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