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1da177e4 LT |
1 | /* |
2 | * 2002-10-18 written by Jim Houston jim.houston@ccur.com | |
3 | * Copyright (C) 2002 by Concurrent Computer Corporation | |
4 | * Distributed under the GNU GPL license version 2. | |
5 | * | |
6 | * Modified by George Anzinger to reuse immediately and to use | |
7 | * find bit instructions. Also removed _irq on spinlocks. | |
8 | * | |
9 | * Small id to pointer translation service. | |
10 | * | |
11 | * It uses a radix tree like structure as a sparse array indexed | |
12 | * by the id to obtain the pointer. The bitmap makes allocating | |
13 | * a new id quick. | |
14 | * | |
15 | * You call it to allocate an id (an int) an associate with that id a | |
16 | * pointer or what ever, we treat it as a (void *). You can pass this | |
17 | * id to a user for him to pass back at a later time. You then pass | |
18 | * that id to this code and it returns your pointer. | |
19 | ||
20 | * You can release ids at any time. When all ids are released, most of | |
21 | * the memory is returned (we keep IDR_FREE_MAX) in a local pool so we | |
22 | * don't need to go to the memory "store" during an id allocate, just | |
23 | * so you don't need to be too concerned about locking and conflicts | |
24 | * with the slab allocator. | |
25 | */ | |
26 | ||
27 | #ifndef TEST // to test in user space... | |
28 | #include <linux/slab.h> | |
29 | #include <linux/init.h> | |
30 | #include <linux/module.h> | |
31 | #endif | |
32 | #include <linux/string.h> | |
33 | #include <linux/idr.h> | |
34 | ||
35 | static kmem_cache_t *idr_layer_cache; | |
36 | ||
37 | static struct idr_layer *alloc_layer(struct idr *idp) | |
38 | { | |
39 | struct idr_layer *p; | |
40 | ||
41 | spin_lock(&idp->lock); | |
42 | if ((p = idp->id_free)) { | |
43 | idp->id_free = p->ary[0]; | |
44 | idp->id_free_cnt--; | |
45 | p->ary[0] = NULL; | |
46 | } | |
47 | spin_unlock(&idp->lock); | |
48 | return(p); | |
49 | } | |
50 | ||
51 | static void free_layer(struct idr *idp, struct idr_layer *p) | |
52 | { | |
53 | /* | |
54 | * Depends on the return element being zeroed. | |
55 | */ | |
56 | spin_lock(&idp->lock); | |
57 | p->ary[0] = idp->id_free; | |
58 | idp->id_free = p; | |
59 | idp->id_free_cnt++; | |
60 | spin_unlock(&idp->lock); | |
61 | } | |
62 | ||
63 | /** | |
64 | * idr_pre_get - reserver resources for idr allocation | |
65 | * @idp: idr handle | |
66 | * @gfp_mask: memory allocation flags | |
67 | * | |
68 | * This function should be called prior to locking and calling the | |
69 | * following function. It preallocates enough memory to satisfy | |
70 | * the worst possible allocation. | |
71 | * | |
72 | * If the system is REALLY out of memory this function returns 0, | |
73 | * otherwise 1. | |
74 | */ | |
75 | int idr_pre_get(struct idr *idp, unsigned gfp_mask) | |
76 | { | |
77 | while (idp->id_free_cnt < IDR_FREE_MAX) { | |
78 | struct idr_layer *new; | |
79 | new = kmem_cache_alloc(idr_layer_cache, gfp_mask); | |
80 | if(new == NULL) | |
81 | return (0); | |
82 | free_layer(idp, new); | |
83 | } | |
84 | return 1; | |
85 | } | |
86 | EXPORT_SYMBOL(idr_pre_get); | |
87 | ||
88 | static int sub_alloc(struct idr *idp, void *ptr, int *starting_id) | |
89 | { | |
90 | int n, m, sh; | |
91 | struct idr_layer *p, *new; | |
92 | struct idr_layer *pa[MAX_LEVEL]; | |
93 | int l, id; | |
94 | long bm; | |
95 | ||
96 | id = *starting_id; | |
97 | p = idp->top; | |
98 | l = idp->layers; | |
99 | pa[l--] = NULL; | |
100 | while (1) { | |
101 | /* | |
102 | * We run around this while until we reach the leaf node... | |
103 | */ | |
104 | n = (id >> (IDR_BITS*l)) & IDR_MASK; | |
105 | bm = ~p->bitmap; | |
106 | m = find_next_bit(&bm, IDR_SIZE, n); | |
107 | if (m == IDR_SIZE) { | |
108 | /* no space available go back to previous layer. */ | |
109 | l++; | |
110 | id = (id | ((1 << (IDR_BITS*l))-1)) + 1; | |
111 | if (!(p = pa[l])) { | |
112 | *starting_id = id; | |
113 | return -2; | |
114 | } | |
115 | continue; | |
116 | } | |
117 | if (m != n) { | |
118 | sh = IDR_BITS*l; | |
119 | id = ((id >> sh) ^ n ^ m) << sh; | |
120 | } | |
121 | if ((id >= MAX_ID_BIT) || (id < 0)) | |
122 | return -3; | |
123 | if (l == 0) | |
124 | break; | |
125 | /* | |
126 | * Create the layer below if it is missing. | |
127 | */ | |
128 | if (!p->ary[m]) { | |
129 | if (!(new = alloc_layer(idp))) | |
130 | return -1; | |
131 | p->ary[m] = new; | |
132 | p->count++; | |
133 | } | |
134 | pa[l--] = p; | |
135 | p = p->ary[m]; | |
136 | } | |
137 | /* | |
138 | * We have reached the leaf node, plant the | |
139 | * users pointer and return the raw id. | |
140 | */ | |
141 | p->ary[m] = (struct idr_layer *)ptr; | |
142 | __set_bit(m, &p->bitmap); | |
143 | p->count++; | |
144 | /* | |
145 | * If this layer is full mark the bit in the layer above | |
146 | * to show that this part of the radix tree is full. | |
147 | * This may complete the layer above and require walking | |
148 | * up the radix tree. | |
149 | */ | |
150 | n = id; | |
151 | while (p->bitmap == IDR_FULL) { | |
152 | if (!(p = pa[++l])) | |
153 | break; | |
154 | n = n >> IDR_BITS; | |
155 | __set_bit((n & IDR_MASK), &p->bitmap); | |
156 | } | |
157 | return(id); | |
158 | } | |
159 | ||
160 | static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id) | |
161 | { | |
162 | struct idr_layer *p, *new; | |
163 | int layers, v, id; | |
164 | ||
165 | id = starting_id; | |
166 | build_up: | |
167 | p = idp->top; | |
168 | layers = idp->layers; | |
169 | if (unlikely(!p)) { | |
170 | if (!(p = alloc_layer(idp))) | |
171 | return -1; | |
172 | layers = 1; | |
173 | } | |
174 | /* | |
175 | * Add a new layer to the top of the tree if the requested | |
176 | * id is larger than the currently allocated space. | |
177 | */ | |
178 | while ((layers < MAX_LEVEL) && (id >= (1 << (layers*IDR_BITS)))) { | |
179 | layers++; | |
180 | if (!p->count) | |
181 | continue; | |
182 | if (!(new = alloc_layer(idp))) { | |
183 | /* | |
184 | * The allocation failed. If we built part of | |
185 | * the structure tear it down. | |
186 | */ | |
187 | for (new = p; p && p != idp->top; new = p) { | |
188 | p = p->ary[0]; | |
189 | new->ary[0] = NULL; | |
190 | new->bitmap = new->count = 0; | |
191 | free_layer(idp, new); | |
192 | } | |
193 | return -1; | |
194 | } | |
195 | new->ary[0] = p; | |
196 | new->count = 1; | |
197 | if (p->bitmap == IDR_FULL) | |
198 | __set_bit(0, &new->bitmap); | |
199 | p = new; | |
200 | } | |
201 | idp->top = p; | |
202 | idp->layers = layers; | |
203 | v = sub_alloc(idp, ptr, &id); | |
204 | if (v == -2) | |
205 | goto build_up; | |
206 | return(v); | |
207 | } | |
208 | ||
209 | /** | |
210 | * idr_get_new_above - allocate new idr entry above a start id | |
211 | * @idp: idr handle | |
212 | * @ptr: pointer you want associated with the ide | |
213 | * @start_id: id to start search at | |
214 | * @id: pointer to the allocated handle | |
215 | * | |
216 | * This is the allocate id function. It should be called with any | |
217 | * required locks. | |
218 | * | |
219 | * If memory is required, it will return -EAGAIN, you should unlock | |
220 | * and go back to the idr_pre_get() call. If the idr is full, it will | |
221 | * return -ENOSPC. | |
222 | * | |
223 | * @id returns a value in the range 0 ... 0x7fffffff | |
224 | */ | |
225 | int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id) | |
226 | { | |
227 | int rv; | |
228 | rv = idr_get_new_above_int(idp, ptr, starting_id); | |
229 | /* | |
230 | * This is a cheap hack until the IDR code can be fixed to | |
231 | * return proper error values. | |
232 | */ | |
233 | if (rv < 0) { | |
234 | if (rv == -1) | |
235 | return -EAGAIN; | |
236 | else /* Will be -3 */ | |
237 | return -ENOSPC; | |
238 | } | |
239 | *id = rv; | |
240 | return 0; | |
241 | } | |
242 | EXPORT_SYMBOL(idr_get_new_above); | |
243 | ||
244 | /** | |
245 | * idr_get_new - allocate new idr entry | |
246 | * @idp: idr handle | |
247 | * @ptr: pointer you want associated with the ide | |
248 | * @id: pointer to the allocated handle | |
249 | * | |
250 | * This is the allocate id function. It should be called with any | |
251 | * required locks. | |
252 | * | |
253 | * If memory is required, it will return -EAGAIN, you should unlock | |
254 | * and go back to the idr_pre_get() call. If the idr is full, it will | |
255 | * return -ENOSPC. | |
256 | * | |
257 | * @id returns a value in the range 0 ... 0x7fffffff | |
258 | */ | |
259 | int idr_get_new(struct idr *idp, void *ptr, int *id) | |
260 | { | |
261 | int rv; | |
262 | rv = idr_get_new_above_int(idp, ptr, 0); | |
263 | /* | |
264 | * This is a cheap hack until the IDR code can be fixed to | |
265 | * return proper error values. | |
266 | */ | |
267 | if (rv < 0) { | |
268 | if (rv == -1) | |
269 | return -EAGAIN; | |
270 | else /* Will be -3 */ | |
271 | return -ENOSPC; | |
272 | } | |
273 | *id = rv; | |
274 | return 0; | |
275 | } | |
276 | EXPORT_SYMBOL(idr_get_new); | |
277 | ||
278 | static void idr_remove_warning(int id) | |
279 | { | |
280 | printk("idr_remove called for id=%d which is not allocated.\n", id); | |
281 | dump_stack(); | |
282 | } | |
283 | ||
284 | static void sub_remove(struct idr *idp, int shift, int id) | |
285 | { | |
286 | struct idr_layer *p = idp->top; | |
287 | struct idr_layer **pa[MAX_LEVEL]; | |
288 | struct idr_layer ***paa = &pa[0]; | |
289 | int n; | |
290 | ||
291 | *paa = NULL; | |
292 | *++paa = &idp->top; | |
293 | ||
294 | while ((shift > 0) && p) { | |
295 | n = (id >> shift) & IDR_MASK; | |
296 | __clear_bit(n, &p->bitmap); | |
297 | *++paa = &p->ary[n]; | |
298 | p = p->ary[n]; | |
299 | shift -= IDR_BITS; | |
300 | } | |
301 | n = id & IDR_MASK; | |
302 | if (likely(p != NULL && test_bit(n, &p->bitmap))){ | |
303 | __clear_bit(n, &p->bitmap); | |
304 | p->ary[n] = NULL; | |
305 | while(*paa && ! --((**paa)->count)){ | |
306 | free_layer(idp, **paa); | |
307 | **paa-- = NULL; | |
308 | } | |
309 | if ( ! *paa ) | |
310 | idp->layers = 0; | |
311 | } else { | |
312 | idr_remove_warning(id); | |
313 | } | |
314 | } | |
315 | ||
316 | /** | |
317 | * idr_remove - remove the given id and free it's slot | |
318 | * idp: idr handle | |
319 | * id: uniqueue key | |
320 | */ | |
321 | void idr_remove(struct idr *idp, int id) | |
322 | { | |
323 | struct idr_layer *p; | |
324 | ||
325 | /* Mask off upper bits we don't use for the search. */ | |
326 | id &= MAX_ID_MASK; | |
327 | ||
328 | sub_remove(idp, (idp->layers - 1) * IDR_BITS, id); | |
329 | if ( idp->top && idp->top->count == 1 && | |
330 | (idp->layers > 1) && | |
331 | idp->top->ary[0]){ // We can drop a layer | |
332 | ||
333 | p = idp->top->ary[0]; | |
334 | idp->top->bitmap = idp->top->count = 0; | |
335 | free_layer(idp, idp->top); | |
336 | idp->top = p; | |
337 | --idp->layers; | |
338 | } | |
339 | while (idp->id_free_cnt >= IDR_FREE_MAX) { | |
340 | ||
341 | p = alloc_layer(idp); | |
342 | kmem_cache_free(idr_layer_cache, p); | |
343 | return; | |
344 | } | |
345 | } | |
346 | EXPORT_SYMBOL(idr_remove); | |
347 | ||
348 | /** | |
349 | * idr_find - return pointer for given id | |
350 | * @idp: idr handle | |
351 | * @id: lookup key | |
352 | * | |
353 | * Return the pointer given the id it has been registered with. A %NULL | |
354 | * return indicates that @id is not valid or you passed %NULL in | |
355 | * idr_get_new(). | |
356 | * | |
357 | * The caller must serialize idr_find() vs idr_get_new() and idr_remove(). | |
358 | */ | |
359 | void *idr_find(struct idr *idp, int id) | |
360 | { | |
361 | int n; | |
362 | struct idr_layer *p; | |
363 | ||
364 | n = idp->layers * IDR_BITS; | |
365 | p = idp->top; | |
366 | ||
367 | /* Mask off upper bits we don't use for the search. */ | |
368 | id &= MAX_ID_MASK; | |
369 | ||
370 | if (id >= (1 << n)) | |
371 | return NULL; | |
372 | ||
373 | while (n > 0 && p) { | |
374 | n -= IDR_BITS; | |
375 | p = p->ary[(id >> n) & IDR_MASK]; | |
376 | } | |
377 | return((void *)p); | |
378 | } | |
379 | EXPORT_SYMBOL(idr_find); | |
380 | ||
381 | static void idr_cache_ctor(void * idr_layer, | |
382 | kmem_cache_t *idr_layer_cache, unsigned long flags) | |
383 | { | |
384 | memset(idr_layer, 0, sizeof(struct idr_layer)); | |
385 | } | |
386 | ||
387 | static int init_id_cache(void) | |
388 | { | |
389 | if (!idr_layer_cache) | |
390 | idr_layer_cache = kmem_cache_create("idr_layer_cache", | |
391 | sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL); | |
392 | return 0; | |
393 | } | |
394 | ||
395 | /** | |
396 | * idr_init - initialize idr handle | |
397 | * @idp: idr handle | |
398 | * | |
399 | * This function is use to set up the handle (@idp) that you will pass | |
400 | * to the rest of the functions. | |
401 | */ | |
402 | void idr_init(struct idr *idp) | |
403 | { | |
404 | init_id_cache(); | |
405 | memset(idp, 0, sizeof(struct idr)); | |
406 | spin_lock_init(&idp->lock); | |
407 | } | |
408 | EXPORT_SYMBOL(idr_init); |