include/linux/radix-tree.h - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (C) 2001 Momchil Velikov
  * Portions Copyright (C) 2001 Christoph Hellwig
  * 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.
  */
 #ifndef _LINUX_RADIX_TREE_H
 #define _LINUX_RADIX_TREE_H

 #include <linux/bitops.h>
 #include <linux/preempt.h>
 #include <linux/types.h>
 #include <linux/bug.h>
 #include <linux/kernel.h>
 #include <linux/rcupdate.h>

 /*
  * An indirect pointer (root->rnode pointing to a radix_tree_node, rather
  * than a data item) is signalled by the low bit set in the root->rnode
  * pointer.
  *
  * In this case root->height is > 0, but the indirect pointer tests are
  * needed for RCU lookups (because root->height is unreliable). The only
  * time callers need worry about this is when doing a lookup_slot under
  * RCU.
  *
  * Indirect pointer in fact is also used to tag the last pointer of a node
  * when it is shrunk, before we rcu free the node. See shrink code for
  * details.
  */
 #define RADIX_TREE_INDIRECT_PTR		1
 /*
  * A common use of the radix tree is to store pointers to struct pages;
  * but shmem/tmpfs needs also to store swap entries in the same tree:
  * those are marked as exceptional entries to distinguish them.
  * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
  */
 #define RADIX_TREE_EXCEPTIONAL_ENTRY	2
 #define RADIX_TREE_EXCEPTIONAL_SHIFT	2

 #define RADIX_DAX_MASK	0xf
 #define RADIX_DAX_SHIFT	4
 #define RADIX_DAX_PTE  (0x4 | RADIX_TREE_EXCEPTIONAL_ENTRY)
 #define RADIX_DAX_PMD  (0x8 | RADIX_TREE_EXCEPTIONAL_ENTRY)
 #define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_MASK)
 #define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
 #define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
 		RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE)))

 static inline int radix_tree_is_indirect_ptr(void *ptr)
 {
 	return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
 }

 /*** radix-tree API starts here ***/

 #define RADIX_TREE_MAX_TAGS 3

 #ifndef RADIX_TREE_MAP_SHIFT
 #define RADIX_TREE_MAP_SHIFT	(CONFIG_BASE_SMALL ? 4 : 6)
 #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)

 #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))

 /* Internally used bits of node->count */
 #define RADIX_TREE_COUNT_SHIFT	(RADIX_TREE_MAP_SHIFT + 1)
 #define RADIX_TREE_COUNT_MASK	((1UL << RADIX_TREE_COUNT_SHIFT) - 1)

 struct radix_tree_node {
 	unsigned char	shift;	/* Bits remaining in each slot */
 	unsigned char	offset;	/* Slot offset in parent */
 	unsigned int	count;
 	union {
 		struct {
 			/* Used when ascending tree */
 			struct radix_tree_node *parent;
 			/* For tree user */
 			void *private_data;
 		};
 		/* Used when freeing node */
 		struct rcu_head	rcu_head;
 	};
 	/* For tree user */
 	struct list_head private_list;
 	void __rcu	*slots[RADIX_TREE_MAP_SIZE];
 	unsigned long	tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
 };

 /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
 struct radix_tree_root {
 	unsigned int		height;
 	gfp_t			gfp_mask;
 	struct radix_tree_node	__rcu *rnode;
 };

 #define RADIX_TREE_INIT(mask)	{					\
 	.height = 0,							\
 	.gfp_mask = (mask),						\
 	.rnode = NULL,							\
 }

 #define RADIX_TREE(name, mask) \
 	struct radix_tree_root name = RADIX_TREE_INIT(mask)

 #define INIT_RADIX_TREE(root, mask)					\
 do {									\
 	(root)->height = 0;						\
 	(root)->gfp_mask = (mask);					\
 	(root)->rnode = NULL;						\
 } while (0)

 static inline bool radix_tree_empty(struct radix_tree_root *root)
 {
 	return root->rnode == NULL;
 }

 /**
  * Radix-tree synchronization
  *
  * The radix-tree API requires that users provide all synchronisation (with
  * specific exceptions, noted below).
  *
  * Synchronization of access to the data items being stored in the tree, and
  * management of their lifetimes must be completely managed by API users.
  *
  * For API usage, in general,
  * - any function _modifying_ the tree or tags (inserting or deleting
  *   items, setting or clearing tags) must exclude other modifications, and
  *   exclude any functions reading the tree.
  * - any function _reading_ the tree or tags (looking up items or tags,
  *   gang lookups) must exclude modifications to the tree, but may occur
  *   concurrently with other readers.
  *
  * The notable exceptions to this rule are the following functions:
  * __radix_tree_lookup
  * radix_tree_lookup
  * radix_tree_lookup_slot
  * radix_tree_tag_get
  * radix_tree_gang_lookup
  * radix_tree_gang_lookup_slot
  * radix_tree_gang_lookup_tag
  * radix_tree_gang_lookup_tag_slot
  * radix_tree_tagged
  *
  * The first 8 functions are able to be called locklessly, using RCU. The
  * caller must ensure calls to these functions are made within rcu_read_lock()
  * regions. Other readers (lock-free or otherwise) and modifications may be
  * running concurrently.
  *
  * It is still required that the caller manage the synchronization and lifetimes
  * of the items. So if RCU lock-free lookups are used, typically this would mean
  * that the items have their own locks, or are amenable to lock-free access; and
  * that the items are freed by RCU (or only freed after having been deleted from
  * the radix tree *and* a synchronize_rcu() grace period).
  *
  * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
  * access to data items when inserting into or looking up from the radix tree)
  *
  * Note that the value returned by radix_tree_tag_get() may not be relied upon
  * if only the RCU read lock is held.  Functions to set/clear tags and to
  * delete nodes running concurrently with it may affect its result such that
  * two consecutive reads in the same locked section may return different
  * values.  If reliability is required, modification functions must also be
  * excluded from concurrency.
  *
  * radix_tree_tagged is able to be called without locking or RCU.
  */

 /**
  * radix_tree_deref_slot	- dereference a slot
  * @pslot:	pointer to slot, returned by radix_tree_lookup_slot
  * Returns:	item that was stored in that slot with any direct pointer flag
  *		removed.
  *
  * For use with radix_tree_lookup_slot().  Caller must hold tree at least read
  * locked across slot lookup and dereference. Not required if write lock is
  * held (ie. items cannot be concurrently inserted).
  *
  * radix_tree_deref_retry must be used to confirm validity of the pointer if
  * only the read lock is held.
  */
 static inline void *radix_tree_deref_slot(void **pslot)
 {
 	return rcu_dereference(*pslot);
 }

 /**
  * radix_tree_deref_slot_protected	- dereference a slot without RCU lock but with tree lock held
  * @pslot:	pointer to slot, returned by radix_tree_lookup_slot
  * Returns:	item that was stored in that slot with any direct pointer flag
  *		removed.
  *
  * Similar to radix_tree_deref_slot but only used during migration when a pages
  * mapping is being moved. The caller does not hold the RCU read lock but it
  * must hold the tree lock to prevent parallel updates.
  */
 static inline void *radix_tree_deref_slot_protected(void **pslot,
 							spinlock_t *treelock)
 {
 	return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
 }

 /**
  * radix_tree_deref_retry	- check radix_tree_deref_slot
  * @arg:	pointer returned by radix_tree_deref_slot
  * Returns:	0 if retry is not required, otherwise retry is required
  *
  * radix_tree_deref_retry must be used with radix_tree_deref_slot.
  */
 static inline int radix_tree_deref_retry(void *arg)
 {
 	return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
 }

 /**
  * radix_tree_exceptional_entry	- radix_tree_deref_slot gave exceptional entry?
  * @arg:	value returned by radix_tree_deref_slot
  * Returns:	0 if well-aligned pointer, non-0 if exceptional entry.
  */
 static inline int radix_tree_exceptional_entry(void *arg)
 {
 	/* Not unlikely because radix_tree_exception often tested first */
 	return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
 }

 /**
  * radix_tree_exception	- radix_tree_deref_slot returned either exception?
  * @arg:	value returned by radix_tree_deref_slot
  * Returns:	0 if well-aligned pointer, non-0 if either kind of exception.
  */
 static inline int radix_tree_exception(void *arg)
 {
 	return unlikely((unsigned long)arg &
 		(RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY));
 }

 /**
  * radix_tree_replace_slot	- replace item in a slot
  * @pslot:	pointer to slot, returned by radix_tree_lookup_slot
  * @item:	new item to store in the slot.
  *
  * For use with radix_tree_lookup_slot().  Caller must hold tree write locked
  * across slot lookup and replacement.
  */
 static inline void radix_tree_replace_slot(void **pslot, void *item)
 {
 	BUG_ON(radix_tree_is_indirect_ptr(item));
 	rcu_assign_pointer(*pslot, item);
 }

 int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 			unsigned order, struct radix_tree_node **nodep,
 			void ***slotp);
 int __radix_tree_insert(struct radix_tree_root *, unsigned long index,
 			unsigned order, void *);
 static inline int radix_tree_insert(struct radix_tree_root *root,
 			unsigned long index, void *entry)
 {
 	return __radix_tree_insert(root, index, 0, entry);
 }
 void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
 			  struct radix_tree_node **nodep, void ***slotp);
 void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
 void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
 bool __radix_tree_delete_node(struct radix_tree_root *root,
 			      struct radix_tree_node *node);
 void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
 void *radix_tree_delete(struct radix_tree_root *, unsigned long);
 unsigned int
 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 			unsigned long first_index, unsigned int max_items);
 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);
 int radix_tree_preload(gfp_t gfp_mask);
 int radix_tree_maybe_preload(gfp_t gfp_mask);
 void radix_tree_init(void);
 void *radix_tree_tag_set(struct radix_tree_root *root,
 			unsigned long index, unsigned int tag);
 void *radix_tree_tag_clear(struct radix_tree_root *root,
 			unsigned long index, unsigned int tag);
 int radix_tree_tag_get(struct radix_tree_root *root,
 			unsigned long index, unsigned int tag);
 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);
 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);
 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 fromtag, unsigned int totag);
 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
 unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item);

 static inline void radix_tree_preload_end(void)
 {
 	preempt_enable();
 }

 /**
  * struct radix_tree_iter - radix tree iterator state
  *
  * @index:	index of current slot
  * @next_index:	one beyond the last index for this chunk
  * @tags:	bit-mask for tag-iterating
  * @shift:	shift for the node that holds our slots
  *
  * This radix tree iterator works in terms of "chunks" of slots.  A chunk is a
  * subinterval of slots contained within one radix tree leaf node.  It is
  * described by a pointer to its first slot and a struct radix_tree_iter
  * which holds the chunk's position in the tree and its size.  For tagged
  * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
  * radix tree tag.
  */
 struct radix_tree_iter {
 	unsigned long	index;
 	unsigned long	next_index;
 	unsigned long	tags;
 #ifdef CONFIG_RADIX_TREE_MULTIORDER
 	unsigned int	shift;
 #endif
 };

 static inline unsigned int iter_shift(struct radix_tree_iter *iter)
 {
 #ifdef CONFIG_RADIX_TREE_MULTIORDER
 	return iter->shift;
 #else
 	return 0;
 #endif
 }

 #define RADIX_TREE_ITER_TAG_MASK	0x00FF	/* tag index in lower byte */
 #define RADIX_TREE_ITER_TAGGED		0x0100	/* lookup tagged slots */
 #define RADIX_TREE_ITER_CONTIG		0x0200	/* stop at first hole */

 /**
  * radix_tree_iter_init - initialize radix tree iterator
  *
  * @iter:	pointer to iterator state
  * @start:	iteration starting index
  * Returns:	NULL
  */
 static __always_inline void **
 radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
 {
 	/*
 	 * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
 	 * in the case of a successful tagged chunk lookup.  If the lookup was
 	 * unsuccessful or non-tagged then nobody cares about ->tags.
 	 *
 	 * Set index to zero to bypass next_index overflow protection.
 	 * See the comment in radix_tree_next_chunk() for details.
 	 */
 	iter->index = 0;
 	iter->next_index = start;
 	return NULL;
 }

 /**
  * 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 there no more left
  *
  * This function looks up the next chunk in the radix tree starting from
  * @iter->next_index.  It returns a pointer to the chunk's first slot.
  * Also it fills @iter with data about chunk: position in the tree (index),
  * its end (next_index), and constructs a bit mask for tagged iterating (tags).
  */
 void **radix_tree_next_chunk(struct radix_tree_root *root,
 			     struct radix_tree_iter *iter, unsigned flags);

 /**
  * radix_tree_iter_retry - retry this chunk of the iteration
  * @iter:	iterator state
  *
  * If we iterate over a tree protected only by the RCU lock, a race
  * against deletion or creation may result in seeing a slot for which
  * radix_tree_deref_retry() returns true.  If so, call this function
  * and continue the iteration.
  */
 static inline __must_check
 void **radix_tree_iter_retry(struct radix_tree_iter *iter)
 {
 	iter->next_index = iter->index;
 	return NULL;
 }

 static inline unsigned long
 __radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
 {
 	return iter->index + (slots << iter_shift(iter));
 }

 /**
  * radix_tree_iter_next - resume iterating when the chunk may be invalid
  * @iter:	iterator state
  *
  * If the iterator needs to release then reacquire a lock, the chunk may
  * have been invalidated by an insertion or deletion.  Call this function
  * to continue the iteration from the next index.
  */
 static inline __must_check
 void **radix_tree_iter_next(struct radix_tree_iter *iter)
 {
 	iter->next_index = __radix_tree_iter_add(iter, 1);
 	iter->tags = 0;
 	return NULL;
 }

 /**
  * radix_tree_chunk_size - get current chunk size
  *
  * @iter:	pointer to radix tree iterator
  * Returns:	current chunk size
  */
 static __always_inline long
 radix_tree_chunk_size(struct radix_tree_iter *iter)
 {
 	return (iter->next_index - iter->index) >> iter_shift(iter);
 }

 static inline void *indirect_to_ptr(void *ptr)
 {
 	return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
 }

 /**
  * radix_tree_next_slot - find next slot in chunk
  *
  * @slot:	pointer to current slot
  * @iter:	pointer to interator state
  * @flags:	RADIX_TREE_ITER_*, should be constant
  * Returns:	pointer to next slot, or NULL if there no more left
  *
  * This function updates @iter->index in the case of a successful lookup.
  * For tagged lookup it also eats @iter->tags.
  */
 static __always_inline void **
 radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags)
 {
 	if (flags & RADIX_TREE_ITER_TAGGED) {
 		void *canon = slot;

 		iter->tags >>= 1;
 		if (unlikely(!iter->tags))
 			return NULL;
 		while (IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
 					radix_tree_is_indirect_ptr(slot[1])) {
 			if (indirect_to_ptr(slot[1]) == canon) {
 				iter->tags >>= 1;
 				iter->index = __radix_tree_iter_add(iter, 1);
 				slot++;
 				continue;
 			}
 			iter->next_index = __radix_tree_iter_add(iter, 1);
 			return NULL;
 		}
 		if (likely(iter->tags & 1ul)) {
 			iter->index = __radix_tree_iter_add(iter, 1);
 			return slot + 1;
 		}
 		if (!(flags & RADIX_TREE_ITER_CONTIG)) {
 			unsigned offset = __ffs(iter->tags);

 			iter->tags >>= offset;
 			iter->index = __radix_tree_iter_add(iter, offset + 1);
 			return slot + offset + 1;
 		}
 	} else {
 		long count = radix_tree_chunk_size(iter);
 		void *canon = slot;

 		while (--count > 0) {
 			slot++;
 			iter->index = __radix_tree_iter_add(iter, 1);

 			if (IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
 			    radix_tree_is_indirect_ptr(*slot)) {
 				if (indirect_to_ptr(*slot) == canon)
 					continue;
 				else {
 					iter->next_index = iter->index;
 					break;
 				}
 			}

 			if (likely(*slot))
 				return slot;
 			if (flags & RADIX_TREE_ITER_CONTIG) {
 				/* forbid switching to the next chunk */
 				iter->next_index = 0;
 				break;
 			}
 		}
 	}
 	return NULL;
 }

 /**
  * radix_tree_for_each_slot - iterate over non-empty slots
  *
  * @slot:	the void** variable for pointer to slot
  * @root:	the struct radix_tree_root pointer
  * @iter:	the struct radix_tree_iter pointer
  * @start:	iteration starting index
  *
  * @slot points to radix tree slot, @iter->index contains its index.
  */
 #define radix_tree_for_each_slot(slot, root, iter, start)		\
 	for (slot = radix_tree_iter_init(iter, start) ;			\
 	     slot || (slot = radix_tree_next_chunk(root, iter, 0)) ;	\
 	     slot = radix_tree_next_slot(slot, iter, 0))

 /**
  * radix_tree_for_each_contig - iterate over contiguous slots
  *
  * @slot:	the void** variable for pointer to slot
  * @root:	the struct radix_tree_root pointer
  * @iter:	the struct radix_tree_iter pointer
  * @start:	iteration starting index
  *
  * @slot points to radix tree slot, @iter->index contains its index.
  */
 #define radix_tree_for_each_contig(slot, root, iter, start)		\
 	for (slot = radix_tree_iter_init(iter, start) ;			\
 	     slot || (slot = radix_tree_next_chunk(root, iter,		\
 				RADIX_TREE_ITER_CONTIG)) ;		\
 	     slot = radix_tree_next_slot(slot, iter,			\
 				RADIX_TREE_ITER_CONTIG))

 /**
  * radix_tree_for_each_tagged - iterate over tagged slots
  *
  * @slot:	the void** variable for pointer to slot
  * @root:	the struct radix_tree_root pointer
  * @iter:	the struct radix_tree_iter pointer
  * @start:	iteration starting index
  * @tag:	tag index
  *
  * @slot points to radix tree slot, @iter->index contains its index.
  */
 #define radix_tree_for_each_tagged(slot, root, iter, start, tag)	\
 	for (slot = radix_tree_iter_init(iter, start) ;			\
 	     slot || (slot = radix_tree_next_chunk(root, iter,		\
 			      RADIX_TREE_ITER_TAGGED | tag)) ;		\
 	     slot = radix_tree_next_slot(slot, iter,			\
 				RADIX_TREE_ITER_TAGGED))

 #endif /* _LINUX_RADIX_TREE_H */
	/*
	* Copyright (C) 2001 Momchil Velikov
	* Portions Copyright (C) 2001 Christoph Hellwig
	* 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.
	*/
	#ifndef _LINUX_RADIX_TREE_H
	#define _LINUX_RADIX_TREE_H

	#include <linux/bitops.h>
	#include <linux/preempt.h>
	#include <linux/types.h>
	#include <linux/bug.h>
	#include <linux/kernel.h>
	#include <linux/rcupdate.h>

	/*
	* An indirect pointer (root->rnode pointing to a radix_tree_node, rather
	* than a data item) is signalled by the low bit set in the root->rnode
	* pointer.
	*
	* In this case root->height is > 0, but the indirect pointer tests are
	* needed for RCU lookups (because root->height is unreliable). The only
	* time callers need worry about this is when doing a lookup_slot under
	* RCU.
	*
	* Indirect pointer in fact is also used to tag the last pointer of a node
	* when it is shrunk, before we rcu free the node. See shrink code for
	* details.
	*/
	#define RADIX_TREE_INDIRECT_PTR 1
	/*
	* A common use of the radix tree is to store pointers to struct pages;
	* but shmem/tmpfs needs also to store swap entries in the same tree:
	* those are marked as exceptional entries to distinguish them.
	* EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
	*/
	#define RADIX_TREE_EXCEPTIONAL_ENTRY 2
	#define RADIX_TREE_EXCEPTIONAL_SHIFT 2

	#define RADIX_DAX_MASK 0xf
	#define RADIX_DAX_SHIFT 4
	#define RADIX_DAX_PTE (0x4 \| RADIX_TREE_EXCEPTIONAL_ENTRY)
	#define RADIX_DAX_PMD (0x8 \| RADIX_TREE_EXCEPTIONAL_ENTRY)
	#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_MASK)
	#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
	#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
	RADIX_DAX_SHIFT \| (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE)))

	static inline int radix_tree_is_indirect_ptr(void *ptr)
	{
	return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
	}

	/* radix-tree API starts here */

	#define RADIX_TREE_MAX_TAGS 3

	#ifndef RADIX_TREE_MAP_SHIFT
	#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
	#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)

	#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))

	/* Internally used bits of node->count */
	#define RADIX_TREE_COUNT_SHIFT (RADIX_TREE_MAP_SHIFT + 1)
	#define RADIX_TREE_COUNT_MASK ((1UL << RADIX_TREE_COUNT_SHIFT) - 1)

	struct radix_tree_node {
	unsigned char shift; /* Bits remaining in each slot */
	unsigned char offset; /* Slot offset in parent */
	unsigned int count;
	union {
	struct {
	/* Used when ascending tree */
	struct radix_tree_node *parent;
	/* For tree user */
	void *private_data;
	};
	/* Used when freeing node */
	struct rcu_head rcu_head;
	};
	/* For tree user */
	struct list_head private_list;
	void __rcu *slots[RADIX_TREE_MAP_SIZE];
	unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
	};

	/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
	struct radix_tree_root {
	unsigned int height;
	gfp_t gfp_mask;
	struct radix_tree_node __rcu *rnode;
	};

	#define RADIX_TREE_INIT(mask) { \
	.height = 0, \
	.gfp_mask = (mask), \
	.rnode = NULL, \
	}

	#define RADIX_TREE(name, mask) \
	struct radix_tree_root name = RADIX_TREE_INIT(mask)

	#define INIT_RADIX_TREE(root, mask) \
	do { \
	(root)->height = 0; \
	(root)->gfp_mask = (mask); \
	(root)->rnode = NULL; \
	} while (0)

	static inline bool radix_tree_empty(struct radix_tree_root *root)
	{
	return root->rnode == NULL;
	}

	/**
	* Radix-tree synchronization
	*
	* The radix-tree API requires that users provide all synchronisation (with
	* specific exceptions, noted below).
	*
	* Synchronization of access to the data items being stored in the tree, and
	* management of their lifetimes must be completely managed by API users.
	*
	* For API usage, in general,
	* - any function _modifying_ the tree or tags (inserting or deleting
	* items, setting or clearing tags) must exclude other modifications, and
	* exclude any functions reading the tree.
	* - any function _reading_ the tree or tags (looking up items or tags,
	* gang lookups) must exclude modifications to the tree, but may occur
	* concurrently with other readers.
	*
	* The notable exceptions to this rule are the following functions:
	* __radix_tree_lookup
	* radix_tree_lookup
	* radix_tree_lookup_slot
	* radix_tree_tag_get
	* radix_tree_gang_lookup
	* radix_tree_gang_lookup_slot
	* radix_tree_gang_lookup_tag
	* radix_tree_gang_lookup_tag_slot
	* radix_tree_tagged
	*
	* The first 8 functions are able to be called locklessly, using RCU. The
	* caller must ensure calls to these functions are made within rcu_read_lock()
	* regions. Other readers (lock-free or otherwise) and modifications may be
	* running concurrently.
	*
	* It is still required that the caller manage the synchronization and lifetimes
	* of the items. So if RCU lock-free lookups are used, typically this would mean
	* that the items have their own locks, or are amenable to lock-free access; and
	* that the items are freed by RCU (or only freed after having been deleted from
	* the radix tree and a synchronize_rcu() grace period).
	*
	* (Note, rcu_assign_pointer and rcu_dereference are not needed to control
	* access to data items when inserting into or looking up from the radix tree)
	*
	* Note that the value returned by radix_tree_tag_get() may not be relied upon
	* if only the RCU read lock is held. Functions to set/clear tags and to
	* delete nodes running concurrently with it may affect its result such that
	* two consecutive reads in the same locked section may return different
	* values. If reliability is required, modification functions must also be
	* excluded from concurrency.
	*
	* radix_tree_tagged is able to be called without locking or RCU.
	*/

	/**
	* radix_tree_deref_slot - dereference a slot
	* @pslot: pointer to slot, returned by radix_tree_lookup_slot
	* Returns: item that was stored in that slot with any direct pointer flag
	* removed.
	*
	* For use with radix_tree_lookup_slot(). Caller must hold tree at least read
	* locked across slot lookup and dereference. Not required if write lock is
	* held (ie. items cannot be concurrently inserted).
	*
	* radix_tree_deref_retry must be used to confirm validity of the pointer if
	* only the read lock is held.
	*/
	static inline void radix_tree_deref_slot(void *pslot)
	{
	return rcu_dereference(*pslot);
	}

	/**
	* radix_tree_deref_slot_protected - dereference a slot without RCU lock but with tree lock held
	* @pslot: pointer to slot, returned by radix_tree_lookup_slot
	* Returns: item that was stored in that slot with any direct pointer flag
	* removed.
	*
	* Similar to radix_tree_deref_slot but only used during migration when a pages
	* mapping is being moved. The caller does not hold the RCU read lock but it
	* must hold the tree lock to prevent parallel updates.
	*/
	static inline void radix_tree_deref_slot_protected(void *pslot,
	spinlock_t *treelock)
	{
	return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
	}

	/**
	* radix_tree_deref_retry - check radix_tree_deref_slot
	* @arg: pointer returned by radix_tree_deref_slot
	* Returns: 0 if retry is not required, otherwise retry is required
	*
	* radix_tree_deref_retry must be used with radix_tree_deref_slot.
	*/
	static inline int radix_tree_deref_retry(void *arg)
	{
	return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
	}

	/**
	* radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry?
	* @arg: value returned by radix_tree_deref_slot
	* Returns: 0 if well-aligned pointer, non-0 if exceptional entry.
	*/
	static inline int radix_tree_exceptional_entry(void *arg)
	{
	/* Not unlikely because radix_tree_exception often tested first */
	return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
	}

	/**
	* radix_tree_exception - radix_tree_deref_slot returned either exception?
	* @arg: value returned by radix_tree_deref_slot
	* Returns: 0 if well-aligned pointer, non-0 if either kind of exception.
	*/
	static inline int radix_tree_exception(void *arg)
	{
	return unlikely((unsigned long)arg &
	(RADIX_TREE_INDIRECT_PTR \| RADIX_TREE_EXCEPTIONAL_ENTRY));
	}

	/**
	* radix_tree_replace_slot - replace item in a slot
	* @pslot: pointer to slot, returned by radix_tree_lookup_slot
	* @item: new item to store in the slot.
	*
	* For use with radix_tree_lookup_slot(). Caller must hold tree write locked
	* across slot lookup and replacement.
	*/
	static inline void radix_tree_replace_slot(void *pslot, void item)
	{
	BUG_ON(radix_tree_is_indirect_ptr(item));
	rcu_assign_pointer(*pslot, item);
	}

	int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
	unsigned order, struct radix_tree_node **nodep,
	void ***slotp);
	int __radix_tree_insert(struct radix_tree_root *, unsigned long index,
	unsigned order, void *);
	static inline int radix_tree_insert(struct radix_tree_root *root,
	unsigned long index, void *entry)
	{
	return __radix_tree_insert(root, index, 0, entry);
	}
	void __radix_tree_lookup(struct radix_tree_root root, unsigned long index,
	struct radix_tree_node nodep, void *slotp);
	void radix_tree_lookup(struct radix_tree_root , unsigned long);
	void *radix_tree_lookup_slot(struct radix_tree_root , unsigned long);
	bool __radix_tree_delete_node(struct radix_tree_root *root,
	struct radix_tree_node *node);
	void radix_tree_delete_item(struct radix_tree_root , unsigned long, void *);
	void radix_tree_delete(struct radix_tree_root , unsigned long);
	unsigned int
	radix_tree_gang_lookup(struct radix_tree_root root, void *results,
	unsigned long first_index, unsigned int max_items);
	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);
	int radix_tree_preload(gfp_t gfp_mask);
	int radix_tree_maybe_preload(gfp_t gfp_mask);
	void radix_tree_init(void);
	void radix_tree_tag_set(struct radix_tree_root root,
	unsigned long index, unsigned int tag);
	void radix_tree_tag_clear(struct radix_tree_root root,
	unsigned long index, unsigned int tag);
	int radix_tree_tag_get(struct radix_tree_root *root,
	unsigned long index, unsigned int tag);
	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);
	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);
	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 fromtag, unsigned int totag);
	int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
	unsigned long radix_tree_locate_item(struct radix_tree_root root, void item);

	static inline void radix_tree_preload_end(void)
	{
	preempt_enable();
	}

	/**
	* struct radix_tree_iter - radix tree iterator state
	*
	* @index: index of current slot
	* @next_index: one beyond the last index for this chunk
	* @tags: bit-mask for tag-iterating
	* @shift: shift for the node that holds our slots
	*
	* This radix tree iterator works in terms of "chunks" of slots. A chunk is a
	* subinterval of slots contained within one radix tree leaf node. It is
	* described by a pointer to its first slot and a struct radix_tree_iter
	* which holds the chunk's position in the tree and its size. For tagged
	* iteration radix_tree_iter also holds the slots' bit-mask for one chosen
	* radix tree tag.
	*/
	struct radix_tree_iter {
	unsigned long index;
	unsigned long next_index;
	unsigned long tags;
	#ifdef CONFIG_RADIX_TREE_MULTIORDER
	unsigned int shift;
	#endif
	};

	static inline unsigned int iter_shift(struct radix_tree_iter *iter)
	{
	#ifdef CONFIG_RADIX_TREE_MULTIORDER
	return iter->shift;
	#else
	return 0;
	#endif
	}

	#define RADIX_TREE_ITER_TAG_MASK 0x00FF /* tag index in lower byte */
	#define RADIX_TREE_ITER_TAGGED 0x0100 /* lookup tagged slots */
	#define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */

	/**
	* radix_tree_iter_init - initialize radix tree iterator
	*
	* @iter: pointer to iterator state
	* @start: iteration starting index
	* Returns: NULL
	*/
	static __always_inline void **
	radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
	{
	/*
	* Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
	* in the case of a successful tagged chunk lookup. If the lookup was
	* unsuccessful or non-tagged then nobody cares about ->tags.
	*
	* Set index to zero to bypass next_index overflow protection.
	* See the comment in radix_tree_next_chunk() for details.
	*/
	iter->index = 0;
	iter->next_index = start;
	return NULL;
	}

	/**
	* 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 there no more left
	*
	* This function looks up the next chunk in the radix tree starting from
	* @iter->next_index. It returns a pointer to the chunk's first slot.
	* Also it fills @iter with data about chunk: position in the tree (index),
	* its end (next_index), and constructs a bit mask for tagged iterating (tags).
	*/
	void *radix_tree_next_chunk(struct radix_tree_root root,
	struct radix_tree_iter *iter, unsigned flags);

	/**
	* radix_tree_iter_retry - retry this chunk of the iteration
	* @iter: iterator state
	*
	* If we iterate over a tree protected only by the RCU lock, a race
	* against deletion or creation may result in seeing a slot for which
	* radix_tree_deref_retry() returns true. If so, call this function
	* and continue the iteration.
	*/
	static inline __must_check
	void *radix_tree_iter_retry(struct radix_tree_iter iter)
	{
	iter->next_index = iter->index;
	return NULL;
	}

	static inline unsigned long
	__radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
	{
	return iter->index + (slots << iter_shift(iter));
	}

	/**
	* radix_tree_iter_next - resume iterating when the chunk may be invalid
	* @iter: iterator state
	*
	* If the iterator needs to release then reacquire a lock, the chunk may
	* have been invalidated by an insertion or deletion. Call this function
	* to continue the iteration from the next index.
	*/
	static inline __must_check
	void *radix_tree_iter_next(struct radix_tree_iter iter)
	{
	iter->next_index = __radix_tree_iter_add(iter, 1);
	iter->tags = 0;
	return NULL;
	}

	/**
	* radix_tree_chunk_size - get current chunk size
	*
	* @iter: pointer to radix tree iterator
	* Returns: current chunk size
	*/
	static __always_inline long
	radix_tree_chunk_size(struct radix_tree_iter *iter)
	{
	return (iter->next_index - iter->index) >> iter_shift(iter);
	}

	static inline void indirect_to_ptr(void ptr)
	{
	return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
	}

	/**
	* radix_tree_next_slot - find next slot in chunk
	*
	* @slot: pointer to current slot
	* @iter: pointer to interator state
	* @flags: RADIX_TREE_ITER_*, should be constant
	* Returns: pointer to next slot, or NULL if there no more left
	*
	* This function updates @iter->index in the case of a successful lookup.
	* For tagged lookup it also eats @iter->tags.
	*/
	static __always_inline void **
	radix_tree_next_slot(void *slot, struct radix_tree_iter iter, unsigned flags)
	{
	if (flags & RADIX_TREE_ITER_TAGGED) {
	void *canon = slot;

	iter->tags >>= 1;
	if (unlikely(!iter->tags))
	return NULL;
	while (IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
	radix_tree_is_indirect_ptr(slot[1])) {
	if (indirect_to_ptr(slot[1]) == canon) {
	iter->tags >>= 1;
	iter->index = __radix_tree_iter_add(iter, 1);
	slot++;
	continue;
	}
	iter->next_index = __radix_tree_iter_add(iter, 1);
	return NULL;
	}
	if (likely(iter->tags & 1ul)) {
	iter->index = __radix_tree_iter_add(iter, 1);
	return slot + 1;
	}
	if (!(flags & RADIX_TREE_ITER_CONTIG)) {
	unsigned offset = __ffs(iter->tags);

	iter->tags >>= offset;
	iter->index = __radix_tree_iter_add(iter, offset + 1);
	return slot + offset + 1;
	}
	} else {
	long count = radix_tree_chunk_size(iter);
	void *canon = slot;

	while (--count > 0) {
	slot++;
	iter->index = __radix_tree_iter_add(iter, 1);

	if (IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
	radix_tree_is_indirect_ptr(*slot)) {
	if (indirect_to_ptr(*slot) == canon)
	continue;
	else {
	iter->next_index = iter->index;
	break;
	}
	}

	if (likely(*slot))
	return slot;
	if (flags & RADIX_TREE_ITER_CONTIG) {
	/* forbid switching to the next chunk */
	iter->next_index = 0;
	break;
	}
	}
	}
	return NULL;
	}

	/**
	* radix_tree_for_each_slot - iterate over non-empty slots
	*
	* @slot: the void** variable for pointer to slot
	* @root: the struct radix_tree_root pointer
	* @iter: the struct radix_tree_iter pointer
	* @start: iteration starting index
	*
	* @slot points to radix tree slot, @iter->index contains its index.
	*/
	#define radix_tree_for_each_slot(slot, root, iter, start) \
	for (slot = radix_tree_iter_init(iter, start) ; \
	slot \|\| (slot = radix_tree_next_chunk(root, iter, 0)) ; \
	slot = radix_tree_next_slot(slot, iter, 0))

	/**
	* radix_tree_for_each_contig - iterate over contiguous slots
	*
	* @slot: the void** variable for pointer to slot
	* @root: the struct radix_tree_root pointer
	* @iter: the struct radix_tree_iter pointer
	* @start: iteration starting index
	*
	* @slot points to radix tree slot, @iter->index contains its index.
	*/
	#define radix_tree_for_each_contig(slot, root, iter, start) \
	for (slot = radix_tree_iter_init(iter, start) ; \
	slot \|\| (slot = radix_tree_next_chunk(root, iter, \
	RADIX_TREE_ITER_CONTIG)) ; \
	slot = radix_tree_next_slot(slot, iter, \
	RADIX_TREE_ITER_CONTIG))

	/**
	* radix_tree_for_each_tagged - iterate over tagged slots
	*
	* @slot: the void** variable for pointer to slot
	* @root: the struct radix_tree_root pointer
	* @iter: the struct radix_tree_iter pointer
	* @start: iteration starting index
	* @tag: tag index
	*
	* @slot points to radix tree slot, @iter->index contains its index.
	*/
	#define radix_tree_for_each_tagged(slot, root, iter, start, tag) \
	for (slot = radix_tree_iter_init(iter, start) ; \
	slot \|\| (slot = radix_tree_next_chunk(root, iter, \
	RADIX_TREE_ITER_TAGGED \| tag)) ; \
	slot = radix_tree_next_slot(slot, iter, \
	RADIX_TREE_ITER_TAGGED))

	#endif /* _LINUX_RADIX_TREE_H */