[linux-block.git] / include / linux / generic-radix-tree.h

#ifndef _LINUX_GENERIC_RADIX_TREE_H
#define _LINUX_GENERIC_RADIX_TREE_H

/**
 * DOC: Generic radix trees/sparse arrays
 *
 * Very simple and minimalistic, supporting arbitrary size entries up to
 * GENRADIX_NODE_SIZE.
 *
 * A genradix is defined with the type it will store, like so:
 *
 * static GENRADIX(struct foo) foo_genradix;
 *
 * The main operations are:
 *
 * - genradix_init(radix) - initialize an empty genradix
 *
 * - genradix_free(radix) - free all memory owned by the genradix and
 *   reinitialize it
 *
 * - genradix_ptr(radix, idx) - gets a pointer to the entry at idx, returning
 *   NULL if that entry does not exist
 *
 * - genradix_ptr_alloc(radix, idx, gfp) - gets a pointer to an entry,
 *   allocating it if necessary
 *
 * - genradix_for_each(radix, iter, p) - iterate over each entry in a genradix
 *
 * The radix tree allocates one page of entries at a time, so entries may exist
 * that were never explicitly allocated - they will be initialized to all
 * zeroes.
 *
 * Internally, a genradix is just a radix tree of pages, and indexing works in
 * terms of byte offsets. The wrappers in this header file use sizeof on the
 * type the radix contains to calculate a byte offset from the index - see
 * __idx_to_offset.
 */

#include <asm/page.h>
#include <linux/bug.h>
#include <linux/limits.h>
#include <linux/log2.h>
#include <linux/math.h>
#include <linux/slab.h>
#include <linux/types.h>

struct genradix_root;

#define GENRADIX_NODE_SHIFT	9
#define GENRADIX_NODE_SIZE	(1U << GENRADIX_NODE_SHIFT)

#define GENRADIX_ARY		(GENRADIX_NODE_SIZE / sizeof(struct genradix_node *))
#define GENRADIX_ARY_SHIFT	ilog2(GENRADIX_ARY)

/* depth that's needed for a genradix that can address up to ULONG_MAX: */
#define GENRADIX_MAX_DEPTH	\
	DIV_ROUND_UP(BITS_PER_LONG - GENRADIX_NODE_SHIFT, GENRADIX_ARY_SHIFT)

#define GENRADIX_DEPTH_MASK				\
	((unsigned long) (roundup_pow_of_two(GENRADIX_MAX_DEPTH + 1) - 1))

static inline int genradix_depth_shift(unsigned depth)
{
	return GENRADIX_NODE_SHIFT + GENRADIX_ARY_SHIFT * depth;
}

/*
 * Returns size (of data, in bytes) that a tree of a given depth holds:
 */
static inline size_t genradix_depth_size(unsigned depth)
{
	return 1UL << genradix_depth_shift(depth);
}

static inline unsigned genradix_root_to_depth(struct genradix_root *r)
{
	return (unsigned long) r & GENRADIX_DEPTH_MASK;
}

static inline struct genradix_node *genradix_root_to_node(struct genradix_root *r)
{
	return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
}

struct __genradix {
	struct genradix_root		*root;
};

struct genradix_node {
	union {
		/* Interior node: */
		struct genradix_node	*children[GENRADIX_ARY];

		/* Leaf: */
		u8			data[GENRADIX_NODE_SIZE];
	};
};

static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
{
	return kzalloc(GENRADIX_NODE_SIZE, gfp_mask);
}

static inline void genradix_free_node(struct genradix_node *node)
{
	kfree(node);
}

/*
 * NOTE: currently, sizeof(_type) must not be larger than GENRADIX_NODE_SIZE:
 */

#define __GENRADIX_INITIALIZER					\
	{							\
		.tree = {					\
			.root = NULL,				\
		}						\
	}

/*
 * We use a 0 size array to stash the type we're storing without taking any
 * space at runtime - then the various accessor macros can use typeof() to get
 * to it for casts/sizeof - we also force the alignment so that storing a type
 * with a ridiculous alignment doesn't blow up the alignment or size of the
 * genradix.
 */

#define GENRADIX(_type)						\
struct {							\
	struct __genradix	tree;				\
	_type			type[0] __aligned(1);		\
}

#define DEFINE_GENRADIX(_name, _type)				\
	GENRADIX(_type) _name = __GENRADIX_INITIALIZER

/**
 * genradix_init - initialize a genradix
 * @_radix:	genradix to initialize
 *
 * Does not fail
 */
#define genradix_init(_radix)					\
do {								\
	*(_radix) = (typeof(*_radix)) __GENRADIX_INITIALIZER;	\
} while (0)

void __genradix_free(struct __genradix *);

/**
 * genradix_free: free all memory owned by a genradix
 * @_radix: the genradix to free
 *
 * After freeing, @_radix will be reinitialized and empty
 */
#define genradix_free(_radix)	__genradix_free(&(_radix)->tree)

static inline size_t __idx_to_offset(size_t idx, size_t obj_size)
{
	if (__builtin_constant_p(obj_size))
		BUILD_BUG_ON(obj_size > GENRADIX_NODE_SIZE);
	else
		BUG_ON(obj_size > GENRADIX_NODE_SIZE);

	if (!is_power_of_2(obj_size)) {
		size_t objs_per_page = GENRADIX_NODE_SIZE / obj_size;

		return (idx / objs_per_page) * GENRADIX_NODE_SIZE +
			(idx % objs_per_page) * obj_size;
	} else {
		return idx * obj_size;
	}
}

#define __genradix_cast(_radix)		(typeof((_radix)->type[0]) *)
#define __genradix_obj_size(_radix)	sizeof((_radix)->type[0])
#define __genradix_objs_per_page(_radix)			\
	(GENRADIX_NODE_SIZE / sizeof((_radix)->type[0]))
#define __genradix_page_remainder(_radix)			\
	(GENRADIX_NODE_SIZE % sizeof((_radix)->type[0]))

#define __genradix_idx_to_offset(_radix, _idx)			\
	__idx_to_offset(_idx, __genradix_obj_size(_radix))

static inline void *__genradix_ptr_inlined(struct __genradix *radix, size_t offset)
{
	struct genradix_root *r = READ_ONCE(radix->root);
	struct genradix_node *n = genradix_root_to_node(r);
	unsigned level		= genradix_root_to_depth(r);
	unsigned shift		= genradix_depth_shift(level);

	if (unlikely(ilog2(offset) >= genradix_depth_shift(level)))
		return NULL;

	while (n && shift > GENRADIX_NODE_SHIFT) {
		shift -= GENRADIX_ARY_SHIFT;
		n = n->children[offset >> shift];
		offset &= (1UL << shift) - 1;
	}

	return n ? &n->data[offset] : NULL;
}

#define genradix_ptr_inlined(_radix, _idx)			\
	(__genradix_cast(_radix)				\
	 __genradix_ptr_inlined(&(_radix)->tree,		\
			__genradix_idx_to_offset(_radix, _idx)))

void *__genradix_ptr(struct __genradix *, size_t);

/**
 * genradix_ptr - get a pointer to a genradix entry
 * @_radix:	genradix to access
 * @_idx:	index to fetch
 *
 * Returns a pointer to entry at @_idx, or NULL if that entry does not exist.
 */
#define genradix_ptr(_radix, _idx)				\
	(__genradix_cast(_radix)				\
	 __genradix_ptr(&(_radix)->tree,			\
			__genradix_idx_to_offset(_radix, _idx)))

void *__genradix_ptr_alloc(struct __genradix *, size_t,
			   struct genradix_node **, gfp_t);

#define genradix_ptr_alloc_inlined(_radix, _idx, _gfp)			\
	(__genradix_cast(_radix)					\
	 (__genradix_ptr_inlined(&(_radix)->tree,			\
			__genradix_idx_to_offset(_radix, _idx)) ?:	\
	  __genradix_ptr_alloc(&(_radix)->tree,				\
			__genradix_idx_to_offset(_radix, _idx),		\
			NULL, _gfp)))

#define genradix_ptr_alloc_preallocated_inlined(_radix, _idx, _new_node, _gfp)\
	(__genradix_cast(_radix)					\
	 (__genradix_ptr_inlined(&(_radix)->tree,			\
			__genradix_idx_to_offset(_radix, _idx)) ?:	\
	  __genradix_ptr_alloc(&(_radix)->tree,				\
			__genradix_idx_to_offset(_radix, _idx),		\
			_new_node, _gfp)))

/**
 * genradix_ptr_alloc - get a pointer to a genradix entry, allocating it
 *			if necessary
 * @_radix:	genradix to access
 * @_idx:	index to fetch
 * @_gfp:	gfp mask
 *
 * Returns a pointer to entry at @_idx, or NULL on allocation failure
 */
#define genradix_ptr_alloc(_radix, _idx, _gfp)			\
	(__genradix_cast(_radix)				\
	 __genradix_ptr_alloc(&(_radix)->tree,			\
			__genradix_idx_to_offset(_radix, _idx),	\
			NULL, _gfp))

#define genradix_ptr_alloc_preallocated(_radix, _idx, _new_node, _gfp)\
	(__genradix_cast(_radix)				\
	 __genradix_ptr_alloc(&(_radix)->tree,			\
			__genradix_idx_to_offset(_radix, _idx),	\
			_new_node, _gfp))

struct genradix_iter {
	size_t			offset;
	size_t			pos;
};

/**
 * genradix_iter_init - initialize a genradix_iter
 * @_radix:	genradix that will be iterated over
 * @_idx:	index to start iterating from
 */
#define genradix_iter_init(_radix, _idx)			\
	((struct genradix_iter) {				\
		.pos	= (_idx),				\
		.offset	= __genradix_idx_to_offset((_radix), (_idx)),\
	})

void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t);

/**
 * genradix_iter_peek - get first entry at or above iterator's current
 *			position
 * @_iter:	a genradix_iter
 * @_radix:	genradix being iterated over
 *
 * If no more entries exist at or above @_iter's current position, returns NULL
 */
#define genradix_iter_peek(_iter, _radix)			\
	(__genradix_cast(_radix)				\
	 __genradix_iter_peek(_iter, &(_radix)->tree,		\
			__genradix_objs_per_page(_radix)))

void *__genradix_iter_peek_prev(struct genradix_iter *, struct __genradix *,
				size_t, size_t);

/**
 * genradix_iter_peek_prev - get first entry at or below iterator's current
 *			     position
 * @_iter:	a genradix_iter
 * @_radix:	genradix being iterated over
 *
 * If no more entries exist at or below @_iter's current position, returns NULL
 */
#define genradix_iter_peek_prev(_iter, _radix)			\
	(__genradix_cast(_radix)				\
	 __genradix_iter_peek_prev(_iter, &(_radix)->tree,	\
			__genradix_objs_per_page(_radix),	\
			__genradix_obj_size(_radix) +		\
			__genradix_page_remainder(_radix)))

static inline void __genradix_iter_advance(struct genradix_iter *iter,
					   size_t obj_size)
{
	if (iter->offset + obj_size < iter->offset) {
		iter->offset	= SIZE_MAX;
		iter->pos	= SIZE_MAX;
		return;
	}

	iter->offset += obj_size;

	if (!is_power_of_2(obj_size) &&
	    (iter->offset & (GENRADIX_NODE_SIZE - 1)) + obj_size > GENRADIX_NODE_SIZE)
		iter->offset = round_up(iter->offset, GENRADIX_NODE_SIZE);

	iter->pos++;
}

#define genradix_iter_advance(_iter, _radix)			\
	__genradix_iter_advance(_iter, __genradix_obj_size(_radix))

static inline void __genradix_iter_rewind(struct genradix_iter *iter,
					  size_t obj_size)
{
	if (iter->offset == 0 ||
	    iter->offset == SIZE_MAX) {
		iter->offset = SIZE_MAX;
		return;
	}

	if ((iter->offset & (GENRADIX_NODE_SIZE - 1)) == 0)
		iter->offset -= GENRADIX_NODE_SIZE % obj_size;

	iter->offset -= obj_size;
	iter->pos--;
}

#define genradix_iter_rewind(_iter, _radix)			\
	__genradix_iter_rewind(_iter, __genradix_obj_size(_radix))

#define genradix_for_each_from(_radix, _iter, _p, _start)	\
	for (_iter = genradix_iter_init(_radix, _start);	\
	     (_p = genradix_iter_peek(&_iter, _radix)) != NULL;	\
	     genradix_iter_advance(&_iter, _radix))

/**
 * genradix_for_each - iterate over entry in a genradix
 * @_radix:	genradix to iterate over
 * @_iter:	a genradix_iter to track current position
 * @_p:		pointer to genradix entry type
 *
 * On every iteration, @_p will point to the current entry, and @_iter.pos
 * will be the current entry's index.
 */
#define genradix_for_each(_radix, _iter, _p)			\
	genradix_for_each_from(_radix, _iter, _p, 0)

#define genradix_last_pos(_radix)				\
	(SIZE_MAX / GENRADIX_NODE_SIZE * __genradix_objs_per_page(_radix) - 1)

/**
 * genradix_for_each_reverse - iterate over entry in a genradix, reverse order
 * @_radix:	genradix to iterate over
 * @_iter:	a genradix_iter to track current position
 * @_p:		pointer to genradix entry type
 *
 * On every iteration, @_p will point to the current entry, and @_iter.pos
 * will be the current entry's index.
 */
#define genradix_for_each_reverse(_radix, _iter, _p)		\
	for (_iter = genradix_iter_init(_radix,	genradix_last_pos(_radix));\
	     (_p = genradix_iter_peek_prev(&_iter, _radix)) != NULL;\
	     genradix_iter_rewind(&_iter, _radix))

int __genradix_prealloc(struct __genradix *, size_t, gfp_t);

/**
 * genradix_prealloc - preallocate entries in a generic radix tree
 * @_radix:	genradix to preallocate
 * @_nr:	number of entries to preallocate
 * @_gfp:	gfp mask
 *
 * Returns 0 on success, -ENOMEM on failure
 */
#define genradix_prealloc(_radix, _nr, _gfp)			\
	 __genradix_prealloc(&(_radix)->tree,			\
			__genradix_idx_to_offset(_radix, _nr + 1),\
			_gfp)


#endif /* _LINUX_GENERIC_RADIX_TREE_H */
Commit	Line	Data
	1	#ifndef _LINUX_GENERIC_RADIX_TREE_H
	2	#define _LINUX_GENERIC_RADIX_TREE_H
	3
	4	/**
	5	* DOC: Generic radix trees/sparse arrays
	6	*
	7	* Very simple and minimalistic, supporting arbitrary size entries up to
	8	* GENRADIX_NODE_SIZE.
	9	*
	10	* A genradix is defined with the type it will store, like so:
	11	*
	12	* static GENRADIX(struct foo) foo_genradix;
	13	*
	14	* The main operations are:
	15	*
	16	* - genradix_init(radix) - initialize an empty genradix
	17	*
	18	* - genradix_free(radix) - free all memory owned by the genradix and
	19	* reinitialize it
	20	*
	21	* - genradix_ptr(radix, idx) - gets a pointer to the entry at idx, returning
	22	* NULL if that entry does not exist
	23	*
	24	* - genradix_ptr_alloc(radix, idx, gfp) - gets a pointer to an entry,
	25	* allocating it if necessary
	26	*
	27	* - genradix_for_each(radix, iter, p) - iterate over each entry in a genradix
	28	*
	29	* The radix tree allocates one page of entries at a time, so entries may exist
	30	* that were never explicitly allocated - they will be initialized to all
	31	* zeroes.
	32	*
	33	* Internally, a genradix is just a radix tree of pages, and indexing works in
	34	* terms of byte offsets. The wrappers in this header file use sizeof on the
	35	* type the radix contains to calculate a byte offset from the index - see
	36	* __idx_to_offset.
	37	*/
	38
	39	#include <asm/page.h>
	40	#include <linux/bug.h>
	41	#include <linux/limits.h>
	42	#include <linux/log2.h>
	43	#include <linux/math.h>
	44	#include <linux/slab.h>
	45	#include <linux/types.h>
	46
	47	struct genradix_root;
	48
	49	#define GENRADIX_NODE_SHIFT 9
	50	#define GENRADIX_NODE_SIZE (1U << GENRADIX_NODE_SHIFT)
	51
	52	#define GENRADIX_ARY (GENRADIX_NODE_SIZE / sizeof(struct genradix_node *))
	53	#define GENRADIX_ARY_SHIFT ilog2(GENRADIX_ARY)
	54
	55	/* depth that's needed for a genradix that can address up to ULONG_MAX: */
	56	#define GENRADIX_MAX_DEPTH \
	57	DIV_ROUND_UP(BITS_PER_LONG - GENRADIX_NODE_SHIFT, GENRADIX_ARY_SHIFT)
	58
	59	#define GENRADIX_DEPTH_MASK \
	60	((unsigned long) (roundup_pow_of_two(GENRADIX_MAX_DEPTH + 1) - 1))
	61
	62	static inline int genradix_depth_shift(unsigned depth)
	63	{
	64	return GENRADIX_NODE_SHIFT + GENRADIX_ARY_SHIFT * depth;
	65	}
	66
	67	/*
	68	* Returns size (of data, in bytes) that a tree of a given depth holds:
	69	*/
	70	static inline size_t genradix_depth_size(unsigned depth)
	71	{
	72	return 1UL << genradix_depth_shift(depth);
	73	}
	74
	75	static inline unsigned genradix_root_to_depth(struct genradix_root *r)
	76	{
	77	return (unsigned long) r & GENRADIX_DEPTH_MASK;
	78	}
	79
	80	static inline struct genradix_node genradix_root_to_node(struct genradix_root r)
	81	{
	82	return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
	83	}
	84
	85	struct __genradix {
	86	struct genradix_root *root;
	87	};
	88
	89	struct genradix_node {
	90	union {
	91	/* Interior node: */
	92	struct genradix_node *children[GENRADIX_ARY];
	93
	94	/* Leaf: */
	95	u8 data[GENRADIX_NODE_SIZE];
	96	};
	97	};
	98
	99	static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
	100	{
	101	return kzalloc(GENRADIX_NODE_SIZE, gfp_mask);
	102	}
	103
	104	static inline void genradix_free_node(struct genradix_node *node)
	105	{
	106	kfree(node);
	107	}
	108
	109	/*
	110	* NOTE: currently, sizeof(_type) must not be larger than GENRADIX_NODE_SIZE:
	111	*/
	112
	113	#define __GENRADIX_INITIALIZER \
	114	{ \
	115	.tree = { \
	116	.root = NULL, \
	117	} \
	118	}
	119
	120	/*
	121	* We use a 0 size array to stash the type we're storing without taking any
	122	* space at runtime - then the various accessor macros can use typeof() to get
	123	* to it for casts/sizeof - we also force the alignment so that storing a type
	124	* with a ridiculous alignment doesn't blow up the alignment or size of the
	125	* genradix.
	126	*/
	127
	128	#define GENRADIX(_type) \
	129	struct { \
	130	struct __genradix tree; \
	131	_type type[0] __aligned(1); \
	132	}
	133
	134	#define DEFINE_GENRADIX(_name, _type) \
	135	GENRADIX(_type) _name = __GENRADIX_INITIALIZER
	136
	137	/**
	138	* genradix_init - initialize a genradix
	139	* @_radix: genradix to initialize
	140	*
	141	* Does not fail
	142	*/
	143	#define genradix_init(_radix) \
	144	do { \
	145	(_radix) = (typeof(_radix)) __GENRADIX_INITIALIZER; \
	146	} while (0)
	147
	148	void __genradix_free(struct __genradix *);
	149
	150	/**
	151	* genradix_free: free all memory owned by a genradix
	152	* @_radix: the genradix to free
	153	*
	154	* After freeing, @_radix will be reinitialized and empty
	155	*/
	156	#define genradix_free(_radix) __genradix_free(&(_radix)->tree)
	157
	158	static inline size_t __idx_to_offset(size_t idx, size_t obj_size)
	159	{
	160	if (__builtin_constant_p(obj_size))
	161	BUILD_BUG_ON(obj_size > GENRADIX_NODE_SIZE);
	162	else
	163	BUG_ON(obj_size > GENRADIX_NODE_SIZE);
	164
	165	if (!is_power_of_2(obj_size)) {
	166	size_t objs_per_page = GENRADIX_NODE_SIZE / obj_size;
	167
	168	return (idx / objs_per_page) * GENRADIX_NODE_SIZE +
	169	(idx % objs_per_page) * obj_size;
	170	} else {
	171	return idx * obj_size;
	172	}
	173	}
	174
	175	#define __genradix_cast(_radix) (typeof((_radix)->type[0]) *)
	176	#define __genradix_obj_size(_radix) sizeof((_radix)->type[0])
	177	#define __genradix_objs_per_page(_radix) \
	178	(GENRADIX_NODE_SIZE / sizeof((_radix)->type[0]))
	179	#define __genradix_page_remainder(_radix) \
	180	(GENRADIX_NODE_SIZE % sizeof((_radix)->type[0]))
	181
	182	#define __genradix_idx_to_offset(_radix, _idx) \
	183	__idx_to_offset(_idx, __genradix_obj_size(_radix))
	184
	185	static inline void __genradix_ptr_inlined(struct __genradix radix, size_t offset)
	186	{
	187	struct genradix_root *r = READ_ONCE(radix->root);
	188	struct genradix_node *n = genradix_root_to_node(r);
	189	unsigned level = genradix_root_to_depth(r);
	190	unsigned shift = genradix_depth_shift(level);
	191
	192	if (unlikely(ilog2(offset) >= genradix_depth_shift(level)))
	193	return NULL;
	194
	195	while (n && shift > GENRADIX_NODE_SHIFT) {
	196	shift -= GENRADIX_ARY_SHIFT;
	197	n = n->children[offset >> shift];
	198	offset &= (1UL << shift) - 1;
	199	}
	200
	201	return n ? &n->data[offset] : NULL;
	202	}
	203
	204	#define genradix_ptr_inlined(_radix, _idx) \
	205	(__genradix_cast(_radix) \
	206	__genradix_ptr_inlined(&(_radix)->tree, \
	207	__genradix_idx_to_offset(_radix, _idx)))
	208
	209	void __genradix_ptr(struct __genradix , size_t);
	210
	211	/**
	212	* genradix_ptr - get a pointer to a genradix entry
	213	* @_radix: genradix to access
	214	* @_idx: index to fetch
	215	*
	216	* Returns a pointer to entry at @_idx, or NULL if that entry does not exist.
	217	*/
	218	#define genradix_ptr(_radix, _idx) \
	219	(__genradix_cast(_radix) \
	220	__genradix_ptr(&(_radix)->tree, \
	221	__genradix_idx_to_offset(_radix, _idx)))
	222
	223	void __genradix_ptr_alloc(struct __genradix , size_t,
	224	struct genradix_node **, gfp_t);
	225
	226	#define genradix_ptr_alloc_inlined(_radix, _idx, _gfp) \
	227	(__genradix_cast(_radix) \
	228	(__genradix_ptr_inlined(&(_radix)->tree, \
	229	__genradix_idx_to_offset(_radix, _idx)) ?: \
	230	__genradix_ptr_alloc(&(_radix)->tree, \
	231	__genradix_idx_to_offset(_radix, _idx), \
	232	NULL, _gfp)))
	233
	234	#define genradix_ptr_alloc_preallocated_inlined(_radix, _idx, _new_node, _gfp)\
	235	(__genradix_cast(_radix) \
	236	(__genradix_ptr_inlined(&(_radix)->tree, \
	237	__genradix_idx_to_offset(_radix, _idx)) ?: \
	238	__genradix_ptr_alloc(&(_radix)->tree, \
	239	__genradix_idx_to_offset(_radix, _idx), \
	240	_new_node, _gfp)))
	241
	242	/**
	243	* genradix_ptr_alloc - get a pointer to a genradix entry, allocating it
	244	* if necessary
	245	* @_radix: genradix to access
	246	* @_idx: index to fetch
	247	* @_gfp: gfp mask
	248	*
	249	* Returns a pointer to entry at @_idx, or NULL on allocation failure
	250	*/
	251	#define genradix_ptr_alloc(_radix, _idx, _gfp) \
	252	(__genradix_cast(_radix) \
	253	__genradix_ptr_alloc(&(_radix)->tree, \
	254	__genradix_idx_to_offset(_radix, _idx), \
	255	NULL, _gfp))
	256
	257	#define genradix_ptr_alloc_preallocated(_radix, _idx, _new_node, _gfp)\
	258	(__genradix_cast(_radix) \
	259	__genradix_ptr_alloc(&(_radix)->tree, \
	260	__genradix_idx_to_offset(_radix, _idx), \
	261	_new_node, _gfp))
	262
	263	struct genradix_iter {
	264	size_t offset;
	265	size_t pos;
	266	};
	267
	268	/**
	269	* genradix_iter_init - initialize a genradix_iter
	270	* @_radix: genradix that will be iterated over
	271	* @_idx: index to start iterating from
	272	*/
	273	#define genradix_iter_init(_radix, _idx) \
	274	((struct genradix_iter) { \
	275	.pos = (_idx), \
	276	.offset = __genradix_idx_to_offset((_radix), (_idx)),\
	277	})
	278
	279	void __genradix_iter_peek(struct genradix_iter , struct __genradix *, size_t);
	280
	281	/**
	282	* genradix_iter_peek - get first entry at or above iterator's current
	283	* position
	284	* @_iter: a genradix_iter
	285	* @_radix: genradix being iterated over
	286	*
	287	* If no more entries exist at or above @_iter's current position, returns NULL
	288	*/
	289	#define genradix_iter_peek(_iter, _radix) \
	290	(__genradix_cast(_radix) \
	291	__genradix_iter_peek(_iter, &(_radix)->tree, \
	292	__genradix_objs_per_page(_radix)))
	293
	294	void __genradix_iter_peek_prev(struct genradix_iter , struct __genradix *,
	295	size_t, size_t);
	296
	297	/**
	298	* genradix_iter_peek_prev - get first entry at or below iterator's current
	299	* position
	300	* @_iter: a genradix_iter
	301	* @_radix: genradix being iterated over
	302	*
	303	* If no more entries exist at or below @_iter's current position, returns NULL
	304	*/
	305	#define genradix_iter_peek_prev(_iter, _radix) \
	306	(__genradix_cast(_radix) \
	307	__genradix_iter_peek_prev(_iter, &(_radix)->tree, \
	308	__genradix_objs_per_page(_radix), \
	309	__genradix_obj_size(_radix) + \
	310	__genradix_page_remainder(_radix)))
	311
	312	static inline void __genradix_iter_advance(struct genradix_iter *iter,
	313	size_t obj_size)
	314	{
	315	if (iter->offset + obj_size < iter->offset) {
	316	iter->offset = SIZE_MAX;
	317	iter->pos = SIZE_MAX;
	318	return;
	319	}
	320
	321	iter->offset += obj_size;
	322
	323	if (!is_power_of_2(obj_size) &&
	324	(iter->offset & (GENRADIX_NODE_SIZE - 1)) + obj_size > GENRADIX_NODE_SIZE)
	325	iter->offset = round_up(iter->offset, GENRADIX_NODE_SIZE);
	326
	327	iter->pos++;
	328	}
	329
	330	#define genradix_iter_advance(_iter, _radix) \
	331	__genradix_iter_advance(_iter, __genradix_obj_size(_radix))
	332
	333	static inline void __genradix_iter_rewind(struct genradix_iter *iter,
	334	size_t obj_size)
	335	{
	336	if (iter->offset == 0 \|\|
	337	iter->offset == SIZE_MAX) {
	338	iter->offset = SIZE_MAX;
	339	return;
	340	}
	341
	342	if ((iter->offset & (GENRADIX_NODE_SIZE - 1)) == 0)
	343	iter->offset -= GENRADIX_NODE_SIZE % obj_size;
	344
	345	iter->offset -= obj_size;
	346	iter->pos--;
	347	}
	348
	349	#define genradix_iter_rewind(_iter, _radix) \
	350	__genradix_iter_rewind(_iter, __genradix_obj_size(_radix))
	351
	352	#define genradix_for_each_from(_radix, _iter, _p, _start) \
	353	for (_iter = genradix_iter_init(_radix, _start); \
	354	(_p = genradix_iter_peek(&_iter, _radix)) != NULL; \
	355	genradix_iter_advance(&_iter, _radix))
	356
	357	/**
	358	* genradix_for_each - iterate over entry in a genradix
	359	* @_radix: genradix to iterate over
	360	* @_iter: a genradix_iter to track current position
	361	* @_p: pointer to genradix entry type
	362	*
	363	* On every iteration, @_p will point to the current entry, and @_iter.pos
	364	* will be the current entry's index.
	365	*/
	366	#define genradix_for_each(_radix, _iter, _p) \
	367	genradix_for_each_from(_radix, _iter, _p, 0)
	368
	369	#define genradix_last_pos(_radix) \
	370	(SIZE_MAX / GENRADIX_NODE_SIZE * __genradix_objs_per_page(_radix) - 1)
	371
	372	/**
	373	* genradix_for_each_reverse - iterate over entry in a genradix, reverse order
	374	* @_radix: genradix to iterate over
	375	* @_iter: a genradix_iter to track current position
	376	* @_p: pointer to genradix entry type
	377	*
	378	* On every iteration, @_p will point to the current entry, and @_iter.pos
	379	* will be the current entry's index.
	380	*/
	381	#define genradix_for_each_reverse(_radix, _iter, _p) \
	382	for (_iter = genradix_iter_init(_radix, genradix_last_pos(_radix));\
	383	(_p = genradix_iter_peek_prev(&_iter, _radix)) != NULL;\
	384	genradix_iter_rewind(&_iter, _radix))
	385
	386	int __genradix_prealloc(struct __genradix *, size_t, gfp_t);
	387
	388	/**
	389	* genradix_prealloc - preallocate entries in a generic radix tree
	390	* @_radix: genradix to preallocate
	391	* @_nr: number of entries to preallocate
	392	* @_gfp: gfp mask
	393	*
	394	* Returns 0 on success, -ENOMEM on failure
	395	*/
	396	#define genradix_prealloc(_radix, _nr, _gfp) \
	397	__genradix_prealloc(&(_radix)->tree, \
	398	__genradix_idx_to_offset(_radix, _nr + 1),\
	399	_gfp)
	400
	401
	402	#endif /* _LINUX_GENERIC_RADIX_TREE_H */