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 40 if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr))) 41 return -EINVAL; 42 if (WARN_ON_ONCE(!(idr->idr_rt.gfp_mask & ROOT_IS_IDR))) 43 idr->idr_rt.gfp_mask |= IDR_RT_MARKER; 44 45 radix_tree_iter_init(&iter, *nextid); 46 slot = idr_get_free(&idr->idr_rt, &iter, gfp, max); 47 if (IS_ERR(slot)) 48 return PTR_ERR(slot); 49 50 *nextid = iter.index; 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_for_each() - Iterate through all stored pointers. 140 * @idr: IDR handle. 141 * @fn: Function to be called for each pointer. 142 * @data: Data passed to callback function. 143 * 144 * The callback function will be called for each entry in @idr, passing 145 * the ID, the entry and @data. 146 * 147 * If @fn returns anything other than %0, the iteration stops and that 148 * value is returned from this function. 149 * 150 * idr_for_each() can be called concurrently with idr_alloc() and 151 * idr_remove() if protected by RCU. Newly added entries may not be 152 * seen and deleted entries may be seen, but adding and removing entries 153 * will not cause other entries to be skipped, nor spurious ones to be seen. 154 */ 155 int idr_for_each(const struct idr *idr, 156 int (*fn)(int id, void *p, void *data), void *data) 157 { 158 struct radix_tree_iter iter; 159 void __rcu **slot; 160 161 radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) { 162 int ret = fn(iter.index, rcu_dereference_raw(*slot), data); 163 if (ret) 164 return ret; 165 } 166 167 return 0; 168 } 169 EXPORT_SYMBOL(idr_for_each); 170 171 /** 172 * idr_get_next() - Find next populated entry. 173 * @idr: IDR handle. 174 * @nextid: Pointer to an ID. 175 * 176 * Returns the next populated entry in the tree with an ID greater than 177 * or equal to the value pointed to by @nextid. On exit, @nextid is updated 178 * to the ID of the found value. To use in a loop, the value pointed to by 179 * nextid must be incremented by the user. 180 */ 181 void *idr_get_next(struct idr *idr, int *nextid) 182 { 183 struct radix_tree_iter iter; 184 void __rcu **slot; 185 186 slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid); 187 if (!slot) 188 return NULL; 189 190 *nextid = iter.index; 191 return rcu_dereference_raw(*slot); 192 } 193 EXPORT_SYMBOL(idr_get_next); 194 195 /** 196 * idr_get_next_ul() - Find next populated entry. 197 * @idr: IDR handle. 198 * @nextid: Pointer to an ID. 199 * 200 * Returns the next populated entry in the tree with an ID greater than 201 * or equal to the value pointed to by @nextid. On exit, @nextid is updated 202 * to the ID of the found value. To use in a loop, the value pointed to by 203 * nextid must be incremented by the user. 204 */ 205 void *idr_get_next_ul(struct idr *idr, unsigned long *nextid) 206 { 207 struct radix_tree_iter iter; 208 void __rcu **slot; 209 210 slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid); 211 if (!slot) 212 return NULL; 213 214 *nextid = iter.index; 215 return rcu_dereference_raw(*slot); 216 } 217 EXPORT_SYMBOL(idr_get_next_ul); 218 219 /** 220 * idr_replace() - replace pointer for given ID. 221 * @idr: IDR handle. 222 * @ptr: New pointer to associate with the ID. 223 * @id: ID to change. 224 * 225 * Replace the pointer registered with an ID and return the old value. 226 * This function can be called under the RCU read lock concurrently with 227 * idr_alloc() and idr_remove() (as long as the ID being removed is not 228 * the one being replaced!). 229 * 230 * Returns: the old value on success. %-ENOENT indicates that @id was not 231 * found. %-EINVAL indicates that @ptr was not valid. 232 */ 233 void *idr_replace(struct idr *idr, void *ptr, unsigned long id) 234 { 235 struct radix_tree_node *node; 236 void __rcu **slot = NULL; 237 void *entry; 238 239 if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr))) 240 return ERR_PTR(-EINVAL); 241 242 entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot); 243 if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE)) 244 return ERR_PTR(-ENOENT); 245 246 __radix_tree_replace(&idr->idr_rt, node, slot, ptr, NULL); 247 248 return entry; 249 } 250 EXPORT_SYMBOL(idr_replace); 251 252 /** 253 * DOC: IDA description 254 * 255 * The IDA is an ID allocator which does not provide the ability to 256 * associate an ID with a pointer. As such, it only needs to store one 257 * bit per ID, and so is more space efficient than an IDR. To use an IDA, 258 * define it using DEFINE_IDA() (or embed a &struct ida in a data structure, 259 * then initialise it using ida_init()). To allocate a new ID, call 260 * ida_simple_get(). To free an ID, call ida_simple_remove(). 261 * 262 * If you have more complex locking requirements, use a loop around 263 * ida_pre_get() and ida_get_new() to allocate a new ID. Then use 264 * ida_remove() to free an ID. You must make sure that ida_get_new() and 265 * ida_remove() cannot be called at the same time as each other for the 266 * same IDA. 267 * 268 * You can also use ida_get_new_above() if you need an ID to be allocated 269 * above a particular number. ida_destroy() can be used to dispose of an 270 * IDA without needing to free the individual IDs in it. You can use 271 * ida_is_empty() to find out whether the IDA has any IDs currently allocated. 272 * 273 * IDs are currently limited to the range [0-INT_MAX]. If this is an awkward 274 * limitation, it should be quite straightforward to raise the maximum. 275 */ 276 277 /* 278 * Developer's notes: 279 * 280 * The IDA uses the functionality provided by the IDR & radix tree to store 281 * bitmaps in each entry. The IDR_FREE tag means there is at least one bit 282 * free, unlike the IDR where it means at least one entry is free. 283 * 284 * I considered telling the radix tree that each slot is an order-10 node 285 * and storing the bit numbers in the radix tree, but the radix tree can't 286 * allow a single multiorder entry at index 0, which would significantly 287 * increase memory consumption for the IDA. So instead we divide the index 288 * by the number of bits in the leaf bitmap before doing a radix tree lookup. 289 * 290 * As an optimisation, if there are only a few low bits set in any given 291 * leaf, instead of allocating a 128-byte bitmap, we use the 'exceptional 292 * entry' functionality of the radix tree to store BITS_PER_LONG - 2 bits 293 * directly in the entry. By being really tricksy, we could store 294 * BITS_PER_LONG - 1 bits, but there're diminishing returns after optimising 295 * for 0-3 allocated IDs. 296 * 297 * We allow the radix tree 'exceptional' count to get out of date. Nothing 298 * in the IDA nor the radix tree code checks it. If it becomes important 299 * to maintain an accurate exceptional count, switch the rcu_assign_pointer() 300 * calls to radix_tree_iter_replace() which will correct the exceptional 301 * count. 302 * 303 * The IDA always requires a lock to alloc/free. If we add a 'test_bit' 304 * equivalent, it will still need locking. Going to RCU lookup would require 305 * using RCU to free bitmaps, and that's not trivial without embedding an 306 * RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte 307 * bitmap, which is excessive. 308 */ 309 310 #define IDA_MAX (0x80000000U / IDA_BITMAP_BITS - 1) 311 312 /** 313 * ida_get_new_above - allocate new ID above or equal to a start id 314 * @ida: ida handle 315 * @start: id to start search at 316 * @id: pointer to the allocated handle 317 * 318 * Allocate new ID above or equal to @start. It should be called 319 * with any required locks to ensure that concurrent calls to 320 * ida_get_new_above() / ida_get_new() / ida_remove() are not allowed. 321 * Consider using ida_simple_get() if you do not have complex locking 322 * requirements. 323 * 324 * If memory is required, it will return %-EAGAIN, you should unlock 325 * and go back to the ida_pre_get() call. If the ida is full, it will 326 * return %-ENOSPC. On success, it will return 0. 327 * 328 * @id returns a value in the range @start ... %0x7fffffff. 329 */ 330 int ida_get_new_above(struct ida *ida, int start, int *id) 331 { 332 struct radix_tree_root *root = &ida->ida_rt; 333 void __rcu **slot; 334 struct radix_tree_iter iter; 335 struct ida_bitmap *bitmap; 336 unsigned long index; 337 unsigned bit, ebit; 338 int new; 339 340 index = start / IDA_BITMAP_BITS; 341 bit = start % IDA_BITMAP_BITS; 342 ebit = bit + RADIX_TREE_EXCEPTIONAL_SHIFT; 343 344 slot = radix_tree_iter_init(&iter, index); 345 for (;;) { 346 if (slot) 347 slot = radix_tree_next_slot(slot, &iter, 348 RADIX_TREE_ITER_TAGGED); 349 if (!slot) { 350 slot = idr_get_free(root, &iter, GFP_NOWAIT, IDA_MAX); 351 if (IS_ERR(slot)) { 352 if (slot == ERR_PTR(-ENOMEM)) 353 return -EAGAIN; 354 return PTR_ERR(slot); 355 } 356 } 357 if (iter.index > index) { 358 bit = 0; 359 ebit = RADIX_TREE_EXCEPTIONAL_SHIFT; 360 } 361 new = iter.index * IDA_BITMAP_BITS; 362 bitmap = rcu_dereference_raw(*slot); 363 if (radix_tree_exception(bitmap)) { 364 unsigned long tmp = (unsigned long)bitmap; 365 ebit = find_next_zero_bit(&tmp, BITS_PER_LONG, ebit); 366 if (ebit < BITS_PER_LONG) { 367 tmp |= 1UL << ebit; 368 rcu_assign_pointer(*slot, (void *)tmp); 369 *id = new + ebit - RADIX_TREE_EXCEPTIONAL_SHIFT; 370 return 0; 371 } 372 bitmap = this_cpu_xchg(ida_bitmap, NULL); 373 if (!bitmap) 374 return -EAGAIN; 375 memset(bitmap, 0, sizeof(*bitmap)); 376 bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT; 377 rcu_assign_pointer(*slot, bitmap); 378 } 379 380 if (bitmap) { 381 bit = find_next_zero_bit(bitmap->bitmap, 382 IDA_BITMAP_BITS, bit); 383 new += bit; 384 if (new < 0) 385 return -ENOSPC; 386 if (bit == IDA_BITMAP_BITS) 387 continue; 388 389 __set_bit(bit, bitmap->bitmap); 390 if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS)) 391 radix_tree_iter_tag_clear(root, &iter, 392 IDR_FREE); 393 } else { 394 new += bit; 395 if (new < 0) 396 return -ENOSPC; 397 if (ebit < BITS_PER_LONG) { 398 bitmap = (void *)((1UL << ebit) | 399 RADIX_TREE_EXCEPTIONAL_ENTRY); 400 radix_tree_iter_replace(root, &iter, slot, 401 bitmap); 402 *id = new; 403 return 0; 404 } 405 bitmap = this_cpu_xchg(ida_bitmap, NULL); 406 if (!bitmap) 407 return -EAGAIN; 408 memset(bitmap, 0, sizeof(*bitmap)); 409 __set_bit(bit, bitmap->bitmap); 410 radix_tree_iter_replace(root, &iter, slot, bitmap); 411 } 412 413 *id = new; 414 return 0; 415 } 416 } 417 EXPORT_SYMBOL(ida_get_new_above); 418 419 /** 420 * ida_remove - Free the given ID 421 * @ida: ida handle 422 * @id: ID to free 423 * 424 * This function should not be called at the same time as ida_get_new_above(). 425 */ 426 void ida_remove(struct ida *ida, int id) 427 { 428 unsigned long index = id / IDA_BITMAP_BITS; 429 unsigned offset = id % IDA_BITMAP_BITS; 430 struct ida_bitmap *bitmap; 431 unsigned long *btmp; 432 struct radix_tree_iter iter; 433 void __rcu **slot; 434 435 slot = radix_tree_iter_lookup(&ida->ida_rt, &iter, index); 436 if (!slot) 437 goto err; 438 439 bitmap = rcu_dereference_raw(*slot); 440 if (radix_tree_exception(bitmap)) { 441 btmp = (unsigned long *)slot; 442 offset += RADIX_TREE_EXCEPTIONAL_SHIFT; 443 if (offset >= BITS_PER_LONG) 444 goto err; 445 } else { 446 btmp = bitmap->bitmap; 447 } 448 if (!test_bit(offset, btmp)) 449 goto err; 450 451 __clear_bit(offset, btmp); 452 radix_tree_iter_tag_set(&ida->ida_rt, &iter, IDR_FREE); 453 if (radix_tree_exception(bitmap)) { 454 if (rcu_dereference_raw(*slot) == 455 (void *)RADIX_TREE_EXCEPTIONAL_ENTRY) 456 radix_tree_iter_delete(&ida->ida_rt, &iter, slot); 457 } else if (bitmap_empty(btmp, IDA_BITMAP_BITS)) { 458 kfree(bitmap); 459 radix_tree_iter_delete(&ida->ida_rt, &iter, slot); 460 } 461 return; 462 err: 463 WARN(1, "ida_remove called for id=%d which is not allocated.\n", id); 464 } 465 EXPORT_SYMBOL(ida_remove); 466 467 /** 468 * ida_destroy - Free the contents of an ida 469 * @ida: ida handle 470 * 471 * Calling this function releases all resources associated with an IDA. When 472 * this call returns, the IDA is empty and can be reused or freed. The caller 473 * should not allow ida_remove() or ida_get_new_above() to be called at the 474 * same time. 475 */ 476 void ida_destroy(struct ida *ida) 477 { 478 struct radix_tree_iter iter; 479 void __rcu **slot; 480 481 radix_tree_for_each_slot(slot, &ida->ida_rt, &iter, 0) { 482 struct ida_bitmap *bitmap = rcu_dereference_raw(*slot); 483 if (!radix_tree_exception(bitmap)) 484 kfree(bitmap); 485 radix_tree_iter_delete(&ida->ida_rt, &iter, slot); 486 } 487 } 488 EXPORT_SYMBOL(ida_destroy); 489 490 /** 491 * ida_simple_get - get a new id. 492 * @ida: the (initialized) ida. 493 * @start: the minimum id (inclusive, < 0x8000000) 494 * @end: the maximum id (exclusive, < 0x8000000 or 0) 495 * @gfp_mask: memory allocation flags 496 * 497 * Allocates an id in the range start <= id < end, or returns -ENOSPC. 498 * On memory allocation failure, returns -ENOMEM. 499 * 500 * Compared to ida_get_new_above() this function does its own locking, and 501 * should be used unless there are special requirements. 502 * 503 * Use ida_simple_remove() to get rid of an id. 504 */ 505 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end, 506 gfp_t gfp_mask) 507 { 508 int ret, id; 509 unsigned int max; 510 unsigned long flags; 511 512 BUG_ON((int)start < 0); 513 BUG_ON((int)end < 0); 514 515 if (end == 0) 516 max = 0x80000000; 517 else { 518 BUG_ON(end < start); 519 max = end - 1; 520 } 521 522 again: 523 if (!ida_pre_get(ida, gfp_mask)) 524 return -ENOMEM; 525 526 spin_lock_irqsave(&simple_ida_lock, flags); 527 ret = ida_get_new_above(ida, start, &id); 528 if (!ret) { 529 if (id > max) { 530 ida_remove(ida, id); 531 ret = -ENOSPC; 532 } else { 533 ret = id; 534 } 535 } 536 spin_unlock_irqrestore(&simple_ida_lock, flags); 537 538 if (unlikely(ret == -EAGAIN)) 539 goto again; 540 541 return ret; 542 } 543 EXPORT_SYMBOL(ida_simple_get); 544 545 /** 546 * ida_simple_remove - remove an allocated id. 547 * @ida: the (initialized) ida. 548 * @id: the id returned by ida_simple_get. 549 * 550 * Use to release an id allocated with ida_simple_get(). 551 * 552 * Compared to ida_remove() this function does its own locking, and should be 553 * used unless there are special requirements. 554 */ 555 void ida_simple_remove(struct ida *ida, unsigned int id) 556 { 557 unsigned long flags; 558 559 BUG_ON((int)id < 0); 560 spin_lock_irqsave(&simple_ida_lock, flags); 561 ida_remove(ida, id); 562 spin_unlock_irqrestore(&simple_ida_lock, flags); 563 } 564 EXPORT_SYMBOL(ida_simple_remove); 565