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0a835c4f 1#include <linux/bitmap.h>
8bc3bcc9 2#include <linux/export.h>
1da177e4 3#include <linux/idr.h>
0a835c4f 4#include <linux/slab.h>
88eca020 5#include <linux/spinlock.h>
1da177e4 6
7ad3d4d8 7DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
88eca020 8static DEFINE_SPINLOCK(simple_ida_lock);
1da177e4 9
388f79fd
CM
10int idr_alloc_cmn(struct idr *idr, void *ptr, unsigned long *index,
11 unsigned long start, unsigned long end, gfp_t gfp,
12 bool ext)
d5c7409f 13{
0a835c4f 14 struct radix_tree_iter iter;
388f79fd 15 void __rcu **slot;
d5c7409f 16
0a835c4f
MW
17 if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
18 return -EINVAL;
d5c7409f 19
0a835c4f 20 radix_tree_iter_init(&iter, start);
388f79fd
CM
21 if (ext)
22 slot = idr_get_free_ext(&idr->idr_rt, &iter, gfp, end);
23 else
24 slot = idr_get_free(&idr->idr_rt, &iter, gfp, end);
0a835c4f
MW
25 if (IS_ERR(slot))
26 return PTR_ERR(slot);
d5c7409f 27
0a835c4f
MW
28 radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
29 radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
388f79fd
CM
30
31 if (index)
32 *index = iter.index;
33 return 0;
d5c7409f 34}
388f79fd 35EXPORT_SYMBOL_GPL(idr_alloc_cmn);
d5c7409f 36
3e6628c4
JL
37/**
38 * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
0a835c4f 39 * @idr: idr handle
3e6628c4
JL
40 * @ptr: pointer to be associated with the new id
41 * @start: the minimum id (inclusive)
0a835c4f
MW
42 * @end: the maximum id (exclusive)
43 * @gfp: memory allocation flags
9bb26bc1 44 *
0a835c4f
MW
45 * Allocates an ID larger than the last ID allocated if one is available.
46 * If not, it will attempt to allocate the smallest ID that is larger or
47 * equal to @start.
8d3b3591 48 */
0a835c4f 49int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
1da177e4 50{
0a835c4f 51 int id, curr = idr->idr_next;
1da177e4 52
0a835c4f
MW
53 if (curr < start)
54 curr = start;
e8c8d1bc 55
0a835c4f
MW
56 id = idr_alloc(idr, ptr, curr, end, gfp);
57 if ((id == -ENOSPC) && (curr > start))
58 id = idr_alloc(idr, ptr, start, curr, gfp);
1da177e4 59
0a835c4f
MW
60 if (id >= 0)
61 idr->idr_next = id + 1U;
1da177e4 62
0a835c4f 63 return id;
1da177e4 64}
0a835c4f 65EXPORT_SYMBOL(idr_alloc_cyclic);
1da177e4 66
96d7fa42
KH
67/**
68 * idr_for_each - iterate through all stored pointers
0a835c4f 69 * @idr: idr handle
96d7fa42 70 * @fn: function to be called for each pointer
0a835c4f 71 * @data: data passed to callback function
96d7fa42 72 *
0a835c4f
MW
73 * The callback function will be called for each entry in @idr, passing
74 * the id, the pointer and the data pointer passed to this function.
96d7fa42 75 *
0a835c4f
MW
76 * If @fn returns anything other than %0, the iteration stops and that
77 * value is returned from this function.
96d7fa42 78 *
0a835c4f
MW
79 * idr_for_each() can be called concurrently with idr_alloc() and
80 * idr_remove() if protected by RCU. Newly added entries may not be
81 * seen and deleted entries may be seen, but adding and removing entries
82 * will not cause other entries to be skipped, nor spurious ones to be seen.
96d7fa42 83 */
0a835c4f
MW
84int idr_for_each(const struct idr *idr,
85 int (*fn)(int id, void *p, void *data), void *data)
96d7fa42 86{
0a835c4f 87 struct radix_tree_iter iter;
7e73eb0b 88 void __rcu **slot;
96d7fa42 89
0a835c4f
MW
90 radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
91 int ret = fn(iter.index, rcu_dereference_raw(*slot), data);
92 if (ret)
93 return ret;
96d7fa42
KH
94 }
95
0a835c4f 96 return 0;
96d7fa42
KH
97}
98EXPORT_SYMBOL(idr_for_each);
99
38460b48 100/**
0a835c4f
MW
101 * idr_get_next - Find next populated entry
102 * @idr: idr handle
103 * @nextid: Pointer to lowest possible ID to return
104 *
105 * Returns the next populated entry in the tree with an ID greater than
106 * or equal to the value pointed to by @nextid. On exit, @nextid is updated
107 * to the ID of the found value. To use in a loop, the value pointed to by
108 * nextid must be incremented by the user.
38460b48 109 */
0a835c4f 110void *idr_get_next(struct idr *idr, int *nextid)
38460b48 111{
0a835c4f 112 struct radix_tree_iter iter;
7e73eb0b 113 void __rcu **slot;
38460b48 114
0a835c4f
MW
115 slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid);
116 if (!slot)
38460b48 117 return NULL;
38460b48 118
0a835c4f
MW
119 *nextid = iter.index;
120 return rcu_dereference_raw(*slot);
38460b48 121}
4d1ee80f 122EXPORT_SYMBOL(idr_get_next);
38460b48 123
388f79fd
CM
124void *idr_get_next_ext(struct idr *idr, unsigned long *nextid)
125{
126 struct radix_tree_iter iter;
127 void __rcu **slot;
128
129 slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid);
130 if (!slot)
131 return NULL;
132
133 *nextid = iter.index;
134 return rcu_dereference_raw(*slot);
135}
136EXPORT_SYMBOL(idr_get_next_ext);
137
5806f07c
JM
138/**
139 * idr_replace - replace pointer for given id
0a835c4f
MW
140 * @idr: idr handle
141 * @ptr: New pointer to associate with the ID
142 * @id: Lookup key
5806f07c 143 *
0a835c4f
MW
144 * Replace the pointer registered with an ID and return the old value.
145 * This function can be called under the RCU read lock concurrently with
146 * idr_alloc() and idr_remove() (as long as the ID being removed is not
147 * the one being replaced!).
5806f07c 148 *
a70e43a5
EB
149 * Returns: the old value on success. %-ENOENT indicates that @id was not
150 * found. %-EINVAL indicates that @id or @ptr were not valid.
5806f07c 151 */
0a835c4f 152void *idr_replace(struct idr *idr, void *ptr, int id)
388f79fd 153{
a47f68d6 154 if (id < 0)
388f79fd
CM
155 return ERR_PTR(-EINVAL);
156
157 return idr_replace_ext(idr, ptr, id);
158}
159EXPORT_SYMBOL(idr_replace);
160
161void *idr_replace_ext(struct idr *idr, void *ptr, unsigned long id)
5806f07c 162{
0a835c4f 163 struct radix_tree_node *node;
7e73eb0b 164 void __rcu **slot = NULL;
0a835c4f 165 void *entry;
5806f07c 166
0a835c4f 167 if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
e8c8d1bc
TH
168 return ERR_PTR(-EINVAL);
169
0a835c4f
MW
170 entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
171 if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
5806f07c
JM
172 return ERR_PTR(-ENOENT);
173
c7df8ad2 174 __radix_tree_replace(&idr->idr_rt, node, slot, ptr, NULL);
5806f07c 175
0a835c4f 176 return entry;
5806f07c 177}
388f79fd 178EXPORT_SYMBOL(idr_replace_ext);
5806f07c 179
56083ab1
RD
180/**
181 * DOC: IDA description
72dba584 182 *
0a835c4f
MW
183 * The IDA is an ID allocator which does not provide the ability to
184 * associate an ID with a pointer. As such, it only needs to store one
185 * bit per ID, and so is more space efficient than an IDR. To use an IDA,
186 * define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
187 * then initialise it using ida_init()). To allocate a new ID, call
188 * ida_simple_get(). To free an ID, call ida_simple_remove().
189 *
190 * If you have more complex locking requirements, use a loop around
191 * ida_pre_get() and ida_get_new() to allocate a new ID. Then use
192 * ida_remove() to free an ID. You must make sure that ida_get_new() and
193 * ida_remove() cannot be called at the same time as each other for the
194 * same IDA.
195 *
196 * You can also use ida_get_new_above() if you need an ID to be allocated
197 * above a particular number. ida_destroy() can be used to dispose of an
198 * IDA without needing to free the individual IDs in it. You can use
199 * ida_is_empty() to find out whether the IDA has any IDs currently allocated.
200 *
201 * IDs are currently limited to the range [0-INT_MAX]. If this is an awkward
202 * limitation, it should be quite straightforward to raise the maximum.
72dba584
TH
203 */
204
d37cacc5
MW
205/*
206 * Developer's notes:
207 *
208 * The IDA uses the functionality provided by the IDR & radix tree to store
209 * bitmaps in each entry. The IDR_FREE tag means there is at least one bit
210 * free, unlike the IDR where it means at least one entry is free.
211 *
212 * I considered telling the radix tree that each slot is an order-10 node
213 * and storing the bit numbers in the radix tree, but the radix tree can't
214 * allow a single multiorder entry at index 0, which would significantly
215 * increase memory consumption for the IDA. So instead we divide the index
216 * by the number of bits in the leaf bitmap before doing a radix tree lookup.
217 *
218 * As an optimisation, if there are only a few low bits set in any given
219 * leaf, instead of allocating a 128-byte bitmap, we use the 'exceptional
220 * entry' functionality of the radix tree to store BITS_PER_LONG - 2 bits
221 * directly in the entry. By being really tricksy, we could store
222 * BITS_PER_LONG - 1 bits, but there're diminishing returns after optimising
223 * for 0-3 allocated IDs.
224 *
225 * We allow the radix tree 'exceptional' count to get out of date. Nothing
226 * in the IDA nor the radix tree code checks it. If it becomes important
227 * to maintain an accurate exceptional count, switch the rcu_assign_pointer()
228 * calls to radix_tree_iter_replace() which will correct the exceptional
229 * count.
230 *
231 * The IDA always requires a lock to alloc/free. If we add a 'test_bit'
232 * equivalent, it will still need locking. Going to RCU lookup would require
233 * using RCU to free bitmaps, and that's not trivial without embedding an
234 * RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte
235 * bitmap, which is excessive.
236 */
237
0a835c4f
MW
238#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS)
239
72dba584
TH
240/**
241 * ida_get_new_above - allocate new ID above or equal to a start id
0a835c4f
MW
242 * @ida: ida handle
243 * @start: id to start search at
244 * @id: pointer to the allocated handle
72dba584 245 *
0a835c4f
MW
246 * Allocate new ID above or equal to @start. It should be called
247 * with any required locks to ensure that concurrent calls to
248 * ida_get_new_above() / ida_get_new() / ida_remove() are not allowed.
249 * Consider using ida_simple_get() if you do not have complex locking
250 * requirements.
72dba584 251 *
56083ab1 252 * If memory is required, it will return %-EAGAIN, you should unlock
72dba584 253 * and go back to the ida_pre_get() call. If the ida is full, it will
0a835c4f 254 * return %-ENOSPC. On success, it will return 0.
a2ef9471 255 *
0a835c4f 256 * @id returns a value in the range @start ... %0x7fffffff.
72dba584 257 */
0a835c4f 258int ida_get_new_above(struct ida *ida, int start, int *id)
72dba584 259{
0a835c4f 260 struct radix_tree_root *root = &ida->ida_rt;
7e73eb0b 261 void __rcu **slot;
0a835c4f 262 struct radix_tree_iter iter;
72dba584 263 struct ida_bitmap *bitmap;
0a835c4f 264 unsigned long index;
d37cacc5 265 unsigned bit, ebit;
0a835c4f
MW
266 int new;
267
268 index = start / IDA_BITMAP_BITS;
269 bit = start % IDA_BITMAP_BITS;
d37cacc5 270 ebit = bit + RADIX_TREE_EXCEPTIONAL_SHIFT;
0a835c4f
MW
271
272 slot = radix_tree_iter_init(&iter, index);
273 for (;;) {
274 if (slot)
275 slot = radix_tree_next_slot(slot, &iter,
276 RADIX_TREE_ITER_TAGGED);
277 if (!slot) {
278 slot = idr_get_free(root, &iter, GFP_NOWAIT, IDA_MAX);
279 if (IS_ERR(slot)) {
280 if (slot == ERR_PTR(-ENOMEM))
281 return -EAGAIN;
282 return PTR_ERR(slot);
283 }
284 }
d37cacc5 285 if (iter.index > index) {
0a835c4f 286 bit = 0;
d37cacc5
MW
287 ebit = RADIX_TREE_EXCEPTIONAL_SHIFT;
288 }
0a835c4f
MW
289 new = iter.index * IDA_BITMAP_BITS;
290 bitmap = rcu_dereference_raw(*slot);
d37cacc5
MW
291 if (radix_tree_exception(bitmap)) {
292 unsigned long tmp = (unsigned long)bitmap;
293 ebit = find_next_zero_bit(&tmp, BITS_PER_LONG, ebit);
294 if (ebit < BITS_PER_LONG) {
295 tmp |= 1UL << ebit;
296 rcu_assign_pointer(*slot, (void *)tmp);
297 *id = new + ebit - RADIX_TREE_EXCEPTIONAL_SHIFT;
298 return 0;
299 }
300 bitmap = this_cpu_xchg(ida_bitmap, NULL);
301 if (!bitmap)
302 return -EAGAIN;
303 memset(bitmap, 0, sizeof(*bitmap));
304 bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
305 rcu_assign_pointer(*slot, bitmap);
306 }
307
0a835c4f
MW
308 if (bitmap) {
309 bit = find_next_zero_bit(bitmap->bitmap,
310 IDA_BITMAP_BITS, bit);
311 new += bit;
312 if (new < 0)
313 return -ENOSPC;
314 if (bit == IDA_BITMAP_BITS)
315 continue;
72dba584 316
0a835c4f
MW
317 __set_bit(bit, bitmap->bitmap);
318 if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
319 radix_tree_iter_tag_clear(root, &iter,
320 IDR_FREE);
321 } else {
322 new += bit;
323 if (new < 0)
324 return -ENOSPC;
d37cacc5
MW
325 if (ebit < BITS_PER_LONG) {
326 bitmap = (void *)((1UL << ebit) |
327 RADIX_TREE_EXCEPTIONAL_ENTRY);
328 radix_tree_iter_replace(root, &iter, slot,
329 bitmap);
330 *id = new;
331 return 0;
332 }
7ad3d4d8 333 bitmap = this_cpu_xchg(ida_bitmap, NULL);
0a835c4f
MW
334 if (!bitmap)
335 return -EAGAIN;
0a835c4f
MW
336 memset(bitmap, 0, sizeof(*bitmap));
337 __set_bit(bit, bitmap->bitmap);
338 radix_tree_iter_replace(root, &iter, slot, bitmap);
339 }
72dba584 340
0a835c4f
MW
341 *id = new;
342 return 0;
72dba584 343 }
72dba584
TH
344}
345EXPORT_SYMBOL(ida_get_new_above);
346
72dba584 347/**
0a835c4f
MW
348 * ida_remove - Free the given ID
349 * @ida: ida handle
350 * @id: ID to free
351 *
352 * This function should not be called at the same time as ida_get_new_above().
72dba584
TH
353 */
354void ida_remove(struct ida *ida, int id)
355{
0a835c4f
MW
356 unsigned long index = id / IDA_BITMAP_BITS;
357 unsigned offset = id % IDA_BITMAP_BITS;
72dba584 358 struct ida_bitmap *bitmap;
d37cacc5 359 unsigned long *btmp;
0a835c4f 360 struct radix_tree_iter iter;
7e73eb0b 361 void __rcu **slot;
72dba584 362
0a835c4f
MW
363 slot = radix_tree_iter_lookup(&ida->ida_rt, &iter, index);
364 if (!slot)
8f9f665a
LJ
365 goto err;
366
0a835c4f 367 bitmap = rcu_dereference_raw(*slot);
d37cacc5
MW
368 if (radix_tree_exception(bitmap)) {
369 btmp = (unsigned long *)slot;
370 offset += RADIX_TREE_EXCEPTIONAL_SHIFT;
371 if (offset >= BITS_PER_LONG)
372 goto err;
373 } else {
374 btmp = bitmap->bitmap;
375 }
376 if (!test_bit(offset, btmp))
72dba584
TH
377 goto err;
378
d37cacc5 379 __clear_bit(offset, btmp);
0a835c4f 380 radix_tree_iter_tag_set(&ida->ida_rt, &iter, IDR_FREE);
d37cacc5
MW
381 if (radix_tree_exception(bitmap)) {
382 if (rcu_dereference_raw(*slot) ==
383 (void *)RADIX_TREE_EXCEPTIONAL_ENTRY)
384 radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
385 } else if (bitmap_empty(btmp, IDA_BITMAP_BITS)) {
0a835c4f
MW
386 kfree(bitmap);
387 radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
72dba584 388 }
72dba584 389 return;
72dba584 390 err:
dd04b452 391 WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
72dba584
TH
392}
393EXPORT_SYMBOL(ida_remove);
394
395/**
0a835c4f
MW
396 * ida_destroy - Free the contents of an ida
397 * @ida: ida handle
398 *
399 * Calling this function releases all resources associated with an IDA. When
400 * this call returns, the IDA is empty and can be reused or freed. The caller
401 * should not allow ida_remove() or ida_get_new_above() to be called at the
402 * same time.
72dba584
TH
403 */
404void ida_destroy(struct ida *ida)
405{
0a835c4f 406 struct radix_tree_iter iter;
7e73eb0b 407 void __rcu **slot;
0a835c4f
MW
408
409 radix_tree_for_each_slot(slot, &ida->ida_rt, &iter, 0) {
410 struct ida_bitmap *bitmap = rcu_dereference_raw(*slot);
d37cacc5
MW
411 if (!radix_tree_exception(bitmap))
412 kfree(bitmap);
0a835c4f
MW
413 radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
414 }
72dba584
TH
415}
416EXPORT_SYMBOL(ida_destroy);
417
88eca020
RR
418/**
419 * ida_simple_get - get a new id.
420 * @ida: the (initialized) ida.
421 * @start: the minimum id (inclusive, < 0x8000000)
422 * @end: the maximum id (exclusive, < 0x8000000 or 0)
423 * @gfp_mask: memory allocation flags
424 *
425 * Allocates an id in the range start <= id < end, or returns -ENOSPC.
426 * On memory allocation failure, returns -ENOMEM.
427 *
a2ef9471
DV
428 * Compared to ida_get_new_above() this function does its own locking, and
429 * should be used unless there are special requirements.
430 *
88eca020
RR
431 * Use ida_simple_remove() to get rid of an id.
432 */
433int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
434 gfp_t gfp_mask)
435{
436 int ret, id;
437 unsigned int max;
46cbc1d3 438 unsigned long flags;
88eca020
RR
439
440 BUG_ON((int)start < 0);
441 BUG_ON((int)end < 0);
442
443 if (end == 0)
444 max = 0x80000000;
445 else {
446 BUG_ON(end < start);
447 max = end - 1;
448 }
449
450again:
451 if (!ida_pre_get(ida, gfp_mask))
452 return -ENOMEM;
453
46cbc1d3 454 spin_lock_irqsave(&simple_ida_lock, flags);
88eca020
RR
455 ret = ida_get_new_above(ida, start, &id);
456 if (!ret) {
457 if (id > max) {
458 ida_remove(ida, id);
459 ret = -ENOSPC;
460 } else {
461 ret = id;
462 }
463 }
46cbc1d3 464 spin_unlock_irqrestore(&simple_ida_lock, flags);
88eca020
RR
465
466 if (unlikely(ret == -EAGAIN))
467 goto again;
468
469 return ret;
470}
471EXPORT_SYMBOL(ida_simple_get);
472
473/**
474 * ida_simple_remove - remove an allocated id.
475 * @ida: the (initialized) ida.
476 * @id: the id returned by ida_simple_get.
a2ef9471
DV
477 *
478 * Use to release an id allocated with ida_simple_get().
479 *
480 * Compared to ida_remove() this function does its own locking, and should be
481 * used unless there are special requirements.
88eca020
RR
482 */
483void ida_simple_remove(struct ida *ida, unsigned int id)
484{
46cbc1d3
TH
485 unsigned long flags;
486
88eca020 487 BUG_ON((int)id < 0);
46cbc1d3 488 spin_lock_irqsave(&simple_ida_lock, flags);
88eca020 489 ida_remove(ida, id);
46cbc1d3 490 spin_unlock_irqrestore(&simple_ida_lock, flags);
88eca020
RR
491}
492EXPORT_SYMBOL(ida_simple_remove);