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Dave Hansen534acc02009-07-29 15:04:18 -07001/*
2 * Flexible array managed in PAGE_SIZE parts
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright IBM Corporation, 2009
19 *
20 * Author: Dave Hansen <dave@linux.vnet.ibm.com>
21 */
22
23#include <linux/flex_array.h>
24#include <linux/slab.h>
25#include <linux/stddef.h>
26
27struct flex_array_part {
28 char elements[FLEX_ARRAY_PART_SIZE];
29};
30
Dave Hansen534acc02009-07-29 15:04:18 -070031/*
32 * If a user requests an allocation which is small
33 * enough, we may simply use the space in the
34 * flex_array->parts[] array to store the user
35 * data.
36 */
37static inline int elements_fit_in_base(struct flex_array *fa)
38{
39 int data_size = fa->element_size * fa->total_nr_elements;
David Rientjes45b588d2009-09-21 17:04:33 -070040 if (data_size <= FLEX_ARRAY_BASE_BYTES_LEFT)
Dave Hansen534acc02009-07-29 15:04:18 -070041 return 1;
42 return 0;
43}
44
45/**
46 * flex_array_alloc - allocate a new flexible array
47 * @element_size: the size of individual elements in the array
48 * @total: total number of elements that this should hold
David Rientjesfc0d8d92009-09-21 17:04:33 -070049 * @flags: page allocation flags to use for base array
Dave Hansen534acc02009-07-29 15:04:18 -070050 *
51 * Note: all locking must be provided by the caller.
52 *
53 * @total is used to size internal structures. If the user ever
54 * accesses any array indexes >=@total, it will produce errors.
55 *
56 * The maximum number of elements is defined as: the number of
57 * elements that can be stored in a page times the number of
58 * page pointers that we can fit in the base structure or (using
59 * integer math):
60 *
61 * (PAGE_SIZE/element_size) * (PAGE_SIZE-8)/sizeof(void *)
62 *
63 * Here's a table showing example capacities. Note that the maximum
64 * index that the get/put() functions is just nr_objects-1. This
65 * basically means that you get 4MB of storage on 32-bit and 2MB on
66 * 64-bit.
67 *
68 *
69 * Element size | Objects | Objects |
70 * PAGE_SIZE=4k | 32-bit | 64-bit |
71 * ---------------------------------|
72 * 1 bytes | 4186112 | 2093056 |
73 * 2 bytes | 2093056 | 1046528 |
74 * 3 bytes | 1395030 | 697515 |
75 * 4 bytes | 1046528 | 523264 |
76 * 32 bytes | 130816 | 65408 |
77 * 33 bytes | 126728 | 63364 |
78 * 2048 bytes | 2044 | 1022 |
79 * 2049 bytes | 1022 | 511 |
80 * void * | 1046528 | 261632 |
81 *
82 * Since 64-bit pointers are twice the size, we lose half the
83 * capacity in the base structure. Also note that no effort is made
84 * to efficiently pack objects across page boundaries.
85 */
David Rientjesb62e4082009-08-26 14:29:22 -070086struct flex_array *flex_array_alloc(int element_size, unsigned int total,
87 gfp_t flags)
Dave Hansen534acc02009-07-29 15:04:18 -070088{
89 struct flex_array *ret;
David Rientjes45b588d2009-09-21 17:04:33 -070090 int max_size = FLEX_ARRAY_NR_BASE_PTRS *
91 FLEX_ARRAY_ELEMENTS_PER_PART(element_size);
Dave Hansen534acc02009-07-29 15:04:18 -070092
93 /* max_size will end up 0 if element_size > PAGE_SIZE */
94 if (total > max_size)
95 return NULL;
96 ret = kzalloc(sizeof(struct flex_array), flags);
97 if (!ret)
98 return NULL;
99 ret->element_size = element_size;
100 ret->total_nr_elements = total;
David Rientjes19da3dd2009-09-21 17:04:31 -0700101 if (elements_fit_in_base(ret) && !(flags & __GFP_ZERO))
Changli Gaoe59464c2010-04-23 13:17:45 -0400102 memset(&ret->parts[0], FLEX_ARRAY_FREE,
David Rientjes45b588d2009-09-21 17:04:33 -0700103 FLEX_ARRAY_BASE_BYTES_LEFT);
Dave Hansen534acc02009-07-29 15:04:18 -0700104 return ret;
105}
106
David Rientjesb62e4082009-08-26 14:29:22 -0700107static int fa_element_to_part_nr(struct flex_array *fa,
108 unsigned int element_nr)
Dave Hansen534acc02009-07-29 15:04:18 -0700109{
David Rientjes45b588d2009-09-21 17:04:33 -0700110 return element_nr / FLEX_ARRAY_ELEMENTS_PER_PART(fa->element_size);
Dave Hansen534acc02009-07-29 15:04:18 -0700111}
112
113/**
114 * flex_array_free_parts - just free the second-level pages
David Rientjesfc0d8d92009-09-21 17:04:33 -0700115 * @fa: the flex array from which to free parts
Dave Hansen534acc02009-07-29 15:04:18 -0700116 *
117 * This is to be used in cases where the base 'struct flex_array'
118 * has been statically allocated and should not be free.
119 */
120void flex_array_free_parts(struct flex_array *fa)
121{
122 int part_nr;
Dave Hansen534acc02009-07-29 15:04:18 -0700123
124 if (elements_fit_in_base(fa))
125 return;
David Rientjes45b588d2009-09-21 17:04:33 -0700126 for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++)
Dave Hansen534acc02009-07-29 15:04:18 -0700127 kfree(fa->parts[part_nr]);
128}
129
130void flex_array_free(struct flex_array *fa)
131{
132 flex_array_free_parts(fa);
133 kfree(fa);
134}
135
David Rientjesb62e4082009-08-26 14:29:22 -0700136static unsigned int index_inside_part(struct flex_array *fa,
137 unsigned int element_nr)
Dave Hansen534acc02009-07-29 15:04:18 -0700138{
David Rientjesb62e4082009-08-26 14:29:22 -0700139 unsigned int part_offset;
Dave Hansen534acc02009-07-29 15:04:18 -0700140
David Rientjes45b588d2009-09-21 17:04:33 -0700141 part_offset = element_nr %
142 FLEX_ARRAY_ELEMENTS_PER_PART(fa->element_size);
Dave Hansen534acc02009-07-29 15:04:18 -0700143 return part_offset * fa->element_size;
144}
145
146static struct flex_array_part *
147__fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags)
148{
149 struct flex_array_part *part = fa->parts[part_nr];
150 if (!part) {
David Rientjes19da3dd2009-09-21 17:04:31 -0700151 part = kmalloc(sizeof(struct flex_array_part), flags);
Dave Hansen534acc02009-07-29 15:04:18 -0700152 if (!part)
153 return NULL;
David Rientjes19da3dd2009-09-21 17:04:31 -0700154 if (!(flags & __GFP_ZERO))
155 memset(part, FLEX_ARRAY_FREE,
156 sizeof(struct flex_array_part));
Dave Hansen534acc02009-07-29 15:04:18 -0700157 fa->parts[part_nr] = part;
158 }
159 return part;
160}
161
162/**
163 * flex_array_put - copy data into the array at @element_nr
David Rientjesfc0d8d92009-09-21 17:04:33 -0700164 * @fa: the flex array to copy data into
Dave Hansen534acc02009-07-29 15:04:18 -0700165 * @element_nr: index of the position in which to insert
166 * the new element.
David Rientjesfc0d8d92009-09-21 17:04:33 -0700167 * @src: address of data to copy into the array
168 * @flags: page allocation flags to use for array expansion
169 *
Dave Hansen534acc02009-07-29 15:04:18 -0700170 *
171 * Note that this *copies* the contents of @src into
172 * the array. If you are trying to store an array of
173 * pointers, make sure to pass in &ptr instead of ptr.
Eric Parisea98eed2010-08-09 17:20:56 -0700174 * You may instead wish to use the flex_array_put_ptr()
175 * helper function.
Dave Hansen534acc02009-07-29 15:04:18 -0700176 *
177 * Locking must be provided by the caller.
178 */
David Rientjesb62e4082009-08-26 14:29:22 -0700179int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
180 gfp_t flags)
Dave Hansen534acc02009-07-29 15:04:18 -0700181{
182 int part_nr = fa_element_to_part_nr(fa, element_nr);
183 struct flex_array_part *part;
184 void *dst;
185
186 if (element_nr >= fa->total_nr_elements)
187 return -ENOSPC;
188 if (elements_fit_in_base(fa))
189 part = (struct flex_array_part *)&fa->parts[0];
David Rientjesa30b5952009-08-26 14:29:20 -0700190 else {
Dave Hansen534acc02009-07-29 15:04:18 -0700191 part = __fa_get_part(fa, part_nr, flags);
David Rientjesa30b5952009-08-26 14:29:20 -0700192 if (!part)
193 return -ENOMEM;
194 }
Dave Hansen534acc02009-07-29 15:04:18 -0700195 dst = &part->elements[index_inside_part(fa, element_nr)];
196 memcpy(dst, src, fa->element_size);
197 return 0;
198}
199
200/**
David Rientjese6de3982009-09-21 17:04:30 -0700201 * flex_array_clear - clear element in array at @element_nr
David Rientjesfc0d8d92009-09-21 17:04:33 -0700202 * @fa: the flex array of the element.
David Rientjese6de3982009-09-21 17:04:30 -0700203 * @element_nr: index of the position to clear.
204 *
205 * Locking must be provided by the caller.
206 */
207int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
208{
209 int part_nr = fa_element_to_part_nr(fa, element_nr);
210 struct flex_array_part *part;
211 void *dst;
212
213 if (element_nr >= fa->total_nr_elements)
214 return -ENOSPC;
215 if (elements_fit_in_base(fa))
216 part = (struct flex_array_part *)&fa->parts[0];
217 else {
218 part = fa->parts[part_nr];
219 if (!part)
220 return -EINVAL;
221 }
222 dst = &part->elements[index_inside_part(fa, element_nr)];
David Rientjes19da3dd2009-09-21 17:04:31 -0700223 memset(dst, FLEX_ARRAY_FREE, fa->element_size);
David Rientjese6de3982009-09-21 17:04:30 -0700224 return 0;
225}
226
227/**
Dave Hansen534acc02009-07-29 15:04:18 -0700228 * flex_array_prealloc - guarantee that array space exists
David Rientjesfc0d8d92009-09-21 17:04:33 -0700229 * @fa: the flex array for which to preallocate parts
Dave Hansen534acc02009-07-29 15:04:18 -0700230 * @start: index of first array element for which space is allocated
231 * @end: index of last (inclusive) element for which space is allocated
David Rientjesfc0d8d92009-09-21 17:04:33 -0700232 * @flags: page allocation flags
Dave Hansen534acc02009-07-29 15:04:18 -0700233 *
234 * This will guarantee that no future calls to flex_array_put()
235 * will allocate memory. It can be used if you are expecting to
236 * be holding a lock or in some atomic context while writing
237 * data into the array.
238 *
239 * Locking must be provided by the caller.
240 */
David Rientjesb62e4082009-08-26 14:29:22 -0700241int flex_array_prealloc(struct flex_array *fa, unsigned int start,
242 unsigned int end, gfp_t flags)
Dave Hansen534acc02009-07-29 15:04:18 -0700243{
244 int start_part;
245 int end_part;
246 int part_nr;
247 struct flex_array_part *part;
248
249 if (start >= fa->total_nr_elements || end >= fa->total_nr_elements)
250 return -ENOSPC;
251 if (elements_fit_in_base(fa))
252 return 0;
253 start_part = fa_element_to_part_nr(fa, start);
254 end_part = fa_element_to_part_nr(fa, end);
255 for (part_nr = start_part; part_nr <= end_part; part_nr++) {
256 part = __fa_get_part(fa, part_nr, flags);
257 if (!part)
258 return -ENOMEM;
259 }
260 return 0;
261}
262
263/**
264 * flex_array_get - pull data back out of the array
David Rientjesfc0d8d92009-09-21 17:04:33 -0700265 * @fa: the flex array from which to extract data
Dave Hansen534acc02009-07-29 15:04:18 -0700266 * @element_nr: index of the element to fetch from the array
267 *
268 * Returns a pointer to the data at index @element_nr. Note
269 * that this is a copy of the data that was passed in. If you
Eric Parisea98eed2010-08-09 17:20:56 -0700270 * are using this to store pointers, you'll get back &ptr. You
271 * may instead wish to use the flex_array_get_ptr helper.
Dave Hansen534acc02009-07-29 15:04:18 -0700272 *
273 * Locking must be provided by the caller.
274 */
David Rientjesb62e4082009-08-26 14:29:22 -0700275void *flex_array_get(struct flex_array *fa, unsigned int element_nr)
Dave Hansen534acc02009-07-29 15:04:18 -0700276{
277 int part_nr = fa_element_to_part_nr(fa, element_nr);
278 struct flex_array_part *part;
Dave Hansen534acc02009-07-29 15:04:18 -0700279
280 if (element_nr >= fa->total_nr_elements)
281 return NULL;
Dave Hansen534acc02009-07-29 15:04:18 -0700282 if (elements_fit_in_base(fa))
283 part = (struct flex_array_part *)&fa->parts[0];
David Rientjesa30b5952009-08-26 14:29:20 -0700284 else {
Dave Hansen534acc02009-07-29 15:04:18 -0700285 part = fa->parts[part_nr];
David Rientjesa30b5952009-08-26 14:29:20 -0700286 if (!part)
287 return NULL;
288 }
Dave Hansen534acc02009-07-29 15:04:18 -0700289 return &part->elements[index_inside_part(fa, element_nr)];
290}
David Rientjes4af5a2f2009-09-21 17:04:31 -0700291
Eric Parisea98eed2010-08-09 17:20:56 -0700292/**
293 * flex_array_get_ptr - pull a ptr back out of the array
294 * @fa: the flex array from which to extract data
295 * @element_nr: index of the element to fetch from the array
296 *
297 * Returns the pointer placed in the flex array at element_nr using
298 * flex_array_put_ptr(). This function should not be called if the
299 * element in question was not set using the _put_ptr() helper.
300 */
301void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr)
302{
303 void **tmp;
304
305 tmp = flex_array_get(fa, element_nr);
306 if (!tmp)
307 return NULL;
308
309 return *tmp;
310}
311
David Rientjes4af5a2f2009-09-21 17:04:31 -0700312static int part_is_free(struct flex_array_part *part)
313{
314 int i;
315
316 for (i = 0; i < sizeof(struct flex_array_part); i++)
317 if (part->elements[i] != FLEX_ARRAY_FREE)
318 return 0;
319 return 1;
320}
321
322/**
323 * flex_array_shrink - free unused second-level pages
David Rientjesfc0d8d92009-09-21 17:04:33 -0700324 * @fa: the flex array to shrink
David Rientjes4af5a2f2009-09-21 17:04:31 -0700325 *
326 * Frees all second-level pages that consist solely of unused
327 * elements. Returns the number of pages freed.
328 *
329 * Locking must be provided by the caller.
330 */
331int flex_array_shrink(struct flex_array *fa)
332{
333 struct flex_array_part *part;
David Rientjes4af5a2f2009-09-21 17:04:31 -0700334 int part_nr;
335 int ret = 0;
336
337 if (elements_fit_in_base(fa))
338 return ret;
David Rientjes45b588d2009-09-21 17:04:33 -0700339 for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) {
David Rientjes4af5a2f2009-09-21 17:04:31 -0700340 part = fa->parts[part_nr];
341 if (!part)
342 continue;
343 if (part_is_free(part)) {
344 fa->parts[part_nr] = NULL;
345 kfree(part);
346 ret++;
347 }
348 }
349 return ret;
350}