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