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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
35static kmem_cache_t *idr_layer_cache;
36
37static 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
51static 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 */
75int 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}
86EXPORT_SYMBOL(idr_pre_get);
87
88static 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
160static 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;
166build_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 */
225int 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}
242EXPORT_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 */
259int 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}
276EXPORT_SYMBOL(idr_get_new);
277
278static 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
284static 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 */
321void 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}
346EXPORT_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 */
359void *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}
379EXPORT_SYMBOL(idr_find);
380
381static 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
387static 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 */
402void idr_init(struct idr *idp)
403{
404 init_id_cache();
405 memset(idp, 0, sizeof(struct idr));
406 spin_lock_init(&idp->lock);
407}
408EXPORT_SYMBOL(idr_init);