generic-radix-tree.h

  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
 47struct 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
 62static 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 */
 70static inline size_t genradix_depth_size(unsigned depth)
 71{
 72	return 1UL << genradix_depth_shift(depth);
 73}
 74
 75static inline unsigned genradix_root_to_depth(struct genradix_root *r)
 76{
 77	return (unsigned long) r & GENRADIX_DEPTH_MASK;
 78}
 79
 80static inline struct genradix_node *genradix_root_to_node(struct genradix_root *r)
 81{
 82	return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
 83}
 84
 85struct __genradix {
 86	struct genradix_root		*root;
 87};
 88
 89struct 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
 99static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
100{
101	return kzalloc(GENRADIX_NODE_SIZE, gfp_mask);
102}
103
104static 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)						\
129struct {							\
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)					\
144do {								\
145	*(_radix) = (typeof(*_radix)) __GENRADIX_INITIALIZER;	\
146} while (0)
147
148void __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
158static 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
185static 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
209void *__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
223void *__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
263struct 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
279void *__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
294void *__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
312static 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
333static 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
386int __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 */