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1#include <linux/bitmap.h>
2#include <linux/bug.h>
3#include <linux/export.h>
4#include <linux/idr.h>
5#include <linux/slab.h>
6#include <linux/spinlock.h>
7
8DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
9static DEFINE_SPINLOCK(simple_ida_lock);
10
11/**
12 * idr_alloc_u32() - Allocate an ID.
13 * @idr: IDR handle.
14 * @ptr: Pointer to be associated with the new ID.
15 * @nextid: Pointer to an ID.
16 * @max: The maximum ID to allocate (inclusive).
17 * @gfp: Memory allocation flags.
18 *
19 * Allocates an unused ID in the range specified by @nextid and @max.
20 * Note that @max is inclusive whereas the @end parameter to idr_alloc()
21 * is exclusive. The new ID is assigned to @nextid before the pointer
22 * is inserted into the IDR, so if @nextid points into the object pointed
23 * to by @ptr, a concurrent lookup will not find an uninitialised ID.
24 *
25 * The caller should provide their own locking to ensure that two
26 * concurrent modifications to the IDR are not possible. Read-only
27 * accesses to the IDR may be done under the RCU read lock or may
28 * exclude simultaneous writers.
29 *
30 * Return: 0 if an ID was allocated, -ENOMEM if memory allocation failed,
31 * or -ENOSPC if no free IDs could be found. If an error occurred,
32 * @nextid is unchanged.
33 */
34int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
35 unsigned long max, gfp_t gfp)
36{
37 struct radix_tree_iter iter;
38 void __rcu **slot;
39 unsigned int base = idr->idr_base;
40 unsigned int id = *nextid;
41
42 if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
43 return -EINVAL;
44 if (WARN_ON_ONCE(!(idr->idr_rt.gfp_mask & ROOT_IS_IDR)))
45 idr->idr_rt.gfp_mask |= IDR_RT_MARKER;
46
47 id = (id < base) ? 0 : id - base;
48 radix_tree_iter_init(&iter, id);
49 slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base);
50 if (IS_ERR(slot))
51 return PTR_ERR(slot);
52
53 *nextid = iter.index + base;
54 /* there is a memory barrier inside radix_tree_iter_replace() */
55 radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
56 radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
57
58 return 0;
59}
60EXPORT_SYMBOL_GPL(idr_alloc_u32);
61
62/**
63 * idr_alloc() - Allocate an ID.
64 * @idr: IDR handle.
65 * @ptr: Pointer to be associated with the new ID.
66 * @start: The minimum ID (inclusive).
67 * @end: The maximum ID (exclusive).
68 * @gfp: Memory allocation flags.
69 *
70 * Allocates an unused ID in the range specified by @start and @end. If
71 * @end is <= 0, it is treated as one larger than %INT_MAX. This allows
72 * callers to use @start + N as @end as long as N is within integer range.
73 *
74 * The caller should provide their own locking to ensure that two
75 * concurrent modifications to the IDR are not possible. Read-only
76 * accesses to the IDR may be done under the RCU read lock or may
77 * exclude simultaneous writers.
78 *
79 * Return: The newly allocated ID, -ENOMEM if memory allocation failed,
80 * or -ENOSPC if no free IDs could be found.
81 */
82int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
83{
84 u32 id = start;
85 int ret;
86
87 if (WARN_ON_ONCE(start < 0))
88 return -EINVAL;
89
90 ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp);
91 if (ret)
92 return ret;
93
94 return id;
95}
96EXPORT_SYMBOL_GPL(idr_alloc);
97
98/**
99 * idr_alloc_cyclic() - Allocate an ID cyclically.
100 * @idr: IDR handle.
101 * @ptr: Pointer to be associated with the new ID.
102 * @start: The minimum ID (inclusive).
103 * @end: The maximum ID (exclusive).
104 * @gfp: Memory allocation flags.
105 *
106 * Allocates an unused ID in the range specified by @nextid and @end. If
107 * @end is <= 0, it is treated as one larger than %INT_MAX. This allows
108 * callers to use @start + N as @end as long as N is within integer range.
109 * The search for an unused ID will start at the last ID allocated and will
110 * wrap around to @start if no free IDs are found before reaching @end.
111 *
112 * The caller should provide their own locking to ensure that two
113 * concurrent modifications to the IDR are not possible. Read-only
114 * accesses to the IDR may be done under the RCU read lock or may
115 * exclude simultaneous writers.
116 *
117 * Return: The newly allocated ID, -ENOMEM if memory allocation failed,
118 * or -ENOSPC if no free IDs could be found.
119 */
120int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
121{
122 u32 id = idr->idr_next;
123 int err, max = end > 0 ? end - 1 : INT_MAX;
124
125 if ((int)id < start)
126 id = start;
127
128 err = idr_alloc_u32(idr, ptr, &id, max, gfp);
129 if ((err == -ENOSPC) && (id > start)) {
130 id = start;
131 err = idr_alloc_u32(idr, ptr, &id, max, gfp);
132 }
133 if (err)
134 return err;
135
136 idr->idr_next = id + 1;
137 return id;
138}
139EXPORT_SYMBOL(idr_alloc_cyclic);
140
141/**
142 * idr_remove() - Remove an ID from the IDR.
143 * @idr: IDR handle.
144 * @id: Pointer ID.
145 *
146 * Removes this ID from the IDR. If the ID was not previously in the IDR,
147 * this function returns %NULL.
148 *
149 * Since this function modifies the IDR, the caller should provide their
150 * own locking to ensure that concurrent modification of the same IDR is
151 * not possible.
152 *
153 * Return: The pointer formerly associated with this ID.
154 */
155void *idr_remove(struct idr *idr, unsigned long id)
156{
157 return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL);
158}
159EXPORT_SYMBOL_GPL(idr_remove);
160
161/**
162 * idr_find() - Return pointer for given ID.
163 * @idr: IDR handle.
164 * @id: Pointer ID.
165 *
166 * Looks up the pointer associated with this ID. A %NULL pointer may
167 * indicate that @id is not allocated or that the %NULL pointer was
168 * associated with this ID.
169 *
170 * This function can be called under rcu_read_lock(), given that the leaf
171 * pointers lifetimes are correctly managed.
172 *
173 * Return: The pointer associated with this ID.
174 */
175void *idr_find(const struct idr *idr, unsigned long id)
176{
177 return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base);
178}
179EXPORT_SYMBOL_GPL(idr_find);
180
181/**
182 * idr_for_each() - Iterate through all stored pointers.
183 * @idr: IDR handle.
184 * @fn: Function to be called for each pointer.
185 * @data: Data passed to callback function.
186 *
187 * The callback function will be called for each entry in @idr, passing
188 * the ID, the entry and @data.
189 *
190 * If @fn returns anything other than %0, the iteration stops and that
191 * value is returned from this function.
192 *
193 * idr_for_each() can be called concurrently with idr_alloc() and
194 * idr_remove() if protected by RCU. Newly added entries may not be
195 * seen and deleted entries may be seen, but adding and removing entries
196 * will not cause other entries to be skipped, nor spurious ones to be seen.
197 */
198int idr_for_each(const struct idr *idr,
199 int (*fn)(int id, void *p, void *data), void *data)
200{
201 struct radix_tree_iter iter;
202 void __rcu **slot;
203 int base = idr->idr_base;
204
205 radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
206 int ret;
207 unsigned long id = iter.index + base;
208
209 if (WARN_ON_ONCE(id > INT_MAX))
210 break;
211 ret = fn(id, rcu_dereference_raw(*slot), data);
212 if (ret)
213 return ret;
214 }
215
216 return 0;
217}
218EXPORT_SYMBOL(idr_for_each);
219
220/**
221 * idr_get_next() - Find next populated entry.
222 * @idr: IDR handle.
223 * @nextid: Pointer to an ID.
224 *
225 * Returns the next populated entry in the tree with an ID greater than
226 * or equal to the value pointed to by @nextid. On exit, @nextid is updated
227 * to the ID of the found value. To use in a loop, the value pointed to by
228 * nextid must be incremented by the user.
229 */
230void *idr_get_next(struct idr *idr, int *nextid)
231{
232 struct radix_tree_iter iter;
233 void __rcu **slot;
234 unsigned long base = idr->idr_base;
235 unsigned long id = *nextid;
236
237 id = (id < base) ? 0 : id - base;
238 slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
239 if (!slot)
240 return NULL;
241 id = iter.index + base;
242
243 if (WARN_ON_ONCE(id > INT_MAX))
244 return NULL;
245
246 *nextid = id;
247 return rcu_dereference_raw(*slot);
248}
249EXPORT_SYMBOL(idr_get_next);
250
251/**
252 * idr_get_next_ul() - Find next populated entry.
253 * @idr: IDR handle.
254 * @nextid: Pointer to an ID.
255 *
256 * Returns the next populated entry in the tree with an ID greater than
257 * or equal to the value pointed to by @nextid. On exit, @nextid is updated
258 * to the ID of the found value. To use in a loop, the value pointed to by
259 * nextid must be incremented by the user.
260 */
261void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
262{
263 struct radix_tree_iter iter;
264 void __rcu **slot;
265 unsigned long base = idr->idr_base;
266 unsigned long id = *nextid;
267
268 id = (id < base) ? 0 : id - base;
269 slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
270 if (!slot)
271 return NULL;
272
273 *nextid = iter.index + base;
274 return rcu_dereference_raw(*slot);
275}
276EXPORT_SYMBOL(idr_get_next_ul);
277
278/**
279 * idr_replace() - replace pointer for given ID.
280 * @idr: IDR handle.
281 * @ptr: New pointer to associate with the ID.
282 * @id: ID to change.
283 *
284 * Replace the pointer registered with an ID and return the old value.
285 * This function can be called under the RCU read lock concurrently with
286 * idr_alloc() and idr_remove() (as long as the ID being removed is not
287 * the one being replaced!).
288 *
289 * Returns: the old value on success. %-ENOENT indicates that @id was not
290 * found. %-EINVAL indicates that @ptr was not valid.
291 */
292void *idr_replace(struct idr *idr, void *ptr, unsigned long id)
293{
294 struct radix_tree_node *node;
295 void __rcu **slot = NULL;
296 void *entry;
297
298 if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
299 return ERR_PTR(-EINVAL);
300 id -= idr->idr_base;
301
302 entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
303 if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
304 return ERR_PTR(-ENOENT);
305
306 __radix_tree_replace(&idr->idr_rt, node, slot, ptr, NULL);
307
308 return entry;
309}
310EXPORT_SYMBOL(idr_replace);
311
312/**
313 * DOC: IDA description
314 *
315 * The IDA is an ID allocator which does not provide the ability to
316 * associate an ID with a pointer. As such, it only needs to store one
317 * bit per ID, and so is more space efficient than an IDR. To use an IDA,
318 * define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
319 * then initialise it using ida_init()). To allocate a new ID, call
320 * ida_simple_get(). To free an ID, call ida_simple_remove().
321 *
322 * If you have more complex locking requirements, use a loop around
323 * ida_pre_get() and ida_get_new() to allocate a new ID. Then use
324 * ida_remove() to free an ID. You must make sure that ida_get_new() and
325 * ida_remove() cannot be called at the same time as each other for the
326 * same IDA.
327 *
328 * You can also use ida_get_new_above() if you need an ID to be allocated
329 * above a particular number. ida_destroy() can be used to dispose of an
330 * IDA without needing to free the individual IDs in it. You can use
331 * ida_is_empty() to find out whether the IDA has any IDs currently allocated.
332 *
333 * IDs are currently limited to the range [0-INT_MAX]. If this is an awkward
334 * limitation, it should be quite straightforward to raise the maximum.
335 */
336
337/*
338 * Developer's notes:
339 *
340 * The IDA uses the functionality provided by the IDR & radix tree to store
341 * bitmaps in each entry. The IDR_FREE tag means there is at least one bit
342 * free, unlike the IDR where it means at least one entry is free.
343 *
344 * I considered telling the radix tree that each slot is an order-10 node
345 * and storing the bit numbers in the radix tree, but the radix tree can't
346 * allow a single multiorder entry at index 0, which would significantly
347 * increase memory consumption for the IDA. So instead we divide the index
348 * by the number of bits in the leaf bitmap before doing a radix tree lookup.
349 *
350 * As an optimisation, if there are only a few low bits set in any given
351 * leaf, instead of allocating a 128-byte bitmap, we use the 'exceptional
352 * entry' functionality of the radix tree to store BITS_PER_LONG - 2 bits
353 * directly in the entry. By being really tricksy, we could store
354 * BITS_PER_LONG - 1 bits, but there're diminishing returns after optimising
355 * for 0-3 allocated IDs.
356 *
357 * We allow the radix tree 'exceptional' count to get out of date. Nothing
358 * in the IDA nor the radix tree code checks it. If it becomes important
359 * to maintain an accurate exceptional count, switch the rcu_assign_pointer()
360 * calls to radix_tree_iter_replace() which will correct the exceptional
361 * count.
362 *
363 * The IDA always requires a lock to alloc/free. If we add a 'test_bit'
364 * equivalent, it will still need locking. Going to RCU lookup would require
365 * using RCU to free bitmaps, and that's not trivial without embedding an
366 * RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte
367 * bitmap, which is excessive.
368 */
369
370#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS - 1)
371
372/**
373 * ida_get_new_above - allocate new ID above or equal to a start id
374 * @ida: ida handle
375 * @start: id to start search at
376 * @id: pointer to the allocated handle
377 *
378 * Allocate new ID above or equal to @start. It should be called
379 * with any required locks to ensure that concurrent calls to
380 * ida_get_new_above() / ida_get_new() / ida_remove() are not allowed.
381 * Consider using ida_simple_get() if you do not have complex locking
382 * requirements.
383 *
384 * If memory is required, it will return %-EAGAIN, you should unlock
385 * and go back to the ida_pre_get() call. If the ida is full, it will
386 * return %-ENOSPC. On success, it will return 0.
387 *
388 * @id returns a value in the range @start ... %0x7fffffff.
389 */
390int ida_get_new_above(struct ida *ida, int start, int *id)
391{
392 struct radix_tree_root *root = &ida->ida_rt;
393 void __rcu **slot;
394 struct radix_tree_iter iter;
395 struct ida_bitmap *bitmap;
396 unsigned long index;
397 unsigned bit, ebit;
398 int new;
399
400 index = start / IDA_BITMAP_BITS;
401 bit = start % IDA_BITMAP_BITS;
402 ebit = bit + RADIX_TREE_EXCEPTIONAL_SHIFT;
403
404 slot = radix_tree_iter_init(&iter, index);
405 for (;;) {
406 if (slot)
407 slot = radix_tree_next_slot(slot, &iter,
408 RADIX_TREE_ITER_TAGGED);
409 if (!slot) {
410 slot = idr_get_free(root, &iter, GFP_NOWAIT, IDA_MAX);
411 if (IS_ERR(slot)) {
412 if (slot == ERR_PTR(-ENOMEM))
413 return -EAGAIN;
414 return PTR_ERR(slot);
415 }
416 }
417 if (iter.index > index) {
418 bit = 0;
419 ebit = RADIX_TREE_EXCEPTIONAL_SHIFT;
420 }
421 new = iter.index * IDA_BITMAP_BITS;
422 bitmap = rcu_dereference_raw(*slot);
423 if (radix_tree_exception(bitmap)) {
424 unsigned long tmp = (unsigned long)bitmap;
425 ebit = find_next_zero_bit(&tmp, BITS_PER_LONG, ebit);
426 if (ebit < BITS_PER_LONG) {
427 tmp |= 1UL << ebit;
428 rcu_assign_pointer(*slot, (void *)tmp);
429 *id = new + ebit - RADIX_TREE_EXCEPTIONAL_SHIFT;
430 return 0;
431 }
432 bitmap = this_cpu_xchg(ida_bitmap, NULL);
433 if (!bitmap)
434 return -EAGAIN;
435 bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
436 rcu_assign_pointer(*slot, bitmap);
437 }
438
439 if (bitmap) {
440 bit = find_next_zero_bit(bitmap->bitmap,
441 IDA_BITMAP_BITS, bit);
442 new += bit;
443 if (new < 0)
444 return -ENOSPC;
445 if (bit == IDA_BITMAP_BITS)
446 continue;
447
448 __set_bit(bit, bitmap->bitmap);
449 if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
450 radix_tree_iter_tag_clear(root, &iter,
451 IDR_FREE);
452 } else {
453 new += bit;
454 if (new < 0)
455 return -ENOSPC;
456 if (ebit < BITS_PER_LONG) {
457 bitmap = (void *)((1UL << ebit) |
458 RADIX_TREE_EXCEPTIONAL_ENTRY);
459 radix_tree_iter_replace(root, &iter, slot,
460 bitmap);
461 *id = new;
462 return 0;
463 }
464 bitmap = this_cpu_xchg(ida_bitmap, NULL);
465 if (!bitmap)
466 return -EAGAIN;
467 __set_bit(bit, bitmap->bitmap);
468 radix_tree_iter_replace(root, &iter, slot, bitmap);
469 }
470
471 *id = new;
472 return 0;
473 }
474}
475EXPORT_SYMBOL(ida_get_new_above);
476
477/**
478 * ida_remove - Free the given ID
479 * @ida: ida handle
480 * @id: ID to free
481 *
482 * This function should not be called at the same time as ida_get_new_above().
483 */
484void ida_remove(struct ida *ida, int id)
485{
486 unsigned long index = id / IDA_BITMAP_BITS;
487 unsigned offset = id % IDA_BITMAP_BITS;
488 struct ida_bitmap *bitmap;
489 unsigned long *btmp;
490 struct radix_tree_iter iter;
491 void __rcu **slot;
492
493 slot = radix_tree_iter_lookup(&ida->ida_rt, &iter, index);
494 if (!slot)
495 goto err;
496
497 bitmap = rcu_dereference_raw(*slot);
498 if (radix_tree_exception(bitmap)) {
499 btmp = (unsigned long *)slot;
500 offset += RADIX_TREE_EXCEPTIONAL_SHIFT;
501 if (offset >= BITS_PER_LONG)
502 goto err;
503 } else {
504 btmp = bitmap->bitmap;
505 }
506 if (!test_bit(offset, btmp))
507 goto err;
508
509 __clear_bit(offset, btmp);
510 radix_tree_iter_tag_set(&ida->ida_rt, &iter, IDR_FREE);
511 if (radix_tree_exception(bitmap)) {
512 if (rcu_dereference_raw(*slot) ==
513 (void *)RADIX_TREE_EXCEPTIONAL_ENTRY)
514 radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
515 } else if (bitmap_empty(btmp, IDA_BITMAP_BITS)) {
516 kfree(bitmap);
517 radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
518 }
519 return;
520 err:
521 WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
522}
523EXPORT_SYMBOL(ida_remove);
524
525/**
526 * ida_destroy - Free the contents of an ida
527 * @ida: ida handle
528 *
529 * Calling this function releases all resources associated with an IDA. When
530 * this call returns, the IDA is empty and can be reused or freed. The caller
531 * should not allow ida_remove() or ida_get_new_above() to be called at the
532 * same time.
533 */
534void ida_destroy(struct ida *ida)
535{
536 struct radix_tree_iter iter;
537 void __rcu **slot;
538
539 radix_tree_for_each_slot(slot, &ida->ida_rt, &iter, 0) {
540 struct ida_bitmap *bitmap = rcu_dereference_raw(*slot);
541 if (!radix_tree_exception(bitmap))
542 kfree(bitmap);
543 radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
544 }
545}
546EXPORT_SYMBOL(ida_destroy);
547
548/**
549 * ida_simple_get - get a new id.
550 * @ida: the (initialized) ida.
551 * @start: the minimum id (inclusive, < 0x8000000)
552 * @end: the maximum id (exclusive, < 0x8000000 or 0)
553 * @gfp_mask: memory allocation flags
554 *
555 * Allocates an id in the range start <= id < end, or returns -ENOSPC.
556 * On memory allocation failure, returns -ENOMEM.
557 *
558 * Compared to ida_get_new_above() this function does its own locking, and
559 * should be used unless there are special requirements.
560 *
561 * Use ida_simple_remove() to get rid of an id.
562 */
563int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
564 gfp_t gfp_mask)
565{
566 int ret, id;
567 unsigned int max;
568 unsigned long flags;
569
570 BUG_ON((int)start < 0);
571 BUG_ON((int)end < 0);
572
573 if (end == 0)
574 max = 0x80000000;
575 else {
576 BUG_ON(end < start);
577 max = end - 1;
578 }
579
580again:
581 if (!ida_pre_get(ida, gfp_mask))
582 return -ENOMEM;
583
584 spin_lock_irqsave(&simple_ida_lock, flags);
585 ret = ida_get_new_above(ida, start, &id);
586 if (!ret) {
587 if (id > max) {
588 ida_remove(ida, id);
589 ret = -ENOSPC;
590 } else {
591 ret = id;
592 }
593 }
594 spin_unlock_irqrestore(&simple_ida_lock, flags);
595
596 if (unlikely(ret == -EAGAIN))
597 goto again;
598
599 return ret;
600}
601EXPORT_SYMBOL(ida_simple_get);
602
603/**
604 * ida_simple_remove - remove an allocated id.
605 * @ida: the (initialized) ida.
606 * @id: the id returned by ida_simple_get.
607 *
608 * Use to release an id allocated with ida_simple_get().
609 *
610 * Compared to ida_remove() this function does its own locking, and should be
611 * used unless there are special requirements.
612 */
613void ida_simple_remove(struct ida *ida, unsigned int id)
614{
615 unsigned long flags;
616
617 BUG_ON((int)id < 0);
618 spin_lock_irqsave(&simple_ida_lock, flags);
619 ida_remove(ida, id);
620 spin_unlock_irqrestore(&simple_ida_lock, flags);
621}
622EXPORT_SYMBOL(ida_simple_remove);
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 * Modified by Nadia Derbey to make it RCU safe.
10 *
11 * Small id to pointer translation service.
12 *
13 * It uses a radix tree like structure as a sparse array indexed
14 * by the id to obtain the pointer. The bitmap makes allocating
15 * a new id quick.
16 *
17 * You call it to allocate an id (an int) an associate with that id a
18 * pointer or what ever, we treat it as a (void *). You can pass this
19 * id to a user for him to pass back at a later time. You then pass
20 * that id to this code and it returns your pointer.
21
22 * You can release ids at any time. When all ids are released, most of
23 * the memory is returned (we keep MAX_IDR_FREE) in a local pool so we
24 * don't need to go to the memory "store" during an id allocate, just
25 * so you don't need to be too concerned about locking and conflicts
26 * with the slab allocator.
27 */
28
29#ifndef TEST // to test in user space...
30#include <linux/slab.h>
31#include <linux/init.h>
32#include <linux/export.h>
33#endif
34#include <linux/err.h>
35#include <linux/string.h>
36#include <linux/idr.h>
37#include <linux/spinlock.h>
38#include <linux/percpu.h>
39#include <linux/hardirq.h>
40
41#define MAX_IDR_SHIFT (sizeof(int) * 8 - 1)
42#define MAX_IDR_BIT (1U << MAX_IDR_SHIFT)
43
44/* Leave the possibility of an incomplete final layer */
45#define MAX_IDR_LEVEL ((MAX_IDR_SHIFT + IDR_BITS - 1) / IDR_BITS)
46
47/* Number of id_layer structs to leave in free list */
48#define MAX_IDR_FREE (MAX_IDR_LEVEL * 2)
49
50static struct kmem_cache *idr_layer_cache;
51static DEFINE_PER_CPU(struct idr_layer *, idr_preload_head);
52static DEFINE_PER_CPU(int, idr_preload_cnt);
53static DEFINE_SPINLOCK(simple_ida_lock);
54
55/* the maximum ID which can be allocated given idr->layers */
56static int idr_max(int layers)
57{
58 int bits = min_t(int, layers * IDR_BITS, MAX_IDR_SHIFT);
59
60 return (1 << bits) - 1;
61}
62
63/*
64 * Prefix mask for an idr_layer at @layer. For layer 0, the prefix mask is
65 * all bits except for the lower IDR_BITS. For layer 1, 2 * IDR_BITS, and
66 * so on.
67 */
68static int idr_layer_prefix_mask(int layer)
69{
70 return ~idr_max(layer + 1);
71}
72
73static struct idr_layer *get_from_free_list(struct idr *idp)
74{
75 struct idr_layer *p;
76 unsigned long flags;
77
78 spin_lock_irqsave(&idp->lock, flags);
79 if ((p = idp->id_free)) {
80 idp->id_free = p->ary[0];
81 idp->id_free_cnt--;
82 p->ary[0] = NULL;
83 }
84 spin_unlock_irqrestore(&idp->lock, flags);
85 return(p);
86}
87
88/**
89 * idr_layer_alloc - allocate a new idr_layer
90 * @gfp_mask: allocation mask
91 * @layer_idr: optional idr to allocate from
92 *
93 * If @layer_idr is %NULL, directly allocate one using @gfp_mask or fetch
94 * one from the per-cpu preload buffer. If @layer_idr is not %NULL, fetch
95 * an idr_layer from @idr->id_free.
96 *
97 * @layer_idr is to maintain backward compatibility with the old alloc
98 * interface - idr_pre_get() and idr_get_new*() - and will be removed
99 * together with per-pool preload buffer.
100 */
101static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr)
102{
103 struct idr_layer *new;
104
105 /* this is the old path, bypass to get_from_free_list() */
106 if (layer_idr)
107 return get_from_free_list(layer_idr);
108
109 /*
110 * Try to allocate directly from kmem_cache. We want to try this
111 * before preload buffer; otherwise, non-preloading idr_alloc()
112 * users will end up taking advantage of preloading ones. As the
113 * following is allowed to fail for preloaded cases, suppress
114 * warning this time.
115 */
116 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask | __GFP_NOWARN);
117 if (new)
118 return new;
119
120 /*
121 * Try to fetch one from the per-cpu preload buffer if in process
122 * context. See idr_preload() for details.
123 */
124 if (!in_interrupt()) {
125 preempt_disable();
126 new = __this_cpu_read(idr_preload_head);
127 if (new) {
128 __this_cpu_write(idr_preload_head, new->ary[0]);
129 __this_cpu_dec(idr_preload_cnt);
130 new->ary[0] = NULL;
131 }
132 preempt_enable();
133 if (new)
134 return new;
135 }
136
137 /*
138 * Both failed. Try kmem_cache again w/o adding __GFP_NOWARN so
139 * that memory allocation failure warning is printed as intended.
140 */
141 return kmem_cache_zalloc(idr_layer_cache, gfp_mask);
142}
143
144static void idr_layer_rcu_free(struct rcu_head *head)
145{
146 struct idr_layer *layer;
147
148 layer = container_of(head, struct idr_layer, rcu_head);
149 kmem_cache_free(idr_layer_cache, layer);
150}
151
152static inline void free_layer(struct idr *idr, struct idr_layer *p)
153{
154 if (idr->hint && idr->hint == p)
155 RCU_INIT_POINTER(idr->hint, NULL);
156 call_rcu(&p->rcu_head, idr_layer_rcu_free);
157}
158
159/* only called when idp->lock is held */
160static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
161{
162 p->ary[0] = idp->id_free;
163 idp->id_free = p;
164 idp->id_free_cnt++;
165}
166
167static void move_to_free_list(struct idr *idp, struct idr_layer *p)
168{
169 unsigned long flags;
170
171 /*
172 * Depends on the return element being zeroed.
173 */
174 spin_lock_irqsave(&idp->lock, flags);
175 __move_to_free_list(idp, p);
176 spin_unlock_irqrestore(&idp->lock, flags);
177}
178
179static void idr_mark_full(struct idr_layer **pa, int id)
180{
181 struct idr_layer *p = pa[0];
182 int l = 0;
183
184 __set_bit(id & IDR_MASK, p->bitmap);
185 /*
186 * If this layer is full mark the bit in the layer above to
187 * show that this part of the radix tree is full. This may
188 * complete the layer above and require walking up the radix
189 * tree.
190 */
191 while (bitmap_full(p->bitmap, IDR_SIZE)) {
192 if (!(p = pa[++l]))
193 break;
194 id = id >> IDR_BITS;
195 __set_bit((id & IDR_MASK), p->bitmap);
196 }
197}
198
199static int __idr_pre_get(struct idr *idp, gfp_t gfp_mask)
200{
201 while (idp->id_free_cnt < MAX_IDR_FREE) {
202 struct idr_layer *new;
203 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
204 if (new == NULL)
205 return (0);
206 move_to_free_list(idp, new);
207 }
208 return 1;
209}
210
211/**
212 * sub_alloc - try to allocate an id without growing the tree depth
213 * @idp: idr handle
214 * @starting_id: id to start search at
215 * @pa: idr_layer[MAX_IDR_LEVEL] used as backtrack buffer
216 * @gfp_mask: allocation mask for idr_layer_alloc()
217 * @layer_idr: optional idr passed to idr_layer_alloc()
218 *
219 * Allocate an id in range [@starting_id, INT_MAX] from @idp without
220 * growing its depth. Returns
221 *
222 * the allocated id >= 0 if successful,
223 * -EAGAIN if the tree needs to grow for allocation to succeed,
224 * -ENOSPC if the id space is exhausted,
225 * -ENOMEM if more idr_layers need to be allocated.
226 */
227static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa,
228 gfp_t gfp_mask, struct idr *layer_idr)
229{
230 int n, m, sh;
231 struct idr_layer *p, *new;
232 int l, id, oid;
233
234 id = *starting_id;
235 restart:
236 p = idp->top;
237 l = idp->layers;
238 pa[l--] = NULL;
239 while (1) {
240 /*
241 * We run around this while until we reach the leaf node...
242 */
243 n = (id >> (IDR_BITS*l)) & IDR_MASK;
244 m = find_next_zero_bit(p->bitmap, IDR_SIZE, n);
245 if (m == IDR_SIZE) {
246 /* no space available go back to previous layer. */
247 l++;
248 oid = id;
249 id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
250
251 /* if already at the top layer, we need to grow */
252 if (id >= 1 << (idp->layers * IDR_BITS)) {
253 *starting_id = id;
254 return -EAGAIN;
255 }
256 p = pa[l];
257 BUG_ON(!p);
258
259 /* If we need to go up one layer, continue the
260 * loop; otherwise, restart from the top.
261 */
262 sh = IDR_BITS * (l + 1);
263 if (oid >> sh == id >> sh)
264 continue;
265 else
266 goto restart;
267 }
268 if (m != n) {
269 sh = IDR_BITS*l;
270 id = ((id >> sh) ^ n ^ m) << sh;
271 }
272 if ((id >= MAX_IDR_BIT) || (id < 0))
273 return -ENOSPC;
274 if (l == 0)
275 break;
276 /*
277 * Create the layer below if it is missing.
278 */
279 if (!p->ary[m]) {
280 new = idr_layer_alloc(gfp_mask, layer_idr);
281 if (!new)
282 return -ENOMEM;
283 new->layer = l-1;
284 new->prefix = id & idr_layer_prefix_mask(new->layer);
285 rcu_assign_pointer(p->ary[m], new);
286 p->count++;
287 }
288 pa[l--] = p;
289 p = p->ary[m];
290 }
291
292 pa[l] = p;
293 return id;
294}
295
296static int idr_get_empty_slot(struct idr *idp, int starting_id,
297 struct idr_layer **pa, gfp_t gfp_mask,
298 struct idr *layer_idr)
299{
300 struct idr_layer *p, *new;
301 int layers, v, id;
302 unsigned long flags;
303
304 id = starting_id;
305build_up:
306 p = idp->top;
307 layers = idp->layers;
308 if (unlikely(!p)) {
309 if (!(p = idr_layer_alloc(gfp_mask, layer_idr)))
310 return -ENOMEM;
311 p->layer = 0;
312 layers = 1;
313 }
314 /*
315 * Add a new layer to the top of the tree if the requested
316 * id is larger than the currently allocated space.
317 */
318 while (id > idr_max(layers)) {
319 layers++;
320 if (!p->count) {
321 /* special case: if the tree is currently empty,
322 * then we grow the tree by moving the top node
323 * upwards.
324 */
325 p->layer++;
326 WARN_ON_ONCE(p->prefix);
327 continue;
328 }
329 if (!(new = idr_layer_alloc(gfp_mask, layer_idr))) {
330 /*
331 * The allocation failed. If we built part of
332 * the structure tear it down.
333 */
334 spin_lock_irqsave(&idp->lock, flags);
335 for (new = p; p && p != idp->top; new = p) {
336 p = p->ary[0];
337 new->ary[0] = NULL;
338 new->count = 0;
339 bitmap_clear(new->bitmap, 0, IDR_SIZE);
340 __move_to_free_list(idp, new);
341 }
342 spin_unlock_irqrestore(&idp->lock, flags);
343 return -ENOMEM;
344 }
345 new->ary[0] = p;
346 new->count = 1;
347 new->layer = layers-1;
348 new->prefix = id & idr_layer_prefix_mask(new->layer);
349 if (bitmap_full(p->bitmap, IDR_SIZE))
350 __set_bit(0, new->bitmap);
351 p = new;
352 }
353 rcu_assign_pointer(idp->top, p);
354 idp->layers = layers;
355 v = sub_alloc(idp, &id, pa, gfp_mask, layer_idr);
356 if (v == -EAGAIN)
357 goto build_up;
358 return(v);
359}
360
361/*
362 * @id and @pa are from a successful allocation from idr_get_empty_slot().
363 * Install the user pointer @ptr and mark the slot full.
364 */
365static void idr_fill_slot(struct idr *idr, void *ptr, int id,
366 struct idr_layer **pa)
367{
368 /* update hint used for lookup, cleared from free_layer() */
369 rcu_assign_pointer(idr->hint, pa[0]);
370
371 rcu_assign_pointer(pa[0]->ary[id & IDR_MASK], (struct idr_layer *)ptr);
372 pa[0]->count++;
373 idr_mark_full(pa, id);
374}
375
376
377/**
378 * idr_preload - preload for idr_alloc()
379 * @gfp_mask: allocation mask to use for preloading
380 *
381 * Preload per-cpu layer buffer for idr_alloc(). Can only be used from
382 * process context and each idr_preload() invocation should be matched with
383 * idr_preload_end(). Note that preemption is disabled while preloaded.
384 *
385 * The first idr_alloc() in the preloaded section can be treated as if it
386 * were invoked with @gfp_mask used for preloading. This allows using more
387 * permissive allocation masks for idrs protected by spinlocks.
388 *
389 * For example, if idr_alloc() below fails, the failure can be treated as
390 * if idr_alloc() were called with GFP_KERNEL rather than GFP_NOWAIT.
391 *
392 * idr_preload(GFP_KERNEL);
393 * spin_lock(lock);
394 *
395 * id = idr_alloc(idr, ptr, start, end, GFP_NOWAIT);
396 *
397 * spin_unlock(lock);
398 * idr_preload_end();
399 * if (id < 0)
400 * error;
401 */
402void idr_preload(gfp_t gfp_mask)
403{
404 /*
405 * Consuming preload buffer from non-process context breaks preload
406 * allocation guarantee. Disallow usage from those contexts.
407 */
408 WARN_ON_ONCE(in_interrupt());
409 might_sleep_if(gfp_mask & __GFP_WAIT);
410
411 preempt_disable();
412
413 /*
414 * idr_alloc() is likely to succeed w/o full idr_layer buffer and
415 * return value from idr_alloc() needs to be checked for failure
416 * anyway. Silently give up if allocation fails. The caller can
417 * treat failures from idr_alloc() as if idr_alloc() were called
418 * with @gfp_mask which should be enough.
419 */
420 while (__this_cpu_read(idr_preload_cnt) < MAX_IDR_FREE) {
421 struct idr_layer *new;
422
423 preempt_enable();
424 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
425 preempt_disable();
426 if (!new)
427 break;
428
429 /* link the new one to per-cpu preload list */
430 new->ary[0] = __this_cpu_read(idr_preload_head);
431 __this_cpu_write(idr_preload_head, new);
432 __this_cpu_inc(idr_preload_cnt);
433 }
434}
435EXPORT_SYMBOL(idr_preload);
436
437/**
438 * idr_alloc - allocate new idr entry
439 * @idr: the (initialized) idr
440 * @ptr: pointer to be associated with the new id
441 * @start: the minimum id (inclusive)
442 * @end: the maximum id (exclusive, <= 0 for max)
443 * @gfp_mask: memory allocation flags
444 *
445 * Allocate an id in [start, end) and associate it with @ptr. If no ID is
446 * available in the specified range, returns -ENOSPC. On memory allocation
447 * failure, returns -ENOMEM.
448 *
449 * Note that @end is treated as max when <= 0. This is to always allow
450 * using @start + N as @end as long as N is inside integer range.
451 *
452 * The user is responsible for exclusively synchronizing all operations
453 * which may modify @idr. However, read-only accesses such as idr_find()
454 * or iteration can be performed under RCU read lock provided the user
455 * destroys @ptr in RCU-safe way after removal from idr.
456 */
457int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
458{
459 int max = end > 0 ? end - 1 : INT_MAX; /* inclusive upper limit */
460 struct idr_layer *pa[MAX_IDR_LEVEL + 1];
461 int id;
462
463 might_sleep_if(gfp_mask & __GFP_WAIT);
464
465 /* sanity checks */
466 if (WARN_ON_ONCE(start < 0))
467 return -EINVAL;
468 if (unlikely(max < start))
469 return -ENOSPC;
470
471 /* allocate id */
472 id = idr_get_empty_slot(idr, start, pa, gfp_mask, NULL);
473 if (unlikely(id < 0))
474 return id;
475 if (unlikely(id > max))
476 return -ENOSPC;
477
478 idr_fill_slot(idr, ptr, id, pa);
479 return id;
480}
481EXPORT_SYMBOL_GPL(idr_alloc);
482
483/**
484 * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
485 * @idr: the (initialized) idr
486 * @ptr: pointer to be associated with the new id
487 * @start: the minimum id (inclusive)
488 * @end: the maximum id (exclusive, <= 0 for max)
489 * @gfp_mask: memory allocation flags
490 *
491 * Essentially the same as idr_alloc, but prefers to allocate progressively
492 * higher ids if it can. If the "cur" counter wraps, then it will start again
493 * at the "start" end of the range and allocate one that has already been used.
494 */
495int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end,
496 gfp_t gfp_mask)
497{
498 int id;
499
500 id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask);
501 if (id == -ENOSPC)
502 id = idr_alloc(idr, ptr, start, end, gfp_mask);
503
504 if (likely(id >= 0))
505 idr->cur = id + 1;
506 return id;
507}
508EXPORT_SYMBOL(idr_alloc_cyclic);
509
510static void idr_remove_warning(int id)
511{
512 WARN(1, "idr_remove called for id=%d which is not allocated.\n", id);
513}
514
515static void sub_remove(struct idr *idp, int shift, int id)
516{
517 struct idr_layer *p = idp->top;
518 struct idr_layer **pa[MAX_IDR_LEVEL + 1];
519 struct idr_layer ***paa = &pa[0];
520 struct idr_layer *to_free;
521 int n;
522
523 *paa = NULL;
524 *++paa = &idp->top;
525
526 while ((shift > 0) && p) {
527 n = (id >> shift) & IDR_MASK;
528 __clear_bit(n, p->bitmap);
529 *++paa = &p->ary[n];
530 p = p->ary[n];
531 shift -= IDR_BITS;
532 }
533 n = id & IDR_MASK;
534 if (likely(p != NULL && test_bit(n, p->bitmap))) {
535 __clear_bit(n, p->bitmap);
536 RCU_INIT_POINTER(p->ary[n], NULL);
537 to_free = NULL;
538 while(*paa && ! --((**paa)->count)){
539 if (to_free)
540 free_layer(idp, to_free);
541 to_free = **paa;
542 **paa-- = NULL;
543 }
544 if (!*paa)
545 idp->layers = 0;
546 if (to_free)
547 free_layer(idp, to_free);
548 } else
549 idr_remove_warning(id);
550}
551
552/**
553 * idr_remove - remove the given id and free its slot
554 * @idp: idr handle
555 * @id: unique key
556 */
557void idr_remove(struct idr *idp, int id)
558{
559 struct idr_layer *p;
560 struct idr_layer *to_free;
561
562 if (id < 0)
563 return;
564
565 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
566 if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
567 idp->top->ary[0]) {
568 /*
569 * Single child at leftmost slot: we can shrink the tree.
570 * This level is not needed anymore since when layers are
571 * inserted, they are inserted at the top of the existing
572 * tree.
573 */
574 to_free = idp->top;
575 p = idp->top->ary[0];
576 rcu_assign_pointer(idp->top, p);
577 --idp->layers;
578 to_free->count = 0;
579 bitmap_clear(to_free->bitmap, 0, IDR_SIZE);
580 free_layer(idp, to_free);
581 }
582 while (idp->id_free_cnt >= MAX_IDR_FREE) {
583 p = get_from_free_list(idp);
584 /*
585 * Note: we don't call the rcu callback here, since the only
586 * layers that fall into the freelist are those that have been
587 * preallocated.
588 */
589 kmem_cache_free(idr_layer_cache, p);
590 }
591 return;
592}
593EXPORT_SYMBOL(idr_remove);
594
595static void __idr_remove_all(struct idr *idp)
596{
597 int n, id, max;
598 int bt_mask;
599 struct idr_layer *p;
600 struct idr_layer *pa[MAX_IDR_LEVEL + 1];
601 struct idr_layer **paa = &pa[0];
602
603 n = idp->layers * IDR_BITS;
604 p = idp->top;
605 RCU_INIT_POINTER(idp->top, NULL);
606 max = idr_max(idp->layers);
607
608 id = 0;
609 while (id >= 0 && id <= max) {
610 while (n > IDR_BITS && p) {
611 n -= IDR_BITS;
612 *paa++ = p;
613 p = p->ary[(id >> n) & IDR_MASK];
614 }
615
616 bt_mask = id;
617 id += 1 << n;
618 /* Get the highest bit that the above add changed from 0->1. */
619 while (n < fls(id ^ bt_mask)) {
620 if (p)
621 free_layer(idp, p);
622 n += IDR_BITS;
623 p = *--paa;
624 }
625 }
626 idp->layers = 0;
627}
628
629/**
630 * idr_destroy - release all cached layers within an idr tree
631 * @idp: idr handle
632 *
633 * Free all id mappings and all idp_layers. After this function, @idp is
634 * completely unused and can be freed / recycled. The caller is
635 * responsible for ensuring that no one else accesses @idp during or after
636 * idr_destroy().
637 *
638 * A typical clean-up sequence for objects stored in an idr tree will use
639 * idr_for_each() to free all objects, if necessay, then idr_destroy() to
640 * free up the id mappings and cached idr_layers.
641 */
642void idr_destroy(struct idr *idp)
643{
644 __idr_remove_all(idp);
645
646 while (idp->id_free_cnt) {
647 struct idr_layer *p = get_from_free_list(idp);
648 kmem_cache_free(idr_layer_cache, p);
649 }
650}
651EXPORT_SYMBOL(idr_destroy);
652
653void *idr_find_slowpath(struct idr *idp, int id)
654{
655 int n;
656 struct idr_layer *p;
657
658 if (id < 0)
659 return NULL;
660
661 p = rcu_dereference_raw(idp->top);
662 if (!p)
663 return NULL;
664 n = (p->layer+1) * IDR_BITS;
665
666 if (id > idr_max(p->layer + 1))
667 return NULL;
668 BUG_ON(n == 0);
669
670 while (n > 0 && p) {
671 n -= IDR_BITS;
672 BUG_ON(n != p->layer*IDR_BITS);
673 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
674 }
675 return((void *)p);
676}
677EXPORT_SYMBOL(idr_find_slowpath);
678
679/**
680 * idr_for_each - iterate through all stored pointers
681 * @idp: idr handle
682 * @fn: function to be called for each pointer
683 * @data: data passed back to callback function
684 *
685 * Iterate over the pointers registered with the given idr. The
686 * callback function will be called for each pointer currently
687 * registered, passing the id, the pointer and the data pointer passed
688 * to this function. It is not safe to modify the idr tree while in
689 * the callback, so functions such as idr_get_new and idr_remove are
690 * not allowed.
691 *
692 * We check the return of @fn each time. If it returns anything other
693 * than %0, we break out and return that value.
694 *
695 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
696 */
697int idr_for_each(struct idr *idp,
698 int (*fn)(int id, void *p, void *data), void *data)
699{
700 int n, id, max, error = 0;
701 struct idr_layer *p;
702 struct idr_layer *pa[MAX_IDR_LEVEL + 1];
703 struct idr_layer **paa = &pa[0];
704
705 n = idp->layers * IDR_BITS;
706 p = rcu_dereference_raw(idp->top);
707 max = idr_max(idp->layers);
708
709 id = 0;
710 while (id >= 0 && id <= max) {
711 while (n > 0 && p) {
712 n -= IDR_BITS;
713 *paa++ = p;
714 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
715 }
716
717 if (p) {
718 error = fn(id, (void *)p, data);
719 if (error)
720 break;
721 }
722
723 id += 1 << n;
724 while (n < fls(id)) {
725 n += IDR_BITS;
726 p = *--paa;
727 }
728 }
729
730 return error;
731}
732EXPORT_SYMBOL(idr_for_each);
733
734/**
735 * idr_get_next - lookup next object of id to given id.
736 * @idp: idr handle
737 * @nextidp: pointer to lookup key
738 *
739 * Returns pointer to registered object with id, which is next number to
740 * given id. After being looked up, *@nextidp will be updated for the next
741 * iteration.
742 *
743 * This function can be called under rcu_read_lock(), given that the leaf
744 * pointers lifetimes are correctly managed.
745 */
746void *idr_get_next(struct idr *idp, int *nextidp)
747{
748 struct idr_layer *p, *pa[MAX_IDR_LEVEL + 1];
749 struct idr_layer **paa = &pa[0];
750 int id = *nextidp;
751 int n, max;
752
753 /* find first ent */
754 p = rcu_dereference_raw(idp->top);
755 if (!p)
756 return NULL;
757 n = (p->layer + 1) * IDR_BITS;
758 max = idr_max(p->layer + 1);
759
760 while (id >= 0 && id <= max) {
761 while (n > 0 && p) {
762 n -= IDR_BITS;
763 *paa++ = p;
764 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
765 }
766
767 if (p) {
768 *nextidp = id;
769 return p;
770 }
771
772 /*
773 * Proceed to the next layer at the current level. Unlike
774 * idr_for_each(), @id isn't guaranteed to be aligned to
775 * layer boundary at this point and adding 1 << n may
776 * incorrectly skip IDs. Make sure we jump to the
777 * beginning of the next layer using round_up().
778 */
779 id = round_up(id + 1, 1 << n);
780 while (n < fls(id)) {
781 n += IDR_BITS;
782 p = *--paa;
783 }
784 }
785 return NULL;
786}
787EXPORT_SYMBOL(idr_get_next);
788
789
790/**
791 * idr_replace - replace pointer for given id
792 * @idp: idr handle
793 * @ptr: pointer you want associated with the id
794 * @id: lookup key
795 *
796 * Replace the pointer registered with an id and return the old value.
797 * A %-ENOENT return indicates that @id was not found.
798 * A %-EINVAL return indicates that @id was not within valid constraints.
799 *
800 * The caller must serialize with writers.
801 */
802void *idr_replace(struct idr *idp, void *ptr, int id)
803{
804 int n;
805 struct idr_layer *p, *old_p;
806
807 if (id < 0)
808 return ERR_PTR(-EINVAL);
809
810 p = idp->top;
811 if (!p)
812 return ERR_PTR(-EINVAL);
813
814 n = (p->layer+1) * IDR_BITS;
815
816 if (id >= (1 << n))
817 return ERR_PTR(-EINVAL);
818
819 n -= IDR_BITS;
820 while ((n > 0) && p) {
821 p = p->ary[(id >> n) & IDR_MASK];
822 n -= IDR_BITS;
823 }
824
825 n = id & IDR_MASK;
826 if (unlikely(p == NULL || !test_bit(n, p->bitmap)))
827 return ERR_PTR(-ENOENT);
828
829 old_p = p->ary[n];
830 rcu_assign_pointer(p->ary[n], ptr);
831
832 return old_p;
833}
834EXPORT_SYMBOL(idr_replace);
835
836void __init idr_init_cache(void)
837{
838 idr_layer_cache = kmem_cache_create("idr_layer_cache",
839 sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
840}
841
842/**
843 * idr_init - initialize idr handle
844 * @idp: idr handle
845 *
846 * This function is use to set up the handle (@idp) that you will pass
847 * to the rest of the functions.
848 */
849void idr_init(struct idr *idp)
850{
851 memset(idp, 0, sizeof(struct idr));
852 spin_lock_init(&idp->lock);
853}
854EXPORT_SYMBOL(idr_init);
855
856static int idr_has_entry(int id, void *p, void *data)
857{
858 return 1;
859}
860
861bool idr_is_empty(struct idr *idp)
862{
863 return !idr_for_each(idp, idr_has_entry, NULL);
864}
865EXPORT_SYMBOL(idr_is_empty);
866
867/**
868 * DOC: IDA description
869 * IDA - IDR based ID allocator
870 *
871 * This is id allocator without id -> pointer translation. Memory
872 * usage is much lower than full blown idr because each id only
873 * occupies a bit. ida uses a custom leaf node which contains
874 * IDA_BITMAP_BITS slots.
875 *
876 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
877 */
878
879static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
880{
881 unsigned long flags;
882
883 if (!ida->free_bitmap) {
884 spin_lock_irqsave(&ida->idr.lock, flags);
885 if (!ida->free_bitmap) {
886 ida->free_bitmap = bitmap;
887 bitmap = NULL;
888 }
889 spin_unlock_irqrestore(&ida->idr.lock, flags);
890 }
891
892 kfree(bitmap);
893}
894
895/**
896 * ida_pre_get - reserve resources for ida allocation
897 * @ida: ida handle
898 * @gfp_mask: memory allocation flag
899 *
900 * This function should be called prior to locking and calling the
901 * following function. It preallocates enough memory to satisfy the
902 * worst possible allocation.
903 *
904 * If the system is REALLY out of memory this function returns %0,
905 * otherwise %1.
906 */
907int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
908{
909 /* allocate idr_layers */
910 if (!__idr_pre_get(&ida->idr, gfp_mask))
911 return 0;
912
913 /* allocate free_bitmap */
914 if (!ida->free_bitmap) {
915 struct ida_bitmap *bitmap;
916
917 bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
918 if (!bitmap)
919 return 0;
920
921 free_bitmap(ida, bitmap);
922 }
923
924 return 1;
925}
926EXPORT_SYMBOL(ida_pre_get);
927
928/**
929 * ida_get_new_above - allocate new ID above or equal to a start id
930 * @ida: ida handle
931 * @starting_id: id to start search at
932 * @p_id: pointer to the allocated handle
933 *
934 * Allocate new ID above or equal to @starting_id. It should be called
935 * with any required locks.
936 *
937 * If memory is required, it will return %-EAGAIN, you should unlock
938 * and go back to the ida_pre_get() call. If the ida is full, it will
939 * return %-ENOSPC.
940 *
941 * @p_id returns a value in the range @starting_id ... %0x7fffffff.
942 */
943int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
944{
945 struct idr_layer *pa[MAX_IDR_LEVEL + 1];
946 struct ida_bitmap *bitmap;
947 unsigned long flags;
948 int idr_id = starting_id / IDA_BITMAP_BITS;
949 int offset = starting_id % IDA_BITMAP_BITS;
950 int t, id;
951
952 restart:
953 /* get vacant slot */
954 t = idr_get_empty_slot(&ida->idr, idr_id, pa, 0, &ida->idr);
955 if (t < 0)
956 return t == -ENOMEM ? -EAGAIN : t;
957
958 if (t * IDA_BITMAP_BITS >= MAX_IDR_BIT)
959 return -ENOSPC;
960
961 if (t != idr_id)
962 offset = 0;
963 idr_id = t;
964
965 /* if bitmap isn't there, create a new one */
966 bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
967 if (!bitmap) {
968 spin_lock_irqsave(&ida->idr.lock, flags);
969 bitmap = ida->free_bitmap;
970 ida->free_bitmap = NULL;
971 spin_unlock_irqrestore(&ida->idr.lock, flags);
972
973 if (!bitmap)
974 return -EAGAIN;
975
976 memset(bitmap, 0, sizeof(struct ida_bitmap));
977 rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
978 (void *)bitmap);
979 pa[0]->count++;
980 }
981
982 /* lookup for empty slot */
983 t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
984 if (t == IDA_BITMAP_BITS) {
985 /* no empty slot after offset, continue to the next chunk */
986 idr_id++;
987 offset = 0;
988 goto restart;
989 }
990
991 id = idr_id * IDA_BITMAP_BITS + t;
992 if (id >= MAX_IDR_BIT)
993 return -ENOSPC;
994
995 __set_bit(t, bitmap->bitmap);
996 if (++bitmap->nr_busy == IDA_BITMAP_BITS)
997 idr_mark_full(pa, idr_id);
998
999 *p_id = id;
1000
1001 /* Each leaf node can handle nearly a thousand slots and the
1002 * whole idea of ida is to have small memory foot print.
1003 * Throw away extra resources one by one after each successful
1004 * allocation.
1005 */
1006 if (ida->idr.id_free_cnt || ida->free_bitmap) {
1007 struct idr_layer *p = get_from_free_list(&ida->idr);
1008 if (p)
1009 kmem_cache_free(idr_layer_cache, p);
1010 }
1011
1012 return 0;
1013}
1014EXPORT_SYMBOL(ida_get_new_above);
1015
1016/**
1017 * ida_remove - remove the given ID
1018 * @ida: ida handle
1019 * @id: ID to free
1020 */
1021void ida_remove(struct ida *ida, int id)
1022{
1023 struct idr_layer *p = ida->idr.top;
1024 int shift = (ida->idr.layers - 1) * IDR_BITS;
1025 int idr_id = id / IDA_BITMAP_BITS;
1026 int offset = id % IDA_BITMAP_BITS;
1027 int n;
1028 struct ida_bitmap *bitmap;
1029
1030 /* clear full bits while looking up the leaf idr_layer */
1031 while ((shift > 0) && p) {
1032 n = (idr_id >> shift) & IDR_MASK;
1033 __clear_bit(n, p->bitmap);
1034 p = p->ary[n];
1035 shift -= IDR_BITS;
1036 }
1037
1038 if (p == NULL)
1039 goto err;
1040
1041 n = idr_id & IDR_MASK;
1042 __clear_bit(n, p->bitmap);
1043
1044 bitmap = (void *)p->ary[n];
1045 if (!test_bit(offset, bitmap->bitmap))
1046 goto err;
1047
1048 /* update bitmap and remove it if empty */
1049 __clear_bit(offset, bitmap->bitmap);
1050 if (--bitmap->nr_busy == 0) {
1051 __set_bit(n, p->bitmap); /* to please idr_remove() */
1052 idr_remove(&ida->idr, idr_id);
1053 free_bitmap(ida, bitmap);
1054 }
1055
1056 return;
1057
1058 err:
1059 WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
1060}
1061EXPORT_SYMBOL(ida_remove);
1062
1063/**
1064 * ida_destroy - release all cached layers within an ida tree
1065 * @ida: ida handle
1066 */
1067void ida_destroy(struct ida *ida)
1068{
1069 idr_destroy(&ida->idr);
1070 kfree(ida->free_bitmap);
1071}
1072EXPORT_SYMBOL(ida_destroy);
1073
1074/**
1075 * ida_simple_get - get a new id.
1076 * @ida: the (initialized) ida.
1077 * @start: the minimum id (inclusive, < 0x8000000)
1078 * @end: the maximum id (exclusive, < 0x8000000 or 0)
1079 * @gfp_mask: memory allocation flags
1080 *
1081 * Allocates an id in the range start <= id < end, or returns -ENOSPC.
1082 * On memory allocation failure, returns -ENOMEM.
1083 *
1084 * Use ida_simple_remove() to get rid of an id.
1085 */
1086int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
1087 gfp_t gfp_mask)
1088{
1089 int ret, id;
1090 unsigned int max;
1091 unsigned long flags;
1092
1093 BUG_ON((int)start < 0);
1094 BUG_ON((int)end < 0);
1095
1096 if (end == 0)
1097 max = 0x80000000;
1098 else {
1099 BUG_ON(end < start);
1100 max = end - 1;
1101 }
1102
1103again:
1104 if (!ida_pre_get(ida, gfp_mask))
1105 return -ENOMEM;
1106
1107 spin_lock_irqsave(&simple_ida_lock, flags);
1108 ret = ida_get_new_above(ida, start, &id);
1109 if (!ret) {
1110 if (id > max) {
1111 ida_remove(ida, id);
1112 ret = -ENOSPC;
1113 } else {
1114 ret = id;
1115 }
1116 }
1117 spin_unlock_irqrestore(&simple_ida_lock, flags);
1118
1119 if (unlikely(ret == -EAGAIN))
1120 goto again;
1121
1122 return ret;
1123}
1124EXPORT_SYMBOL(ida_simple_get);
1125
1126/**
1127 * ida_simple_remove - remove an allocated id.
1128 * @ida: the (initialized) ida.
1129 * @id: the id returned by ida_simple_get.
1130 */
1131void ida_simple_remove(struct ida *ida, unsigned int id)
1132{
1133 unsigned long flags;
1134
1135 BUG_ON((int)id < 0);
1136 spin_lock_irqsave(&simple_ida_lock, flags);
1137 ida_remove(ida, id);
1138 spin_unlock_irqrestore(&simple_ida_lock, flags);
1139}
1140EXPORT_SYMBOL(ida_simple_remove);
1141
1142/**
1143 * ida_init - initialize ida handle
1144 * @ida: ida handle
1145 *
1146 * This function is use to set up the handle (@ida) that you will pass
1147 * to the rest of the functions.
1148 */
1149void ida_init(struct ida *ida)
1150{
1151 memset(ida, 0, sizeof(struct ida));
1152 idr_init(&ida->idr);
1153
1154}
1155EXPORT_SYMBOL(ida_init);