linux/lib/idr.c
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   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 * You can release ids at any time. When all ids are released, most of
  23 * the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
  24 * don't need to go to the memory "store" during an id allocate, just
  25 * so you don't need to be too concerned about locking and conflicts
  26 * with the slab allocator.
  27 */
  28
  29#ifndef TEST                        // to test in user space...
  30#include <linux/slab.h>
  31#include <linux/init.h>
  32#include <linux/module.h>
  33#endif
  34#include <linux/err.h>
  35#include <linux/string.h>
  36#include <linux/idr.h>
  37
  38static struct kmem_cache *idr_layer_cache;
  39
  40static struct idr_layer *get_from_free_list(struct idr *idp)
  41{
  42        struct idr_layer *p;
  43        unsigned long flags;
  44
  45        spin_lock_irqsave(&idp->lock, flags);
  46        if ((p = idp->id_free)) {
  47                idp->id_free = p->ary[0];
  48                idp->id_free_cnt--;
  49                p->ary[0] = NULL;
  50        }
  51        spin_unlock_irqrestore(&idp->lock, flags);
  52        return(p);
  53}
  54
  55static void idr_layer_rcu_free(struct rcu_head *head)
  56{
  57        struct idr_layer *layer;
  58
  59        layer = container_of(head, struct idr_layer, rcu_head);
  60        kmem_cache_free(idr_layer_cache, layer);
  61}
  62
  63static inline void free_layer(struct idr_layer *p)
  64{
  65        call_rcu(&p->rcu_head, idr_layer_rcu_free);
  66}
  67
  68/* only called when idp->lock is held */
  69static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
  70{
  71        p->ary[0] = idp->id_free;
  72        idp->id_free = p;
  73        idp->id_free_cnt++;
  74}
  75
  76static void move_to_free_list(struct idr *idp, struct idr_layer *p)
  77{
  78        unsigned long flags;
  79
  80        /*
  81         * Depends on the return element being zeroed.
  82         */
  83        spin_lock_irqsave(&idp->lock, flags);
  84        __move_to_free_list(idp, p);
  85        spin_unlock_irqrestore(&idp->lock, flags);
  86}
  87
  88static void idr_mark_full(struct idr_layer **pa, int id)
  89{
  90        struct idr_layer *p = pa[0];
  91        int l = 0;
  92
  93        __set_bit(id & IDR_MASK, &p->bitmap);
  94        /*
  95         * If this layer is full mark the bit in the layer above to
  96         * show that this part of the radix tree is full.  This may
  97         * complete the layer above and require walking up the radix
  98         * tree.
  99         */
 100        while (p->bitmap == IDR_FULL) {
 101                if (!(p = pa[++l]))
 102                        break;
 103                id = id >> IDR_BITS;
 104                __set_bit((id & IDR_MASK), &p->bitmap);
 105        }
 106}
 107
 108/**
 109 * idr_pre_get - reserver resources for idr allocation
 110 * @idp:        idr handle
 111 * @gfp_mask:   memory allocation flags
 112 *
 113 * This function should be called prior to locking and calling the
 114 * idr_get_new* functions. It preallocates enough memory to satisfy
 115 * the worst possible allocation.
 116 *
 117 * If the system is REALLY out of memory this function returns 0,
 118 * otherwise 1.
 119 */
 120int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
 121{
 122        while (idp->id_free_cnt < IDR_FREE_MAX) {
 123                struct idr_layer *new;
 124                new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
 125                if (new == NULL)
 126                        return (0);
 127                move_to_free_list(idp, new);
 128        }
 129        return 1;
 130}
 131EXPORT_SYMBOL(idr_pre_get);
 132
 133static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
 134{
 135        int n, m, sh;
 136        struct idr_layer *p, *new;
 137        int l, id, oid;
 138        unsigned long bm;
 139
 140        id = *starting_id;
 141 restart:
 142        p = idp->top;
 143        l = idp->layers;
 144        pa[l--] = NULL;
 145        while (1) {
 146                /*
 147                 * We run around this while until we reach the leaf node...
 148                 */
 149                n = (id >> (IDR_BITS*l)) & IDR_MASK;
 150                bm = ~p->bitmap;
 151                m = find_next_bit(&bm, IDR_SIZE, n);
 152                if (m == IDR_SIZE) {
 153                        /* no space available go back to previous layer. */
 154                        l++;
 155                        oid = id;
 156                        id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
 157
 158                        /* if already at the top layer, we need to grow */
 159                        if (!(p = pa[l])) {
 160                                *starting_id = id;
 161                                return IDR_NEED_TO_GROW;
 162                        }
 163
 164                        /* If we need to go up one layer, continue the
 165                         * loop; otherwise, restart from the top.
 166                         */
 167                        sh = IDR_BITS * (l + 1);
 168                        if (oid >> sh == id >> sh)
 169                                continue;
 170                        else
 171                                goto restart;
 172                }
 173                if (m != n) {
 174                        sh = IDR_BITS*l;
 175                        id = ((id >> sh) ^ n ^ m) << sh;
 176                }
 177                if ((id >= MAX_ID_BIT) || (id < 0))
 178                        return IDR_NOMORE_SPACE;
 179                if (l == 0)
 180                        break;
 181                /*
 182                 * Create the layer below if it is missing.
 183                 */
 184                if (!p->ary[m]) {
 185                        new = get_from_free_list(idp);
 186                        if (!new)
 187                                return -1;
 188                        new->layer = l-1;
 189                        rcu_assign_pointer(p->ary[m], new);
 190                        p->count++;
 191                }
 192                pa[l--] = p;
 193                p = p->ary[m];
 194        }
 195
 196        pa[l] = p;
 197        return id;
 198}
 199
 200static int idr_get_empty_slot(struct idr *idp, int starting_id,
 201                              struct idr_layer **pa)
 202{
 203        struct idr_layer *p, *new;
 204        int layers, v, id;
 205        unsigned long flags;
 206
 207        id = starting_id;
 208build_up:
 209        p = idp->top;
 210        layers = idp->layers;
 211        if (unlikely(!p)) {
 212                if (!(p = get_from_free_list(idp)))
 213                        return -1;
 214                p->layer = 0;
 215                layers = 1;
 216        }
 217        /*
 218         * Add a new layer to the top of the tree if the requested
 219         * id is larger than the currently allocated space.
 220         */
 221        while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
 222                layers++;
 223                if (!p->count) {
 224                        /* special case: if the tree is currently empty,
 225                         * then we grow the tree by moving the top node
 226                         * upwards.
 227                         */
 228                        p->layer++;
 229                        continue;
 230                }
 231                if (!(new = get_from_free_list(idp))) {
 232                        /*
 233                         * The allocation failed.  If we built part of
 234                         * the structure tear it down.
 235                         */
 236                        spin_lock_irqsave(&idp->lock, flags);
 237                        for (new = p; p && p != idp->top; new = p) {
 238                                p = p->ary[0];
 239                                new->ary[0] = NULL;
 240                                new->bitmap = new->count = 0;
 241                                __move_to_free_list(idp, new);
 242                        }
 243                        spin_unlock_irqrestore(&idp->lock, flags);
 244                        return -1;
 245                }
 246                new->ary[0] = p;
 247                new->count = 1;
 248                new->layer = layers-1;
 249                if (p->bitmap == IDR_FULL)
 250                        __set_bit(0, &new->bitmap);
 251                p = new;
 252        }
 253        rcu_assign_pointer(idp->top, p);
 254        idp->layers = layers;
 255        v = sub_alloc(idp, &id, pa);
 256        if (v == IDR_NEED_TO_GROW)
 257                goto build_up;
 258        return(v);
 259}
 260
 261static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
 262{
 263        struct idr_layer *pa[MAX_LEVEL];
 264        int id;
 265
 266        id = idr_get_empty_slot(idp, starting_id, pa);
 267        if (id >= 0) {
 268                /*
 269                 * Successfully found an empty slot.  Install the user
 270                 * pointer and mark the slot full.
 271                 */
 272                rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
 273                                (struct idr_layer *)ptr);
 274                pa[0]->count++;
 275                idr_mark_full(pa, id);
 276        }
 277
 278        return id;
 279}
 280
 281/**
 282 * idr_get_new_above - allocate new idr entry above or equal to a start id
 283 * @idp: idr handle
 284 * @ptr: pointer you want associated with the ide
 285 * @start_id: id to start search at
 286 * @id: pointer to the allocated handle
 287 *
 288 * This is the allocate id function.  It should be called with any
 289 * required locks.
 290 *
 291 * If memory is required, it will return -EAGAIN, you should unlock
 292 * and go back to the idr_pre_get() call.  If the idr is full, it will
 293 * return -ENOSPC.
 294 *
 295 * @id returns a value in the range @starting_id ... 0x7fffffff
 296 */
 297int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
 298{
 299        int rv;
 300
 301        rv = idr_get_new_above_int(idp, ptr, starting_id);
 302        /*
 303         * This is a cheap hack until the IDR code can be fixed to
 304         * return proper error values.
 305         */
 306        if (rv < 0)
 307                return _idr_rc_to_errno(rv);
 308        *id = rv;
 309        return 0;
 310}
 311EXPORT_SYMBOL(idr_get_new_above);
 312
 313/**
 314 * idr_get_new - allocate new idr entry
 315 * @idp: idr handle
 316 * @ptr: pointer you want associated with the ide
 317 * @id: pointer to the allocated handle
 318 *
 319 * This is the allocate id function.  It should be called with any
 320 * required locks.
 321 *
 322 * If memory is required, it will return -EAGAIN, you should unlock
 323 * and go back to the idr_pre_get() call.  If the idr is full, it will
 324 * return -ENOSPC.
 325 *
 326 * @id returns a value in the range 0 ... 0x7fffffff
 327 */
 328int idr_get_new(struct idr *idp, void *ptr, int *id)
 329{
 330        int rv;
 331
 332        rv = idr_get_new_above_int(idp, ptr, 0);
 333        /*
 334         * This is a cheap hack until the IDR code can be fixed to
 335         * return proper error values.
 336         */
 337        if (rv < 0)
 338                return _idr_rc_to_errno(rv);
 339        *id = rv;
 340        return 0;
 341}
 342EXPORT_SYMBOL(idr_get_new);
 343
 344static void idr_remove_warning(int id)
 345{
 346        printk(KERN_WARNING
 347                "idr_remove called for id=%d which is not allocated.\n", id);
 348        dump_stack();
 349}
 350
 351static void sub_remove(struct idr *idp, int shift, int id)
 352{
 353        struct idr_layer *p = idp->top;
 354        struct idr_layer **pa[MAX_LEVEL];
 355        struct idr_layer ***paa = &pa[0];
 356        struct idr_layer *to_free;
 357        int n;
 358
 359        *paa = NULL;
 360        *++paa = &idp->top;
 361
 362        while ((shift > 0) && p) {
 363                n = (id >> shift) & IDR_MASK;
 364                __clear_bit(n, &p->bitmap);
 365                *++paa = &p->ary[n];
 366                p = p->ary[n];
 367                shift -= IDR_BITS;
 368        }
 369        n = id & IDR_MASK;
 370        if (likely(p != NULL && test_bit(n, &p->bitmap))){
 371                __clear_bit(n, &p->bitmap);
 372                rcu_assign_pointer(p->ary[n], NULL);
 373                to_free = NULL;
 374                while(*paa && ! --((**paa)->count)){
 375                        if (to_free)
 376                                free_layer(to_free);
 377                        to_free = **paa;
 378                        **paa-- = NULL;
 379                }
 380                if (!*paa)
 381                        idp->layers = 0;
 382                if (to_free)
 383                        free_layer(to_free);
 384        } else
 385                idr_remove_warning(id);
 386}
 387
 388/**
 389 * idr_remove - remove the given id and free it's slot
 390 * @idp: idr handle
 391 * @id: unique key
 392 */
 393void idr_remove(struct idr *idp, int id)
 394{
 395        struct idr_layer *p;
 396        struct idr_layer *to_free;
 397
 398        /* Mask off upper bits we don't use for the search. */
 399        id &= MAX_ID_MASK;
 400
 401        sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
 402        if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
 403            idp->top->ary[0]) {
 404                /*
 405                 * Single child at leftmost slot: we can shrink the tree.
 406                 * This level is not needed anymore since when layers are
 407                 * inserted, they are inserted at the top of the existing
 408                 * tree.
 409                 */
 410                to_free = idp->top;
 411                p = idp->top->ary[0];
 412                rcu_assign_pointer(idp->top, p);
 413                --idp->layers;
 414                to_free->bitmap = to_free->count = 0;
 415                free_layer(to_free);
 416        }
 417        while (idp->id_free_cnt >= IDR_FREE_MAX) {
 418                p = get_from_free_list(idp);
 419                /*
 420                 * Note: we don't call the rcu callback here, since the only
 421                 * layers that fall into the freelist are those that have been
 422                 * preallocated.
 423                 */
 424                kmem_cache_free(idr_layer_cache, p);
 425        }
 426        return;
 427}
 428EXPORT_SYMBOL(idr_remove);
 429
 430/**
 431 * idr_remove_all - remove all ids from the given idr tree
 432 * @idp: idr handle
 433 *
 434 * idr_destroy() only frees up unused, cached idp_layers, but this
 435 * function will remove all id mappings and leave all idp_layers
 436 * unused.
 437 *
 438 * A typical clean-up sequence for objects stored in an idr tree, will
 439 * use idr_for_each() to free all objects, if necessay, then
 440 * idr_remove_all() to remove all ids, and idr_destroy() to free
 441 * up the cached idr_layers.
 442 */
 443void idr_remove_all(struct idr *idp)
 444{
 445        int n, id, max;
 446        struct idr_layer *p;
 447        struct idr_layer *pa[MAX_LEVEL];
 448        struct idr_layer **paa = &pa[0];
 449
 450        n = idp->layers * IDR_BITS;
 451        p = idp->top;
 452        rcu_assign_pointer(idp->top, NULL);
 453        max = 1 << n;
 454
 455        id = 0;
 456        while (id < max) {
 457                while (n > IDR_BITS && p) {
 458                        n -= IDR_BITS;
 459                        *paa++ = p;
 460                        p = p->ary[(id >> n) & IDR_MASK];
 461                }
 462
 463                id += 1 << n;
 464                while (n < fls(id)) {
 465                        if (p)
 466                                free_layer(p);
 467                        n += IDR_BITS;
 468                        p = *--paa;
 469                }
 470        }
 471        idp->layers = 0;
 472}
 473EXPORT_SYMBOL(idr_remove_all);
 474
 475/**
 476 * idr_destroy - release all cached layers within an idr tree
 477 * idp: idr handle
 478 */
 479void idr_destroy(struct idr *idp)
 480{
 481        while (idp->id_free_cnt) {
 482                struct idr_layer *p = get_from_free_list(idp);
 483                kmem_cache_free(idr_layer_cache, p);
 484        }
 485}
 486EXPORT_SYMBOL(idr_destroy);
 487
 488/**
 489 * idr_find - return pointer for given id
 490 * @idp: idr handle
 491 * @id: lookup key
 492 *
 493 * Return the pointer given the id it has been registered with.  A %NULL
 494 * return indicates that @id is not valid or you passed %NULL in
 495 * idr_get_new().
 496 *
 497 * This function can be called under rcu_read_lock(), given that the leaf
 498 * pointers lifetimes are correctly managed.
 499 */
 500void *idr_find(struct idr *idp, int id)
 501{
 502        int n;
 503        struct idr_layer *p;
 504
 505        p = rcu_dereference(idp->top);
 506        if (!p)
 507                return NULL;
 508        n = (p->layer+1) * IDR_BITS;
 509
 510        /* Mask off upper bits we don't use for the search. */
 511        id &= MAX_ID_MASK;
 512
 513        if (id >= (1 << n))
 514                return NULL;
 515        BUG_ON(n == 0);
 516
 517        while (n > 0 && p) {
 518                n -= IDR_BITS;
 519                BUG_ON(n != p->layer*IDR_BITS);
 520                p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
 521        }
 522        return((void *)p);
 523}
 524EXPORT_SYMBOL(idr_find);
 525
 526/**
 527 * idr_for_each - iterate through all stored pointers
 528 * @idp: idr handle
 529 * @fn: function to be called for each pointer
 530 * @data: data passed back to callback function
 531 *
 532 * Iterate over the pointers registered with the given idr.  The
 533 * callback function will be called for each pointer currently
 534 * registered, passing the id, the pointer and the data pointer passed
 535 * to this function.  It is not safe to modify the idr tree while in
 536 * the callback, so functions such as idr_get_new and idr_remove are
 537 * not allowed.
 538 *
 539 * We check the return of @fn each time. If it returns anything other
 540 * than 0, we break out and return that value.
 541 *
 542 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
 543 */
 544int idr_for_each(struct idr *idp,
 545                 int (*fn)(int id, void *p, void *data), void *data)
 546{
 547        int n, id, max, error = 0;
 548        struct idr_layer *p;
 549        struct idr_layer *pa[MAX_LEVEL];
 550        struct idr_layer **paa = &pa[0];
 551
 552        n = idp->layers * IDR_BITS;
 553        p = rcu_dereference(idp->top);
 554        max = 1 << n;
 555
 556        id = 0;
 557        while (id < max) {
 558                while (n > 0 && p) {
 559                        n -= IDR_BITS;
 560                        *paa++ = p;
 561                        p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
 562                }
 563
 564                if (p) {
 565                        error = fn(id, (void *)p, data);
 566                        if (error)
 567                                break;
 568                }
 569
 570                id += 1 << n;
 571                while (n < fls(id)) {
 572                        n += IDR_BITS;
 573                        p = *--paa;
 574                }
 575        }
 576
 577        return error;
 578}
 579EXPORT_SYMBOL(idr_for_each);
 580
 581/**
 582 * idr_get_next - lookup next object of id to given id.
 583 * @idp: idr handle
 584 * @id:  pointer to lookup key
 585 *
 586 * Returns pointer to registered object with id, which is next number to
 587 * given id.
 588 */
 589
 590void *idr_get_next(struct idr *idp, int *nextidp)
 591{
 592        struct idr_layer *p, *pa[MAX_LEVEL];
 593        struct idr_layer **paa = &pa[0];
 594        int id = *nextidp;
 595        int n, max;
 596
 597        /* find first ent */
 598        n = idp->layers * IDR_BITS;
 599        max = 1 << n;
 600        p = rcu_dereference(idp->top);
 601        if (!p)
 602                return NULL;
 603
 604        while (id < max) {
 605                while (n > 0 && p) {
 606                        n -= IDR_BITS;
 607                        *paa++ = p;
 608                        p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
 609                }
 610
 611                if (p) {
 612                        *nextidp = id;
 613                        return p;
 614                }
 615
 616                id += 1 << n;
 617                while (n < fls(id)) {
 618                        n += IDR_BITS;
 619                        p = *--paa;
 620                }
 621        }
 622        return NULL;
 623}
 624
 625
 626
 627/**
 628 * idr_replace - replace pointer for given id
 629 * @idp: idr handle
 630 * @ptr: pointer you want associated with the id
 631 * @id: lookup key
 632 *
 633 * Replace the pointer registered with an id and return the old value.
 634 * A -ENOENT return indicates that @id was not found.
 635 * A -EINVAL return indicates that @id was not within valid constraints.
 636 *
 637 * The caller must serialize with writers.
 638 */
 639void *idr_replace(struct idr *idp, void *ptr, int id)
 640{
 641        int n;
 642        struct idr_layer *p, *old_p;
 643
 644        p = idp->top;
 645        if (!p)
 646                return ERR_PTR(-EINVAL);
 647
 648        n = (p->layer+1) * IDR_BITS;
 649
 650        id &= MAX_ID_MASK;
 651
 652        if (id >= (1 << n))
 653                return ERR_PTR(-EINVAL);
 654
 655        n -= IDR_BITS;
 656        while ((n > 0) && p) {
 657                p = p->ary[(id >> n) & IDR_MASK];
 658                n -= IDR_BITS;
 659        }
 660
 661        n = id & IDR_MASK;
 662        if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
 663                return ERR_PTR(-ENOENT);
 664
 665        old_p = p->ary[n];
 666        rcu_assign_pointer(p->ary[n], ptr);
 667
 668        return old_p;
 669}
 670EXPORT_SYMBOL(idr_replace);
 671
 672void __init idr_init_cache(void)
 673{
 674        idr_layer_cache = kmem_cache_create("idr_layer_cache",
 675                                sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
 676}
 677
 678/**
 679 * idr_init - initialize idr handle
 680 * @idp:        idr handle
 681 *
 682 * This function is use to set up the handle (@idp) that you will pass
 683 * to the rest of the functions.
 684 */
 685void idr_init(struct idr *idp)
 686{
 687        memset(idp, 0, sizeof(struct idr));
 688        spin_lock_init(&idp->lock);
 689}
 690EXPORT_SYMBOL(idr_init);
 691
 692
 693/*
 694 * IDA - IDR based ID allocator
 695 *
 696 * this is id allocator without id -> pointer translation.  Memory
 697 * usage is much lower than full blown idr because each id only
 698 * occupies a bit.  ida uses a custom leaf node which contains
 699 * IDA_BITMAP_BITS slots.
 700 *
 701 * 2007-04-25  written by Tejun Heo <htejun@gmail.com>
 702 */
 703
 704static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
 705{
 706        unsigned long flags;
 707
 708        if (!ida->free_bitmap) {
 709                spin_lock_irqsave(&ida->idr.lock, flags);
 710                if (!ida->free_bitmap) {
 711                        ida->free_bitmap = bitmap;
 712                        bitmap = NULL;
 713                }
 714                spin_unlock_irqrestore(&ida->idr.lock, flags);
 715        }
 716
 717        kfree(bitmap);
 718}
 719
 720/**
 721 * ida_pre_get - reserve resources for ida allocation
 722 * @ida:        ida handle
 723 * @gfp_mask:   memory allocation flag
 724 *
 725 * This function should be called prior to locking and calling the
 726 * following function.  It preallocates enough memory to satisfy the
 727 * worst possible allocation.
 728 *
 729 * If the system is REALLY out of memory this function returns 0,
 730 * otherwise 1.
 731 */
 732int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
 733{
 734        /* allocate idr_layers */
 735        if (!idr_pre_get(&ida->idr, gfp_mask))
 736                return 0;
 737
 738        /* allocate free_bitmap */
 739        if (!ida->free_bitmap) {
 740                struct ida_bitmap *bitmap;
 741
 742                bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
 743                if (!bitmap)
 744                        return 0;
 745
 746                free_bitmap(ida, bitmap);
 747        }
 748
 749        return 1;
 750}
 751EXPORT_SYMBOL(ida_pre_get);
 752
 753/**
 754 * ida_get_new_above - allocate new ID above or equal to a start id
 755 * @ida:        ida handle
 756 * @staring_id: id to start search at
 757 * @p_id:       pointer to the allocated handle
 758 *
 759 * Allocate new ID above or equal to @ida.  It should be called with
 760 * any required locks.
 761 *
 762 * If memory is required, it will return -EAGAIN, you should unlock
 763 * and go back to the ida_pre_get() call.  If the ida is full, it will
 764 * return -ENOSPC.
 765 *
 766 * @p_id returns a value in the range @starting_id ... 0x7fffffff.
 767 */
 768int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
 769{
 770        struct idr_layer *pa[MAX_LEVEL];
 771        struct ida_bitmap *bitmap;
 772        unsigned long flags;
 773        int idr_id = starting_id / IDA_BITMAP_BITS;
 774        int offset = starting_id % IDA_BITMAP_BITS;
 775        int t, id;
 776
 777 restart:
 778        /* get vacant slot */
 779        t = idr_get_empty_slot(&ida->idr, idr_id, pa);
 780        if (t < 0)
 781                return _idr_rc_to_errno(t);
 782
 783        if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
 784                return -ENOSPC;
 785
 786        if (t != idr_id)
 787                offset = 0;
 788        idr_id = t;
 789
 790        /* if bitmap isn't there, create a new one */
 791        bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
 792        if (!bitmap) {
 793                spin_lock_irqsave(&ida->idr.lock, flags);
 794                bitmap = ida->free_bitmap;
 795                ida->free_bitmap = NULL;
 796                spin_unlock_irqrestore(&ida->idr.lock, flags);
 797
 798                if (!bitmap)
 799                        return -EAGAIN;
 800
 801                memset(bitmap, 0, sizeof(struct ida_bitmap));
 802                rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
 803                                (void *)bitmap);
 804                pa[0]->count++;
 805        }
 806
 807        /* lookup for empty slot */
 808        t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
 809        if (t == IDA_BITMAP_BITS) {
 810                /* no empty slot after offset, continue to the next chunk */
 811                idr_id++;
 812                offset = 0;
 813                goto restart;
 814        }
 815
 816        id = idr_id * IDA_BITMAP_BITS + t;
 817        if (id >= MAX_ID_BIT)
 818                return -ENOSPC;
 819
 820        __set_bit(t, bitmap->bitmap);
 821        if (++bitmap->nr_busy == IDA_BITMAP_BITS)
 822                idr_mark_full(pa, idr_id);
 823
 824        *p_id = id;
 825
 826        /* Each leaf node can handle nearly a thousand slots and the
 827         * whole idea of ida is to have small memory foot print.
 828         * Throw away extra resources one by one after each successful
 829         * allocation.
 830         */
 831        if (ida->idr.id_free_cnt || ida->free_bitmap) {
 832                struct idr_layer *p = get_from_free_list(&ida->idr);
 833                if (p)
 834                        kmem_cache_free(idr_layer_cache, p);
 835        }
 836
 837        return 0;
 838}
 839EXPORT_SYMBOL(ida_get_new_above);
 840
 841/**
 842 * ida_get_new - allocate new ID
 843 * @ida:        idr handle
 844 * @p_id:       pointer to the allocated handle
 845 *
 846 * Allocate new ID.  It should be called with any required locks.
 847 *
 848 * If memory is required, it will return -EAGAIN, you should unlock
 849 * and go back to the idr_pre_get() call.  If the idr is full, it will
 850 * return -ENOSPC.
 851 *
 852 * @id returns a value in the range 0 ... 0x7fffffff.
 853 */
 854int ida_get_new(struct ida *ida, int *p_id)
 855{
 856        return ida_get_new_above(ida, 0, p_id);
 857}
 858EXPORT_SYMBOL(ida_get_new);
 859
 860/**
 861 * ida_remove - remove the given ID
 862 * @ida:        ida handle
 863 * @id:         ID to free
 864 */
 865void ida_remove(struct ida *ida, int id)
 866{
 867        struct idr_layer *p = ida->idr.top;
 868        int shift = (ida->idr.layers - 1) * IDR_BITS;
 869        int idr_id = id / IDA_BITMAP_BITS;
 870        int offset = id % IDA_BITMAP_BITS;
 871        int n;
 872        struct ida_bitmap *bitmap;
 873
 874        /* clear full bits while looking up the leaf idr_layer */
 875        while ((shift > 0) && p) {
 876                n = (idr_id >> shift) & IDR_MASK;
 877                __clear_bit(n, &p->bitmap);
 878                p = p->ary[n];
 879                shift -= IDR_BITS;
 880        }
 881
 882        if (p == NULL)
 883                goto err;
 884
 885        n = idr_id & IDR_MASK;
 886        __clear_bit(n, &p->bitmap);
 887
 888        bitmap = (void *)p->ary[n];
 889        if (!test_bit(offset, bitmap->bitmap))
 890                goto err;
 891
 892        /* update bitmap and remove it if empty */
 893        __clear_bit(offset, bitmap->bitmap);
 894        if (--bitmap->nr_busy == 0) {
 895                __set_bit(n, &p->bitmap);       /* to please idr_remove() */
 896                idr_remove(&ida->idr, idr_id);
 897                free_bitmap(ida, bitmap);
 898        }
 899
 900        return;
 901
 902 err:
 903        printk(KERN_WARNING
 904               "ida_remove called for id=%d which is not allocated.\n", id);
 905}
 906EXPORT_SYMBOL(ida_remove);
 907
 908/**
 909 * ida_destroy - release all cached layers within an ida tree
 910 * ida:         ida handle
 911 */
 912void ida_destroy(struct ida *ida)
 913{
 914        idr_destroy(&ida->idr);
 915        kfree(ida->free_bitmap);
 916}
 917EXPORT_SYMBOL(ida_destroy);
 918
 919/**
 920 * ida_init - initialize ida handle
 921 * @ida:        ida handle
 922 *
 923 * This function is use to set up the handle (@ida) that you will pass
 924 * to the rest of the functions.
 925 */
 926void ida_init(struct ida *ida)
 927{
 928        memset(ida, 0, sizeof(struct ida));
 929        idr_init(&ida->idr);
 930
 931}
 932EXPORT_SYMBOL(ida_init);
 933