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

source code of linux/include/linux/generic-radix-tree.h