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/types.h>
45
46struct genradix_root;
47
48#define GENRADIX_NODE_SHIFT	9
49#define GENRADIX_NODE_SIZE	(1U << GENRADIX_NODE_SHIFT)
50
51struct __genradix {
52	struct genradix_root		*root;
53};
54
55/*
56 * NOTE: currently, sizeof(_type) must not be larger than GENRADIX_NODE_SIZE:
57 */
58
59#define __GENRADIX_INITIALIZER					\
60	{							\
61		.tree = {					\
62			.root = NULL,				\
63		}						\
64	}
65
66/*
67 * We use a 0 size array to stash the type we're storing without taking any
68 * space at runtime - then the various accessor macros can use typeof() to get
69 * to it for casts/sizeof - we also force the alignment so that storing a type
70 * with a ridiculous alignment doesn't blow up the alignment or size of the
71 * genradix.
72 */
73
74#define GENRADIX(_type)						\
75struct {							\
76	struct __genradix	tree;				\
77	_type			type[0] __aligned(1);		\
78}
79
80#define DEFINE_GENRADIX(_name, _type)				\
81	GENRADIX(_type) _name = __GENRADIX_INITIALIZER
82
83/**
84 * genradix_init - initialize a genradix
85 * @_radix:	genradix to initialize
86 *
87 * Does not fail
88 */
89#define genradix_init(_radix)					\
90do {								\
91	*(_radix) = (typeof(*_radix)) __GENRADIX_INITIALIZER;	\
92} while (0)
93
94void __genradix_free(struct __genradix *);
95
96/**
97 * genradix_free: free all memory owned by a genradix
98 * @_radix: the genradix to free
99 *
100 * After freeing, @_radix will be reinitialized and empty
101 */
102#define genradix_free(_radix)	__genradix_free(&(_radix)->tree)
103
104static inline size_t __idx_to_offset(size_t idx, size_t obj_size)
105{
106	if (__builtin_constant_p(obj_size))
107		BUILD_BUG_ON(obj_size > GENRADIX_NODE_SIZE);
108	else
109		BUG_ON(obj_size > GENRADIX_NODE_SIZE);
110
111	if (!is_power_of_2(obj_size)) {
112		size_t objs_per_page = GENRADIX_NODE_SIZE / obj_size;
113
114		return (idx / objs_per_page) * GENRADIX_NODE_SIZE +
115			(idx % objs_per_page) * obj_size;
116	} else {
117		return idx * obj_size;
118	}
119}
120
121#define __genradix_cast(_radix)		(typeof((_radix)->type[0]) *)
122#define __genradix_obj_size(_radix)	sizeof((_radix)->type[0])
123#define __genradix_objs_per_page(_radix)			\
124	(GENRADIX_NODE_SIZE / sizeof((_radix)->type[0]))
125#define __genradix_page_remainder(_radix)			\
126	(GENRADIX_NODE_SIZE % sizeof((_radix)->type[0]))
127
128#define __genradix_idx_to_offset(_radix, _idx)			\
129	__idx_to_offset(_idx, __genradix_obj_size(_radix))
130
131void *__genradix_ptr(struct __genradix *, size_t);
132
133/**
134 * genradix_ptr - get a pointer to a genradix entry
135 * @_radix:	genradix to access
136 * @_idx:	index to fetch
137 *
138 * Returns a pointer to entry at @_idx, or NULL if that entry does not exist.
139 */
140#define genradix_ptr(_radix, _idx)				\
141	(__genradix_cast(_radix)				\
142	 __genradix_ptr(&(_radix)->tree,			\
143			__genradix_idx_to_offset(_radix, _idx)))
144
145void *__genradix_ptr_alloc(struct __genradix *, size_t, gfp_t);
146
147/**
148 * genradix_ptr_alloc - get a pointer to a genradix entry, allocating it
149 *			if necessary
150 * @_radix:	genradix to access
151 * @_idx:	index to fetch
152 * @_gfp:	gfp mask
153 *
154 * Returns a pointer to entry at @_idx, or NULL on allocation failure
155 */
156#define genradix_ptr_alloc(_radix, _idx, _gfp)			\
157	(__genradix_cast(_radix)				\
158	 __genradix_ptr_alloc(&(_radix)->tree,			\
159			__genradix_idx_to_offset(_radix, _idx),	\
160			_gfp))
161
162struct genradix_iter {
163	size_t			offset;
164	size_t			pos;
165};
166
167/**
168 * genradix_iter_init - initialize a genradix_iter
169 * @_radix:	genradix that will be iterated over
170 * @_idx:	index to start iterating from
171 */
172#define genradix_iter_init(_radix, _idx)			\
173	((struct genradix_iter) {				\
174		.pos	= (_idx),				\
175		.offset	= __genradix_idx_to_offset((_radix), (_idx)),\
176	})
177
178void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t);
179
180/**
181 * genradix_iter_peek - get first entry at or above iterator's current
182 *			position
183 * @_iter:	a genradix_iter
184 * @_radix:	genradix being iterated over
185 *
186 * If no more entries exist at or above @_iter's current position, returns NULL
187 */
188#define genradix_iter_peek(_iter, _radix)			\
189	(__genradix_cast(_radix)				\
190	 __genradix_iter_peek(_iter, &(_radix)->tree,		\
191			__genradix_objs_per_page(_radix)))
192
193void *__genradix_iter_peek_prev(struct genradix_iter *, struct __genradix *,
194				size_t, size_t);
195
196/**
197 * genradix_iter_peek_prev - get first entry at or below iterator's current
198 *			     position
199 * @_iter:	a genradix_iter
200 * @_radix:	genradix being iterated over
201 *
202 * If no more entries exist at or below @_iter's current position, returns NULL
203 */
204#define genradix_iter_peek_prev(_iter, _radix)			\
205	(__genradix_cast(_radix)				\
206	 __genradix_iter_peek_prev(_iter, &(_radix)->tree,	\
207			__genradix_objs_per_page(_radix),	\
208			__genradix_obj_size(_radix) +		\
209			__genradix_page_remainder(_radix)))
210
211static inline void __genradix_iter_advance(struct genradix_iter *iter,
212					   size_t obj_size)
213{
214	if (iter->offset + obj_size < iter->offset) {
215		iter->offset	= SIZE_MAX;
216		iter->pos	= SIZE_MAX;
217		return;
218	}
219
220	iter->offset += obj_size;
221
222	if (!is_power_of_2(obj_size) &&
223	    (iter->offset & (GENRADIX_NODE_SIZE - 1)) + obj_size > GENRADIX_NODE_SIZE)
224		iter->offset = round_up(iter->offset, GENRADIX_NODE_SIZE);
225
226	iter->pos++;
227}
228
229#define genradix_iter_advance(_iter, _radix)			\
230	__genradix_iter_advance(_iter, __genradix_obj_size(_radix))
231
232static inline void __genradix_iter_rewind(struct genradix_iter *iter,
233					  size_t obj_size)
234{
235	if (iter->offset == 0 ||
236	    iter->offset == SIZE_MAX) {
237		iter->offset = SIZE_MAX;
238		return;
239	}
240
241	if ((iter->offset & (GENRADIX_NODE_SIZE - 1)) == 0)
242		iter->offset -= GENRADIX_NODE_SIZE % obj_size;
243
244	iter->offset -= obj_size;
245	iter->pos--;
246}
247
248#define genradix_iter_rewind(_iter, _radix)			\
249	__genradix_iter_rewind(_iter, __genradix_obj_size(_radix))
250
251#define genradix_for_each_from(_radix, _iter, _p, _start)	\
252	for (_iter = genradix_iter_init(_radix, _start);	\
253	     (_p = genradix_iter_peek(&_iter, _radix)) != NULL;	\
254	     genradix_iter_advance(&_iter, _radix))
255
256/**
257 * genradix_for_each - iterate over entry in a genradix
258 * @_radix:	genradix to iterate over
259 * @_iter:	a genradix_iter to track current position
260 * @_p:		pointer to genradix entry type
261 *
262 * On every iteration, @_p will point to the current entry, and @_iter.pos
263 * will be the current entry's index.
264 */
265#define genradix_for_each(_radix, _iter, _p)			\
266	genradix_for_each_from(_radix, _iter, _p, 0)
267
268#define genradix_last_pos(_radix)				\
269	(SIZE_MAX / GENRADIX_NODE_SIZE * __genradix_objs_per_page(_radix) - 1)
270
271/**
272 * genradix_for_each_reverse - iterate over entry in a genradix, reverse order
273 * @_radix:	genradix to iterate over
274 * @_iter:	a genradix_iter to track current position
275 * @_p:		pointer to genradix entry type
276 *
277 * On every iteration, @_p will point to the current entry, and @_iter.pos
278 * will be the current entry's index.
279 */
280#define genradix_for_each_reverse(_radix, _iter, _p)		\
281	for (_iter = genradix_iter_init(_radix,	genradix_last_pos(_radix));\
282	     (_p = genradix_iter_peek_prev(&_iter, _radix)) != NULL;\
283	     genradix_iter_rewind(&_iter, _radix))
284
285int __genradix_prealloc(struct __genradix *, size_t, gfp_t);
286
287/**
288 * genradix_prealloc - preallocate entries in a generic radix tree
289 * @_radix:	genradix to preallocate
290 * @_nr:	number of entries to preallocate
291 * @_gfp:	gfp mask
292 *
293 * Returns 0 on success, -ENOMEM on failure
294 */
295#define genradix_prealloc(_radix, _nr, _gfp)			\
296	 __genradix_prealloc(&(_radix)->tree,			\
297			__genradix_idx_to_offset(_radix, _nr + 1),\
298			_gfp)
299
300
301#endif /* _LINUX_GENERIC_RADIX_TREE_H */
302