_tree_root *root)
+{
+	return (__force unsigned)root->xa_flags >> ROOT_TAG_SHIFT;
+}
+
+static inline bool is_idr(const struct radix_tree_root *root)
+{
+	return !!(root->xa_flags & ROOT_IS_IDR);
+}
+
+/*
+ * Returns 1 if any slot in the node has this tag set.
+ * Otherwise returns 0.
+ */
+static inline int any_tag_set(const struct radix_tree_node *node,
+							unsigned int tag)
+{
+	unsigned idx;
+	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
+		if (node->tags[tag][idx])
+			return 1;
+	}
+	return 0;
+}
+
+static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag)
+{
+	bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE);
+}
+
+/**
+ * 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(struct radix_tree_node *node, unsigned int tag,
+			 unsigned long offset)
+{
+	const unsigned long *addr = node->tags[tag];
+
+	if (offset < RADIX_TREE_MAP_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 < RADIX_TREE_MAP_SIZE) {
+			tmp = *++addr;
+			if (tmp)
+				return __ffs(tmp) + offset;
+			offset += BITS_PER_LONG;
+		}
+	}
+	return RADIX_TREE_MAP_SIZE;
+}
+
+static unsigned int iter_offset(const struct radix_tree_iter *iter)
+{
+	return iter->index & RADIX_TREE_MAP_MASK;
+}
+
+/*
+ * The maximum index which can be stored in a radix tree
+ */
+static inline unsigned long shift_maxindex(unsigned int shift)
+{
+	return (RADIX_TREE_MAP_SIZE << shift) - 1;
+}
+
+static inline unsigned long node_maxindex(const struct radix_tree_node *node)
+{
+	return shift_maxindex(node->shift);
+}
+
+static unsigned long next_index(unsigned long index,
+				const struct radix_tree_node *node,
+				unsigned long offset)
+{
+	return (index & ~node_maxindex(node)) + (offset << node->shift);
+}
+
+/*
+ * 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(gfp_t gfp_mask, struct radix_tree_node *parent,
+			struct radix_tree_root *root,
+			unsigned int shift, unsigned int offset,
+			unsigned int count, unsigned int nr_values)
+{
+	struct radix_tree_node *ret = NULL;
+
+	/*
+	 * Preload code isn't irq safe and it doesn't make sense to use
+	 * preloading during an interrupt anyway as all the allocations have
+	 * to be atomic. So just do normal allocation when in interrupt.
+	 */
+	if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
+		struct radix_tree_preload *rtp;
+
+		/*
+		 * Even if the caller has preloaded, try to allocate from the
+		 * cache first for the new node to get accounted to the memory
+		 * cgroup.
+		 */
+		ret = kmem_cache_alloc(radix_tree_node_cachep,
+				       gfp_mask | __GFP_NOWARN);
+		if (ret)
+			goto out;
+
+		/*
+		 * Provided the caller has preloaded here, we will always
+		 * succeed in getting a node here (and never reach
+		 * kmem_cache_alloc)
+		 */
+		rtp = this_cpu_ptr(&radix_tree_preloads);
+		if (rtp->nr) {
+			ret = rtp->nodes;
+			rtp->nodes = ret->parent;
+			rtp->nr--;
+		}
+		/*
+		 * Update the allocation stack trace as this is more useful
+		 * for debugging.
+		 */
+		kmemleak_update_trace(ret);
+		goto out;
+	}
+	ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
+out:
+	BUG_ON(radix_tree_is_internal_node(ret));
+	if (ret) {
+		ret->shift = shift;
+		ret->offset = offset;
+		ret->count = count;
+		ret->nr_values = nr_values;
+		ret->parent = parent;
+		ret->array = root;
+	}
+	return ret;
+}
+
+void radix_tree_node_rcu_free(struct rcu_head *head)
+{
+	struct radix_tree_node *node =
+			container_of(head, struct radix_tree_node, rcu_head);
+
+	/*
+	 * Must only free zeroed nodes into the slab.  We can be left with
+	 * non-NULL entries by radix_tree_free_nodes, so clear the entries
+	 * and tags here.
+	 */
+	memset(node->slots, 0, sizeof(node->slots));
+	memset(node->tags, 0, sizeof(node->tags));
+	INIT_LIST_HEAD(&node->private_list);
+
+	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);
+}
+
+/*
+ * 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_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
+ */
+static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
+{
+	struct radix_tree_preload *rtp;
+	struct radix_tree_node *node;
+	int ret = -ENOMEM;
+
+	/*
+	 * Nodes preloaded by one cgroup can be used by another cgroup, so
+	 * they should never be accounted to any particular memory cgroup.
+	 */
+	gfp_mask &= ~__GFP_ACCOUNT;
+
+	local_lock(&radix_tree_preloads.lock);
+	rtp = this_cpu_ptr(&radix_tree_preloads);
+	while (rtp->nr < nr) {
+		local_unlock(&radix_tree_preloads.lock);
+		node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
+		if (node == NULL)
+			goto out;
+		local_lock(&radix_tree_preloads.lock);
+		rtp = this_cpu_ptr(&radix_tree_preloads);
+		if (rtp->nr < nr) {
+			node->parent = rtp->nodes;
+			rtp->nodes = node;
+			rtp->nr++;
+		} else {
+			kmem_cache_free(radix_tree_node_cachep, node);
+		}
+	}
+	ret = 0;
+out:
+	return ret;
+}
+
+/*
+ * 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_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
+ */
+int radix_tree_preload(gfp_t gfp_mask)
+{
+	/* Warn on non-sensical use... */
+	WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
+	return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
+}
+EXPORT_SYMBOL(radix_tree_preload);
+
+/*
+ * The same as above function, except we don't guarantee preloading happens.
+ * We do it, if we decide it helps. On success, return zero with preemption
+ * disabled. On error, return -ENOMEM with preemption not disabled.
+ */
+int radix_tree_maybe_preload(gfp_t gfp_mask)
+{
+	if (gfpflags_allow_blocking(gfp_mask))
+		return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
+	/* Preloading doesn't help anything with this gfp mask, skip it */
+	local_lock(&radix_tree_preloads.lock);
+	return 0;
+}
+EXPORT_SYMBOL(radix_tree_maybe_preload);
+
+static unsigned radix_tree_load_root(const struct radix_tree_root *root,
+		struct radix_tree_node **nodep, unsigned long *maxindex)
+{
+	struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
+
+	*nodep = node;
+
+	if (likely(radix_tree_is_internal_node(node))) {
+		node = entry_to_node(node);
+		*maxindex = node_maxindex(node);
+		return node->shift + RADIX_TREE_MAP_SHIFT;
+	}
+
+	*maxindex = 0;
+	return 0;
+}
+
+/*
+ *	Extend a radix tree so it can store key @index.
+ */
+static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
+				unsigned long index, unsigned int shift)
+{
+	void *entry;
+	unsigned int maxshift;
+	int tag;
+
+	/* Figure out what the shift should be.  */
+	maxshift = shift;
+	while (index > shift_maxindex(maxshift))
+		maxshift += RADIX_TREE_MAP_SHIFT;
+
+	entry = rcu_dereference_raw(root->xa_head);
+	if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE)))
+		goto out;
+
+	do {
+		struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
+							root, shift, 0, 1, 0);
+		if (!node)
+			return -ENOMEM;
+
+		if (is_idr(root)) {
+			all_tag_set(node, IDR_FREE);
+			if (!root_tag_get(root, IDR_FREE)) {
+				tag_clear(node, IDR_FREE, 0);
+				root_tag_set(root, IDR_FREE);
+			}
+		} else {
+			/* Propagate the aggregated tag info to the new child */
+			for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
+				if (root_tag_get(root, tag))
+					tag_set(node, tag, 0);
+			}
+		}
+
+		BUG_ON(shift > BITS_PER_LONG);
+		if (radix_tree_is_internal_node(entry)) {
+			entry_to_node(entry)->parent = node;
+		} else if (xa_is_value(entry)) {
+			/* Moving a value entry root->xa_head to a node */
+			node->nr_values = 1;
+		}
+		/*
+		 * entry was already in the radix tree, so we do not need
+		 * rcu_assign_pointer here
+		 */
+		node->slots[0] = (void __rcu *)entry;
+		entry = node_to_entry(node);
+		rcu_assign_pointer(root->xa_head, entry);
+		shift += RADIX_TREE_MAP_SHIFT;
+	} while (shift <= maxshift);
+out:
+	return maxshift + RADIX_TREE_MAP_SHIFT;
+}
+
+/**
+ *	radix_tree_shrink    -    shrink radix tree to minimum height
+ *	@root		radix tree root
+ */
+static inline bool radix_tree_shrink(struct radix_tree_root *root)
+{
+	bool shrunk = false;
+
+	for (;;) {
+		struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
+		struct radix_tree_node *child;
+
+		if (!radix_tree_is_internal_node(node))
+			break;
+		node = entry_to_node(node);
+
+		/*
+		 * The candidate node has more than one child, or its child
+		 * is not at the leftmost slot, we cannot shrink.
+		 */
+		if (node->count != 1)
+			break;
+		child = rcu_dereference_raw(node->slots[0]);
+		if (!child)
+			break;
+
+		/*
+		 * For an IDR, we must not shrink entry 0 into the root in
+		 * case somebody calls idr_replace() with a pointer that
+		 * appears to be an internal entry
+		 */
+		if (!node->shift && is_idr(root))
+			break;
+
+		if (radix_tree_is_internal_node(child))
+			entry_to_node(child)->parent = NULL;
+
+		/*
+		 * 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
+		 * (node->slots[0]), it will be safe to dereference the new
+		 * one (root->xa_head) as far as dependent read barriers go.
+		 */
+		root->xa_head = (void __rcu *)child;
+		if (is_idr(root) && !tag_get(node, IDR_FREE, 0))
+			root_tag_clear(root, IDR_FREE);
+
+		/*
+		 * 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 has 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.
+		 */
+		node->count = 0;
+		if (!radix_tree_is_internal_node(child)) {
+			node->slots[0] = (void __rcu *)RADIX_TREE_RETRY;
+		}
+
+		WARN_ON_ONCE(!list_empty(&node->private_list));
+		radix_tree_node_free(node);
+		shrunk = true;
+	}
+
+	return shrunk;
+}
+
+static bool delete_node(struct radix_tree_root *root,
+			struct radix_tree_node *node)
+{
+	bool deleted = false;
+
+	do {
+		struct radix_tree_node *parent;
+
+		if (node->count) {
+			if (node_to_entry(node) ==
+					rcu_dereference_raw(root->xa_head))
+				deleted |= radix_tree_shrink(root);
+			return deleted;
+		}
+
+		parent = node->parent;
+		if (parent) {
+			parent->slots[node->offset] = NULL;
+			parent->count--;
+		} else {
+			/*
+			 * Shouldn't the tags already have all been cleared
+			 * by the caller?
+			 */
+			if (!is_idr(root))
+				root_tag_clear_all(root);
+			root->xa_head = NULL;
+		}
+
+		WARN_ON_ONCE(!list_empty(&node->private_list));
+		radix_tree_node_free(node);
+		deleted = true;
+
+		node = parent;
+	} while (node);
+
+	return deleted;
+}
+
+/**
+ *	__radix_tree_create	-	create a slot in a radix tree
+ *	@root:		radix tree root
+ *	@index:		index key
+ *	@nodep:		returns node
+ *	@slotp:		returns slot
+ *
+ *	Create, if necessary, and return the node and slot for an item
+ *	at position @index in the radix tree @root.
+ *
+ *	Until there is more than one item in the tree, no nodes are
+ *	allocated and @root->xa_head is used as a direct slot instead of
+ *	pointing to a node, in which case *@nodep will be NULL.
+ *
+ *	Returns -ENOMEM, or 0 for success.
+ */
+static int __radix_tree_create(struct radix_tree_root *root,
+		unsigned long index, struct radix_tree_node **nodep,
+		void __rcu ***slotp)
+{
+	struct radix_tree_node *node = NULL, *child;
+	void __rcu **slot = (void __rcu **)&root->xa_head;
+	unsigned long maxindex;
+	unsigned int shift, offset = 0;
+	unsigned long max = index;
+	gfp_t gfp = root_gfp_mask(root);
+
+	shift = radix_tree_load_root(root, &child, &maxindex);
+
+	/* Make sure the tree is high enough.  */
+	if (max > maxindex) {
+		int error = radix_tree_extend(root, gfp, max, shift);
+		if (error < 0)
+			return error;
+		shift = error;
+		child = rcu_dereference_raw(root->xa_head);
+	}
+
+	while (shift > 0) {
+		shift -= RADIX_TREE_MAP_SHIFT;
+		if (child == NULL) {
+			/* Have to add a child node.  */
+			child = radix_tree_node_alloc(gfp, node, root, shift,
+							offset, 0, 0);
+			if (!child)
+				return -ENOMEM;
+			rcu_assign_pointer(*slot, node_to_entry(child));
+			if (node)
+				node->count++;
+		} else if (!radix_tree_is_internal_node(child))
+			break;
+
+		/* Go a level down */
+		node = entry_to_node(child);
+		offset = radix_tree_descend(node, &child, index);
+		slot = &node->slots[offset];
+	}
+
+	if (nodep)
+		*nodep = node;
+	if (slotp)
+		*slotp = slot;
+	return 0;
+}
+
+/*
+ * Free any nodes below this node.  The tree is presumed to not need
+ * shrinking, and any user data in the tree is presumed to not need a
+ * destructor called on it.  If we need to add a destructor, we can
+ * add that functionality later.  Note that we may not clear tags or
+ * slots from the tree as an RCU walker may still have a pointer into
+ * this subtree.  We could replace the entries with RADIX_TREE_RETRY,
+ * but we'll still have to clear those in rcu_free.
+ */
+static void radix_tree_free_nodes(struct radix_tree_node *node)
+{
+	unsigned offset = 0;
+	struct radix_tree_node *child = entry_to_node(node);
+
+	for (;;) {
+		void *entry = rcu_dereference_raw(child->slots[offset]);
+		if (xa_is_node(entry) && child->shift) {
+			child = entry_to_node(entry);
+			offset = 0;
+			continue;
+		}
+		offset++;
+		while (offset == RADIX_TREE_MAP_SIZE) {
+			struct radix_tree_node *old = child;
+			offset = child->offset + 1;
+			child = child->parent;
+			WARN_ON_ONCE(!list_empty(&old->private_list));
+			radix_tree_node_free(old);
+			if (old == entry_to_node(node))
+				return;
+		}
+	}
+}
+
+static inline int insert_entries(struct radix_tree_node *node,
+		void __rcu **slot, void *item, bool replace)
+{
+	if (*slot)
+		return -EEXIST;
+	rcu_assign_pointer(*slot, item);
+	if (node) {
+		node->count++;
+		if (xa_is_value(item))
+			node->nr_values++;
+	}
+	return 1;
+}
+
+/**
+ *	__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;
+	void __rcu **slot;
+	int error;
+
+	BUG_ON(radix_tree_is_internal_node(item));
+
+	error = __radix_tree_create(root, index, &node, &slot);
+	if (error)
+		return error;
+
+	error = insert_entries(node, slot, item, false);
+	if (error < 0)
+		return error;
+
+	if (node) {
+		unsigned offset = get_slot_offset(node, slot);
+		BUG_ON(tag_get(node, 0, offset));
+		BUG_ON(tag_get(node, 1, offset));
+		BUG_ON(tag_get(node, 2, offset));
+	} else {
+		BUG_ON(root_tags_get(root));
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(radix_tree_insert);
+
+/**
+ *	__radix_tree_lookup	-	lookup an item in a radix tree
+ *	@root:		radix tree root
+ *	@index:		index key
+ *	@nodep:		returns node
+ *	@slotp:		returns slot
+ *
+ *	Lookup and return the item at position @index in the radix
+ *	tree @root.
+ *
+ *	Until there is more than one item in the tree, no nodes are
+ *	allocated and @root->xa_head is used as a direct slot instead of
+ *	pointing to a node, in which case *@nodep will be NULL.
+ */
+void *__radix_tree_lookup(const struct radix_tree_root *root,
+			  unsigned long index, struct radix_tree_node **nodep,
+			  void __rcu ***slotp)
+{
+	struct radix_tree_node *node, *parent;
+	unsigned long maxindex;
+	void __rcu **slot;
+
+ restart:
+	parent = NULL;
+	slot = (void __rcu **)&root->xa_head;
+	radix_tree_load_root(root, &node, &maxindex);
+	if (index > maxindex)
+		return NULL;
+
+	while (radix_tree_is_internal_node(node)) {
+		unsigned offset;
+
+		parent = entry_to_node(node);
+		offset = radix_tree_descend(parent, &node, index);
+		slot = parent->slots + offset;
+		if (node == RADIX_TREE_RETRY)
+			goto restart;
+		if (parent->shift == 0)
+			break;
+	}
+
+	if (nodep)
+		*nodep = parent;
+	if (slotp)
+		*slotp = slot;
+	return 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 __rcu **radix_tree_lookup_slot(const struct radix_tree_root *root,
+				unsigned long index)
+{
+	void __rcu **slot;
+
+	if (!__radix_tree_lookup(root, index, NULL, &slot))
+		return NULL;
+	return slot;
+}
+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(const struct radix_tree_root *root, unsigned long index)
+{
+	return __radix_tree_lookup(root, index, NULL, NULL);
+}
+EXPORT_SYMBOL(radix_tree_lookup);
+
+static void replace_slot(void __rcu **slot, void *item,
+		struct radix_tree_node *node, int count, int values)
+{
+	if (node && (count || values)) {
+		node->count += count;
+		node->nr_values += values;
+	}
+
+	rcu_assign_pointer(*slot, item);
+}
+
+static bool node_tag_get(const struct radix_tree_root *root,
+				const struct radix_tree_node *node,
+				unsigned int tag, unsigned int offset)
+{
+	if (node)
+		return tag_get(node, tag, offset);
+	return root_tag_get(root, tag);
+}
+
+/*
+ * IDR users want to be able to store NULL in the tree, so if the slot isn't
+ * free, don't adjust the count, even if it's transitioning between NULL and
+ * non-NULL.  For the IDA, we mark slots as being IDR_FREE while they still
+ * have empty bits, but it only stores NULL in slots when they're being
+ * deleted.
+ */
+static int calculate_count(struct radix_tree_root *root,
+				struct radix_tree_node *node, void __rcu **slot,
+				void *item, void *old)
+{
+	if (is_idr(root)) {
+		unsigned offset = get_slot_offset(node, slot);
+		bool free = node_tag_get(root, node, IDR_FREE, offset);
+		if (!free)
+			return 0;
+		if (!old)
+			return 1;
+	}
+	return !!item - !!old;
+}
+
+/**
+ * __radix_tree_replace		- replace item in a slot
+ * @root:		radix tree root
+ * @node:		pointer to tree node
+ * @slot:		pointer to slot in @node
+ * @item:		new item to store in the slot.
+ *
+ * For use with __radix_tree_lookup().  Caller must hold tree write locked
+ * across slot lookup and replacement.
+ */
+void __radix_tree_replace(struct radix_tree_root *root,
+			  struct radix_tree_node *node,
+			  void __rcu **slot, void *item)
+{
+	void *old = rcu_dereference_raw(*slot);
+	int values = !!xa_is_value(item) - !!xa_is_value(old);
+	int count = calculate_count(root, node, slot, item, old);
+
+	/*
+	 * This function supports replacing value entries and
+	 * deleting entries, but that needs accounting against the
+	 * node unless the slot is root->xa_head.
+	 */
+	WARN_ON_ONCE(!node && (slot != (void __rcu **)&root->xa_head) &&
+			(count || values));
+	replace_slot(slot, item, node, count, values);
+
+	if (!node)
+		return;
+
+	delete_node(root, node);
+}
+
+/**
+ * radix_tree_replace_slot	- replace item in a slot
+ * @root:	radix tree root
+ * @slot:	pointer to slot
+ * @item:	new item to store in the slot.
+ *
+ * For use with radix_tree_lookup_slot() and
+ * radix_tree_gang_lookup_tag_slot().  Caller must hold tree write locked
+ * across slot lookup and replacement.
+ *
+ * NOTE: This cannot be used to switch between non-entries (empty slots),
+ * regular entries, and value entries, as that requires accounting
+ * inside the radix tree node. When switching from one type of entry or
+ * deleting, use __radix_tree_lookup() and __radix_tree_replace() or
+ * radix_tree_iter_replace().
+ */
+void radix_tree_replace_slot(struct radix_tree_root *root,
+			     void __rcu **slot, void *item)
+{
+	__radix_tree_replace(root, NULL, slot, item);
+}
+EXPORT_SYMBOL(radix_tree_replace_slot);
+
+/**
+ * radix_tree_iter_replace - replace item in a slot
+ * @root:	radix tree root
+ * @slot:	pointer to slot
+ * @item:	new item to store in the slot.
+ *
+ * For use with radix_tree_for_each_slot().
+ * Caller must hold tree write locked.
+ */
+void radix_tree_iter_replace(struct radix_tree_root *root,
+				const struct radix_tree_iter *iter,
+				void __rcu **slot, void *item)
+{
+	__radix_tree_replace(root, iter->node, slot, item);
+}
+
+static void node_tag_set(struct radix_tree_root *root,
+				struct radix_tree_node *node,
+				unsigned int tag, unsigned int offset)
+{
+	while (node) {
+		if (tag_get(node, tag, offset))
+			return;
+		tag_set(node, tag, offset);
+		offset = node->offset;
+		node = node->parent;
+	}
+
+	if (!root_tag_get(root, tag))
+		root_tag_set(root, tag);
+}
+
+/**
+ *	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)
+{
+	struct radix_tree_node *node, *parent;
+	unsigned long maxindex;
+
+	radix_tree_load_root(root, &node, &maxindex);
+	BUG_ON(index > maxindex);
+
+	while (radix_tree_is_internal_node(node)) {
+		unsigned offset;
+
+		parent = entry_to_node(node);
+		offset = radix_tree_descend(parent, &node, index);
+		BUG_ON(!node);
+
+		if (!tag_get(parent, tag, offset))
+			tag_set(parent, tag, offset);
+	}
+
+	/* set the root's tag bit */
+	if (!root_tag_get(root, tag))
+		root_tag_set(root, tag);
+
+	return node;
+}
+EXPORT_SYMBOL(radix_tree_tag_set);
+
+static void node_tag_clear(struct radix_tree_root *root,
+				struct radix_tree_node *node,
+				unsigned int tag, unsigned int offset)
+{
+	while (node) {
+		if (!tag_get(node, tag, offset))
+			return;
+		tag_clear(node, tag, offset);
+		if (any_tag_set(node, tag))
+			return;
+
+		offset = node->offset;
+		node = node->parent;
+	}
+
+	/* clear the root's tag bit */
+	if (root_tag_get(root, tag))
+		root_tag_clear(root, tag);
+}
+
+/**
+ *	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, *parent;
+	unsigned long maxindex;
+	int offset;
+
+	radix_tree_load_root(root, &node, &maxindex);
+	if (index > maxindex)
+		return NULL;
+
+	parent = NULL;
+
+	while (radix_tree_is_internal_node(node)) {
+		parent = entry_to_node(node);
+		offset = radix_tree_descend(parent, &node, index);
+	}
+
+	if (node)
+		node_tag_clear(root, parent, tag, offset);
+
+	return node;
+}
+EXPORT_SYMBOL(radix_tree_tag_clear);
+
+/**
+  * radix_tree_iter_tag_clear - clear a tag on the current iterator entry
+  * @root: radix tree root
+  * @iter: iterator state
+  * @tag: tag to clear
+  */
+void radix_tree_iter_tag_clear(struct radix_tree_root *root,
+			const struct radix_tree_iter *iter, unsigned int tag)
+{
+	node_tag_clear(root, iter->node, tag, iter_offset(iter));
+}
+
+/**
+ * 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(const struct radix_tree_root *root,
+			unsigned long index, unsigned int tag)
+{
+	struct radix_tree_node *node, *parent;
+	unsigned long maxindex;
+
+	if (!root_tag_get(root, tag))
+		return 0;
+
+	radix_tree_load_root(root, &node, &maxindex);
+	if (index > maxindex)
+		return 0;
+
+	while (radix_tree_is_internal_node(node)) {
+		unsigned offset;
+
+		parent = entry_to_node(node);
+		offset = radix_tree_descend(parent, &node, index);
+
+		if (!tag_get(parent, tag, offset))
+			return 0;
+		if (node == RADIX_TREE_RETRY)
+			break;
+	}
+
+	return 1;
+}
+EXPORT_SYMBOL(radix_tree_tag_get);
+
+/* Construct iter->tags bit-mask from node->tags[tag] array */
+static void set_iter_tags(struct radix_tree_iter *iter,
+				struct radix_tree_node *node, unsigned offset,
+				unsigned tag)
+{
+	unsigned tag_long = offset / BITS_PER_LONG;
+	unsigned tag_bit  = offset % BITS_PER_LONG;
+
+	if (!node) {
+		iter->tags = 1;
+		return;
+	}
+
+	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 = __radix_tree_iter_add(iter, BITS_PER_LONG);
+	}
+}
+
+void __rcu **radix_tree_iter_resume(void __rcu **slot,
+					struct radix_tree_iter *iter)
+{
+	iter->index = __radix_tree_iter_add(iter, 1);
+	iter->next_index = iter->index;
+	iter->tags = 0;
+	return NULL;
+}
+EXPORT_SYMBOL(radix_tree_iter_resume);
+
+/**
+ * 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 __rcu **radix_tree_next_chunk(const struct radix_tree_root *root,
+			     struct radix_tree_iter *iter, unsigned flags)
+{
+	unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
+	struct radix_tree_node *node, *child;
+	unsigned long index, offset, maxindex;
+
+	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 switching to the next chunk.
+	 */
+	index = iter->next_index;
+	if (!index && iter->index)
+		return NULL;
+
+ restart:
+	radix_tree_load_root(root, &child, &maxindex);
+	if (index > maxindex)
+		return NULL;
+	if (!child)
+		return NULL;
+
+	if (!radix_tree_is_internal_node(child)) {
+		/* Single-slot tree */
+		iter->index = index;
+		iter->next_index = maxindex + 1;
+		iter->tags = 1;
+		iter->node = NULL;
+		return (void __rcu **)&root->xa_head;
+	}
+
+	do {
+		node = entry_to_node(child);
+		offset = radix_tree_descend(node, &child, index);
+
+		if ((flags & RADIX_TREE_ITER_TAGGED) ?
+				!tag_get(node, tag, offset) : !child) {
+			/* Hole detected */
+			if (flags & RADIX_TREE_ITER_CONTIG)
+				return NULL;
+
+			if (flags & RADIX_TREE_ITER_TAGGED)
+				offset = radix_tree_find_next_bit(node, tag,
+						offset + 1);
+			else
+				while (++offset	< RADIX_TREE_MAP_SIZE) {
+					void *slot = rcu_dereference_raw(
+							node->slots[offset]);
+					if (slot)
+						break;
+				}
+			index &= ~node_maxindex(node);
+			index += offset << node->shift;
+			/* Overflow after ~0UL */
+			if (!index)
+				return NULL;
+			if (offset == RADIX_TREE_MAP_SIZE)
+				goto restart;
+			child = rcu_dereference_raw(node->slots[offset]);
+		}
+
+		if (!child)
+			goto restart;
+		if (child == RADIX_TREE_RETRY)
+			break;
+	} while (node->shift && radix_tree_is_internal_node(child));
+
+	/* Update the iterator state */
+	iter->index = (index &~ node_maxindex(node)) | offset;
+	iter->next_index = (index | node_maxindex(node)) + 1;
+	iter->node = node;
+
+	if (flags & RADIX_TREE_ITER_TAGGED)
+		set_iter_tags(iter, node, offset, tag);
+
+	return node->slots + offset;
+}
+EXPORT_SYMBOL(radix_tree_next_chunk);
+
+/**
+ *	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(const struct radix_tree_root *root, void **results,
+			unsigned long first_index, unsigned int max_items)
+{
+	struct radix_tree_iter iter;
+	void __rcu **slot;
+	unsigned int ret = 0;
+
+	if (unlikely(!max_items))
+		return 0;
+
+	radix_tree_for_each_slot(slot, root, &iter, first_index) {
+		results[ret] = rcu_dereference_raw(*slot);
+		if (!results[ret])
+			continue;
+		if (radix_tree_is_internal_node(results[ret])) {
+			slot = radix_tree_iter_retry(&iter);
+			continue;
+		}
+		if (++ret == max_items)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup);
+
+/**
+ *	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(const struct radix_tree_root *root, void **results,
+		unsigned long first_index, unsigned int max_items,
+		unsigned int tag)
+{
+	struct radix_tree_iter iter;
+	void __rcu **slot;
+	unsigned int ret = 0;
+
+	if (unlikely(!max_items))
+		return 0;
+
+	radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
+		results[ret] = rcu_dereference_raw(*slot);
+		if (!results[ret])
+			continue;
+		if (radix_tree_is_internal_node(results[ret])) {
+			slot = radix_tree_iter_retry(&iter);
+			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(const struct radix_tree_root *root,
+		void __rcu ***results, unsigned long first_index,
+		unsigned int max_items, unsigned int tag)
+{
+	struct radix_tree_iter iter;
+	void __rcu **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);
+
+static bool __radix_tree_delete(struct radix_tree_root *root,
+				struct radix_tree_node *node, void __rcu **slot)
+{
+	void *old = rcu_dereference_raw(*slot);
+	int values = xa_is_value(old) ? -1 : 0;
+	unsigned offset = get_slot_offset(node, slot);
+	int tag;
+
+	if (is_idr(root))
+		node_tag_set(root, node, IDR_FREE, offset);
+	else
+		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
+			node_tag_clear(root, node, tag, offset);
+
+	replace_slot(slot, NULL, node, -1, values);
+	return node && delete_node(root, node);
+}
+
+/**
+ * radix_tree_iter_delete - delete the entry at this iterator position
+ * @root: radix tree root
+ * @iter: iterator state
+ * @slot: pointer to slot
+ *
+ * Delete the entry at the position currently pointed to by the iterator.
+ * This may result in the current node being freed; if it is, the iterator
+ * is advanced so that it will not reference the freed memory.  This
+ * function may be called without any locking if there are no other threads
+ * which can access this tree.
+ */
+void radix_tree_iter_delete(struct radix_tree_root *root,
+				struct radix_tree_iter *iter, void __rcu **slot)
+{
+	if (__radix_tree_delete(root, iter->node, slot))
+		iter->index = iter->next_index;
+}
+EXPORT_SYMBOL(radix_tree_iter_delete);
+
+/**
+ * radix_tree_delete_item - delete an item from a radix tree
+ * @root: radix tree root
+ * @index: index key
+ * @item: expected item
+ *
+ * Remove @item at @index from the radix tree rooted at @root.
+ *
+ * Return: the deleted entry, or %NULL if it was not present
+ * or the entry at the given @index was not @item.
+ */
+void *radix_tree_delete_item(struct radix_tree_root *root,
+			     unsigned long index, void *item)
+{
+	struct radix_tree_node *node = NULL;
+	void __rcu **slot = NULL;
+	void *entry;
+
+	entry = __radix_tree_lookup(root, index, &node, &slot);
+	if (!slot)
+		return NULL;
+	if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,
+						get_slot_offset(node, slot))))
+		return NULL;
+
+	if (item && entry != item)
+		return NULL;
+
+	__radix_tree_delete(root, node, slot);
+
+	return entry;
+}
+EXPORT_SYMBOL(radix_tree_delete_item);
+
+/**
+ * radix_tree_delete - delete an entry from a radix tree
+ * @root: radix tree root
+ * @index: index key
+ *
+ * Remove the entry at @index from the radix tree rooted at @root.
+ *
+ * Return: The deleted entry, or %NULL if it was not present.
+ */
+void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
+{
+	return radix_tree_delete_item(root, index, NULL);
+}
+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(const struct radix_tree_root *root, unsigned int tag)
+{
+	return root_tag_get(root, tag);
+}
+EXPORT_SYMBOL(radix_tree_tagged);
+
+/**
+ * idr_preload - preload for idr_alloc()
+ * @gfp_mask: allocation mask to use for preloading
+ *
+ * Preallocate memory to use for the next call to idr_alloc().  This function
+ * returns with preemption disabled.  It will be enabled by idr_preload_end().
+ */
+void idr_preload(gfp_t gfp_mask)
+{
+	if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
+		local_lock(&radix_tree_preloads.lock);
+}
+EXPORT_SYMBOL(idr_preload);
+
+void __rcu **idr_get_free(struct radix_tree_root *root,
+			      struct radix_tree_iter *iter, gfp_t gfp,
+			      unsigned long max)
+{
+	struct radix_tree_node *node = NULL, *child;
+	void __rcu **slot = (void __rcu **)&root->xa_head;
+	unsigned long maxindex, start = iter->next_index;
+	unsigned int shift, offset = 0;
+
+ grow:
+	shift = radix_tree_load_root(root, &child, &maxindex);
+	if (!radix_tree_tagged(root, IDR_FREE))
+		start = max(start, maxindex + 1);
+	if (start > max)
+		return ERR_PTR(-ENOSPC);
+
+	if (start > maxindex) {
+		int error = radix_tree_extend(root, gfp, start, shift);
+		if (error < 0)
+			return ERR_PTR(error);
+		shift = error;
+		child = rcu_dereference_raw(root->xa_head);
+	}
+	if (start == 0 && shift == 0)
+		shift = RADIX_TREE_MAP_SHIFT;
+
+	while (shift) {
+		shift -= RADIX_TREE_MAP_SHIFT;
+		if (child == NULL) {
+			/* Have to add a child node.  */
+			child = radix_tree_node_alloc(gfp, node, root, shift,
+							offset, 0, 0);
+			if (!child)
+				return ERR_PTR(-ENOMEM);
+			all_tag_set(child, IDR_FREE);
+			rcu_assign_pointer(*slot, node_to_entry(child));
+			if (node)
+				node->count++;
+		} else if (!radix_tree_is_internal_node(child))
+			break;
+
+		node = entry_to_node(child);
+		offset = radix_tree_descend(node, &child, start);
+		if (!tag_get(node, IDR_FREE, offset)) {
+			offset = radix_tree_find_next_bit(node, IDR_FREE,
+							offset + 1);
+			start = next_index(start, node, offset);
+			if (start > max || start == 0)
+				return ERR_PTR(-ENOSPC);
+			while (offset == RADIX_TREE_MAP_SIZE) {
+				offset = node->offset + 1;
+				node = node->parent;
+				if (!node)
+					goto grow;
+				shift = node->shift;
+			}
+			child = rcu_dereference_raw(node->slots[offset]);
+		}
+		slot = &node->slots[offset];
+	}
+
+	iter->index = start;
+	if (node)
+		iter->next_index = 1 + min(max, (start | node_maxindex(node)));
+	else
+		iter->next_index = 1;
+	iter->node = node;
+	set_iter_tags(iter, node, offset, IDR_FREE);
+
+	return slot;
+}
+
+/**
+ * idr_destroy - release all internal memory from an IDR
+ * @idr: idr handle
+ *
+ * After this function is called, the IDR is empty, and may be reused or
+ * the data structure containing it may be freed.
+ *
+ * A typical clean-up sequence for objects stored in an idr tree will use
+ * idr_for_each() to free all objects, if necessary, then idr_destroy() to
+ * free the memory used to keep track of those objects.
+ */
+void idr_destroy(struct idr *idr)
+{
+	struct radix_tree_node *node = rcu_dereference_raw(idr->idr_rt.xa_head);
+	if (radix_tree_is_internal_node(node))
+		radix_tree_free_nodes(node);
+	idr->idr_rt.xa_head = NULL;
+	root_tag_set(&idr->idr_rt, IDR_FREE);
+}
+EXPORT_SYMBOL(idr_destroy);
+
+static void
+radix_tree_node_ctor(void *arg)
+{
+	struct radix_tree_node *node = arg;
+
+	memset(node, 0, sizeof(*node));
+	INIT_LIST_HEAD(&node->private_list);
+}
+
+static int radix_tree_cpu_dead(unsigned int cpu)
+{
+	struct radix_tree_preload *rtp;
+	struct radix_tree_node *node;
+
+	/* Free per-cpu pool of preloaded nodes */
+	rtp = &per_cpu(radix_tree_preloads, cpu);
+	while (rtp->nr) {
+		node = rtp->nodes;
+		rtp->nodes = node->parent;
+		kmem_cache_free(radix_tree_node_cachep, node);
+		rtp->nr--;
+	}
+	return 0;
+}
+
+void __init radix_tree_init(void)
+{
+	int ret;
+
+	BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
+	BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK);
+	BUILD_BUG_ON(XA_CHUNK_SIZE > 255);
+	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);
+	ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
+					NULL, radix_tree_cpu_dead);
+	WARN_ON(ret < 0);
+}