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/log2.h>
42 #include <linux/math.h>
43 #include <linux/types.h>
44
45 struct genradix_root;
46
47 struct __genradix {
48 struct genradix_root *root;
49 };
50
51 /*
52 * NOTE: currently, sizeof(_type) must not be larger than PAGE_SIZE:
53 */
54
55 #define __GENRADIX_INITIALIZER \
56 { \
57 .tree = { \
58 .root = NULL, \
59 } \
60 }
61
62 /*
63 * We use a 0 size array to stash the type we're storing without taking any
64 * space at runtime - then the various accessor macros can use typeof() to get
65 * to it for casts/sizeof - we also force the alignment so that storing a type
66 * with a ridiculous alignment doesn't blow up the alignment or size of the
67 * genradix.
68 */
69
70 #define GENRADIX(_type) \
71 struct { \
72 struct __genradix tree; \
73 _type type[0] __aligned(1); \
74 }
75
76 #define DEFINE_GENRADIX(_name, _type) \
77 GENRADIX(_type) _name = __GENRADIX_INITIALIZER
78
79 /**
80 * genradix_init - initialize a genradix
81 * @_radix: genradix to initialize
82 *
83 * Does not fail
84 */
85 #define genradix_init(_radix) \
86 do { \
87 *(_radix) = (typeof(*_radix)) __GENRADIX_INITIALIZER; \
88 } while (0)
89
90 void __genradix_free(struct __genradix *);
91
92 /**
93 * genradix_free: free all memory owned by a genradix
94 * @_radix: the genradix to free
95 *
96 * After freeing, @_radix will be reinitialized and empty
97 */
98 #define genradix_free(_radix) __genradix_free(&(_radix)->tree)
99
__idx_to_offset(size_t idx,size_t obj_size)100 static inline size_t __idx_to_offset(size_t idx, size_t obj_size)
101 {
102 if (__builtin_constant_p(obj_size))
103 BUILD_BUG_ON(obj_size > PAGE_SIZE);
104 else
105 BUG_ON(obj_size > PAGE_SIZE);
106
107 if (!is_power_of_2(obj_size)) {
108 size_t objs_per_page = PAGE_SIZE / obj_size;
109
110 return (idx / objs_per_page) * PAGE_SIZE +
111 (idx % objs_per_page) * obj_size;
112 } else {
113 return idx * obj_size;
114 }
115 }
116
117 #define __genradix_cast(_radix) (typeof((_radix)->type[0]) *)
118 #define __genradix_obj_size(_radix) sizeof((_radix)->type[0])
119 #define __genradix_idx_to_offset(_radix, _idx) \
120 __idx_to_offset(_idx, __genradix_obj_size(_radix))
121
122 void *__genradix_ptr(struct __genradix *, size_t);
123
124 /**
125 * genradix_ptr - get a pointer to a genradix entry
126 * @_radix: genradix to access
127 * @_idx: index to fetch
128 *
129 * Returns a pointer to entry at @_idx, or NULL if that entry does not exist.
130 */
131 #define genradix_ptr(_radix, _idx) \
132 (__genradix_cast(_radix) \
133 __genradix_ptr(&(_radix)->tree, \
134 __genradix_idx_to_offset(_radix, _idx)))
135
136 void *__genradix_ptr_alloc(struct __genradix *, size_t, gfp_t);
137
138 /**
139 * genradix_ptr_alloc - get a pointer to a genradix entry, allocating it
140 * if necessary
141 * @_radix: genradix to access
142 * @_idx: index to fetch
143 * @_gfp: gfp mask
144 *
145 * Returns a pointer to entry at @_idx, or NULL on allocation failure
146 */
147 #define genradix_ptr_alloc(_radix, _idx, _gfp) \
148 (__genradix_cast(_radix) \
149 __genradix_ptr_alloc(&(_radix)->tree, \
150 __genradix_idx_to_offset(_radix, _idx), \
151 _gfp))
152
153 struct genradix_iter {
154 size_t offset;
155 size_t pos;
156 };
157
158 /**
159 * genradix_iter_init - initialize a genradix_iter
160 * @_radix: genradix that will be iterated over
161 * @_idx: index to start iterating from
162 */
163 #define genradix_iter_init(_radix, _idx) \
164 ((struct genradix_iter) { \
165 .pos = (_idx), \
166 .offset = __genradix_idx_to_offset((_radix), (_idx)),\
167 })
168
169 void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t);
170
171 /**
172 * genradix_iter_peek - get first entry at or above iterator's current
173 * position
174 * @_iter: a genradix_iter
175 * @_radix: genradix being iterated over
176 *
177 * If no more entries exist at or above @_iter's current position, returns NULL
178 */
179 #define genradix_iter_peek(_iter, _radix) \
180 (__genradix_cast(_radix) \
181 __genradix_iter_peek(_iter, &(_radix)->tree, \
182 PAGE_SIZE / __genradix_obj_size(_radix)))
183
__genradix_iter_advance(struct genradix_iter * iter,size_t obj_size)184 static inline void __genradix_iter_advance(struct genradix_iter *iter,
185 size_t obj_size)
186 {
187 iter->offset += obj_size;
188
189 if (!is_power_of_2(obj_size) &&
190 (iter->offset & (PAGE_SIZE - 1)) + obj_size > PAGE_SIZE)
191 iter->offset = round_up(iter->offset, PAGE_SIZE);
192
193 iter->pos++;
194 }
195
196 #define genradix_iter_advance(_iter, _radix) \
197 __genradix_iter_advance(_iter, __genradix_obj_size(_radix))
198
199 #define genradix_for_each_from(_radix, _iter, _p, _start) \
200 for (_iter = genradix_iter_init(_radix, _start); \
201 (_p = genradix_iter_peek(&_iter, _radix)) != NULL; \
202 genradix_iter_advance(&_iter, _radix))
203
204 /**
205 * genradix_for_each - iterate over entry in a genradix
206 * @_radix: genradix to iterate over
207 * @_iter: a genradix_iter to track current position
208 * @_p: pointer to genradix entry type
209 *
210 * On every iteration, @_p will point to the current entry, and @_iter.pos
211 * will be the current entry's index.
212 */
213 #define genradix_for_each(_radix, _iter, _p) \
214 genradix_for_each_from(_radix, _iter, _p, 0)
215
216 int __genradix_prealloc(struct __genradix *, size_t, gfp_t);
217
218 /**
219 * genradix_prealloc - preallocate entries in a generic radix tree
220 * @_radix: genradix to preallocate
221 * @_nr: number of entries to preallocate
222 * @_gfp: gfp mask
223 *
224 * Returns 0 on success, -ENOMEM on failure
225 */
226 #define genradix_prealloc(_radix, _nr, _gfp) \
227 __genradix_prealloc(&(_radix)->tree, \
228 __genradix_idx_to_offset(_radix, _nr + 1),\
229 _gfp)
230
231
232 #endif /* _LINUX_GENERIC_RADIX_TREE_H */
233