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
46 struct genradix_root;
47
48 struct __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) \
72 struct { \
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) \
87 do { \
88 *(_radix) = (typeof(*_radix)) __GENRADIX_INITIALIZER; \
89 } while (0)
90
91 void __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
__idx_to_offset(size_t idx,size_t obj_size)101 static 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(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_idx_to_offset(_radix, _idx) \
121 __idx_to_offset(_idx, __genradix_obj_size(_radix))
122
123 void *__genradix_ptr(struct __genradix *, size_t);
124
125 /**
126 * genradix_ptr - get a pointer to a genradix entry
127 * @_radix: genradix to access
128 * @_idx: index to fetch
129 *
130 * Returns a pointer to entry at @_idx, or NULL if that entry does not exist.
131 */
132 #define genradix_ptr(_radix, _idx) \
133 (__genradix_cast(_radix) \
134 __genradix_ptr(&(_radix)->tree, \
135 __genradix_idx_to_offset(_radix, _idx)))
136
137 void *__genradix_ptr_alloc(struct __genradix *, size_t, gfp_t);
138
139 /**
140 * genradix_ptr_alloc - get a pointer to a genradix entry, allocating it
141 * if necessary
142 * @_radix: genradix to access
143 * @_idx: index to fetch
144 * @_gfp: gfp mask
145 *
146 * Returns a pointer to entry at @_idx, or NULL on allocation failure
147 */
148 #define genradix_ptr_alloc(_radix, _idx, _gfp) \
149 (__genradix_cast(_radix) \
150 __genradix_ptr_alloc(&(_radix)->tree, \
151 __genradix_idx_to_offset(_radix, _idx), \
152 _gfp))
153
154 struct genradix_iter {
155 size_t offset;
156 size_t pos;
157 };
158
159 /**
160 * genradix_iter_init - initialize a genradix_iter
161 * @_radix: genradix that will be iterated over
162 * @_idx: index to start iterating from
163 */
164 #define genradix_iter_init(_radix, _idx) \
165 ((struct genradix_iter) { \
166 .pos = (_idx), \
167 .offset = __genradix_idx_to_offset((_radix), (_idx)),\
168 })
169
170 void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t);
171
172 /**
173 * genradix_iter_peek - get first entry at or above iterator's current
174 * position
175 * @_iter: a genradix_iter
176 * @_radix: genradix being iterated over
177 *
178 * If no more entries exist at or above @_iter's current position, returns NULL
179 */
180 #define genradix_iter_peek(_iter, _radix) \
181 (__genradix_cast(_radix) \
182 __genradix_iter_peek(_iter, &(_radix)->tree, \
183 PAGE_SIZE / __genradix_obj_size(_radix)))
184
__genradix_iter_advance(struct genradix_iter * iter,size_t obj_size)185 static inline void __genradix_iter_advance(struct genradix_iter *iter,
186 size_t obj_size)
187 {
188 if (iter->offset + obj_size < iter->offset) {
189 iter->offset = SIZE_MAX;
190 iter->pos = SIZE_MAX;
191 return;
192 }
193
194 iter->offset += obj_size;
195
196 if (!is_power_of_2(obj_size) &&
197 (iter->offset & (PAGE_SIZE - 1)) + obj_size > PAGE_SIZE)
198 iter->offset = round_up(iter->offset, PAGE_SIZE);
199
200 iter->pos++;
201 }
202
203 #define genradix_iter_advance(_iter, _radix) \
204 __genradix_iter_advance(_iter, __genradix_obj_size(_radix))
205
206 #define genradix_for_each_from(_radix, _iter, _p, _start) \
207 for (_iter = genradix_iter_init(_radix, _start); \
208 (_p = genradix_iter_peek(&_iter, _radix)) != NULL; \
209 genradix_iter_advance(&_iter, _radix))
210
211 /**
212 * genradix_for_each - iterate over entry in a genradix
213 * @_radix: genradix to iterate over
214 * @_iter: a genradix_iter to track current position
215 * @_p: pointer to genradix entry type
216 *
217 * On every iteration, @_p will point to the current entry, and @_iter.pos
218 * will be the current entry's index.
219 */
220 #define genradix_for_each(_radix, _iter, _p) \
221 genradix_for_each_from(_radix, _iter, _p, 0)
222
223 int __genradix_prealloc(struct __genradix *, size_t, gfp_t);
224
225 /**
226 * genradix_prealloc - preallocate entries in a generic radix tree
227 * @_radix: genradix to preallocate
228 * @_nr: number of entries to preallocate
229 * @_gfp: gfp mask
230 *
231 * Returns 0 on success, -ENOMEM on failure
232 */
233 #define genradix_prealloc(_radix, _nr, _gfp) \
234 __genradix_prealloc(&(_radix)->tree, \
235 __genradix_idx_to_offset(_radix, _nr + 1),\
236 _gfp)
237
238
239 #endif /* _LINUX_GENERIC_RADIX_TREE_H */
240