1 /* 2 * 2002-10-18 written by Jim Houston jim.houston@ccur.com 3 * Copyright (C) 2002 by Concurrent Computer Corporation 4 * Distributed under the GNU GPL license version 2. 5 * 6 * Modified by George Anzinger to reuse immediately and to use 7 * find bit instructions. Also removed _irq on spinlocks. 8 * 9 * Modified by Nadia Derbey to make it RCU safe. 10 * 11 * Small id to pointer translation service. 12 * 13 * It uses a radix tree like structure as a sparse array indexed 14 * by the id to obtain the pointer. The bitmap makes allocating 15 * a new id quick. 16 * 17 * You call it to allocate an id (an int) an associate with that id a 18 * pointer or what ever, we treat it as a (void *). You can pass this 19 * id to a user for him to pass back at a later time. You then pass 20 * that id to this code and it returns your pointer. 21 */ 22 23 #ifndef TEST // to test in user space... 24 #include <linux/slab.h> 25 #include <linux/init.h> 26 #include <linux/export.h> 27 #endif 28 #include <linux/err.h> 29 #include <linux/string.h> 30 #include <linux/idr.h> 31 #include <linux/spinlock.h> 32 #include <linux/percpu.h> 33 #include <linux/hardirq.h> 34 35 #define MAX_IDR_SHIFT (sizeof(int) * 8 - 1) 36 #define MAX_IDR_BIT (1U << MAX_IDR_SHIFT) 37 38 /* Leave the possibility of an incomplete final layer */ 39 #define MAX_IDR_LEVEL ((MAX_IDR_SHIFT + IDR_BITS - 1) / IDR_BITS) 40 41 /* Number of id_layer structs to leave in free list */ 42 #define MAX_IDR_FREE (MAX_IDR_LEVEL * 2) 43 44 static struct kmem_cache *idr_layer_cache; 45 static DEFINE_PER_CPU(struct idr_layer *, idr_preload_head); 46 static DEFINE_PER_CPU(int, idr_preload_cnt); 47 static DEFINE_SPINLOCK(simple_ida_lock); 48 49 /* the maximum ID which can be allocated given idr->layers */ 50 static int idr_max(int layers) 51 { 52 int bits = min_t(int, layers * IDR_BITS, MAX_IDR_SHIFT); 53 54 return (1 << bits) - 1; 55 } 56 57 /* 58 * Prefix mask for an idr_layer at @layer. For layer 0, the prefix mask is 59 * all bits except for the lower IDR_BITS. For layer 1, 2 * IDR_BITS, and 60 * so on. 61 */ 62 static int idr_layer_prefix_mask(int layer) 63 { 64 return ~idr_max(layer + 1); 65 } 66 67 static struct idr_layer *get_from_free_list(struct idr *idp) 68 { 69 struct idr_layer *p; 70 unsigned long flags; 71 72 spin_lock_irqsave(&idp->lock, flags); 73 if ((p = idp->id_free)) { 74 idp->id_free = p->ary[0]; 75 idp->id_free_cnt--; 76 p->ary[0] = NULL; 77 } 78 spin_unlock_irqrestore(&idp->lock, flags); 79 return(p); 80 } 81 82 /** 83 * idr_layer_alloc - allocate a new idr_layer 84 * @gfp_mask: allocation mask 85 * @layer_idr: optional idr to allocate from 86 * 87 * If @layer_idr is %NULL, directly allocate one using @gfp_mask or fetch 88 * one from the per-cpu preload buffer. If @layer_idr is not %NULL, fetch 89 * an idr_layer from @idr->id_free. 90 * 91 * @layer_idr is to maintain backward compatibility with the old alloc 92 * interface - idr_pre_get() and idr_get_new*() - and will be removed 93 * together with per-pool preload buffer. 94 */ 95 static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr) 96 { 97 struct idr_layer *new; 98 99 /* this is the old path, bypass to get_from_free_list() */ 100 if (layer_idr) 101 return get_from_free_list(layer_idr); 102 103 /* 104 * Try to allocate directly from kmem_cache. We want to try this 105 * before preload buffer; otherwise, non-preloading idr_alloc() 106 * users will end up taking advantage of preloading ones. As the 107 * following is allowed to fail for preloaded cases, suppress 108 * warning this time. 109 */ 110 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask | __GFP_NOWARN); 111 if (new) 112 return new; 113 114 /* 115 * Try to fetch one from the per-cpu preload buffer if in process 116 * context. See idr_preload() for details. 117 */ 118 if (!in_interrupt()) { 119 preempt_disable(); 120 new = __this_cpu_read(idr_preload_head); 121 if (new) { 122 __this_cpu_write(idr_preload_head, new->ary[0]); 123 __this_cpu_dec(idr_preload_cnt); 124 new->ary[0] = NULL; 125 } 126 preempt_enable(); 127 if (new) 128 return new; 129 } 130 131 /* 132 * Both failed. Try kmem_cache again w/o adding __GFP_NOWARN so 133 * that memory allocation failure warning is printed as intended. 134 */ 135 return kmem_cache_zalloc(idr_layer_cache, gfp_mask); 136 } 137 138 static void idr_layer_rcu_free(struct rcu_head *head) 139 { 140 struct idr_layer *layer; 141 142 layer = container_of(head, struct idr_layer, rcu_head); 143 kmem_cache_free(idr_layer_cache, layer); 144 } 145 146 static inline void free_layer(struct idr *idr, struct idr_layer *p) 147 { 148 if (idr->hint == p) 149 RCU_INIT_POINTER(idr->hint, NULL); 150 call_rcu(&p->rcu_head, idr_layer_rcu_free); 151 } 152 153 /* only called when idp->lock is held */ 154 static void __move_to_free_list(struct idr *idp, struct idr_layer *p) 155 { 156 p->ary[0] = idp->id_free; 157 idp->id_free = p; 158 idp->id_free_cnt++; 159 } 160 161 static void move_to_free_list(struct idr *idp, struct idr_layer *p) 162 { 163 unsigned long flags; 164 165 /* 166 * Depends on the return element being zeroed. 167 */ 168 spin_lock_irqsave(&idp->lock, flags); 169 __move_to_free_list(idp, p); 170 spin_unlock_irqrestore(&idp->lock, flags); 171 } 172 173 static void idr_mark_full(struct idr_layer **pa, int id) 174 { 175 struct idr_layer *p = pa[0]; 176 int l = 0; 177 178 __set_bit(id & IDR_MASK, p->bitmap); 179 /* 180 * If this layer is full mark the bit in the layer above to 181 * show that this part of the radix tree is full. This may 182 * complete the layer above and require walking up the radix 183 * tree. 184 */ 185 while (bitmap_full(p->bitmap, IDR_SIZE)) { 186 if (!(p = pa[++l])) 187 break; 188 id = id >> IDR_BITS; 189 __set_bit((id & IDR_MASK), p->bitmap); 190 } 191 } 192 193 static int __idr_pre_get(struct idr *idp, gfp_t gfp_mask) 194 { 195 while (idp->id_free_cnt < MAX_IDR_FREE) { 196 struct idr_layer *new; 197 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask); 198 if (new == NULL) 199 return (0); 200 move_to_free_list(idp, new); 201 } 202 return 1; 203 } 204 205 /** 206 * sub_alloc - try to allocate an id without growing the tree depth 207 * @idp: idr handle 208 * @starting_id: id to start search at 209 * @pa: idr_layer[MAX_IDR_LEVEL] used as backtrack buffer 210 * @gfp_mask: allocation mask for idr_layer_alloc() 211 * @layer_idr: optional idr passed to idr_layer_alloc() 212 * 213 * Allocate an id in range [@starting_id, INT_MAX] from @idp without 214 * growing its depth. Returns 215 * 216 * the allocated id >= 0 if successful, 217 * -EAGAIN if the tree needs to grow for allocation to succeed, 218 * -ENOSPC if the id space is exhausted, 219 * -ENOMEM if more idr_layers need to be allocated. 220 */ 221 static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa, 222 gfp_t gfp_mask, struct idr *layer_idr) 223 { 224 int n, m, sh; 225 struct idr_layer *p, *new; 226 int l, id, oid; 227 228 id = *starting_id; 229 restart: 230 p = idp->top; 231 l = idp->layers; 232 pa[l--] = NULL; 233 while (1) { 234 /* 235 * We run around this while until we reach the leaf node... 236 */ 237 n = (id >> (IDR_BITS*l)) & IDR_MASK; 238 m = find_next_zero_bit(p->bitmap, IDR_SIZE, n); 239 if (m == IDR_SIZE) { 240 /* no space available go back to previous layer. */ 241 l++; 242 oid = id; 243 id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1; 244 245 /* if already at the top layer, we need to grow */ 246 if (id > idr_max(idp->layers)) { 247 *starting_id = id; 248 return -EAGAIN; 249 } 250 p = pa[l]; 251 BUG_ON(!p); 252 253 /* If we need to go up one layer, continue the 254 * loop; otherwise, restart from the top. 255 */ 256 sh = IDR_BITS * (l + 1); 257 if (oid >> sh == id >> sh) 258 continue; 259 else 260 goto restart; 261 } 262 if (m != n) { 263 sh = IDR_BITS*l; 264 id = ((id >> sh) ^ n ^ m) << sh; 265 } 266 if ((id >= MAX_IDR_BIT) || (id < 0)) 267 return -ENOSPC; 268 if (l == 0) 269 break; 270 /* 271 * Create the layer below if it is missing. 272 */ 273 if (!p->ary[m]) { 274 new = idr_layer_alloc(gfp_mask, layer_idr); 275 if (!new) 276 return -ENOMEM; 277 new->layer = l-1; 278 new->prefix = id & idr_layer_prefix_mask(new->layer); 279 rcu_assign_pointer(p->ary[m], new); 280 p->count++; 281 } 282 pa[l--] = p; 283 p = p->ary[m]; 284 } 285 286 pa[l] = p; 287 return id; 288 } 289 290 static int idr_get_empty_slot(struct idr *idp, int starting_id, 291 struct idr_layer **pa, gfp_t gfp_mask, 292 struct idr *layer_idr) 293 { 294 struct idr_layer *p, *new; 295 int layers, v, id; 296 unsigned long flags; 297 298 id = starting_id; 299 build_up: 300 p = idp->top; 301 layers = idp->layers; 302 if (unlikely(!p)) { 303 if (!(p = idr_layer_alloc(gfp_mask, layer_idr))) 304 return -ENOMEM; 305 p->layer = 0; 306 layers = 1; 307 } 308 /* 309 * Add a new layer to the top of the tree if the requested 310 * id is larger than the currently allocated space. 311 */ 312 while (id > idr_max(layers)) { 313 layers++; 314 if (!p->count) { 315 /* special case: if the tree is currently empty, 316 * then we grow the tree by moving the top node 317 * upwards. 318 */ 319 p->layer++; 320 WARN_ON_ONCE(p->prefix); 321 continue; 322 } 323 if (!(new = idr_layer_alloc(gfp_mask, layer_idr))) { 324 /* 325 * The allocation failed. If we built part of 326 * the structure tear it down. 327 */ 328 spin_lock_irqsave(&idp->lock, flags); 329 for (new = p; p && p != idp->top; new = p) { 330 p = p->ary[0]; 331 new->ary[0] = NULL; 332 new->count = 0; 333 bitmap_clear(new->bitmap, 0, IDR_SIZE); 334 __move_to_free_list(idp, new); 335 } 336 spin_unlock_irqrestore(&idp->lock, flags); 337 return -ENOMEM; 338 } 339 new->ary[0] = p; 340 new->count = 1; 341 new->layer = layers-1; 342 new->prefix = id & idr_layer_prefix_mask(new->layer); 343 if (bitmap_full(p->bitmap, IDR_SIZE)) 344 __set_bit(0, new->bitmap); 345 p = new; 346 } 347 rcu_assign_pointer(idp->top, p); 348 idp->layers = layers; 349 v = sub_alloc(idp, &id, pa, gfp_mask, layer_idr); 350 if (v == -EAGAIN) 351 goto build_up; 352 return(v); 353 } 354 355 /* 356 * @id and @pa are from a successful allocation from idr_get_empty_slot(). 357 * Install the user pointer @ptr and mark the slot full. 358 */ 359 static void idr_fill_slot(struct idr *idr, void *ptr, int id, 360 struct idr_layer **pa) 361 { 362 /* update hint used for lookup, cleared from free_layer() */ 363 rcu_assign_pointer(idr->hint, pa[0]); 364 365 rcu_assign_pointer(pa[0]->ary[id & IDR_MASK], (struct idr_layer *)ptr); 366 pa[0]->count++; 367 idr_mark_full(pa, id); 368 } 369 370 371 /** 372 * idr_preload - preload for idr_alloc() 373 * @gfp_mask: allocation mask to use for preloading 374 * 375 * Preload per-cpu layer buffer for idr_alloc(). Can only be used from 376 * process context and each idr_preload() invocation should be matched with 377 * idr_preload_end(). Note that preemption is disabled while preloaded. 378 * 379 * The first idr_alloc() in the preloaded section can be treated as if it 380 * were invoked with @gfp_mask used for preloading. This allows using more 381 * permissive allocation masks for idrs protected by spinlocks. 382 * 383 * For example, if idr_alloc() below fails, the failure can be treated as 384 * if idr_alloc() were called with GFP_KERNEL rather than GFP_NOWAIT. 385 * 386 * idr_preload(GFP_KERNEL); 387 * spin_lock(lock); 388 * 389 * id = idr_alloc(idr, ptr, start, end, GFP_NOWAIT); 390 * 391 * spin_unlock(lock); 392 * idr_preload_end(); 393 * if (id < 0) 394 * error; 395 */ 396 void idr_preload(gfp_t gfp_mask) 397 { 398 /* 399 * Consuming preload buffer from non-process context breaks preload 400 * allocation guarantee. Disallow usage from those contexts. 401 */ 402 WARN_ON_ONCE(in_interrupt()); 403 might_sleep_if(gfp_mask & __GFP_WAIT); 404 405 preempt_disable(); 406 407 /* 408 * idr_alloc() is likely to succeed w/o full idr_layer buffer and 409 * return value from idr_alloc() needs to be checked for failure 410 * anyway. Silently give up if allocation fails. The caller can 411 * treat failures from idr_alloc() as if idr_alloc() were called 412 * with @gfp_mask which should be enough. 413 */ 414 while (__this_cpu_read(idr_preload_cnt) < MAX_IDR_FREE) { 415 struct idr_layer *new; 416 417 preempt_enable(); 418 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask); 419 preempt_disable(); 420 if (!new) 421 break; 422 423 /* link the new one to per-cpu preload list */ 424 new->ary[0] = __this_cpu_read(idr_preload_head); 425 __this_cpu_write(idr_preload_head, new); 426 __this_cpu_inc(idr_preload_cnt); 427 } 428 } 429 EXPORT_SYMBOL(idr_preload); 430 431 /** 432 * idr_alloc - allocate new idr entry 433 * @idr: the (initialized) idr 434 * @ptr: pointer to be associated with the new id 435 * @start: the minimum id (inclusive) 436 * @end: the maximum id (exclusive, <= 0 for max) 437 * @gfp_mask: memory allocation flags 438 * 439 * Allocate an id in [start, end) and associate it with @ptr. If no ID is 440 * available in the specified range, returns -ENOSPC. On memory allocation 441 * failure, returns -ENOMEM. 442 * 443 * Note that @end is treated as max when <= 0. This is to always allow 444 * using @start + N as @end as long as N is inside integer range. 445 * 446 * The user is responsible for exclusively synchronizing all operations 447 * which may modify @idr. However, read-only accesses such as idr_find() 448 * or iteration can be performed under RCU read lock provided the user 449 * destroys @ptr in RCU-safe way after removal from idr. 450 */ 451 int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask) 452 { 453 int max = end > 0 ? end - 1 : INT_MAX; /* inclusive upper limit */ 454 struct idr_layer *pa[MAX_IDR_LEVEL + 1]; 455 int id; 456 457 might_sleep_if(gfp_mask & __GFP_WAIT); 458 459 /* sanity checks */ 460 if (WARN_ON_ONCE(start < 0)) 461 return -EINVAL; 462 if (unlikely(max < start)) 463 return -ENOSPC; 464 465 /* allocate id */ 466 id = idr_get_empty_slot(idr, start, pa, gfp_mask, NULL); 467 if (unlikely(id < 0)) 468 return id; 469 if (unlikely(id > max)) 470 return -ENOSPC; 471 472 idr_fill_slot(idr, ptr, id, pa); 473 return id; 474 } 475 EXPORT_SYMBOL_GPL(idr_alloc); 476 477 /** 478 * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion 479 * @idr: the (initialized) idr 480 * @ptr: pointer to be associated with the new id 481 * @start: the minimum id (inclusive) 482 * @end: the maximum id (exclusive, <= 0 for max) 483 * @gfp_mask: memory allocation flags 484 * 485 * Essentially the same as idr_alloc, but prefers to allocate progressively 486 * higher ids if it can. If the "cur" counter wraps, then it will start again 487 * at the "start" end of the range and allocate one that has already been used. 488 */ 489 int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, 490 gfp_t gfp_mask) 491 { 492 int id; 493 494 id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask); 495 if (id == -ENOSPC) 496 id = idr_alloc(idr, ptr, start, end, gfp_mask); 497 498 if (likely(id >= 0)) 499 idr->cur = id + 1; 500 return id; 501 } 502 EXPORT_SYMBOL(idr_alloc_cyclic); 503 504 static void idr_remove_warning(int id) 505 { 506 WARN(1, "idr_remove called for id=%d which is not allocated.\n", id); 507 } 508 509 static void sub_remove(struct idr *idp, int shift, int id) 510 { 511 struct idr_layer *p = idp->top; 512 struct idr_layer **pa[MAX_IDR_LEVEL + 1]; 513 struct idr_layer ***paa = &pa[0]; 514 struct idr_layer *to_free; 515 int n; 516 517 *paa = NULL; 518 *++paa = &idp->top; 519 520 while ((shift > 0) && p) { 521 n = (id >> shift) & IDR_MASK; 522 __clear_bit(n, p->bitmap); 523 *++paa = &p->ary[n]; 524 p = p->ary[n]; 525 shift -= IDR_BITS; 526 } 527 n = id & IDR_MASK; 528 if (likely(p != NULL && test_bit(n, p->bitmap))) { 529 __clear_bit(n, p->bitmap); 530 RCU_INIT_POINTER(p->ary[n], NULL); 531 to_free = NULL; 532 while(*paa && ! --((**paa)->count)){ 533 if (to_free) 534 free_layer(idp, to_free); 535 to_free = **paa; 536 **paa-- = NULL; 537 } 538 if (!*paa) 539 idp->layers = 0; 540 if (to_free) 541 free_layer(idp, to_free); 542 } else 543 idr_remove_warning(id); 544 } 545 546 /** 547 * idr_remove - remove the given id and free its slot 548 * @idp: idr handle 549 * @id: unique key 550 */ 551 void idr_remove(struct idr *idp, int id) 552 { 553 struct idr_layer *p; 554 struct idr_layer *to_free; 555 556 if (id < 0) 557 return; 558 559 if (id > idr_max(idp->layers)) { 560 idr_remove_warning(id); 561 return; 562 } 563 564 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id); 565 if (idp->top && idp->top->count == 1 && (idp->layers > 1) && 566 idp->top->ary[0]) { 567 /* 568 * Single child at leftmost slot: we can shrink the tree. 569 * This level is not needed anymore since when layers are 570 * inserted, they are inserted at the top of the existing 571 * tree. 572 */ 573 to_free = idp->top; 574 p = idp->top->ary[0]; 575 rcu_assign_pointer(idp->top, p); 576 --idp->layers; 577 to_free->count = 0; 578 bitmap_clear(to_free->bitmap, 0, IDR_SIZE); 579 free_layer(idp, to_free); 580 } 581 } 582 EXPORT_SYMBOL(idr_remove); 583 584 static void __idr_remove_all(struct idr *idp) 585 { 586 int n, id, max; 587 int bt_mask; 588 struct idr_layer *p; 589 struct idr_layer *pa[MAX_IDR_LEVEL + 1]; 590 struct idr_layer **paa = &pa[0]; 591 592 n = idp->layers * IDR_BITS; 593 *paa = idp->top; 594 RCU_INIT_POINTER(idp->top, NULL); 595 max = idr_max(idp->layers); 596 597 id = 0; 598 while (id >= 0 && id <= max) { 599 p = *paa; 600 while (n > IDR_BITS && p) { 601 n -= IDR_BITS; 602 p = p->ary[(id >> n) & IDR_MASK]; 603 *++paa = p; 604 } 605 606 bt_mask = id; 607 id += 1 << n; 608 /* Get the highest bit that the above add changed from 0->1. */ 609 while (n < fls(id ^ bt_mask)) { 610 if (*paa) 611 free_layer(idp, *paa); 612 n += IDR_BITS; 613 --paa; 614 } 615 } 616 idp->layers = 0; 617 } 618 619 /** 620 * idr_destroy - release all cached layers within an idr tree 621 * @idp: idr handle 622 * 623 * Free all id mappings and all idp_layers. After this function, @idp is 624 * completely unused and can be freed / recycled. The caller is 625 * responsible for ensuring that no one else accesses @idp during or after 626 * idr_destroy(). 627 * 628 * A typical clean-up sequence for objects stored in an idr tree will use 629 * idr_for_each() to free all objects, if necessary, then idr_destroy() to 630 * free up the id mappings and cached idr_layers. 631 */ 632 void idr_destroy(struct idr *idp) 633 { 634 __idr_remove_all(idp); 635 636 while (idp->id_free_cnt) { 637 struct idr_layer *p = get_from_free_list(idp); 638 kmem_cache_free(idr_layer_cache, p); 639 } 640 } 641 EXPORT_SYMBOL(idr_destroy); 642 643 void *idr_find_slowpath(struct idr *idp, int id) 644 { 645 int n; 646 struct idr_layer *p; 647 648 if (id < 0) 649 return NULL; 650 651 p = rcu_dereference_raw(idp->top); 652 if (!p) 653 return NULL; 654 n = (p->layer+1) * IDR_BITS; 655 656 if (id > idr_max(p->layer + 1)) 657 return NULL; 658 BUG_ON(n == 0); 659 660 while (n > 0 && p) { 661 n -= IDR_BITS; 662 BUG_ON(n != p->layer*IDR_BITS); 663 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]); 664 } 665 return((void *)p); 666 } 667 EXPORT_SYMBOL(idr_find_slowpath); 668 669 /** 670 * idr_for_each - iterate through all stored pointers 671 * @idp: idr handle 672 * @fn: function to be called for each pointer 673 * @data: data passed back to callback function 674 * 675 * Iterate over the pointers registered with the given idr. The 676 * callback function will be called for each pointer currently 677 * registered, passing the id, the pointer and the data pointer passed 678 * to this function. It is not safe to modify the idr tree while in 679 * the callback, so functions such as idr_get_new and idr_remove are 680 * not allowed. 681 * 682 * We check the return of @fn each time. If it returns anything other 683 * than %0, we break out and return that value. 684 * 685 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove(). 686 */ 687 int idr_for_each(struct idr *idp, 688 int (*fn)(int id, void *p, void *data), void *data) 689 { 690 int n, id, max, error = 0; 691 struct idr_layer *p; 692 struct idr_layer *pa[MAX_IDR_LEVEL + 1]; 693 struct idr_layer **paa = &pa[0]; 694 695 n = idp->layers * IDR_BITS; 696 *paa = rcu_dereference_raw(idp->top); 697 max = idr_max(idp->layers); 698 699 id = 0; 700 while (id >= 0 && id <= max) { 701 p = *paa; 702 while (n > 0 && p) { 703 n -= IDR_BITS; 704 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]); 705 *++paa = p; 706 } 707 708 if (p) { 709 error = fn(id, (void *)p, data); 710 if (error) 711 break; 712 } 713 714 id += 1 << n; 715 while (n < fls(id)) { 716 n += IDR_BITS; 717 --paa; 718 } 719 } 720 721 return error; 722 } 723 EXPORT_SYMBOL(idr_for_each); 724 725 /** 726 * idr_get_next - lookup next object of id to given id. 727 * @idp: idr handle 728 * @nextidp: pointer to lookup key 729 * 730 * Returns pointer to registered object with id, which is next number to 731 * given id. After being looked up, *@nextidp will be updated for the next 732 * iteration. 733 * 734 * This function can be called under rcu_read_lock(), given that the leaf 735 * pointers lifetimes are correctly managed. 736 */ 737 void *idr_get_next(struct idr *idp, int *nextidp) 738 { 739 struct idr_layer *p, *pa[MAX_IDR_LEVEL + 1]; 740 struct idr_layer **paa = &pa[0]; 741 int id = *nextidp; 742 int n, max; 743 744 /* find first ent */ 745 p = *paa = rcu_dereference_raw(idp->top); 746 if (!p) 747 return NULL; 748 n = (p->layer + 1) * IDR_BITS; 749 max = idr_max(p->layer + 1); 750 751 while (id >= 0 && id <= max) { 752 p = *paa; 753 while (n > 0 && p) { 754 n -= IDR_BITS; 755 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]); 756 *++paa = p; 757 } 758 759 if (p) { 760 *nextidp = id; 761 return p; 762 } 763 764 /* 765 * Proceed to the next layer at the current level. Unlike 766 * idr_for_each(), @id isn't guaranteed to be aligned to 767 * layer boundary at this point and adding 1 << n may 768 * incorrectly skip IDs. Make sure we jump to the 769 * beginning of the next layer using round_up(). 770 */ 771 id = round_up(id + 1, 1 << n); 772 while (n < fls(id)) { 773 n += IDR_BITS; 774 --paa; 775 } 776 } 777 return NULL; 778 } 779 EXPORT_SYMBOL(idr_get_next); 780 781 782 /** 783 * idr_replace - replace pointer for given id 784 * @idp: idr handle 785 * @ptr: pointer you want associated with the id 786 * @id: lookup key 787 * 788 * Replace the pointer registered with an id and return the old value. 789 * A %-ENOENT return indicates that @id was not found. 790 * A %-EINVAL return indicates that @id was not within valid constraints. 791 * 792 * The caller must serialize with writers. 793 */ 794 void *idr_replace(struct idr *idp, void *ptr, int id) 795 { 796 int n; 797 struct idr_layer *p, *old_p; 798 799 if (id < 0) 800 return ERR_PTR(-EINVAL); 801 802 p = idp->top; 803 if (!p) 804 return ERR_PTR(-ENOENT); 805 806 if (id > idr_max(p->layer + 1)) 807 return ERR_PTR(-ENOENT); 808 809 n = p->layer * IDR_BITS; 810 while ((n > 0) && p) { 811 p = p->ary[(id >> n) & IDR_MASK]; 812 n -= IDR_BITS; 813 } 814 815 n = id & IDR_MASK; 816 if (unlikely(p == NULL || !test_bit(n, p->bitmap))) 817 return ERR_PTR(-ENOENT); 818 819 old_p = p->ary[n]; 820 rcu_assign_pointer(p->ary[n], ptr); 821 822 return old_p; 823 } 824 EXPORT_SYMBOL(idr_replace); 825 826 void __init idr_init_cache(void) 827 { 828 idr_layer_cache = kmem_cache_create("idr_layer_cache", 829 sizeof(struct idr_layer), 0, SLAB_PANIC, NULL); 830 } 831 832 /** 833 * idr_init - initialize idr handle 834 * @idp: idr handle 835 * 836 * This function is use to set up the handle (@idp) that you will pass 837 * to the rest of the functions. 838 */ 839 void idr_init(struct idr *idp) 840 { 841 memset(idp, 0, sizeof(struct idr)); 842 spin_lock_init(&idp->lock); 843 } 844 EXPORT_SYMBOL(idr_init); 845 846 static int idr_has_entry(int id, void *p, void *data) 847 { 848 return 1; 849 } 850 851 bool idr_is_empty(struct idr *idp) 852 { 853 return !idr_for_each(idp, idr_has_entry, NULL); 854 } 855 EXPORT_SYMBOL(idr_is_empty); 856 857 /** 858 * DOC: IDA description 859 * IDA - IDR based ID allocator 860 * 861 * This is id allocator without id -> pointer translation. Memory 862 * usage is much lower than full blown idr because each id only 863 * occupies a bit. ida uses a custom leaf node which contains 864 * IDA_BITMAP_BITS slots. 865 * 866 * 2007-04-25 written by Tejun Heo <htejun@gmail.com> 867 */ 868 869 static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap) 870 { 871 unsigned long flags; 872 873 if (!ida->free_bitmap) { 874 spin_lock_irqsave(&ida->idr.lock, flags); 875 if (!ida->free_bitmap) { 876 ida->free_bitmap = bitmap; 877 bitmap = NULL; 878 } 879 spin_unlock_irqrestore(&ida->idr.lock, flags); 880 } 881 882 kfree(bitmap); 883 } 884 885 /** 886 * ida_pre_get - reserve resources for ida allocation 887 * @ida: ida handle 888 * @gfp_mask: memory allocation flag 889 * 890 * This function should be called prior to locking and calling the 891 * following function. It preallocates enough memory to satisfy the 892 * worst possible allocation. 893 * 894 * If the system is REALLY out of memory this function returns %0, 895 * otherwise %1. 896 */ 897 int ida_pre_get(struct ida *ida, gfp_t gfp_mask) 898 { 899 /* allocate idr_layers */ 900 if (!__idr_pre_get(&ida->idr, gfp_mask)) 901 return 0; 902 903 /* allocate free_bitmap */ 904 if (!ida->free_bitmap) { 905 struct ida_bitmap *bitmap; 906 907 bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask); 908 if (!bitmap) 909 return 0; 910 911 free_bitmap(ida, bitmap); 912 } 913 914 return 1; 915 } 916 EXPORT_SYMBOL(ida_pre_get); 917 918 /** 919 * ida_get_new_above - allocate new ID above or equal to a start id 920 * @ida: ida handle 921 * @starting_id: id to start search at 922 * @p_id: pointer to the allocated handle 923 * 924 * Allocate new ID above or equal to @starting_id. It should be called 925 * with any required locks. 926 * 927 * If memory is required, it will return %-EAGAIN, you should unlock 928 * and go back to the ida_pre_get() call. If the ida is full, it will 929 * return %-ENOSPC. 930 * 931 * @p_id returns a value in the range @starting_id ... %0x7fffffff. 932 */ 933 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id) 934 { 935 struct idr_layer *pa[MAX_IDR_LEVEL + 1]; 936 struct ida_bitmap *bitmap; 937 unsigned long flags; 938 int idr_id = starting_id / IDA_BITMAP_BITS; 939 int offset = starting_id % IDA_BITMAP_BITS; 940 int t, id; 941 942 restart: 943 /* get vacant slot */ 944 t = idr_get_empty_slot(&ida->idr, idr_id, pa, 0, &ida->idr); 945 if (t < 0) 946 return t == -ENOMEM ? -EAGAIN : t; 947 948 if (t * IDA_BITMAP_BITS >= MAX_IDR_BIT) 949 return -ENOSPC; 950 951 if (t != idr_id) 952 offset = 0; 953 idr_id = t; 954 955 /* if bitmap isn't there, create a new one */ 956 bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK]; 957 if (!bitmap) { 958 spin_lock_irqsave(&ida->idr.lock, flags); 959 bitmap = ida->free_bitmap; 960 ida->free_bitmap = NULL; 961 spin_unlock_irqrestore(&ida->idr.lock, flags); 962 963 if (!bitmap) 964 return -EAGAIN; 965 966 memset(bitmap, 0, sizeof(struct ida_bitmap)); 967 rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK], 968 (void *)bitmap); 969 pa[0]->count++; 970 } 971 972 /* lookup for empty slot */ 973 t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset); 974 if (t == IDA_BITMAP_BITS) { 975 /* no empty slot after offset, continue to the next chunk */ 976 idr_id++; 977 offset = 0; 978 goto restart; 979 } 980 981 id = idr_id * IDA_BITMAP_BITS + t; 982 if (id >= MAX_IDR_BIT) 983 return -ENOSPC; 984 985 __set_bit(t, bitmap->bitmap); 986 if (++bitmap->nr_busy == IDA_BITMAP_BITS) 987 idr_mark_full(pa, idr_id); 988 989 *p_id = id; 990 991 /* Each leaf node can handle nearly a thousand slots and the 992 * whole idea of ida is to have small memory foot print. 993 * Throw away extra resources one by one after each successful 994 * allocation. 995 */ 996 if (ida->idr.id_free_cnt || ida->free_bitmap) { 997 struct idr_layer *p = get_from_free_list(&ida->idr); 998 if (p) 999 kmem_cache_free(idr_layer_cache, p); 1000 } 1001 1002 return 0; 1003 } 1004 EXPORT_SYMBOL(ida_get_new_above); 1005 1006 /** 1007 * ida_remove - remove the given ID 1008 * @ida: ida handle 1009 * @id: ID to free 1010 */ 1011 void ida_remove(struct ida *ida, int id) 1012 { 1013 struct idr_layer *p = ida->idr.top; 1014 int shift = (ida->idr.layers - 1) * IDR_BITS; 1015 int idr_id = id / IDA_BITMAP_BITS; 1016 int offset = id % IDA_BITMAP_BITS; 1017 int n; 1018 struct ida_bitmap *bitmap; 1019 1020 if (idr_id > idr_max(ida->idr.layers)) 1021 goto err; 1022 1023 /* clear full bits while looking up the leaf idr_layer */ 1024 while ((shift > 0) && p) { 1025 n = (idr_id >> shift) & IDR_MASK; 1026 __clear_bit(n, p->bitmap); 1027 p = p->ary[n]; 1028 shift -= IDR_BITS; 1029 } 1030 1031 if (p == NULL) 1032 goto err; 1033 1034 n = idr_id & IDR_MASK; 1035 __clear_bit(n, p->bitmap); 1036 1037 bitmap = (void *)p->ary[n]; 1038 if (!bitmap || !test_bit(offset, bitmap->bitmap)) 1039 goto err; 1040 1041 /* update bitmap and remove it if empty */ 1042 __clear_bit(offset, bitmap->bitmap); 1043 if (--bitmap->nr_busy == 0) { 1044 __set_bit(n, p->bitmap); /* to please idr_remove() */ 1045 idr_remove(&ida->idr, idr_id); 1046 free_bitmap(ida, bitmap); 1047 } 1048 1049 return; 1050 1051 err: 1052 WARN(1, "ida_remove called for id=%d which is not allocated.\n", id); 1053 } 1054 EXPORT_SYMBOL(ida_remove); 1055 1056 /** 1057 * ida_destroy - release all cached layers within an ida tree 1058 * @ida: ida handle 1059 */ 1060 void ida_destroy(struct ida *ida) 1061 { 1062 idr_destroy(&ida->idr); 1063 kfree(ida->free_bitmap); 1064 } 1065 EXPORT_SYMBOL(ida_destroy); 1066 1067 /** 1068 * ida_simple_get - get a new id. 1069 * @ida: the (initialized) ida. 1070 * @start: the minimum id (inclusive, < 0x8000000) 1071 * @end: the maximum id (exclusive, < 0x8000000 or 0) 1072 * @gfp_mask: memory allocation flags 1073 * 1074 * Allocates an id in the range start <= id < end, or returns -ENOSPC. 1075 * On memory allocation failure, returns -ENOMEM. 1076 * 1077 * Use ida_simple_remove() to get rid of an id. 1078 */ 1079 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end, 1080 gfp_t gfp_mask) 1081 { 1082 int ret, id; 1083 unsigned int max; 1084 unsigned long flags; 1085 1086 BUG_ON((int)start < 0); 1087 BUG_ON((int)end < 0); 1088 1089 if (end == 0) 1090 max = 0x80000000; 1091 else { 1092 BUG_ON(end < start); 1093 max = end - 1; 1094 } 1095 1096 again: 1097 if (!ida_pre_get(ida, gfp_mask)) 1098 return -ENOMEM; 1099 1100 spin_lock_irqsave(&simple_ida_lock, flags); 1101 ret = ida_get_new_above(ida, start, &id); 1102 if (!ret) { 1103 if (id > max) { 1104 ida_remove(ida, id); 1105 ret = -ENOSPC; 1106 } else { 1107 ret = id; 1108 } 1109 } 1110 spin_unlock_irqrestore(&simple_ida_lock, flags); 1111 1112 if (unlikely(ret == -EAGAIN)) 1113 goto again; 1114 1115 return ret; 1116 } 1117 EXPORT_SYMBOL(ida_simple_get); 1118 1119 /** 1120 * ida_simple_remove - remove an allocated id. 1121 * @ida: the (initialized) ida. 1122 * @id: the id returned by ida_simple_get. 1123 */ 1124 void ida_simple_remove(struct ida *ida, unsigned int id) 1125 { 1126 unsigned long flags; 1127 1128 BUG_ON((int)id < 0); 1129 spin_lock_irqsave(&simple_ida_lock, flags); 1130 ida_remove(ida, id); 1131 spin_unlock_irqrestore(&simple_ida_lock, flags); 1132 } 1133 EXPORT_SYMBOL(ida_simple_remove); 1134 1135 /** 1136 * ida_init - initialize ida handle 1137 * @ida: ida handle 1138 * 1139 * This function is use to set up the handle (@ida) that you will pass 1140 * to the rest of the functions. 1141 */ 1142 void ida_init(struct ida *ida) 1143 { 1144 memset(ida, 0, sizeof(struct ida)); 1145 idr_init(&ida->idr); 1146 1147 } 1148 EXPORT_SYMBOL(ida_init); 1149