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