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