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. It is safe to call this function without 376 * locking in your code. 377 * Return: The allocated ID, or %-ENOMEM if memory could not be allocated, 378 * or %-ENOSPC if there are no free IDs. 379 */ 380 int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max, 381 gfp_t gfp) 382 { 383 XA_STATE(xas, &ida->xa, min / IDA_BITMAP_BITS); 384 unsigned bit = min % IDA_BITMAP_BITS; 385 unsigned long flags; 386 struct ida_bitmap *bitmap, *alloc = NULL; 387 388 if ((int)min < 0) 389 return -ENOSPC; 390 391 if ((int)max < 0) 392 max = INT_MAX; 393 394 retry: 395 xas_lock_irqsave(&xas, flags); 396 next: 397 bitmap = xas_find_marked(&xas, max / IDA_BITMAP_BITS, XA_FREE_MARK); 398 if (xas.xa_index > min / IDA_BITMAP_BITS) 399 bit = 0; 400 if (xas.xa_index * IDA_BITMAP_BITS + bit > max) 401 goto nospc; 402 403 if (xa_is_value(bitmap)) { 404 unsigned long tmp = xa_to_value(bitmap); 405 406 if (bit < BITS_PER_XA_VALUE) { 407 bit = find_next_zero_bit(&tmp, BITS_PER_XA_VALUE, bit); 408 if (xas.xa_index * IDA_BITMAP_BITS + bit > max) 409 goto nospc; 410 if (bit < BITS_PER_XA_VALUE) { 411 tmp |= 1UL << bit; 412 xas_store(&xas, xa_mk_value(tmp)); 413 goto out; 414 } 415 } 416 bitmap = alloc; 417 if (!bitmap) 418 bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT); 419 if (!bitmap) 420 goto alloc; 421 bitmap->bitmap[0] = tmp; 422 xas_store(&xas, bitmap); 423 if (xas_error(&xas)) { 424 bitmap->bitmap[0] = 0; 425 goto out; 426 } 427 } 428 429 if (bitmap) { 430 bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit); 431 if (xas.xa_index * IDA_BITMAP_BITS + bit > max) 432 goto nospc; 433 if (bit == IDA_BITMAP_BITS) 434 goto next; 435 436 __set_bit(bit, bitmap->bitmap); 437 if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS)) 438 xas_clear_mark(&xas, XA_FREE_MARK); 439 } else { 440 if (bit < BITS_PER_XA_VALUE) { 441 bitmap = xa_mk_value(1UL << bit); 442 } else { 443 bitmap = alloc; 444 if (!bitmap) 445 bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT); 446 if (!bitmap) 447 goto alloc; 448 __set_bit(bit, bitmap->bitmap); 449 } 450 xas_store(&xas, bitmap); 451 } 452 out: 453 xas_unlock_irqrestore(&xas, flags); 454 if (xas_nomem(&xas, gfp)) { 455 xas.xa_index = min / IDA_BITMAP_BITS; 456 bit = min % IDA_BITMAP_BITS; 457 goto retry; 458 } 459 if (bitmap != alloc) 460 kfree(alloc); 461 if (xas_error(&xas)) 462 return xas_error(&xas); 463 return xas.xa_index * IDA_BITMAP_BITS + bit; 464 alloc: 465 xas_unlock_irqrestore(&xas, flags); 466 alloc = kzalloc(sizeof(*bitmap), gfp); 467 if (!alloc) 468 return -ENOMEM; 469 xas_set(&xas, min / IDA_BITMAP_BITS); 470 bit = min % IDA_BITMAP_BITS; 471 goto retry; 472 nospc: 473 xas_unlock_irqrestore(&xas, flags); 474 kfree(alloc); 475 return -ENOSPC; 476 } 477 EXPORT_SYMBOL(ida_alloc_range); 478 479 /** 480 * ida_free() - Release an allocated ID. 481 * @ida: IDA handle. 482 * @id: Previously allocated ID. 483 * 484 * Context: Any context. It is safe to call this function without 485 * locking in your code. 486 */ 487 void ida_free(struct ida *ida, unsigned int id) 488 { 489 XA_STATE(xas, &ida->xa, id / IDA_BITMAP_BITS); 490 unsigned bit = id % IDA_BITMAP_BITS; 491 struct ida_bitmap *bitmap; 492 unsigned long flags; 493 494 BUG_ON((int)id < 0); 495 496 xas_lock_irqsave(&xas, flags); 497 bitmap = xas_load(&xas); 498 499 if (xa_is_value(bitmap)) { 500 unsigned long v = xa_to_value(bitmap); 501 if (bit >= BITS_PER_XA_VALUE) 502 goto err; 503 if (!(v & (1UL << bit))) 504 goto err; 505 v &= ~(1UL << bit); 506 if (!v) 507 goto delete; 508 xas_store(&xas, xa_mk_value(v)); 509 } else { 510 if (!test_bit(bit, bitmap->bitmap)) 511 goto err; 512 __clear_bit(bit, bitmap->bitmap); 513 xas_set_mark(&xas, XA_FREE_MARK); 514 if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) { 515 kfree(bitmap); 516 delete: 517 xas_store(&xas, NULL); 518 } 519 } 520 xas_unlock_irqrestore(&xas, flags); 521 return; 522 err: 523 xas_unlock_irqrestore(&xas, flags); 524 WARN(1, "ida_free called for id=%d which is not allocated.\n", id); 525 } 526 EXPORT_SYMBOL(ida_free); 527 528 /** 529 * ida_destroy() - Free all IDs. 530 * @ida: IDA handle. 531 * 532 * Calling this function frees all IDs and releases all resources used 533 * by an IDA. When this call returns, the IDA is empty and can be reused 534 * or freed. If the IDA is already empty, there is no need to call this 535 * function. 536 * 537 * Context: Any context. It is safe to call this function without 538 * locking in your code. 539 */ 540 void ida_destroy(struct ida *ida) 541 { 542 XA_STATE(xas, &ida->xa, 0); 543 struct ida_bitmap *bitmap; 544 unsigned long flags; 545 546 xas_lock_irqsave(&xas, flags); 547 xas_for_each(&xas, bitmap, ULONG_MAX) { 548 if (!xa_is_value(bitmap)) 549 kfree(bitmap); 550 xas_store(&xas, NULL); 551 } 552 xas_unlock_irqrestore(&xas, flags); 553 } 554 EXPORT_SYMBOL(ida_destroy); 555 556 #ifndef __KERNEL__ 557 extern void xa_dump_index(unsigned long index, unsigned int shift); 558 #define IDA_CHUNK_SHIFT ilog2(IDA_BITMAP_BITS) 559 560 static void ida_dump_entry(void *entry, unsigned long index) 561 { 562 unsigned long i; 563 564 if (!entry) 565 return; 566 567 if (xa_is_node(entry)) { 568 struct xa_node *node = xa_to_node(entry); 569 unsigned int shift = node->shift + IDA_CHUNK_SHIFT + 570 XA_CHUNK_SHIFT; 571 572 xa_dump_index(index * IDA_BITMAP_BITS, shift); 573 xa_dump_node(node); 574 for (i = 0; i < XA_CHUNK_SIZE; i++) 575 ida_dump_entry(node->slots[i], 576 index | (i << node->shift)); 577 } else if (xa_is_value(entry)) { 578 xa_dump_index(index * IDA_BITMAP_BITS, ilog2(BITS_PER_LONG)); 579 pr_cont("value: data %lx [%px]\n", xa_to_value(entry), entry); 580 } else { 581 struct ida_bitmap *bitmap = entry; 582 583 xa_dump_index(index * IDA_BITMAP_BITS, IDA_CHUNK_SHIFT); 584 pr_cont("bitmap: %p data", bitmap); 585 for (i = 0; i < IDA_BITMAP_LONGS; i++) 586 pr_cont(" %lx", bitmap->bitmap[i]); 587 pr_cont("\n"); 588 } 589 } 590 591 static void ida_dump(struct ida *ida) 592 { 593 struct xarray *xa = &ida->xa; 594 pr_debug("ida: %p node %p free %d\n", ida, xa->xa_head, 595 xa->xa_flags >> ROOT_TAG_SHIFT); 596 ida_dump_entry(xa->xa_head, 0); 597 } 598 #endif 599