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
46 struct genradix_root;
47
48 #define GENRADIX_NODE_SHIFT 9
49 #define GENRADIX_NODE_SIZE (1U << GENRADIX_NODE_SHIFT)
50
51 struct __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) \
75 struct { \
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) \
90 do { \
91 *(_radix) = (typeof(*_radix)) __GENRADIX_INITIALIZER; \
92 } while (0)
93
94 void __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
__idx_to_offset(size_t idx,size_t obj_size)104 static 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
131 void *__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
145 void *__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
162 struct 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
178 void *__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
193 void *__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
__genradix_iter_advance(struct genradix_iter * iter,size_t obj_size)211 static 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
__genradix_iter_rewind(struct genradix_iter * iter,size_t obj_size)232 static 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
285 int __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