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 MAX_IDR_FREE) 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/export.h>
  33#endif
  34#include <linux/err.h>
  35#include <linux/string.h>
  36#include <linux/idr.h>
  37#include <linux/spinlock.h>
  38
  39static struct kmem_cache *idr_layer_cache;
  40static DEFINE_SPINLOCK(simple_ida_lock);
  41
  42static struct idr_layer *get_from_free_list(struct idr *idp)
  43{
  44        struct idr_layer *p;
  45        unsigned long flags;
  46
  47        spin_lock_irqsave(&idp->lock, flags);
  48        if ((p = idp->id_free)) {
  49                idp->id_free = p->ary[0];
  50                idp->id_free_cnt--;
  51                p->ary[0] = NULL;
  52        }
  53        spin_unlock_irqrestore(&idp->lock, flags);
  54        return(p);
  55}
  56
  57static void idr_layer_rcu_free(struct rcu_head *head)
  58{
  59        struct idr_layer *layer;
  60
  61        layer = container_of(head, struct idr_layer, rcu_head);
  62        kmem_cache_free(idr_layer_cache, layer);
  63}
  64
  65static inline void free_layer(struct idr_layer *p)
  66{
  67        call_rcu(&p->rcu_head, idr_layer_rcu_free);
  68}
  69
  70/* only called when idp->lock is held */
  71static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
  72{
  73        p->ary[0] = idp->id_free;
  74        idp->id_free = p;
  75        idp->id_free_cnt++;
  76}
  77
  78static void move_to_free_list(struct idr *idp, struct idr_layer *p)
  79{
  80        unsigned long flags;
  81
  82        /*
  83         * Depends on the return element being zeroed.
  84         */
  85        spin_lock_irqsave(&idp->lock, flags);
  86        __move_to_free_list(idp, p);
  87        spin_unlock_irqrestore(&idp->lock, flags);
  88}
  89
  90static void idr_mark_full(struct idr_layer **pa, int id)
  91{
  92        struct idr_layer *p = pa[0];
  93        int l = 0;
  94
  95        __set_bit(id & IDR_MASK, &p->bitmap);
  96        /*
  97         * If this layer is full mark the bit in the layer above to
  98         * show that this part of the radix tree is full.  This may
  99         * complete the layer above and require walking up the radix
 100         * tree.
 101         */
 102        while (p->bitmap == IDR_FULL) {
 103                if (!(p = pa[++l]))
 104                        break;
 105                id = id >> IDR_BITS;
 106                __set_bit((id & IDR_MASK), &p->bitmap);
 107        }
 108}
 109
 110/**
 111 * idr_pre_get - reserve resources for idr allocation
 112 * @idp:        idr handle
 113 * @gfp_mask:   memory allocation flags
 114 *
 115 * This function should be called prior to calling the idr_get_new* functions.
 116 * It preallocates enough memory to satisfy the worst possible allocation. The
 117 * caller should pass in GFP_KERNEL if possible.  This of course requires that
 118 * no spinning locks be held.
 119 *
 120 * If the system is REALLY out of memory this function returns %0,
 121 * otherwise %1.
 122 */
 123int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
 124{
 125        while (idp->id_free_cnt < MAX_IDR_FREE) {
 126                struct idr_layer *new;
 127                new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
 128                if (new == NULL)
 129                        return (0);
 130                move_to_free_list(idp, new);
 131        }
 132        return 1;
 133}
 134EXPORT_SYMBOL(idr_pre_get);
 135
 136static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
 137{
 138        int n, m, sh;
 139        struct idr_layer *p, *new;
 140        int l, id, oid;
 141        unsigned long bm;
 142
 143        id = *starting_id;
 144 restart:
 145        p = idp->top;
 146        l = idp->layers;
 147        pa[l--] = NULL;
 148        while (1) {
 149                /*
 150                 * We run around this while until we reach the leaf node...
 151                 */
 152                n = (id >> (IDR_BITS*l)) & IDR_MASK;
 153                bm = ~p->bitmap;
 154                m = find_next_bit(&bm, IDR_SIZE, n);
 155                if (m == IDR_SIZE) {
 156                        /* no space available go back to previous layer. */
 157                        l++;
 158                        oid = id;
 159                        id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
 160
 161                        /* if already at the top layer, we need to grow */
 162                        if (id >= 1 << (idp->layers * IDR_BITS)) {
 163                                *starting_id = id;
 164                                return IDR_NEED_TO_GROW;
 165                        }
 166                        p = pa[l];
 167                        BUG_ON(!p);
 168
 169                        /* If we need to go up one layer, continue the
 170                         * loop; otherwise, restart from the top.
 171                         */
 172                        sh = IDR_BITS * (l + 1);
 173                        if (oid >> sh == id >> sh)
 174                                continue;
 175                        else
 176                                goto restart;
 177                }
 178                if (m != n) {
 179                        sh = IDR_BITS*l;
 180                        id = ((id >> sh) ^ n ^ m) << sh;
 181                }
 182                if ((id >= MAX_IDR_BIT) || (id < 0))
 183                        return IDR_NOMORE_SPACE;
 184                if (l == 0)
 185                        break;
 186                /*
 187                 * Create the layer below if it is missing.
 188                 */
 189                if (!p->ary[m]) {
 190                        new = get_from_free_list(idp);
 191                        if (!new)
 192                                return -1;
 193                        new->layer = l-1;
 194                        rcu_assign_pointer(p->ary[m], new);
 195                        p->count++;
 196                }
 197                pa[l--] = p;
 198                p = p->ary[m];
 199        }
 200
 201        pa[l] = p;
 202        return id;
 203}
 204
 205static int idr_get_empty_slot(struct idr *idp, int starting_id,
 206                              struct idr_layer **pa)
 207{
 208        struct idr_layer *p, *new;
 209        int layers, v, id;
 210        unsigned long flags;
 211
 212        id = starting_id;
 213build_up:
 214        p = idp->top;
 215        layers = idp->layers;
 216        if (unlikely(!p)) {
 217                if (!(p = get_from_free_list(idp)))
 218                        return -1;
 219                p->layer = 0;
 220                layers = 1;
 221        }
 222        /*
 223         * Add a new layer to the top of the tree if the requested
 224         * id is larger than the currently allocated space.
 225         */
 226        while ((layers < (MAX_IDR_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
 227                layers++;
 228                if (!p->count) {
 229                        /* special case: if the tree is currently empty,
 230                         * then we grow the tree by moving the top node
 231                         * upwards.
 232                         */
 233                        p->layer++;
 234                        continue;
 235                }
 236                if (!(new = get_from_free_list(idp))) {
 237                        /*
 238                         * The allocation failed.  If we built part of
 239                         * the structure tear it down.
 240                         */
 241                        spin_lock_irqsave(&idp->lock, flags);
 242                        for (new = p; p && p != idp->top; new = p) {
 243                                p = p->ary[0];
 244                                new->ary[0] = NULL;
 245                                new->bitmap = new->count = 0;
 246                                __move_to_free_list(idp, new);
 247                        }
 248                        spin_unlock_irqrestore(&idp->lock, flags);
 249                        return -1;
 250                }
 251                new->ary[0] = p;
 252                new->count = 1;
 253                new->layer = layers-1;
 254                if (p->bitmap == IDR_FULL)
 255                        __set_bit(0, &new->bitmap);
 256                p = new;
 257        }
 258        rcu_assign_pointer(idp->top, p);
 259        idp->layers = layers;
 260        v = sub_alloc(idp, &id, pa);
 261        if (v == IDR_NEED_TO_GROW)
 262                goto build_up;
 263        return(v);
 264}
 265
 266static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
 267{
 268        struct idr_layer *pa[MAX_IDR_LEVEL];
 269        int id;
 270
 271        id = idr_get_empty_slot(idp, starting_id, pa);
 272        if (id >= 0) {
 273                /*
 274                 * Successfully found an empty slot.  Install the user
 275                 * pointer and mark the slot full.
 276                 */
 277                rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
 278                                (struct idr_layer *)ptr);
 279                pa[0]->count++;
 280                idr_mark_full(pa, id);
 281        }
 282
 283        return id;
 284}
 285
 286/**
 287 * idr_get_new_above - allocate new idr entry above or equal to a start id
 288 * @idp: idr handle
 289 * @ptr: pointer you want associated with the id
 290 * @starting_id: id to start search at
 291 * @id: pointer to the allocated handle
 292 *
 293 * This is the allocate id function.  It should be called with any
 294 * required locks.
 295 *
 296 * If allocation from IDR's private freelist fails, idr_get_new_above() will
 297 * return %-EAGAIN.  The caller should retry the idr_pre_get() call to refill
 298 * IDR's preallocation and then retry the idr_get_new_above() call.
 299 *
 300 * If the idr is full idr_get_new_above() will return %-ENOSPC.
 301 *
 302 * @id returns a value in the range @starting_id ... %0x7fffffff
 303 */
 304int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
 305{
 306        int rv;
 307
 308        rv = idr_get_new_above_int(idp, ptr, starting_id);
 309        /*
 310         * This is a cheap hack until the IDR code can be fixed to
 311         * return proper error values.
 312         */
 313        if (rv < 0)
 314                return _idr_rc_to_errno(rv);
 315        *id = rv;
 316        return 0;
 317}
 318EXPORT_SYMBOL(idr_get_new_above);
 319
 320/**
 321 * idr_get_new - allocate new idr entry
 322 * @idp: idr handle
 323 * @ptr: pointer you want associated with the id
 324 * @id: pointer to the allocated handle
 325 *
 326 * If allocation from IDR's private freelist fails, idr_get_new_above() will
 327 * return %-EAGAIN.  The caller should retry the idr_pre_get() call to refill
 328 * IDR's preallocation and then retry the idr_get_new_above() call.
 329 *
 330 * If the idr is full idr_get_new_above() will return %-ENOSPC.
 331 *
 332 * @id returns a value in the range %0 ... %0x7fffffff
 333 */
 334int idr_get_new(struct idr *idp, void *ptr, int *id)
 335{
 336        int rv;
 337
 338        rv = idr_get_new_above_int(idp, ptr, 0);
 339        /*
 340         * This is a cheap hack until the IDR code can be fixed to
 341         * return proper error values.
 342         */
 343        if (rv < 0)
 344                return _idr_rc_to_errno(rv);
 345        *id = rv;
 346        return 0;
 347}
 348EXPORT_SYMBOL(idr_get_new);
 349
 350static void idr_remove_warning(int id)
 351{
 352        printk(KERN_WARNING
 353                "idr_remove called for id=%d which is not allocated.\n", id);
 354        dump_stack();
 355}
 356
 357static void sub_remove(struct idr *idp, int shift, int id)
 358{
 359        struct idr_layer *p = idp->top;
 360        struct idr_layer **pa[MAX_IDR_LEVEL];
 361        struct idr_layer ***paa = &pa[0];
 362        struct idr_layer *to_free;
 363        int n;
 364
 365        *paa = NULL;
 366        *++paa = &idp->top;
 367
 368        while ((shift > 0) && p) {
 369                n = (id >> shift) & IDR_MASK;
 370                __clear_bit(n, &p->bitmap);
 371                *++paa = &p->ary[n];
 372                p = p->ary[n];
 373                shift -= IDR_BITS;
 374        }
 375        n = id & IDR_MASK;
 376        if (likely(p != NULL && test_bit(n, &p->bitmap))){
 377                __clear_bit(n, &p->bitmap);
 378                rcu_assign_pointer(p->ary[n], NULL);
 379                to_free = NULL;
 380                while(*paa && ! --((**paa)->count)){
 381                        if (to_free)
 382                                free_layer(to_free);
 383                        to_free = **paa;
 384                        **paa-- = NULL;
 385                }
 386                if (!*paa)
 387                        idp->layers = 0;
 388                if (to_free)
 389                        free_layer(to_free);
 390        } else
 391                idr_remove_warning(id);
 392}
 393
 394/**
 395 * idr_remove - remove the given id and free its slot
 396 * @idp: idr handle
 397 * @id: unique key
 398 */
 399void idr_remove(struct idr *idp, int id)
 400{
 401        struct idr_layer *p;
 402        struct idr_layer *to_free;
 403
 404        /* Mask off upper bits we don't use for the search. */
 405        id &= MAX_IDR_MASK;
 406
 407        sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
 408        if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
 409            idp->top->ary[0]) {
 410                /*
 411                 * Single child at leftmost slot: we can shrink the tree.
 412                 * This level is not needed anymore since when layers are
 413                 * inserted, they are inserted at the top of the existing
 414                 * tree.
 415                 */
 416                to_free = idp->top;
 417                p = idp->top->ary[0];
 418                rcu_assign_pointer(idp->top, p);
 419                --idp->layers;
 420                to_free->bitmap = to_free->count = 0;
 421                free_layer(to_free);
 422        }
 423        while (idp->id_free_cnt >= MAX_IDR_FREE) {
 424                p = get_from_free_list(idp);
 425                /*
 426                 * Note: we don't call the rcu callback here, since the only
 427                 * layers that fall into the freelist are those that have been
 428                 * preallocated.
 429                 */
 430                kmem_cache_free(idr_layer_cache, p);
 431        }
 432        return;
 433}
 434EXPORT_SYMBOL(idr_remove);
 435
 436/**
 437 * idr_remove_all - remove all ids from the given idr tree
 438 * @idp: idr handle
 439 *
 440 * idr_destroy() only frees up unused, cached idp_layers, but this
 441 * function will remove all id mappings and leave all idp_layers
 442 * unused.
 443 *
 444 * A typical clean-up sequence for objects stored in an idr tree will
 445 * use idr_for_each() to free all objects, if necessay, then
 446 * idr_remove_all() to remove all ids, and idr_destroy() to free
 447 * up the cached idr_layers.
 448 */
 449void idr_remove_all(struct idr *idp)
 450{
 451        int n, id, max;
 452        int bt_mask;
 453        struct idr_layer *p;
 454        struct idr_layer *pa[MAX_IDR_LEVEL];
 455        struct idr_layer **paa = &pa[0];
 456
 457        n = idp->layers * IDR_BITS;
 458        p = idp->top;
 459        rcu_assign_pointer(idp->top, NULL);
 460        max = 1 << n;
 461
 462        id = 0;
 463        while (id < max) {
 464                while (n > IDR_BITS && p) {
 465                        n -= IDR_BITS;
 466                        *paa++ = p;
 467                        p = p->ary[(id >> n) & IDR_MASK];
 468                }
 469
 470                bt_mask = id;
 471                id += 1 << n;
 472                /* Get the highest bit that the above add changed from 0->1. */
 473                while (n < fls(id ^ bt_mask)) {
 474                        if (p)
 475                                free_layer(p);
 476                        n += IDR_BITS;
 477                        p = *--paa;
 478                }
 479        }
 480        idp->layers = 0;
 481}
 482EXPORT_SYMBOL(idr_remove_all);
 483
 484/**
 485 * idr_destroy - release all cached layers within an idr tree
 486 * @idp: idr handle
 487 */
 488void idr_destroy(struct idr *idp)
 489{
 490        while (idp->id_free_cnt) {
 491                struct idr_layer *p = get_from_free_list(idp);
 492                kmem_cache_free(idr_layer_cache, p);
 493        }
 494}
 495EXPORT_SYMBOL(idr_destroy);
 496
 497/**
 498 * idr_find - return pointer for given id
 499 * @idp: idr handle
 500 * @id: lookup key
 501 *
 502 * Return the pointer given the id it has been registered with.  A %NULL
 503 * return indicates that @id is not valid or you passed %NULL in
 504 * idr_get_new().
 505 *
 506 * This function can be called under rcu_read_lock(), given that the leaf
 507 * pointers lifetimes are correctly managed.
 508 */
 509void *idr_find(struct idr *idp, int id)
 510{
 511        int n;
 512        struct idr_layer *p;
 513
 514        p = rcu_dereference_raw(idp->top);
 515        if (!p)
 516                return NULL;
 517        n = (p->layer+1) * IDR_BITS;
 518
 519        /* Mask off upper bits we don't use for the search. */
 520        id &= MAX_IDR_MASK;
 521
 522        if (id >= (1 << n))
 523                return NULL;
 524        BUG_ON(n == 0);
 525
 526        while (n > 0 && p) {
 527                n -= IDR_BITS;
 528                BUG_ON(n != p->layer*IDR_BITS);
 529                p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
 530        }
 531        return((void *)p);
 532}
 533EXPORT_SYMBOL(idr_find);
 534
 535/**
 536 * idr_for_each - iterate through all stored pointers
 537 * @idp: idr handle
 538 * @fn: function to be called for each pointer
 539 * @data: data passed back to callback function
 540 *
 541 * Iterate over the pointers registered with the given idr.  The
 542 * callback function will be called for each pointer currently
 543 * registered, passing the id, the pointer and the data pointer passed
 544 * to this function.  It is not safe to modify the idr tree while in
 545 * the callback, so functions such as idr_get_new and idr_remove are
 546 * not allowed.
 547 *
 548 * We check the return of @fn each time. If it returns anything other
 549 * than %0, we break out and return that value.
 550 *
 551 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
 552 */
 553int idr_for_each(struct idr *idp,
 554                 int (*fn)(int id, void *p, void *data), void *data)
 555{
 556        int n, id, max, error = 0;
 557        struct idr_layer *p;
 558        struct idr_layer *pa[MAX_IDR_LEVEL];
 559        struct idr_layer **paa = &pa[0];
 560
 561        n = idp->layers * IDR_BITS;
 562        p = rcu_dereference_raw(idp->top);
 563        max = 1 << n;
 564
 565        id = 0;
 566        while (id < max) {
 567                while (n > 0 && p) {
 568                        n -= IDR_BITS;
 569                        *paa++ = p;
 570                        p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
 571                }
 572
 573                if (p) {
 574                        error = fn(id, (void *)p, data);
 575                        if (error)
 576                                break;
 577                }
 578
 579                id += 1 << n;
 580                while (n < fls(id)) {
 581                        n += IDR_BITS;
 582                        p = *--paa;
 583                }
 584        }
 585
 586        return error;
 587}
 588EXPORT_SYMBOL(idr_for_each);
 589
 590/**
 591 * idr_get_next - lookup next object of id to given id.
 592 * @idp: idr handle
 593 * @nextidp:  pointer to lookup key
 594 *
 595 * Returns pointer to registered object with id, which is next number to
 596 * given id. After being looked up, *@nextidp will be updated for the next
 597 * iteration.
 598 *
 599 * This function can be called under rcu_read_lock(), given that the leaf
 600 * pointers lifetimes are correctly managed.
 601 */
 602void *idr_get_next(struct idr *idp, int *nextidp)
 603{
 604        struct idr_layer *p, *pa[MAX_IDR_LEVEL];
 605        struct idr_layer **paa = &pa[0];
 606        int id = *nextidp;
 607        int n, max;
 608
 609        /* find first ent */
 610        p = rcu_dereference_raw(idp->top);
 611        if (!p)
 612                return NULL;
 613        n = (p->layer + 1) * IDR_BITS;
 614        max = 1 << n;
 615
 616        while (id < max) {
 617                while (n > 0 && p) {
 618                        n -= IDR_BITS;
 619                        *paa++ = p;
 620                        p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
 621                }
 622
 623                if (p) {
 624                        *nextidp = id;
 625                        return p;
 626                }
 627
 628                id += 1 << n;
 629                while (n < fls(id)) {
 630                        n += IDR_BITS;
 631                        p = *--paa;
 632                }
 633        }
 634        return NULL;
 635}
 636EXPORT_SYMBOL(idr_get_next);
 637
 638
 639/**
 640 * idr_replace - replace pointer for given id
 641 * @idp: idr handle
 642 * @ptr: pointer you want associated with the id
 643 * @id: lookup key
 644 *
 645 * Replace the pointer registered with an id and return the old value.
 646 * A %-ENOENT return indicates that @id was not found.
 647 * A %-EINVAL return indicates that @id was not within valid constraints.
 648 *
 649 * The caller must serialize with writers.
 650 */
 651void *idr_replace(struct idr *idp, void *ptr, int id)
 652{
 653        int n;
 654        struct idr_layer *p, *old_p;
 655
 656        p = idp->top;
 657        if (!p)
 658                return ERR_PTR(-EINVAL);
 659
 660        n = (p->layer+1) * IDR_BITS;
 661
 662        id &= MAX_IDR_MASK;
 663
 664        if (id >= (1 << n))
 665                return ERR_PTR(-EINVAL);
 666
 667        n -= IDR_BITS;
 668        while ((n > 0) && p) {
 669                p = p->ary[(id >> n) & IDR_MASK];
 670                n -= IDR_BITS;
 671        }
 672
 673        n = id & IDR_MASK;
 674        if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
 675                return ERR_PTR(-ENOENT);
 676
 677        old_p = p->ary[n];
 678        rcu_assign_pointer(p->ary[n], ptr);
 679
 680        return old_p;
 681}
 682EXPORT_SYMBOL(idr_replace);
 683
 684void __init idr_init_cache(void)
 685{
 686        idr_layer_cache = kmem_cache_create("idr_layer_cache",
 687                                sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
 688}
 689
 690/**
 691 * idr_init - initialize idr handle
 692 * @idp:        idr handle
 693 *
 694 * This function is use to set up the handle (@idp) that you will pass
 695 * to the rest of the functions.
 696 */
 697void idr_init(struct idr *idp)
 698{
 699        memset(idp, 0, sizeof(struct idr));
 700        spin_lock_init(&idp->lock);
 701}
 702EXPORT_SYMBOL(idr_init);
 703
 704
 705/**
 706 * DOC: IDA description
 707 * IDA - IDR based ID allocator
 708 *
 709 * This is id allocator without id -> pointer translation.  Memory
 710 * usage is much lower than full blown idr because each id only
 711 * occupies a bit.  ida uses a custom leaf node which contains
 712 * IDA_BITMAP_BITS slots.
 713 *
 714 * 2007-04-25  written by Tejun Heo <htejun@gmail.com>
 715 */
 716
 717static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
 718{
 719        unsigned long flags;
 720
 721        if (!ida->free_bitmap) {
 722                spin_lock_irqsave(&ida->idr.lock, flags);
 723                if (!ida->free_bitmap) {
 724                        ida->free_bitmap = bitmap;
 725                        bitmap = NULL;
 726                }
 727                spin_unlock_irqrestore(&ida->idr.lock, flags);
 728        }
 729
 730        kfree(bitmap);
 731}
 732
 733/**
 734 * ida_pre_get - reserve resources for ida allocation
 735 * @ida:        ida handle
 736 * @gfp_mask:   memory allocation flag
 737 *
 738 * This function should be called prior to locking and calling the
 739 * following function.  It preallocates enough memory to satisfy the
 740 * worst possible allocation.
 741 *
 742 * If the system is REALLY out of memory this function returns %0,
 743 * otherwise %1.
 744 */
 745int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
 746{
 747        /* allocate idr_layers */
 748        if (!idr_pre_get(&ida->idr, gfp_mask))
 749                return 0;
 750
 751        /* allocate free_bitmap */
 752        if (!ida->free_bitmap) {
 753                struct ida_bitmap *bitmap;
 754
 755                bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
 756                if (!bitmap)
 757                        return 0;
 758
 759                free_bitmap(ida, bitmap);
 760        }
 761
 762        return 1;
 763}
 764EXPORT_SYMBOL(ida_pre_get);
 765
 766/**
 767 * ida_get_new_above - allocate new ID above or equal to a start id
 768 * @ida:        ida handle
 769 * @starting_id: id to start search at
 770 * @p_id:       pointer to the allocated handle
 771 *
 772 * Allocate new ID above or equal to @starting_id.  It should be called
 773 * with any required locks.
 774 *
 775 * If memory is required, it will return %-EAGAIN, you should unlock
 776 * and go back to the ida_pre_get() call.  If the ida is full, it will
 777 * return %-ENOSPC.
 778 *
 779 * @p_id returns a value in the range @starting_id ... %0x7fffffff.
 780 */
 781int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
 782{
 783        struct idr_layer *pa[MAX_IDR_LEVEL];
 784        struct ida_bitmap *bitmap;
 785        unsigned long flags;
 786        int idr_id = starting_id / IDA_BITMAP_BITS;
 787        int offset = starting_id % IDA_BITMAP_BITS;
 788        int t, id;
 789
 790 restart:
 791        /* get vacant slot */
 792        t = idr_get_empty_slot(&ida->idr, idr_id, pa);
 793        if (t < 0)
 794                return _idr_rc_to_errno(t);
 795
 796        if (t * IDA_BITMAP_BITS >= MAX_IDR_BIT)
 797                return -ENOSPC;
 798
 799        if (t != idr_id)
 800                offset = 0;
 801        idr_id = t;
 802
 803        /* if bitmap isn't there, create a new one */
 804        bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
 805        if (!bitmap) {
 806                spin_lock_irqsave(&ida->idr.lock, flags);
 807                bitmap = ida->free_bitmap;
 808                ida->free_bitmap = NULL;
 809                spin_unlock_irqrestore(&ida->idr.lock, flags);
 810
 811                if (!bitmap)
 812                        return -EAGAIN;
 813
 814                memset(bitmap, 0, sizeof(struct ida_bitmap));
 815                rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
 816                                (void *)bitmap);
 817                pa[0]->count++;
 818        }
 819
 820        /* lookup for empty slot */
 821        t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
 822        if (t == IDA_BITMAP_BITS) {
 823                /* no empty slot after offset, continue to the next chunk */
 824                idr_id++;
 825                offset = 0;
 826                goto restart;
 827        }
 828
 829        id = idr_id * IDA_BITMAP_BITS + t;
 830        if (id >= MAX_IDR_BIT)
 831                return -ENOSPC;
 832
 833        __set_bit(t, bitmap->bitmap);
 834        if (++bitmap->nr_busy == IDA_BITMAP_BITS)
 835                idr_mark_full(pa, idr_id);
 836
 837        *p_id = id;
 838
 839        /* Each leaf node can handle nearly a thousand slots and the
 840         * whole idea of ida is to have small memory foot print.
 841         * Throw away extra resources one by one after each successful
 842         * allocation.
 843         */
 844        if (ida->idr.id_free_cnt || ida->free_bitmap) {
 845                struct idr_layer *p = get_from_free_list(&ida->idr);
 846                if (p)
 847                        kmem_cache_free(idr_layer_cache, p);
 848        }
 849
 850        return 0;
 851}
 852EXPORT_SYMBOL(ida_get_new_above);
 853
 854/**
 855 * ida_get_new - allocate new ID
 856 * @ida:        idr handle
 857 * @p_id:       pointer to the allocated handle
 858 *
 859 * Allocate new ID.  It should be called with any required locks.
 860 *
 861 * If memory is required, it will return %-EAGAIN, you should unlock
 862 * and go back to the idr_pre_get() call.  If the idr is full, it will
 863 * return %-ENOSPC.
 864 *
 865 * @p_id returns a value in the range %0 ... %0x7fffffff.
 866 */
 867int ida_get_new(struct ida *ida, int *p_id)
 868{
 869        return ida_get_new_above(ida, 0, p_id);
 870}
 871EXPORT_SYMBOL(ida_get_new);
 872
 873/**
 874 * ida_remove - remove the given ID
 875 * @ida:        ida handle
 876 * @id:         ID to free
 877 */
 878void ida_remove(struct ida *ida, int id)
 879{
 880        struct idr_layer *p = ida->idr.top;
 881        int shift = (ida->idr.layers - 1) * IDR_BITS;
 882        int idr_id = id / IDA_BITMAP_BITS;
 883        int offset = id % IDA_BITMAP_BITS;
 884        int n;
 885        struct ida_bitmap *bitmap;
 886
 887        /* clear full bits while looking up the leaf idr_layer */
 888        while ((shift > 0) && p) {
 889                n = (idr_id >> shift) & IDR_MASK;
 890                __clear_bit(n, &p->bitmap);
 891                p = p->ary[n];
 892                shift -= IDR_BITS;
 893        }
 894
 895        if (p == NULL)
 896                goto err;
 897
 898        n = idr_id & IDR_MASK;
 899        __clear_bit(n, &p->bitmap);
 900
 901        bitmap = (void *)p->ary[n];
 902        if (!test_bit(offset, bitmap->bitmap))
 903                goto err;
 904
 905        /* update bitmap and remove it if empty */
 906        __clear_bit(offset, bitmap->bitmap);
 907        if (--bitmap->nr_busy == 0) {
 908                __set_bit(n, &p->bitmap);       /* to please idr_remove() */
 909                idr_remove(&ida->idr, idr_id);
 910                free_bitmap(ida, bitmap);
 911        }
 912
 913        return;
 914
 915 err:
 916        printk(KERN_WARNING
 917               "ida_remove called for id=%d which is not allocated.\n", id);
 918}
 919EXPORT_SYMBOL(ida_remove);
 920
 921/**
 922 * ida_destroy - release all cached layers within an ida tree
 923 * @ida:                ida handle
 924 */
 925void ida_destroy(struct ida *ida)
 926{
 927        idr_destroy(&ida->idr);
 928        kfree(ida->free_bitmap);
 929}
 930EXPORT_SYMBOL(ida_destroy);
 931
 932/**
 933 * ida_simple_get - get a new id.
 934 * @ida: the (initialized) ida.
 935 * @start: the minimum id (inclusive, < 0x8000000)
 936 * @end: the maximum id (exclusive, < 0x8000000 or 0)
 937 * @gfp_mask: memory allocation flags
 938 *
 939 * Allocates an id in the range start <= id < end, or returns -ENOSPC.
 940 * On memory allocation failure, returns -ENOMEM.
 941 *
 942 * Use ida_simple_remove() to get rid of an id.
 943 */
 944int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 945                   gfp_t gfp_mask)
 946{
 947        int ret, id;
 948        unsigned int max;
 949        unsigned long flags;
 950
 951        BUG_ON((int)start < 0);
 952        BUG_ON((int)end < 0);
 953
 954        if (end == 0)
 955                max = 0x80000000;
 956        else {
 957                BUG_ON(end < start);
 958                max = end - 1;
 959        }
 960
 961again:
 962        if (!ida_pre_get(ida, gfp_mask))
 963                return -ENOMEM;
 964
 965        spin_lock_irqsave(&simple_ida_lock, flags);
 966        ret = ida_get_new_above(ida, start, &id);
 967        if (!ret) {
 968                if (id > max) {
 969                        ida_remove(ida, id);
 970                        ret = -ENOSPC;
 971                } else {
 972                        ret = id;
 973                }
 974        }
 975        spin_unlock_irqrestore(&simple_ida_lock, flags);
 976
 977        if (unlikely(ret == -EAGAIN))
 978                goto again;
 979
 980        return ret;
 981}
 982EXPORT_SYMBOL(ida_simple_get);
 983
 984/**
 985 * ida_simple_remove - remove an allocated id.
 986 * @ida: the (initialized) ida.
 987 * @id: the id returned by ida_simple_get.
 988 */
 989void ida_simple_remove(struct ida *ida, unsigned int id)
 990{
 991        unsigned long flags;
 992
 993        BUG_ON((int)id < 0);
 994        spin_lock_irqsave(&simple_ida_lock, flags);
 995        ida_remove(ida, id);
 996        spin_unlock_irqrestore(&simple_ida_lock, flags);
 997}
 998EXPORT_SYMBOL(ida_simple_remove);
 999
1000/**
1001 * ida_init - initialize ida handle
1002 * @ida:        ida handle
1003 *
1004 * This function is use to set up the handle (@ida) that you will pass
1005 * to the rest of the functions.
1006 */
1007void ida_init(struct ida *ida)
1008{
1009        memset(ida, 0, sizeof(struct ida));
1010        idr_init(&ida->idr);
1011
1012}
1013EXPORT_SYMBOL(ida_init);
1014
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