1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/bitmap.h>
3 #include <linux/bug.h>
4 #include <linux/export.h>
5 #include <linux/idr.h>
6 #include <linux/slab.h>
7 #include <linux/spinlock.h>
8 #include <linux/xarray.h>
9
10 /**
11 * idr_alloc_u32() - Allocate an ID.
12 * @idr: IDR handle.
13 * @ptr: Pointer to be associated with the new ID.
14 * @nextid: Pointer to an ID.
15 * @max: The maximum ID to allocate (inclusive).
16 * @gfp: Memory allocation flags.
17 *
18 * Allocates an unused ID in the range specified by @nextid and @max.
19 * Note that @max is inclusive whereas the @end parameter to idr_alloc()
20 * is exclusive. The new ID is assigned to @nextid before the pointer
21 * is inserted into the IDR, so if @nextid points into the object pointed
22 * to by @ptr, a concurrent lookup will not find an uninitialised ID.
23 *
24 * The caller should provide their own locking to ensure that two
25 * concurrent modifications to the IDR are not possible. Read-only
26 * accesses to the IDR may be done under the RCU read lock or may
27 * exclude simultaneous writers.
28 *
29 * Return: 0 if an ID was allocated, -ENOMEM if memory allocation failed,
30 * or -ENOSPC if no free IDs could be found. If an error occurred,
31 * @nextid is unchanged.
32 */
33 int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
34 unsigned long max, gfp_t gfp)
35 {
36 struct radix_tree_iter iter;
37 void __rcu **slot;
38 unsigned int base = idr->idr_base;
39 unsigned int id = *nextid;
40
41 if (WARN_ON_ONCE(!(idr->idr_rt.xa_flags & ROOT_IS_IDR)))
42 idr->idr_rt.xa_flags |= IDR_RT_MARKER;
43
44 id = (id < base) ? 0 : id - base;
45 radix_tree_iter_init(&iter, id);
46 slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base);
47 if (IS_ERR(slot))
48 return PTR_ERR(slot);
49
50 *nextid = iter.index + base;
51 /* there is a memory barrier inside radix_tree_iter_replace() */
52 radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
53 radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
54
55 return 0;
56 }
57 EXPORT_SYMBOL_GPL(idr_alloc_u32);
58
59 /**
60 * idr_alloc() - Allocate an ID.
61 * @idr: IDR handle.
62 * @ptr: Pointer to be associated with the new ID.
63 * @start: The minimum ID (inclusive).
64 * @end: The maximum ID (exclusive).
65 * @gfp: Memory allocation flags.
66 *
67 * Allocates an unused ID in the range specified by @start and @end. If
68 * @end is <= 0, it is treated as one larger than %INT_MAX. This allows
69 * callers to use @start + N as @end as long as N is within integer range.
70 *
71 * The caller should provide their own locking to ensure that two
72 * concurrent modifications to the IDR are not possible. Read-only
73 * accesses to the IDR may be done under the RCU read lock or may
74 * exclude simultaneous writers.
75 *
76 * Return: The newly allocated ID, -ENOMEM if memory allocation failed,
77 * or -ENOSPC if no free IDs could be found.
78 */
79 int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
80 {
81 u32 id = start;
82 int ret;
83
84 if (WARN_ON_ONCE(start < 0))
85 return -EINVAL;
86
87 ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp);
88 if (ret)
89 return ret;
90
91 return id;
92 }
93 EXPORT_SYMBOL_GPL(idr_alloc);
94
95 /**
96 * idr_alloc_cyclic() - Allocate an ID cyclically.
97 * @idr: IDR handle.
98 * @ptr: Pointer to be associated with the new ID.
99 * @start: The minimum ID (inclusive).
100 * @end: The maximum ID (exclusive).
101 * @gfp: Memory allocation flags.
102 *
103 * Allocates an unused ID in the range specified by @nextid and @end. If
104 * @end is <= 0, it is treated as one larger than %INT_MAX. This allows
105 * callers to use @start + N as @end as long as N is within integer range.
106 * The search for an unused ID will start at the last ID allocated and will
107 * wrap around to @start if no free IDs are found before reaching @end.
108 *
109 * The caller should provide their own locking to ensure that two
110 * concurrent modifications to the IDR are not possible. Read-only
111 * accesses to the IDR may be done under the RCU read lock or may
112 * exclude simultaneous writers.
113 *
114 * Return: The newly allocated ID, -ENOMEM if memory allocation failed,
115 * or -ENOSPC if no free IDs could be found.
116 */
117 int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
118 {
119 u32 id = idr->idr_next;
120 int err, max = end > 0 ? end - 1 : INT_MAX;
121
122 if ((int)id < start)
123 id = start;
124
125 err = idr_alloc_u32(idr, ptr, &id, max, gfp);
126 if ((err == -ENOSPC) && (id > start)) {
127 id = start;
128 err = idr_alloc_u32(idr, ptr, &id, max, gfp);
129 }
130 if (err)
131 return err;
132
133 idr->idr_next = id + 1;
134 return id;
135 }
136 EXPORT_SYMBOL(idr_alloc_cyclic);
137
138 /**
139 * idr_remove() - Remove an ID from the IDR.
140 * @idr: IDR handle.
141 * @id: Pointer ID.
142 *
143 * Removes this ID from the IDR. If the ID was not previously in the IDR,
144 * this function returns %NULL.
145 *
146 * Since this function modifies the IDR, the caller should provide their
147 * own locking to ensure that concurrent modification of the same IDR is
148 * not possible.
149 *
150 * Return: The pointer formerly associated with this ID.
151 */
152 void *idr_remove(struct idr *idr, unsigned long id)
153 {
154 return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL);
155 }
156 EXPORT_SYMBOL_GPL(idr_remove);
157
158 /**
159 * idr_find() - Return pointer for given ID.
160 * @idr: IDR handle.
161 * @id: Pointer ID.
162 *
163 * Looks up the pointer associated with this ID. A %NULL pointer may
164 * indicate that @id is not allocated or that the %NULL pointer was
165 * associated with this ID.
166 *
167 * This function can be called under rcu_read_lock(), given that the leaf
168 * pointers lifetimes are correctly managed.
169 *
170 * Return: The pointer associated with this ID.
171 */
172 void *idr_find(const struct idr *idr, unsigned long id)
173 {
174 return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base);
175 }
176 EXPORT_SYMBOL_GPL(idr_find);
177
178 /**
179 * idr_for_each() - Iterate through all stored pointers.
180 * @idr: IDR handle.
181 * @fn: Function to be called for each pointer.
182 * @data: Data passed to callback function.
183 *
184 * The callback function will be called for each entry in @idr, passing
185 * the ID, the entry and @data.
186 *
187 * If @fn returns anything other than %0, the iteration stops and that
188 * value is returned from this function.
189 *
190 * idr_for_each() can be called concurrently with idr_alloc() and
191 * idr_remove() if protected by RCU. Newly added entries may not be
192 * seen and deleted entries may be seen, but adding and removing entries
193 * will not cause other entries to be skipped, nor spurious ones to be seen.
194 */
195 int idr_for_each(const struct idr *idr,
196 int (*fn)(int id, void *p, void *data), void *data)
197 {
198 struct radix_tree_iter iter;
199 void __rcu **slot;
200 int base = idr->idr_base;
201
202 radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
203 int ret;
204 unsigned long id = iter.index + base;
205
206 if (WARN_ON_ONCE(id > INT_MAX))
207 break;
208 ret = fn(id, rcu_dereference_raw(*slot), data);
209 if (ret)
210 return ret;
211 }
212
213 return 0;
214 }
215 EXPORT_SYMBOL(idr_for_each);
216
217 /**
218 * idr_get_next_ul() - Find next populated entry.
219 * @idr: IDR handle.
220 * @nextid: Pointer to an ID.
221 *
222 * Returns the next populated entry in the tree with an ID greater than
223 * or equal to the value pointed to by @nextid. On exit, @nextid is updated
224 * to the ID of the found value. To use in a loop, the value pointed to by
225 * nextid must be incremented by the user.
226 */
227 void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
228 {
229 struct radix_tree_iter iter;
230 void __rcu **slot;
231 void *entry = NULL;
232 unsigned long base = idr->idr_base;
233 unsigned long id = *nextid;
234
235 id = (id < base) ? 0 : id - base;
236 radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, id) {
237 entry = rcu_dereference_raw(*slot);
238 if (!entry)
239 continue;
240 if (!xa_is_internal(entry))
241 break;
242 if (slot != &idr->idr_rt.xa_head && !xa_is_retry(entry))
243 break;
244 slot = radix_tree_iter_retry(&iter);
245 }
246 if (!slot)
247 return NULL;
248
249 *nextid = iter.index + base;
250 return entry;
251 }
252 EXPORT_SYMBOL(idr_get_next_ul);
253
254 /**
255 * idr_get_next() - Find next populated entry.
256 * @idr: IDR handle.
257 * @nextid: Pointer to an ID.
258 *
259 * Returns the next populated entry in the tree with an ID greater than
260 * or equal to the value pointed to by @nextid. On exit, @nextid is updated
261 * to the ID of the found value. To use in a loop, the value pointed to by
262 * nextid must be incremented by the user.
263 */
264 void *idr_get_next(struct idr *idr, int *nextid)
265 {
266 unsigned long id = *nextid;
267 void *entry = idr_get_next_ul(idr, &id);
268
269 if (WARN_ON_ONCE(id > INT_MAX))
270 return NULL;
271 *nextid = id;
272 return entry;
273 }
274 EXPORT_SYMBOL(idr_get_next);
275
276 /**
277 * idr_replace() - replace pointer for given ID.
278 * @idr: IDR handle.
279 * @ptr: New pointer to associate with the ID.
280 * @id: ID to change.
281 *
282 * Replace the pointer registered with an ID and return the old value.
283 * This function can be called under the RCU read lock concurrently with
284 * idr_alloc() and idr_remove() (as long as the ID being removed is not
285 * the one being replaced!).
286 *
287 * Returns: the old value on success. %-ENOENT indicates that @id was not
288 * found. %-EINVAL indicates that @ptr was not valid.
289 */
290 void *idr_replace(struct idr *idr, void *ptr, unsigned long id)
291 {
292 struct radix_tree_node *node;
293 void __rcu **slot = NULL;
294 void *entry;
295
296 id -= idr->idr_base;
297
298 entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
299 if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
300 return ERR_PTR(-ENOENT);
301
302 __radix_tree_replace(&idr->idr_rt, node, slot, ptr);
303
304 return entry;
305 }
306 EXPORT_SYMBOL(idr_replace);
307
308 /**
309 * DOC: IDA description
310 *
311 * The IDA is an ID allocator which does not provide the ability to
312 * associate an ID with a pointer. As such, it only needs to store one
313 * bit per ID, and so is more space efficient than an IDR. To use an IDA,
314 * define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
315 * then initialise it using ida_init()). To allocate a new ID, call
316 * ida_alloc(), ida_alloc_min(), ida_alloc_max() or ida_alloc_range().
317 * To free an ID, call ida_free().
318 *
319 * ida_destroy() can be used to dispose of an IDA without needing to
320 * free the individual IDs in it. You can use ida_is_empty() to find
321 * out whether the IDA has any IDs currently allocated.
322 *
323 * The IDA handles its own locking. It is safe to call any of the IDA
324 * functions without synchronisation in your code.
325 *
326 * IDs are currently limited to the range [0-INT_MAX]. If this is an awkward
327 * limitation, it should be quite straightforward to raise the maximum.
328 */
329
330 /*
331 * Developer's notes:
332 *
333 * The IDA uses the functionality provided by the XArray to store bitmaps in
334 * each entry. The XA_FREE_MARK is only cleared when all bits in the bitmap
335 * have been set.
336 *
337 * I considered telling the XArray that each slot is an order-10 node
338 * and indexing by bit number, but the XArray can't allow a single multi-index
339 * entry in the head, which would significantly increase memory consumption
340 * for the IDA. So instead we divide the index by the number of bits in the
341 * leaf bitmap before doing a radix tree lookup.
342 *
343 * As an optimisation, if there are only a few low bits set in any given
344 * leaf, instead of allocating a 128-byte bitmap, we store the bits
345 * as a value entry. Value entries never have the XA_FREE_MARK cleared
346 * because we can always convert them into a bitmap entry.
347 *
348 * It would be possible to optimise further; once we've run out of a
349 * single 128-byte bitmap, we currently switch to a 576-byte node, put
350 * the 128-byte bitmap in the first entry and then start allocating extra
351 * 128-byte entries. We could instead use the 512 bytes of the node's
352 * data as a bitmap before moving to that scheme. I do not believe this
353 * is a worthwhile optimisation; Rasmus Villemoes surveyed the current
354 * users of the IDA and almost none of them use more than 1024 entries.
355 * Those that do use more than the 8192 IDs that the 512 bytes would
356 * provide.
357 *
358 * The IDA always uses a lock to alloc/free. If we add a 'test_bit'
359 * equivalent, it will still need locking. Going to RCU lookup would require
360 * using RCU to free bitmaps, and that's not trivial without embedding an
361 * RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte
362 * bitmap, which is excessive.
363 */
364
365 /**
366 * ida_alloc_range() - Allocate an unused ID.
367 * @ida: IDA handle.
368 * @min: Lowest ID to allocate.
369 * @max: Highest ID to allocate.
370 * @gfp: Memory allocation flags.
371 *
372 * Allocate an ID between @min and @max, inclusive. The allocated ID will
373 * not exceed %INT_MAX, even if @max is larger.
374 *
375 * Context: Any context.
376 * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,
377 * or %-ENOSPC if there are no free IDs.
378 */
379 int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,
380 gfp_t gfp)
381 {
382 XA_STATE(xas, &ida->xa, min / IDA_BITMAP_BITS);
383 unsigned bit = min % IDA_BITMAP_BITS;
384 unsigned long flags;
385 struct ida_bitmap *bitmap, *alloc = NULL;
386
387 if ((int)min < 0)
388 return -ENOSPC;
389
390 if ((int)max < 0)
391 max = INT_MAX;
392
393 retry:
394 xas_lock_irqsave(&xas, flags);
395 next:
396 bitmap = xas_find_marked(&xas, max / IDA_BITMAP_BITS, XA_FREE_MARK);
397 if (xas.xa_index > min / IDA_BITMAP_BITS)
398 bit = 0;
399 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
400 goto nospc;
401
402 if (xa_is_value(bitmap)) {
403 unsigned long tmp = xa_to_value(bitmap);
404
405 if (bit < BITS_PER_XA_VALUE) {
406 bit = find_next_zero_bit(&tmp, BITS_PER_XA_VALUE, bit);
407 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
408 goto nospc;
409 if (bit < BITS_PER_XA_VALUE) {
410 tmp |= 1UL << bit;
411 xas_store(&xas, xa_mk_value(tmp));
412 goto out;
413 }
414 }
415 bitmap = alloc;
416 if (!bitmap)
417 bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT);
418 if (!bitmap)
419 goto alloc;
420 bitmap->bitmap[0] = tmp;
421 xas_store(&xas, bitmap);
422 if (xas_error(&xas)) {
423 bitmap->bitmap[0] = 0;
424 goto out;
425 }
426 }
427
428 if (bitmap) {
429 bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit);
430 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
431 goto nospc;
432 if (bit == IDA_BITMAP_BITS)
433 goto next;
434
435 __set_bit(bit, bitmap->bitmap);
436 if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
437 xas_clear_mark(&xas, XA_FREE_MARK);
438 } else {
439 if (bit < BITS_PER_XA_VALUE) {
440 bitmap = xa_mk_value(1UL << bit);
441 } else {
442 bitmap = alloc;
443 if (!bitmap)
444 bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT);
445 if (!bitmap)
446 goto alloc;
447 __set_bit(bit, bitmap->bitmap);
448 }
449 xas_store(&xas, bitmap);
450 }
451 out:
452 xas_unlock_irqrestore(&xas, flags);
453 if (xas_nomem(&xas, gfp)) {
454 xas.xa_index = min / IDA_BITMAP_BITS;
455 bit = min % IDA_BITMAP_BITS;
456 goto retry;
457 }
458 if (bitmap != alloc)
459 kfree(alloc);
460 if (xas_error(&xas))
461 return xas_error(&xas);
462 return xas.xa_index * IDA_BITMAP_BITS + bit;
463 alloc:
464 xas_unlock_irqrestore(&xas, flags);
465 alloc = kzalloc(sizeof(*bitmap), gfp);
466 if (!alloc)
467 return -ENOMEM;
468 xas_set(&xas, min / IDA_BITMAP_BITS);
469 bit = min % IDA_BITMAP_BITS;
470 goto retry;
471 nospc:
472 xas_unlock_irqrestore(&xas, flags);
473 return -ENOSPC;
474 }
475 EXPORT_SYMBOL(ida_alloc_range);
476
477 /**
478 * ida_free() - Release an allocated ID.
479 * @ida: IDA handle.
480 * @id: Previously allocated ID.
481 *
482 * Context: Any context.
483 */
484 void ida_free(struct ida *ida, unsigned int id)
485 {
486 XA_STATE(xas, &ida->xa, id / IDA_BITMAP_BITS);
487 unsigned bit = id % IDA_BITMAP_BITS;
488 struct ida_bitmap *bitmap;
489 unsigned long flags;
490
491 BUG_ON((int)id < 0);
492
493 xas_lock_irqsave(&xas, flags);
494 bitmap = xas_load(&xas);
495
496 if (xa_is_value(bitmap)) {
497 unsigned long v = xa_to_value(bitmap);
498 if (bit >= BITS_PER_XA_VALUE)
499 goto err;
500 if (!(v & (1UL << bit)))
501 goto err;
502 v &= ~(1UL << bit);
503 if (!v)
504 goto delete;
505 xas_store(&xas, xa_mk_value(v));
506 } else {
507 if (!test_bit(bit, bitmap->bitmap))
508 goto err;
509 __clear_bit(bit, bitmap->bitmap);
510 xas_set_mark(&xas, XA_FREE_MARK);
511 if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
512 kfree(bitmap);
513 delete:
514 xas_store(&xas, NULL);
515 }
516 }
517 xas_unlock_irqrestore(&xas, flags);
518 return;
519 err:
520 xas_unlock_irqrestore(&xas, flags);
521 WARN(1, "ida_free called for id=%d which is not allocated.\n", id);
522 }
523 EXPORT_SYMBOL(ida_free);
524
525 /**
526 * ida_destroy() - Free all IDs.
527 * @ida: IDA handle.
528 *
529 * Calling this function frees all IDs and releases all resources used
530 * by an IDA. When this call returns, the IDA is empty and can be reused
531 * or freed. If the IDA is already empty, there is no need to call this
532 * function.
533 *
534 * Context: Any context.
535 */
536 void ida_destroy(struct ida *ida)
537 {
538 XA_STATE(xas, &ida->xa, 0);
539 struct ida_bitmap *bitmap;
540 unsigned long flags;
541
542 xas_lock_irqsave(&xas, flags);
543 xas_for_each(&xas, bitmap, ULONG_MAX) {
544 if (!xa_is_value(bitmap))
545 kfree(bitmap);
546 xas_store(&xas, NULL);
547 }
548 xas_unlock_irqrestore(&xas, flags);
549 }
550 EXPORT_SYMBOL(ida_destroy);
551
552 #ifndef __KERNEL__
553 extern void xa_dump_index(unsigned long index, unsigned int shift);
554 #define IDA_CHUNK_SHIFT ilog2(IDA_BITMAP_BITS)
555
556 static void ida_dump_entry(void *entry, unsigned long index)
557 {
558 unsigned long i;
559
560 if (!entry)
561 return;
562
563 if (xa_is_node(entry)) {
564 struct xa_node *node = xa_to_node(entry);
565 unsigned int shift = node->shift + IDA_CHUNK_SHIFT +
566 XA_CHUNK_SHIFT;
567
568 xa_dump_index(index * IDA_BITMAP_BITS, shift);
569 xa_dump_node(node);
570 for (i = 0; i < XA_CHUNK_SIZE; i++)
571 ida_dump_entry(node->slots[i],
572 index | (i << node->shift));
573 } else if (xa_is_value(entry)) {
574 xa_dump_index(index * IDA_BITMAP_BITS, ilog2(BITS_PER_LONG));
575 pr_cont("value: data %lx [%px]\n", xa_to_value(entry), entry);
576 } else {
577 struct ida_bitmap *bitmap = entry;
578
579 xa_dump_index(index * IDA_BITMAP_BITS, IDA_CHUNK_SHIFT);
580 pr_cont("bitmap: %p data", bitmap);
581 for (i = 0; i < IDA_BITMAP_LONGS; i++)
582 pr_cont(" %lx", bitmap->bitmap[i]);
583 pr_cont("\n");
584 }
585 }
586
587 static void ida_dump(struct ida *ida)
588 {
589 struct xarray *xa = &ida->xa;
590 pr_debug("ida: %p node %p free %d\n", ida, xa->xa_head,
591 xa->xa_flags >> ROOT_TAG_SHIFT);
592 ida_dump_entry(xa->xa_head, 0);
593 }
594 #endif