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 8 DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap); 9 static 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 */ 34 int 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 } 60 EXPORT_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 */ 82 int 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 } 96 EXPORT_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 */ 120 int 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 } 139 EXPORT_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 */ 155 void *idr_remove(struct idr *idr, unsigned long id) 156 { 157 return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL); 158 } 159 EXPORT_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 */ 175 void *idr_find(const struct idr *idr, unsigned long id) 176 { 177 return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base); 178 } 179 EXPORT_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 */ 198 int 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 } 218 EXPORT_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 */ 230 void *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 } 249 EXPORT_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 */ 261 void *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 } 276 EXPORT_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 */ 292 void *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 } 310 EXPORT_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 */ 390 int 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 } 475 EXPORT_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 */ 484 void 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 } 523 EXPORT_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 */ 534 void 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 } 546 EXPORT_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 */ 563 int 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 } 579 580 again: 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 } 601 EXPORT_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 */ 613 void 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 } 622 EXPORT_SYMBOL(ida_simple_remove); 623