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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 *
Jesper Juhle15ae2d2005-10-30 15:02:14 -08009 * Small id to pointer translation service.
Linus Torvalds1da177e2005-04-16 15:20:36 -070010 *
Jesper Juhle15ae2d2005-10-30 15:02:14 -080011 * It uses a radix tree like structure as a sparse array indexed
Linus Torvalds1da177e2005-04-16 15:20:36 -070012 * by the id to obtain the pointer. The bitmap makes allocating
Jesper Juhle15ae2d2005-10-30 15:02:14 -080013 * a new id quick.
Linus Torvalds1da177e2005-04-16 15:20:36 -070014 *
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
Jesper Juhle15ae2d2005-10-30 15:02:14 -080020 * You can release ids at any time. When all ids are released, most of
Linus Torvalds1da177e2005-04-16 15:20:36 -070021 * the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
Jesper Juhle15ae2d2005-10-30 15:02:14 -080022 * don't need to go to the memory "store" during an id allocate, just
Linus Torvalds1da177e2005-04-16 15:20:36 -070023 * 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
Jeff Mahoney5806f072006-06-26 00:27:19 -070032#include <linux/err.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070033#include <linux/string.h>
34#include <linux/idr.h>
35
Christoph Lametere18b8902006-12-06 20:33:20 -080036static struct kmem_cache *idr_layer_cache;
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
38static struct idr_layer *alloc_layer(struct idr *idp)
39{
40 struct idr_layer *p;
Roland Dreierc259cc22006-07-14 00:24:23 -070041 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -070042
Roland Dreierc259cc22006-07-14 00:24:23 -070043 spin_lock_irqsave(&idp->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -070044 if ((p = idp->id_free)) {
45 idp->id_free = p->ary[0];
46 idp->id_free_cnt--;
47 p->ary[0] = NULL;
48 }
Roland Dreierc259cc22006-07-14 00:24:23 -070049 spin_unlock_irqrestore(&idp->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -070050 return(p);
51}
52
Sonny Rao1eec0052006-06-25 05:49:34 -070053/* only called when idp->lock is held */
54static void __free_layer(struct idr *idp, struct idr_layer *p)
55{
56 p->ary[0] = idp->id_free;
57 idp->id_free = p;
58 idp->id_free_cnt++;
59}
60
Linus Torvalds1da177e2005-04-16 15:20:36 -070061static void free_layer(struct idr *idp, struct idr_layer *p)
62{
Roland Dreierc259cc22006-07-14 00:24:23 -070063 unsigned long flags;
64
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 /*
66 * Depends on the return element being zeroed.
67 */
Roland Dreierc259cc22006-07-14 00:24:23 -070068 spin_lock_irqsave(&idp->lock, flags);
Sonny Rao1eec0052006-06-25 05:49:34 -070069 __free_layer(idp, p);
Roland Dreierc259cc22006-07-14 00:24:23 -070070 spin_unlock_irqrestore(&idp->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -070071}
72
Tejun Heoe33ac8b2007-06-14 03:45:12 +090073static void idr_mark_full(struct idr_layer **pa, int id)
74{
75 struct idr_layer *p = pa[0];
76 int l = 0;
77
78 __set_bit(id & IDR_MASK, &p->bitmap);
79 /*
80 * If this layer is full mark the bit in the layer above to
81 * show that this part of the radix tree is full. This may
82 * complete the layer above and require walking up the radix
83 * tree.
84 */
85 while (p->bitmap == IDR_FULL) {
86 if (!(p = pa[++l]))
87 break;
88 id = id >> IDR_BITS;
89 __set_bit((id & IDR_MASK), &p->bitmap);
90 }
91}
92
Linus Torvalds1da177e2005-04-16 15:20:36 -070093/**
94 * idr_pre_get - reserver resources for idr allocation
95 * @idp: idr handle
96 * @gfp_mask: memory allocation flags
97 *
98 * This function should be called prior to locking and calling the
99 * following function. It preallocates enough memory to satisfy
100 * the worst possible allocation.
101 *
102 * If the system is REALLY out of memory this function returns 0,
103 * otherwise 1.
104 */
Al Virofd4f2df2005-10-21 03:18:50 -0400105int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106{
107 while (idp->id_free_cnt < IDR_FREE_MAX) {
108 struct idr_layer *new;
109 new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800110 if (new == NULL)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 return (0);
112 free_layer(idp, new);
113 }
114 return 1;
115}
116EXPORT_SYMBOL(idr_pre_get);
117
Tejun Heoe33ac8b2007-06-14 03:45:12 +0900118static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119{
120 int n, m, sh;
121 struct idr_layer *p, *new;
Tejun Heo7aae6dd2007-06-14 03:45:12 +0900122 int l, id, oid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123 long bm;
124
125 id = *starting_id;
Tejun Heo7aae6dd2007-06-14 03:45:12 +0900126 restart:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127 p = idp->top;
128 l = idp->layers;
129 pa[l--] = NULL;
130 while (1) {
131 /*
132 * We run around this while until we reach the leaf node...
133 */
134 n = (id >> (IDR_BITS*l)) & IDR_MASK;
135 bm = ~p->bitmap;
136 m = find_next_bit(&bm, IDR_SIZE, n);
137 if (m == IDR_SIZE) {
138 /* no space available go back to previous layer. */
139 l++;
Tejun Heo7aae6dd2007-06-14 03:45:12 +0900140 oid = id;
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800141 id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
Tejun Heo7aae6dd2007-06-14 03:45:12 +0900142
143 /* if already at the top layer, we need to grow */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700144 if (!(p = pa[l])) {
145 *starting_id = id;
146 return -2;
147 }
Tejun Heo7aae6dd2007-06-14 03:45:12 +0900148
149 /* If we need to go up one layer, continue the
150 * loop; otherwise, restart from the top.
151 */
152 sh = IDR_BITS * (l + 1);
153 if (oid >> sh == id >> sh)
154 continue;
155 else
156 goto restart;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157 }
158 if (m != n) {
159 sh = IDR_BITS*l;
160 id = ((id >> sh) ^ n ^ m) << sh;
161 }
162 if ((id >= MAX_ID_BIT) || (id < 0))
163 return -3;
164 if (l == 0)
165 break;
166 /*
167 * Create the layer below if it is missing.
168 */
169 if (!p->ary[m]) {
170 if (!(new = alloc_layer(idp)))
171 return -1;
172 p->ary[m] = new;
173 p->count++;
174 }
175 pa[l--] = p;
176 p = p->ary[m];
177 }
Tejun Heoe33ac8b2007-06-14 03:45:12 +0900178
179 pa[l] = p;
180 return id;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181}
182
Tejun Heoe33ac8b2007-06-14 03:45:12 +0900183static int idr_get_empty_slot(struct idr *idp, int starting_id,
184 struct idr_layer **pa)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185{
186 struct idr_layer *p, *new;
187 int layers, v, id;
Roland Dreierc259cc22006-07-14 00:24:23 -0700188 unsigned long flags;
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800189
Linus Torvalds1da177e2005-04-16 15:20:36 -0700190 id = starting_id;
191build_up:
192 p = idp->top;
193 layers = idp->layers;
194 if (unlikely(!p)) {
195 if (!(p = alloc_layer(idp)))
196 return -1;
197 layers = 1;
198 }
199 /*
200 * Add a new layer to the top of the tree if the requested
201 * id is larger than the currently allocated space.
202 */
Zaur Kambarov589777e2005-06-21 17:14:31 -0700203 while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204 layers++;
205 if (!p->count)
206 continue;
207 if (!(new = alloc_layer(idp))) {
208 /*
209 * The allocation failed. If we built part of
210 * the structure tear it down.
211 */
Roland Dreierc259cc22006-07-14 00:24:23 -0700212 spin_lock_irqsave(&idp->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 for (new = p; p && p != idp->top; new = p) {
214 p = p->ary[0];
215 new->ary[0] = NULL;
216 new->bitmap = new->count = 0;
Sonny Rao1eec0052006-06-25 05:49:34 -0700217 __free_layer(idp, new);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218 }
Roland Dreierc259cc22006-07-14 00:24:23 -0700219 spin_unlock_irqrestore(&idp->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220 return -1;
221 }
222 new->ary[0] = p;
223 new->count = 1;
224 if (p->bitmap == IDR_FULL)
225 __set_bit(0, &new->bitmap);
226 p = new;
227 }
228 idp->top = p;
229 idp->layers = layers;
Tejun Heoe33ac8b2007-06-14 03:45:12 +0900230 v = sub_alloc(idp, &id, pa);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231 if (v == -2)
232 goto build_up;
233 return(v);
234}
235
Tejun Heoe33ac8b2007-06-14 03:45:12 +0900236static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
237{
238 struct idr_layer *pa[MAX_LEVEL];
239 int id;
240
241 id = idr_get_empty_slot(idp, starting_id, pa);
242 if (id >= 0) {
243 /*
244 * Successfully found an empty slot. Install the user
245 * pointer and mark the slot full.
246 */
247 pa[0]->ary[id & IDR_MASK] = (struct idr_layer *)ptr;
248 pa[0]->count++;
249 idr_mark_full(pa, id);
250 }
251
252 return id;
253}
254
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255/**
John McCutchan7c657f22005-08-26 14:02:04 -0400256 * idr_get_new_above - allocate new idr entry above or equal to a start id
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257 * @idp: idr handle
258 * @ptr: pointer you want associated with the ide
259 * @start_id: id to start search at
260 * @id: pointer to the allocated handle
261 *
262 * This is the allocate id function. It should be called with any
263 * required locks.
264 *
265 * If memory is required, it will return -EAGAIN, you should unlock
266 * and go back to the idr_pre_get() call. If the idr is full, it will
267 * return -ENOSPC.
268 *
269 * @id returns a value in the range 0 ... 0x7fffffff
270 */
271int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
272{
273 int rv;
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800274
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275 rv = idr_get_new_above_int(idp, ptr, starting_id);
276 /*
277 * This is a cheap hack until the IDR code can be fixed to
278 * return proper error values.
279 */
280 if (rv < 0) {
281 if (rv == -1)
282 return -EAGAIN;
283 else /* Will be -3 */
284 return -ENOSPC;
285 }
286 *id = rv;
287 return 0;
288}
289EXPORT_SYMBOL(idr_get_new_above);
290
291/**
292 * idr_get_new - allocate new idr entry
293 * @idp: idr handle
294 * @ptr: pointer you want associated with the ide
295 * @id: pointer to the allocated handle
296 *
297 * This is the allocate id function. It should be called with any
298 * required locks.
299 *
300 * If memory is required, it will return -EAGAIN, you should unlock
301 * and go back to the idr_pre_get() call. If the idr is full, it will
302 * return -ENOSPC.
303 *
304 * @id returns a value in the range 0 ... 0x7fffffff
305 */
306int idr_get_new(struct idr *idp, void *ptr, int *id)
307{
308 int rv;
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800309
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310 rv = idr_get_new_above_int(idp, ptr, 0);
311 /*
312 * This is a cheap hack until the IDR code can be fixed to
313 * return proper error values.
314 */
315 if (rv < 0) {
316 if (rv == -1)
317 return -EAGAIN;
318 else /* Will be -3 */
319 return -ENOSPC;
320 }
321 *id = rv;
322 return 0;
323}
324EXPORT_SYMBOL(idr_get_new);
325
326static void idr_remove_warning(int id)
327{
328 printk("idr_remove called for id=%d which is not allocated.\n", id);
329 dump_stack();
330}
331
332static void sub_remove(struct idr *idp, int shift, int id)
333{
334 struct idr_layer *p = idp->top;
335 struct idr_layer **pa[MAX_LEVEL];
336 struct idr_layer ***paa = &pa[0];
337 int n;
338
339 *paa = NULL;
340 *++paa = &idp->top;
341
342 while ((shift > 0) && p) {
343 n = (id >> shift) & IDR_MASK;
344 __clear_bit(n, &p->bitmap);
345 *++paa = &p->ary[n];
346 p = p->ary[n];
347 shift -= IDR_BITS;
348 }
349 n = id & IDR_MASK;
350 if (likely(p != NULL && test_bit(n, &p->bitmap))){
351 __clear_bit(n, &p->bitmap);
352 p->ary[n] = NULL;
353 while(*paa && ! --((**paa)->count)){
354 free_layer(idp, **paa);
355 **paa-- = NULL;
356 }
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800357 if (!*paa)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358 idp->layers = 0;
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800359 } else
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360 idr_remove_warning(id);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361}
362
363/**
364 * idr_remove - remove the given id and free it's slot
Robert P. J. Day72fd4a32007-02-10 01:45:59 -0800365 * @idp: idr handle
366 * @id: unique key
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 */
368void idr_remove(struct idr *idp, int id)
369{
370 struct idr_layer *p;
371
372 /* Mask off upper bits we don't use for the search. */
373 id &= MAX_ID_MASK;
374
375 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800376 if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
377 idp->top->ary[0]) { // We can drop a layer
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378
379 p = idp->top->ary[0];
380 idp->top->bitmap = idp->top->count = 0;
381 free_layer(idp, idp->top);
382 idp->top = p;
383 --idp->layers;
384 }
385 while (idp->id_free_cnt >= IDR_FREE_MAX) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 p = alloc_layer(idp);
387 kmem_cache_free(idr_layer_cache, p);
388 return;
389 }
390}
391EXPORT_SYMBOL(idr_remove);
392
393/**
Kristian Hoegsberg23936cc2007-07-15 23:37:24 -0700394 * idr_remove_all - remove all ids from the given idr tree
395 * @idp: idr handle
396 *
397 * idr_destroy() only frees up unused, cached idp_layers, but this
398 * function will remove all id mappings and leave all idp_layers
399 * unused.
400 *
401 * A typical clean-up sequence for objects stored in an idr tree, will
402 * use idr_for_each() to free all objects, if necessay, then
403 * idr_remove_all() to remove all ids, and idr_destroy() to free
404 * up the cached idr_layers.
405 */
406void idr_remove_all(struct idr *idp)
407{
408 int n, id, max, error = 0;
409 struct idr_layer *p;
410 struct idr_layer *pa[MAX_LEVEL];
411 struct idr_layer **paa = &pa[0];
412
413 n = idp->layers * IDR_BITS;
414 p = idp->top;
415 max = 1 << n;
416
417 id = 0;
418 while (id < max && !error) {
419 while (n > IDR_BITS && p) {
420 n -= IDR_BITS;
421 *paa++ = p;
422 p = p->ary[(id >> n) & IDR_MASK];
423 }
424
425 id += 1 << n;
426 while (n < fls(id)) {
427 if (p) {
428 memset(p, 0, sizeof *p);
429 free_layer(idp, p);
430 }
431 n += IDR_BITS;
432 p = *--paa;
433 }
434 }
435 idp->top = NULL;
436 idp->layers = 0;
437}
438EXPORT_SYMBOL(idr_remove_all);
439
440/**
Andrew Morton8d3b3592005-10-23 12:57:18 -0700441 * idr_destroy - release all cached layers within an idr tree
442 * idp: idr handle
443 */
444void idr_destroy(struct idr *idp)
445{
446 while (idp->id_free_cnt) {
447 struct idr_layer *p = alloc_layer(idp);
448 kmem_cache_free(idr_layer_cache, p);
449 }
450}
451EXPORT_SYMBOL(idr_destroy);
452
453/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454 * idr_find - return pointer for given id
455 * @idp: idr handle
456 * @id: lookup key
457 *
458 * Return the pointer given the id it has been registered with. A %NULL
459 * return indicates that @id is not valid or you passed %NULL in
460 * idr_get_new().
461 *
462 * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
463 */
464void *idr_find(struct idr *idp, int id)
465{
466 int n;
467 struct idr_layer *p;
468
469 n = idp->layers * IDR_BITS;
470 p = idp->top;
471
472 /* Mask off upper bits we don't use for the search. */
473 id &= MAX_ID_MASK;
474
475 if (id >= (1 << n))
476 return NULL;
477
478 while (n > 0 && p) {
479 n -= IDR_BITS;
480 p = p->ary[(id >> n) & IDR_MASK];
481 }
482 return((void *)p);
483}
484EXPORT_SYMBOL(idr_find);
485
Jeff Mahoney5806f072006-06-26 00:27:19 -0700486/**
Kristian Hoegsberg96d7fa42007-07-15 23:37:24 -0700487 * idr_for_each - iterate through all stored pointers
488 * @idp: idr handle
489 * @fn: function to be called for each pointer
490 * @data: data passed back to callback function
491 *
492 * Iterate over the pointers registered with the given idr. The
493 * callback function will be called for each pointer currently
494 * registered, passing the id, the pointer and the data pointer passed
495 * to this function. It is not safe to modify the idr tree while in
496 * the callback, so functions such as idr_get_new and idr_remove are
497 * not allowed.
498 *
499 * We check the return of @fn each time. If it returns anything other
500 * than 0, we break out and return that value.
501 *
502 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
503 */
504int idr_for_each(struct idr *idp,
505 int (*fn)(int id, void *p, void *data), void *data)
506{
507 int n, id, max, error = 0;
508 struct idr_layer *p;
509 struct idr_layer *pa[MAX_LEVEL];
510 struct idr_layer **paa = &pa[0];
511
512 n = idp->layers * IDR_BITS;
513 p = idp->top;
514 max = 1 << n;
515
516 id = 0;
517 while (id < max) {
518 while (n > 0 && p) {
519 n -= IDR_BITS;
520 *paa++ = p;
521 p = p->ary[(id >> n) & IDR_MASK];
522 }
523
524 if (p) {
525 error = fn(id, (void *)p, data);
526 if (error)
527 break;
528 }
529
530 id += 1 << n;
531 while (n < fls(id)) {
532 n += IDR_BITS;
533 p = *--paa;
534 }
535 }
536
537 return error;
538}
539EXPORT_SYMBOL(idr_for_each);
540
541/**
Jeff Mahoney5806f072006-06-26 00:27:19 -0700542 * idr_replace - replace pointer for given id
543 * @idp: idr handle
544 * @ptr: pointer you want associated with the id
545 * @id: lookup key
546 *
547 * Replace the pointer registered with an id and return the old value.
548 * A -ENOENT return indicates that @id was not found.
549 * A -EINVAL return indicates that @id was not within valid constraints.
550 *
551 * The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
552 */
553void *idr_replace(struct idr *idp, void *ptr, int id)
554{
555 int n;
556 struct idr_layer *p, *old_p;
557
558 n = idp->layers * IDR_BITS;
559 p = idp->top;
560
561 id &= MAX_ID_MASK;
562
563 if (id >= (1 << n))
564 return ERR_PTR(-EINVAL);
565
566 n -= IDR_BITS;
567 while ((n > 0) && p) {
568 p = p->ary[(id >> n) & IDR_MASK];
569 n -= IDR_BITS;
570 }
571
572 n = id & IDR_MASK;
573 if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
574 return ERR_PTR(-ENOENT);
575
576 old_p = p->ary[n];
577 p->ary[n] = ptr;
578
579 return old_p;
580}
581EXPORT_SYMBOL(idr_replace);
582
Christoph Lametere18b8902006-12-06 20:33:20 -0800583static void idr_cache_ctor(void * idr_layer, struct kmem_cache *idr_layer_cache,
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800584 unsigned long flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700585{
586 memset(idr_layer, 0, sizeof(struct idr_layer));
587}
588
589static int init_id_cache(void)
590{
591 if (!idr_layer_cache)
Jesper Juhle15ae2d2005-10-30 15:02:14 -0800592 idr_layer_cache = kmem_cache_create("idr_layer_cache",
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593 sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
594 return 0;
595}
596
597/**
598 * idr_init - initialize idr handle
599 * @idp: idr handle
600 *
601 * This function is use to set up the handle (@idp) that you will pass
602 * to the rest of the functions.
603 */
604void idr_init(struct idr *idp)
605{
606 init_id_cache();
607 memset(idp, 0, sizeof(struct idr));
608 spin_lock_init(&idp->lock);
609}
610EXPORT_SYMBOL(idr_init);
Tejun Heo72dba582007-06-14 03:45:13 +0900611
612
613/*
614 * IDA - IDR based ID allocator
615 *
616 * this is id allocator without id -> pointer translation. Memory
617 * usage is much lower than full blown idr because each id only
618 * occupies a bit. ida uses a custom leaf node which contains
619 * IDA_BITMAP_BITS slots.
620 *
621 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
622 */
623
624static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
625{
626 unsigned long flags;
627
628 if (!ida->free_bitmap) {
629 spin_lock_irqsave(&ida->idr.lock, flags);
630 if (!ida->free_bitmap) {
631 ida->free_bitmap = bitmap;
632 bitmap = NULL;
633 }
634 spin_unlock_irqrestore(&ida->idr.lock, flags);
635 }
636
637 kfree(bitmap);
638}
639
640/**
641 * ida_pre_get - reserve resources for ida allocation
642 * @ida: ida handle
643 * @gfp_mask: memory allocation flag
644 *
645 * This function should be called prior to locking and calling the
646 * following function. It preallocates enough memory to satisfy the
647 * worst possible allocation.
648 *
649 * If the system is REALLY out of memory this function returns 0,
650 * otherwise 1.
651 */
652int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
653{
654 /* allocate idr_layers */
655 if (!idr_pre_get(&ida->idr, gfp_mask))
656 return 0;
657
658 /* allocate free_bitmap */
659 if (!ida->free_bitmap) {
660 struct ida_bitmap *bitmap;
661
662 bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
663 if (!bitmap)
664 return 0;
665
666 free_bitmap(ida, bitmap);
667 }
668
669 return 1;
670}
671EXPORT_SYMBOL(ida_pre_get);
672
673/**
674 * ida_get_new_above - allocate new ID above or equal to a start id
675 * @ida: ida handle
676 * @staring_id: id to start search at
677 * @p_id: pointer to the allocated handle
678 *
679 * Allocate new ID above or equal to @ida. It should be called with
680 * any required locks.
681 *
682 * If memory is required, it will return -EAGAIN, you should unlock
683 * and go back to the ida_pre_get() call. If the ida is full, it will
684 * return -ENOSPC.
685 *
686 * @p_id returns a value in the range 0 ... 0x7fffffff.
687 */
688int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
689{
690 struct idr_layer *pa[MAX_LEVEL];
691 struct ida_bitmap *bitmap;
692 unsigned long flags;
693 int idr_id = starting_id / IDA_BITMAP_BITS;
694 int offset = starting_id % IDA_BITMAP_BITS;
695 int t, id;
696
697 restart:
698 /* get vacant slot */
699 t = idr_get_empty_slot(&ida->idr, idr_id, pa);
700 if (t < 0) {
701 if (t == -1)
702 return -EAGAIN;
703 else /* will be -3 */
704 return -ENOSPC;
705 }
706
707 if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
708 return -ENOSPC;
709
710 if (t != idr_id)
711 offset = 0;
712 idr_id = t;
713
714 /* if bitmap isn't there, create a new one */
715 bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
716 if (!bitmap) {
717 spin_lock_irqsave(&ida->idr.lock, flags);
718 bitmap = ida->free_bitmap;
719 ida->free_bitmap = NULL;
720 spin_unlock_irqrestore(&ida->idr.lock, flags);
721
722 if (!bitmap)
723 return -EAGAIN;
724
725 memset(bitmap, 0, sizeof(struct ida_bitmap));
726 pa[0]->ary[idr_id & IDR_MASK] = (void *)bitmap;
727 pa[0]->count++;
728 }
729
730 /* lookup for empty slot */
731 t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
732 if (t == IDA_BITMAP_BITS) {
733 /* no empty slot after offset, continue to the next chunk */
734 idr_id++;
735 offset = 0;
736 goto restart;
737 }
738
739 id = idr_id * IDA_BITMAP_BITS + t;
740 if (id >= MAX_ID_BIT)
741 return -ENOSPC;
742
743 __set_bit(t, bitmap->bitmap);
744 if (++bitmap->nr_busy == IDA_BITMAP_BITS)
745 idr_mark_full(pa, idr_id);
746
747 *p_id = id;
748
749 /* Each leaf node can handle nearly a thousand slots and the
750 * whole idea of ida is to have small memory foot print.
751 * Throw away extra resources one by one after each successful
752 * allocation.
753 */
754 if (ida->idr.id_free_cnt || ida->free_bitmap) {
755 struct idr_layer *p = alloc_layer(&ida->idr);
756 if (p)
757 kmem_cache_free(idr_layer_cache, p);
758 }
759
760 return 0;
761}
762EXPORT_SYMBOL(ida_get_new_above);
763
764/**
765 * ida_get_new - allocate new ID
766 * @ida: idr handle
767 * @p_id: pointer to the allocated handle
768 *
769 * Allocate new ID. It should be called with any required locks.
770 *
771 * If memory is required, it will return -EAGAIN, you should unlock
772 * and go back to the idr_pre_get() call. If the idr is full, it will
773 * return -ENOSPC.
774 *
775 * @id returns a value in the range 0 ... 0x7fffffff.
776 */
777int ida_get_new(struct ida *ida, int *p_id)
778{
779 return ida_get_new_above(ida, 0, p_id);
780}
781EXPORT_SYMBOL(ida_get_new);
782
783/**
784 * ida_remove - remove the given ID
785 * @ida: ida handle
786 * @id: ID to free
787 */
788void ida_remove(struct ida *ida, int id)
789{
790 struct idr_layer *p = ida->idr.top;
791 int shift = (ida->idr.layers - 1) * IDR_BITS;
792 int idr_id = id / IDA_BITMAP_BITS;
793 int offset = id % IDA_BITMAP_BITS;
794 int n;
795 struct ida_bitmap *bitmap;
796
797 /* clear full bits while looking up the leaf idr_layer */
798 while ((shift > 0) && p) {
799 n = (idr_id >> shift) & IDR_MASK;
800 __clear_bit(n, &p->bitmap);
801 p = p->ary[n];
802 shift -= IDR_BITS;
803 }
804
805 if (p == NULL)
806 goto err;
807
808 n = idr_id & IDR_MASK;
809 __clear_bit(n, &p->bitmap);
810
811 bitmap = (void *)p->ary[n];
812 if (!test_bit(offset, bitmap->bitmap))
813 goto err;
814
815 /* update bitmap and remove it if empty */
816 __clear_bit(offset, bitmap->bitmap);
817 if (--bitmap->nr_busy == 0) {
818 __set_bit(n, &p->bitmap); /* to please idr_remove() */
819 idr_remove(&ida->idr, idr_id);
820 free_bitmap(ida, bitmap);
821 }
822
823 return;
824
825 err:
826 printk(KERN_WARNING
827 "ida_remove called for id=%d which is not allocated.\n", id);
828}
829EXPORT_SYMBOL(ida_remove);
830
831/**
832 * ida_destroy - release all cached layers within an ida tree
833 * ida: ida handle
834 */
835void ida_destroy(struct ida *ida)
836{
837 idr_destroy(&ida->idr);
838 kfree(ida->free_bitmap);
839}
840EXPORT_SYMBOL(ida_destroy);
841
842/**
843 * ida_init - initialize ida handle
844 * @ida: ida handle
845 *
846 * This function is use to set up the handle (@ida) that you will pass
847 * to the rest of the functions.
848 */
849void ida_init(struct ida *ida)
850{
851 memset(ida, 0, sizeof(struct ida));
852 idr_init(&ida->idr);
853
854}
855EXPORT_SYMBOL(ida_init);