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#include <linux/xarray.h>
8
9/**
10 * idr_alloc_u32() - Allocate an ID.
11 * @idr: IDR handle.
12 * @ptr: Pointer to be associated with the new ID.
13 * @nextid: Pointer to an ID.
14 * @max: The maximum ID to allocate (inclusive).
15 * @gfp: Memory allocation flags.
16 *
17 * Allocates an unused ID in the range specified by @nextid and @max.
18 * Note that @max is inclusive whereas the @end parameter to idr_alloc()
19 * is exclusive. The new ID is assigned to @nextid before the pointer
20 * is inserted into the IDR, so if @nextid points into the object pointed
21 * to by @ptr, a concurrent lookup will not find an uninitialised ID.
22 *
23 * The caller should provide their own locking to ensure that two
24 * concurrent modifications to the IDR are not possible. Read-only
25 * accesses to the IDR may be done under the RCU read lock or may
26 * exclude simultaneous writers.
27 *
28 * Return: 0 if an ID was allocated, -ENOMEM if memory allocation failed,
29 * or -ENOSPC if no free IDs could be found. If an error occurred,
30 * @nextid is unchanged.
31 */
32int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
33 unsigned long max, gfp_t gfp)
34{
35 struct radix_tree_iter iter;
36 void __rcu **slot;
37 unsigned int base = idr->idr_base;
38 unsigned int id = *nextid;
39
40 if (WARN_ON_ONCE(!(idr->idr_rt.xa_flags & ROOT_IS_IDR)))
41 idr->idr_rt.xa_flags |= IDR_RT_MARKER;
42
43 id = (id < base) ? 0 : id - base;
44 radix_tree_iter_init(&iter, id);
45 slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base);
46 if (IS_ERR(slot))
47 return PTR_ERR(slot);
48
49 *nextid = iter.index + base;
50 /* there is a memory barrier inside radix_tree_iter_replace() */
51 radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
52 radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
53
54 return 0;
55}
56EXPORT_SYMBOL_GPL(idr_alloc_u32);
57
58/**
59 * idr_alloc() - Allocate an ID.
60 * @idr: IDR handle.
61 * @ptr: Pointer to be associated with the new ID.
62 * @start: The minimum ID (inclusive).
63 * @end: The maximum ID (exclusive).
64 * @gfp: Memory allocation flags.
65 *
66 * Allocates an unused ID in the range specified by @start and @end. If
67 * @end is <= 0, it is treated as one larger than %INT_MAX. This allows
68 * callers to use @start + N as @end as long as N is within integer range.
69 *
70 * The caller should provide their own locking to ensure that two
71 * concurrent modifications to the IDR are not possible. Read-only
72 * accesses to the IDR may be done under the RCU read lock or may
73 * exclude simultaneous writers.
74 *
75 * Return: The newly allocated ID, -ENOMEM if memory allocation failed,
76 * or -ENOSPC if no free IDs could be found.
77 */
78int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
79{
80 u32 id = start;
81 int ret;
82
83 if (WARN_ON_ONCE(start < 0))
84 return -EINVAL;
85
86 ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp);
87 if (ret)
88 return ret;
89
90 return id;
91}
92EXPORT_SYMBOL_GPL(idr_alloc);
93
94/**
95 * idr_alloc_cyclic() - Allocate an ID cyclically.
96 * @idr: IDR handle.
97 * @ptr: Pointer to be associated with the new ID.
98 * @start: The minimum ID (inclusive).
99 * @end: The maximum ID (exclusive).
100 * @gfp: Memory allocation flags.
101 *
102 * Allocates an unused ID in the range specified by @nextid and @end. If
103 * @end is <= 0, it is treated as one larger than %INT_MAX. This allows
104 * callers to use @start + N as @end as long as N is within integer range.
105 * The search for an unused ID will start at the last ID allocated and will
106 * wrap around to @start if no free IDs are found before reaching @end.
107 *
108 * The caller should provide their own locking to ensure that two
109 * concurrent modifications to the IDR are not possible. Read-only
110 * accesses to the IDR may be done under the RCU read lock or may
111 * exclude simultaneous writers.
112 *
113 * Return: The newly allocated ID, -ENOMEM if memory allocation failed,
114 * or -ENOSPC if no free IDs could be found.
115 */
116int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
117{
118 u32 id = idr->idr_next;
119 int err, max = end > 0 ? end - 1 : INT_MAX;
120
121 if ((int)id < start)
122 id = start;
123
124 err = idr_alloc_u32(idr, ptr, &id, max, gfp);
125 if ((err == -ENOSPC) && (id > start)) {
126 id = start;
127 err = idr_alloc_u32(idr, ptr, &id, max, gfp);
128 }
129 if (err)
130 return err;
131
132 idr->idr_next = id + 1;
133 return id;
134}
135EXPORT_SYMBOL(idr_alloc_cyclic);
136
137/**
138 * idr_remove() - Remove an ID from the IDR.
139 * @idr: IDR handle.
140 * @id: Pointer ID.
141 *
142 * Removes this ID from the IDR. If the ID was not previously in the IDR,
143 * this function returns %NULL.
144 *
145 * Since this function modifies the IDR, the caller should provide their
146 * own locking to ensure that concurrent modification of the same IDR is
147 * not possible.
148 *
149 * Return: The pointer formerly associated with this ID.
150 */
151void *idr_remove(struct idr *idr, unsigned long id)
152{
153 return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL);
154}
155EXPORT_SYMBOL_GPL(idr_remove);
156
157/**
158 * idr_find() - Return pointer for given ID.
159 * @idr: IDR handle.
160 * @id: Pointer ID.
161 *
162 * Looks up the pointer associated with this ID. A %NULL pointer may
163 * indicate that @id is not allocated or that the %NULL pointer was
164 * associated with this ID.
165 *
166 * This function can be called under rcu_read_lock(), given that the leaf
167 * pointers lifetimes are correctly managed.
168 *
169 * Return: The pointer associated with this ID.
170 */
171void *idr_find(const struct idr *idr, unsigned long id)
172{
173 return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base);
174}
175EXPORT_SYMBOL_GPL(idr_find);
176
177/**
178 * idr_for_each() - Iterate through all stored pointers.
179 * @idr: IDR handle.
180 * @fn: Function to be called for each pointer.
181 * @data: Data passed to callback function.
182 *
183 * The callback function will be called for each entry in @idr, passing
184 * the ID, the entry and @data.
185 *
186 * If @fn returns anything other than %0, the iteration stops and that
187 * value is returned from this function.
188 *
189 * idr_for_each() can be called concurrently with idr_alloc() and
190 * idr_remove() if protected by RCU. Newly added entries may not be
191 * seen and deleted entries may be seen, but adding and removing entries
192 * will not cause other entries to be skipped, nor spurious ones to be seen.
193 */
194int idr_for_each(const struct idr *idr,
195 int (*fn)(int id, void *p, void *data), void *data)
196{
197 struct radix_tree_iter iter;
198 void __rcu **slot;
199 int base = idr->idr_base;
200
201 radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
202 int ret;
203 unsigned long id = iter.index + base;
204
205 if (WARN_ON_ONCE(id > INT_MAX))
206 break;
207 ret = fn(id, rcu_dereference_raw(*slot), data);
208 if (ret)
209 return ret;
210 }
211
212 return 0;
213}
214EXPORT_SYMBOL(idr_for_each);
215
216/**
217 * idr_get_next() - Find next populated entry.
218 * @idr: IDR handle.
219 * @nextid: Pointer to an ID.
220 *
221 * Returns the next populated entry in the tree with an ID greater than
222 * or equal to the value pointed to by @nextid. On exit, @nextid is updated
223 * to the ID of the found value. To use in a loop, the value pointed to by
224 * nextid must be incremented by the user.
225 */
226void *idr_get_next(struct idr *idr, int *nextid)
227{
228 struct radix_tree_iter iter;
229 void __rcu **slot;
230 unsigned long base = idr->idr_base;
231 unsigned long id = *nextid;
232
233 id = (id < base) ? 0 : id - base;
234 slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
235 if (!slot)
236 return NULL;
237 id = iter.index + base;
238
239 if (WARN_ON_ONCE(id > INT_MAX))
240 return NULL;
241
242 *nextid = id;
243 return rcu_dereference_raw(*slot);
244}
245EXPORT_SYMBOL(idr_get_next);
246
247/**
248 * idr_get_next_ul() - Find next populated entry.
249 * @idr: IDR handle.
250 * @nextid: Pointer to an ID.
251 *
252 * Returns the next populated entry in the tree with an ID greater than
253 * or equal to the value pointed to by @nextid. On exit, @nextid is updated
254 * to the ID of the found value. To use in a loop, the value pointed to by
255 * nextid must be incremented by the user.
256 */
257void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
258{
259 struct radix_tree_iter iter;
260 void __rcu **slot;
261 unsigned long base = idr->idr_base;
262 unsigned long id = *nextid;
263
264 id = (id < base) ? 0 : id - base;
265 slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
266 if (!slot)
267 return NULL;
268
269 *nextid = iter.index + base;
270 return rcu_dereference_raw(*slot);
271}
272EXPORT_SYMBOL(idr_get_next_ul);
273
274/**
275 * idr_replace() - replace pointer for given ID.
276 * @idr: IDR handle.
277 * @ptr: New pointer to associate with the ID.
278 * @id: ID to change.
279 *
280 * Replace the pointer registered with an ID and return the old value.
281 * This function can be called under the RCU read lock concurrently with
282 * idr_alloc() and idr_remove() (as long as the ID being removed is not
283 * the one being replaced!).
284 *
285 * Returns: the old value on success. %-ENOENT indicates that @id was not
286 * found. %-EINVAL indicates that @ptr was not valid.
287 */
288void *idr_replace(struct idr *idr, void *ptr, unsigned long id)
289{
290 struct radix_tree_node *node;
291 void __rcu **slot = NULL;
292 void *entry;
293
294 id -= idr->idr_base;
295
296 entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
297 if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
298 return ERR_PTR(-ENOENT);
299
300 __radix_tree_replace(&idr->idr_rt, node, slot, ptr);
301
302 return entry;
303}
304EXPORT_SYMBOL(idr_replace);
305
306/**
307 * DOC: IDA description
308 *
309 * The IDA is an ID allocator which does not provide the ability to
310 * associate an ID with a pointer. As such, it only needs to store one
311 * bit per ID, and so is more space efficient than an IDR. To use an IDA,
312 * define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
313 * then initialise it using ida_init()). To allocate a new ID, call
314 * ida_alloc(), ida_alloc_min(), ida_alloc_max() or ida_alloc_range().
315 * To free an ID, call ida_free().
316 *
317 * ida_destroy() can be used to dispose of an IDA without needing to
318 * free the individual IDs in it. You can use ida_is_empty() to find
319 * out whether the IDA has any IDs currently allocated.
320 *
321 * The IDA handles its own locking. It is safe to call any of the IDA
322 * functions without synchronisation in your code.
323 *
324 * IDs are currently limited to the range [0-INT_MAX]. If this is an awkward
325 * limitation, it should be quite straightforward to raise the maximum.
326 */
327
328/*
329 * Developer's notes:
330 *
331 * The IDA uses the functionality provided by the XArray to store bitmaps in
332 * each entry. The XA_FREE_MARK is only cleared when all bits in the bitmap
333 * have been set.
334 *
335 * I considered telling the XArray that each slot is an order-10 node
336 * and indexing by bit number, but the XArray can't allow a single multi-index
337 * entry in the head, which would significantly increase memory consumption
338 * for the IDA. So instead we divide the index by the number of bits in the
339 * leaf bitmap before doing a radix tree lookup.
340 *
341 * As an optimisation, if there are only a few low bits set in any given
342 * leaf, instead of allocating a 128-byte bitmap, we store the bits
343 * as a value entry. Value entries never have the XA_FREE_MARK cleared
344 * because we can always convert them into a bitmap entry.
345 *
346 * It would be possible to optimise further; once we've run out of a
347 * single 128-byte bitmap, we currently switch to a 576-byte node, put
348 * the 128-byte bitmap in the first entry and then start allocating extra
349 * 128-byte entries. We could instead use the 512 bytes of the node's
350 * data as a bitmap before moving to that scheme. I do not believe this
351 * is a worthwhile optimisation; Rasmus Villemoes surveyed the current
352 * users of the IDA and almost none of them use more than 1024 entries.
353 * Those that do use more than the 8192 IDs that the 512 bytes would
354 * provide.
355 *
356 * The IDA always uses a lock to alloc/free. If we add a 'test_bit'
357 * equivalent, it will still need locking. Going to RCU lookup would require
358 * using RCU to free bitmaps, and that's not trivial without embedding an
359 * RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte
360 * bitmap, which is excessive.
361 */
362
363/**
364 * ida_alloc_range() - Allocate an unused ID.
365 * @ida: IDA handle.
366 * @min: Lowest ID to allocate.
367 * @max: Highest ID to allocate.
368 * @gfp: Memory allocation flags.
369 *
370 * Allocate an ID between @min and @max, inclusive. The allocated ID will
371 * not exceed %INT_MAX, even if @max is larger.
372 *
373 * Context: Any context.
374 * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,
375 * or %-ENOSPC if there are no free IDs.
376 */
377int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,
378 gfp_t gfp)
379{
380 XA_STATE(xas, &ida->xa, min / IDA_BITMAP_BITS);
381 unsigned bit = min % IDA_BITMAP_BITS;
382 unsigned long flags;
383 struct ida_bitmap *bitmap, *alloc = NULL;
384
385 if ((int)min < 0)
386 return -ENOSPC;
387
388 if ((int)max < 0)
389 max = INT_MAX;
390
391retry:
392 xas_lock_irqsave(&xas, flags);
393next:
394 bitmap = xas_find_marked(&xas, max / IDA_BITMAP_BITS, XA_FREE_MARK);
395 if (xas.xa_index > min / IDA_BITMAP_BITS)
396 bit = 0;
397 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
398 goto nospc;
399
400 if (xa_is_value(bitmap)) {
401 unsigned long tmp = xa_to_value(bitmap);
402
403 if (bit < BITS_PER_XA_VALUE) {
404 bit = find_next_zero_bit(&tmp, BITS_PER_XA_VALUE, bit);
405 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
406 goto nospc;
407 if (bit < BITS_PER_XA_VALUE) {
408 tmp |= 1UL << bit;
409 xas_store(&xas, xa_mk_value(tmp));
410 goto out;
411 }
412 }
413 bitmap = alloc;
414 if (!bitmap)
415 bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT);
416 if (!bitmap)
417 goto alloc;
418 bitmap->bitmap[0] = tmp;
419 xas_store(&xas, bitmap);
420 if (xas_error(&xas)) {
421 bitmap->bitmap[0] = 0;
422 goto out;
423 }
424 }
425
426 if (bitmap) {
427 bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit);
428 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
429 goto nospc;
430 if (bit == IDA_BITMAP_BITS)
431 goto next;
432
433 __set_bit(bit, bitmap->bitmap);
434 if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
435 xas_clear_mark(&xas, XA_FREE_MARK);
436 } else {
437 if (bit < BITS_PER_XA_VALUE) {
438 bitmap = xa_mk_value(1UL << bit);
439 } else {
440 bitmap = alloc;
441 if (!bitmap)
442 bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT);
443 if (!bitmap)
444 goto alloc;
445 __set_bit(bit, bitmap->bitmap);
446 }
447 xas_store(&xas, bitmap);
448 }
449out:
450 xas_unlock_irqrestore(&xas, flags);
451 if (xas_nomem(&xas, gfp)) {
452 xas.xa_index = min / IDA_BITMAP_BITS;
453 bit = min % IDA_BITMAP_BITS;
454 goto retry;
455 }
456 if (bitmap != alloc)
457 kfree(alloc);
458 if (xas_error(&xas))
459 return xas_error(&xas);
460 return xas.xa_index * IDA_BITMAP_BITS + bit;
461alloc:
462 xas_unlock_irqrestore(&xas, flags);
463 alloc = kzalloc(sizeof(*bitmap), gfp);
464 if (!alloc)
465 return -ENOMEM;
466 xas_set(&xas, min / IDA_BITMAP_BITS);
467 bit = min % IDA_BITMAP_BITS;
468 goto retry;
469nospc:
470 xas_unlock_irqrestore(&xas, flags);
471 return -ENOSPC;
472}
473EXPORT_SYMBOL(ida_alloc_range);
474
475/**
476 * ida_free() - Release an allocated ID.
477 * @ida: IDA handle.
478 * @id: Previously allocated ID.
479 *
480 * Context: Any context.
481 */
482void ida_free(struct ida *ida, unsigned int id)
483{
484 XA_STATE(xas, &ida->xa, id / IDA_BITMAP_BITS);
485 unsigned bit = id % IDA_BITMAP_BITS;
486 struct ida_bitmap *bitmap;
487 unsigned long flags;
488
489 BUG_ON((int)id < 0);
490
491 xas_lock_irqsave(&xas, flags);
492 bitmap = xas_load(&xas);
493
494 if (xa_is_value(bitmap)) {
495 unsigned long v = xa_to_value(bitmap);
496 if (bit >= BITS_PER_XA_VALUE)
497 goto err;
498 if (!(v & (1UL << bit)))
499 goto err;
500 v &= ~(1UL << bit);
501 if (!v)
502 goto delete;
503 xas_store(&xas, xa_mk_value(v));
504 } else {
505 if (!test_bit(bit, bitmap->bitmap))
506 goto err;
507 __clear_bit(bit, bitmap->bitmap);
508 xas_set_mark(&xas, XA_FREE_MARK);
509 if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
510 kfree(bitmap);
511delete:
512 xas_store(&xas, NULL);
513 }
514 }
515 xas_unlock_irqrestore(&xas, flags);
516 return;
517 err:
518 xas_unlock_irqrestore(&xas, flags);
519 WARN(1, "ida_free called for id=%d which is not allocated.\n", id);
520}
521EXPORT_SYMBOL(ida_free);
522
523/**
524 * ida_destroy() - Free all IDs.
525 * @ida: IDA handle.
526 *
527 * Calling this function frees all IDs and releases all resources used
528 * by an IDA. When this call returns, the IDA is empty and can be reused
529 * or freed. If the IDA is already empty, there is no need to call this
530 * function.
531 *
532 * Context: Any context.
533 */
534void ida_destroy(struct ida *ida)
535{
536 XA_STATE(xas, &ida->xa, 0);
537 struct ida_bitmap *bitmap;
538 unsigned long flags;
539
540 xas_lock_irqsave(&xas, flags);
541 xas_for_each(&xas, bitmap, ULONG_MAX) {
542 if (!xa_is_value(bitmap))
543 kfree(bitmap);
544 xas_store(&xas, NULL);
545 }
546 xas_unlock_irqrestore(&xas, flags);
547}
548EXPORT_SYMBOL(ida_destroy);
549
550#ifndef __KERNEL__
551extern void xa_dump_index(unsigned long index, unsigned int shift);
552#define IDA_CHUNK_SHIFT ilog2(IDA_BITMAP_BITS)
553
554static void ida_dump_entry(void *entry, unsigned long index)
555{
556 unsigned long i;
557
558 if (!entry)
559 return;
560
561 if (xa_is_node(entry)) {
562 struct xa_node *node = xa_to_node(entry);
563 unsigned int shift = node->shift + IDA_CHUNK_SHIFT +
564 XA_CHUNK_SHIFT;
565
566 xa_dump_index(index * IDA_BITMAP_BITS, shift);
567 xa_dump_node(node);
568 for (i = 0; i < XA_CHUNK_SIZE; i++)
569 ida_dump_entry(node->slots[i],
570 index | (i << node->shift));
571 } else if (xa_is_value(entry)) {
572 xa_dump_index(index * IDA_BITMAP_BITS, ilog2(BITS_PER_LONG));
573 pr_cont("value: data %lx [%px]\n", xa_to_value(entry), entry);
574 } else {
575 struct ida_bitmap *bitmap = entry;
576
577 xa_dump_index(index * IDA_BITMAP_BITS, IDA_CHUNK_SHIFT);
578 pr_cont("bitmap: %p data", bitmap);
579 for (i = 0; i < IDA_BITMAP_LONGS; i++)
580 pr_cont(" %lx", bitmap->bitmap[i]);
581 pr_cont("\n");
582 }
583}
584
585static void ida_dump(struct ida *ida)
586{
587 struct xarray *xa = &ida->xa;
588 pr_debug("ida: %p node %p free %d\n", ida, xa->xa_head,
589 xa->xa_flags >> ROOT_TAG_SHIFT);
590 ida_dump_entry(xa->xa_head, 0);
591}
592#endif
593