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
44struct genradix_root;
45
46struct __genradix {
47 struct genradix_root __rcu *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) \
70struct { \
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) \
85do { \
86 *(_radix) = (typeof(*_radix)) __GENRADIX_INITIALIZER; \
87} while (0)
88
89void __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
99static inline size_t __idx_to_offset(size_t idx, size_t obj_size)
100{
101 if (__builtin_constant_p(obj_size))
102 BUILD_BUG_ON(obj_size > PAGE_SIZE);
103 else
104 BUG_ON(obj_size > PAGE_SIZE);
105
106 if (!is_power_of_2(obj_size)) {
107 size_t objs_per_page = PAGE_SIZE / obj_size;
108
109 return (idx / objs_per_page) * PAGE_SIZE +
110 (idx % objs_per_page) * obj_size;
111 } else {
112 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
121void *__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
135void *__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
152struct 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
168void *__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
183static 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
215int __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 */
232