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