SAFE public projects git trees. - safe/jmp/linux-2.6/blob - lib/radix-tree.c

   1 /*
   2  * Copyright (C) 2001 Momchil Velikov
   3  * Portions Copyright (C) 2001 Christoph Hellwig
   4  * Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2, or (at
   9  * your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 #include <linux/errno.h>
  22 #include <linux/init.h>
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/radix-tree.h>
  26 #include <linux/percpu.h>
  27 #include <linux/slab.h>
  28 #include <linux/notifier.h>
  29 #include <linux/cpu.h>
  30 #include <linux/gfp.h>
  31 #include <linux/string.h>
  32 #include <linux/bitops.h>
  33
  34
  35 #ifdef __KERNEL__
  36 #define RADIX_TREE_MAP_SHIFT    6
  37 #else
  38 #define RADIX_TREE_MAP_SHIFT    3       /* For more stressful testing */
  39 #endif
  40 #define RADIX_TREE_TAGS         2
  41
  42 #define RADIX_TREE_MAP_SIZE     (1UL << RADIX_TREE_MAP_SHIFT)
  43 #define RADIX_TREE_MAP_MASK     (RADIX_TREE_MAP_SIZE-1)
  44
  45 #define RADIX_TREE_TAG_LONGS    \
  46         ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
  47
  48 struct radix_tree_node {
  49         unsigned int    count;
  50         void            *slots[RADIX_TREE_MAP_SIZE];
  51         unsigned long   tags[RADIX_TREE_TAGS][RADIX_TREE_TAG_LONGS];
  52 };
  53
  54 struct radix_tree_path {
  55         struct radix_tree_node *node;
  56         int offset;
  57 };
  58
  59 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
  60 #define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
  61
  62 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH] __read_mostly;
  63
  64 /*
  65  * Radix tree node cache.
  66  */
  67 static kmem_cache_t *radix_tree_node_cachep;
  68
  69 /*
  70  * Per-cpu pool of preloaded nodes
  71  */
  72 struct radix_tree_preload {
  73         int nr;
  74         struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
  75 };
  76 DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
  77
  78 /*
  79  * This assumes that the caller has performed appropriate preallocation, and
  80  * that the caller has pinned this thread of control to the current CPU.
  81  */
  82 static struct radix_tree_node *
  83 radix_tree_node_alloc(struct radix_tree_root *root)
  84 {
  85         struct radix_tree_node *ret;
  86
  87         ret = kmem_cache_alloc(radix_tree_node_cachep, root->gfp_mask);
  88         if (ret == NULL && !(root->gfp_mask & __GFP_WAIT)) {
  89                 struct radix_tree_preload *rtp;
  90
  91                 rtp = &__get_cpu_var(radix_tree_preloads);
  92                 if (rtp->nr) {
  93                         ret = rtp->nodes[rtp->nr - 1];
  94                         rtp->nodes[rtp->nr - 1] = NULL;
  95                         rtp->nr--;
  96                 }
  97         }
  98         return ret;
  99 }
 100
 101 static inline void
 102 radix_tree_node_free(struct radix_tree_node *node)
 103 {
 104         kmem_cache_free(radix_tree_node_cachep, node);
 105 }
 106
 107 /*
 108  * Load up this CPU's radix_tree_node buffer with sufficient objects to
 109  * ensure that the addition of a single element in the tree cannot fail.  On
 110  * success, return zero, with preemption disabled.  On error, return -ENOMEM
 111  * with preemption not disabled.
 112  */
 113 int radix_tree_preload(gfp_t gfp_mask)
 114 {
 115         struct radix_tree_preload *rtp;
 116         struct radix_tree_node *node;
 117         int ret = -ENOMEM;
 118
 119         preempt_disable();
 120         rtp = &__get_cpu_var(radix_tree_preloads);
 121         while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
 122                 preempt_enable();
 123                 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 124                 if (node == NULL)
 125                         goto out;
 126                 preempt_disable();
 127                 rtp = &__get_cpu_var(radix_tree_preloads);
 128                 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
 129                         rtp->nodes[rtp->nr++] = node;
 130                 else
 131                         kmem_cache_free(radix_tree_node_cachep, node);
 132         }
 133         ret = 0;
 134 out:
 135         return ret;
 136 }
 137
 138 static inline void tag_set(struct radix_tree_node *node, int tag, int offset)
 139 {
 140         if (!test_bit(offset, &node->tags[tag][0]))
 141                 __set_bit(offset, &node->tags[tag][0]);
 142 }
 143
 144 static inline void tag_clear(struct radix_tree_node *node, int tag, int offset)
 145 {
 146         __clear_bit(offset, &node->tags[tag][0]);
 147 }
 148
 149 static inline int tag_get(struct radix_tree_node *node, int tag, int offset)
 150 {
 151         return test_bit(offset, &node->tags[tag][0]);
 152 }
 153
 154 /*
 155  *      Return the maximum key which can be store into a
 156  *      radix tree with height HEIGHT.
 157  */
 158 static inline unsigned long radix_tree_maxindex(unsigned int height)
 159 {
 160         return height_to_maxindex[height];
 161 }
 162
 163 /*
 164  *      Extend a radix tree so it can store key @index.
 165  */
 166 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 167 {
 168         struct radix_tree_node *node;
 169         unsigned int height;
 170         char tags[RADIX_TREE_TAGS];
 171         int tag;
 172
 173         /* Figure out what the height should be.  */
 174         height = root->height + 1;
 175         while (index > radix_tree_maxindex(height))
 176                 height++;
 177
 178         if (root->rnode == NULL) {
 179                 root->height = height;
 180                 goto out;
 181         }
 182
 183         /*
 184          * Prepare the tag status of the top-level node for propagation
 185          * into the newly-pushed top-level node(s)
 186          */
 187         for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
 188                 int idx;
 189
 190                 tags[tag] = 0;
 191                 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 192                         if (root->rnode->tags[tag][idx]) {
 193                                 tags[tag] = 1;
 194                                 break;
 195                         }
 196                 }
 197         }
 198
 199         do {
 200                 if (!(node = radix_tree_node_alloc(root)))
 201                         return -ENOMEM;
 202
 203                 /* Increase the height.  */
 204                 node->slots[0] = root->rnode;
 205
 206                 /* Propagate the aggregated tag info into the new root */
 207                 for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
 208                         if (tags[tag])
 209                                 tag_set(node, tag, 0);
 210                 }
 211
 212                 node->count = 1;
 213                 root->rnode = node;
 214                 root->height++;
 215         } while (height > root->height);
 216 out:
 217         return 0;
 218 }
 219
 220 /**
 221  *      radix_tree_insert    -    insert into a radix tree
 222  *      @root:          radix tree root
 223  *      @index:         index key
 224  *      @item:          item to insert
 225  *
 226  *      Insert an item into the radix tree at position @index.
 227  */
 228 int radix_tree_insert(struct radix_tree_root *root,
 229                         unsigned long index, void *item)
 230 {
 231         struct radix_tree_node *node = NULL, *slot;
 232         unsigned int height, shift;
 233         int offset;
 234         int error;
 235
 236         /* Make sure the tree is high enough.  */
 237         if ((!index && !root->rnode) ||
 238                         index > radix_tree_maxindex(root->height)) {
 239                 error = radix_tree_extend(root, index);
 240                 if (error)
 241                         return error;
 242         }
 243
 244         slot = root->rnode;
 245         height = root->height;
 246         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 247
 248         offset = 0;                     /* uninitialised var warning */
 249         while (height > 0) {
 250                 if (slot == NULL) {
 251                         /* Have to add a child node.  */
 252                         if (!(slot = radix_tree_node_alloc(root)))
 253                                 return -ENOMEM;
 254                         if (node) {
 255                                 node->slots[offset] = slot;
 256                                 node->count++;
 257                         } else
 258                                 root->rnode = slot;
 259                 }
 260
 261                 /* Go a level down */
 262                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 263                 node = slot;
 264                 slot = node->slots[offset];
 265                 shift -= RADIX_TREE_MAP_SHIFT;
 266                 height--;
 267         }
 268
 269         if (slot != NULL)
 270                 return -EEXIST;
 271
 272         if (node) {
 273                 node->count++;
 274                 node->slots[offset] = item;
 275                 BUG_ON(tag_get(node, 0, offset));
 276                 BUG_ON(tag_get(node, 1, offset));
 277         } else
 278                 root->rnode = item;
 279
 280         return 0;
 281 }
 282 EXPORT_SYMBOL(radix_tree_insert);
 283
 284 static inline void **__lookup_slot(struct radix_tree_root *root,
 285                                    unsigned long index)
 286 {
 287         unsigned int height, shift;
 288         struct radix_tree_node **slot;
 289
 290         height = root->height;
 291         if (index > radix_tree_maxindex(height))
 292                 return NULL;
 293
 294         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 295         slot = &root->rnode;
 296
 297         while (height > 0) {
 298                 if (*slot == NULL)
 299                         return NULL;
 300
 301                 slot = (struct radix_tree_node **)
 302                         ((*slot)->slots +
 303                                 ((index >> shift) & RADIX_TREE_MAP_MASK));
 304                 shift -= RADIX_TREE_MAP_SHIFT;
 305                 height--;
 306         }
 307
 308         return (void **)slot;
 309 }
 310
 311 /**
 312  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
 313  *      @root:          radix tree root
 314  *      @index:         index key
 315  *
 316  *      Lookup the slot corresponding to the position @index in the radix tree
 317  *      @root. This is useful for update-if-exists operations.
 318  */
 319 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
 320 {
 321         return __lookup_slot(root, index);
 322 }
 323 EXPORT_SYMBOL(radix_tree_lookup_slot);
 324
 325 /**
 326  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 327  *      @root:          radix tree root
 328  *      @index:         index key
 329  *
 330  *      Lookup the item at the position @index in the radix tree @root.
 331  */
 332 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 333 {
 334         void **slot;
 335
 336         slot = __lookup_slot(root, index);
 337         return slot != NULL ? *slot : NULL;
 338 }
 339 EXPORT_SYMBOL(radix_tree_lookup);
 340
 341 /**
 342  *      radix_tree_tag_set - set a tag on a radix tree node
 343  *      @root:          radix tree root
 344  *      @index:         index key
 345  *      @tag:           tag index
 346  *
 347  *      Set the search tag corresponging to @index in the radix tree.  From
 348  *      the root all the way down to the leaf node.
 349  *
 350  *      Returns the address of the tagged item.   Setting a tag on a not-present
 351  *      item is a bug.
 352  */
 353 void *radix_tree_tag_set(struct radix_tree_root *root,
 354                         unsigned long index, int tag)
 355 {
 356         unsigned int height, shift;
 357         struct radix_tree_node *slot;
 358
 359         height = root->height;
 360         if (index > radix_tree_maxindex(height))
 361                 return NULL;
 362
 363         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 364         slot = root->rnode;
 365
 366         while (height > 0) {
 367                 int offset;
 368
 369                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 370                 tag_set(slot, tag, offset);
 371                 slot = slot->slots[offset];
 372                 BUG_ON(slot == NULL);
 373                 shift -= RADIX_TREE_MAP_SHIFT;
 374                 height--;
 375         }
 376
 377         return slot;
 378 }
 379 EXPORT_SYMBOL(radix_tree_tag_set);
 380
 381 /**
 382  *      radix_tree_tag_clear - clear a tag on a radix tree node
 383  *      @root:          radix tree root
 384  *      @index:         index key
 385  *      @tag:           tag index
 386  *
 387  *      Clear the search tag corresponging to @index in the radix tree.  If
 388  *      this causes the leaf node to have no tags set then clear the tag in the
 389  *      next-to-leaf node, etc.
 390  *
 391  *      Returns the address of the tagged item on success, else NULL.  ie:
 392  *      has the same return value and semantics as radix_tree_lookup().
 393  */
 394 void *radix_tree_tag_clear(struct radix_tree_root *root,
 395                         unsigned long index, int tag)
 396 {
 397         struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
 398         struct radix_tree_node *slot;
 399         unsigned int height, shift;
 400         void *ret = NULL;
 401
 402         height = root->height;
 403         if (index > radix_tree_maxindex(height))
 404                 goto out;
 405
 406         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 407         pathp->node = NULL;
 408         slot = root->rnode;
 409
 410         while (height > 0) {
 411                 int offset;
 412
 413                 if (slot == NULL)
 414                         goto out;
 415
 416                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 417                 pathp[1].offset = offset;
 418                 pathp[1].node = slot;
 419                 slot = slot->slots[offset];
 420                 pathp++;
 421                 shift -= RADIX_TREE_MAP_SHIFT;
 422                 height--;
 423         }
 424
 425         ret = slot;
 426         if (ret == NULL)
 427                 goto out;
 428
 429         do {
 430                 int idx;
 431
 432                 tag_clear(pathp->node, tag, pathp->offset);
 433                 for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 434                         if (pathp->node->tags[tag][idx])
 435                                 goto out;
 436                 }
 437                 pathp--;
 438         } while (pathp->node);
 439 out:
 440         return ret;
 441 }
 442 EXPORT_SYMBOL(radix_tree_tag_clear);
 443
 444 #ifndef __KERNEL__      /* Only the test harness uses this at present */
 445 /**
 446  * radix_tree_tag_get - get a tag on a radix tree node
 447  * @root:               radix tree root
 448  * @index:              index key
 449  * @tag:                tag index
 450  *
 451  * Return values:
 452  *
 453  *  0: tag not present
 454  *  1: tag present, set
 455  * -1: tag present, unset
 456  */
 457 int radix_tree_tag_get(struct radix_tree_root *root,
 458                         unsigned long index, int tag)
 459 {
 460         unsigned int height, shift;
 461         struct radix_tree_node *slot;
 462         int saw_unset_tag = 0;
 463
 464         height = root->height;
 465         if (index > radix_tree_maxindex(height))
 466                 return 0;
 467
 468         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 469         slot = root->rnode;
 470
 471         for ( ; ; ) {
 472                 int offset;
 473
 474                 if (slot == NULL)
 475                         return 0;
 476
 477                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 478
 479                 /*
 480                  * This is just a debug check.  Later, we can bale as soon as
 481                  * we see an unset tag.
 482                  */
 483                 if (!tag_get(slot, tag, offset))
 484                         saw_unset_tag = 1;
 485                 if (height == 1) {
 486                         int ret = tag_get(slot, tag, offset);
 487
 488                         BUG_ON(ret && saw_unset_tag);
 489                         return ret ? 1 : -1;
 490                 }
 491                 slot = slot->slots[offset];
 492                 shift -= RADIX_TREE_MAP_SHIFT;
 493                 height--;
 494         }
 495 }
 496 EXPORT_SYMBOL(radix_tree_tag_get);
 497 #endif
 498
 499 static unsigned int
 500 __lookup(struct radix_tree_root *root, void **results, unsigned long index,
 501         unsigned int max_items, unsigned long *next_index)
 502 {
 503         unsigned int nr_found = 0;
 504         unsigned int shift, height;
 505         struct radix_tree_node *slot;
 506         unsigned long i;
 507
 508         height = root->height;
 509         if (height == 0)
 510                 goto out;
 511
 512         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 513         slot = root->rnode;
 514
 515         for ( ; height > 1; height--) {
 516
 517                 for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
 518                                 i < RADIX_TREE_MAP_SIZE; i++) {
 519                         if (slot->slots[i] != NULL)
 520                                 break;
 521                         index &= ~((1UL << shift) - 1);
 522                         index += 1UL << shift;
 523                         if (index == 0)
 524                                 goto out;       /* 32-bit wraparound */
 525                 }
 526                 if (i == RADIX_TREE_MAP_SIZE)
 527                         goto out;
 528
 529                 shift -= RADIX_TREE_MAP_SHIFT;
 530                 slot = slot->slots[i];
 531         }
 532
 533         /* Bottom level: grab some items */
 534         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
 535                 index++;
 536                 if (slot->slots[i]) {
 537                         results[nr_found++] = slot->slots[i];
 538                         if (nr_found == max_items)
 539                                 goto out;
 540                 }
 541         }
 542 out:
 543         *next_index = index;
 544         return nr_found;
 545 }
 546
 547 /**
 548  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
 549  *      @root:          radix tree root
 550  *      @results:       where the results of the lookup are placed
 551  *      @first_index:   start the lookup from this key
 552  *      @max_items:     place up to this many items at *results
 553  *
 554  *      Performs an index-ascending scan of the tree for present items.  Places
 555  *      them at *@results and returns the number of items which were placed at
 556  *      *@results.
 557  *
 558  *      The implementation is naive.
 559  */
 560 unsigned int
 561 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 562                         unsigned long first_index, unsigned int max_items)
 563 {
 564         const unsigned long max_index = radix_tree_maxindex(root->height);
 565         unsigned long cur_index = first_index;
 566         unsigned int ret = 0;
 567
 568         while (ret < max_items) {
 569                 unsigned int nr_found;
 570                 unsigned long next_index;       /* Index of next search */
 571
 572                 if (cur_index > max_index)
 573                         break;
 574                 nr_found = __lookup(root, results + ret, cur_index,
 575                                         max_items - ret, &next_index);
 576                 ret += nr_found;
 577                 if (next_index == 0)
 578                         break;
 579                 cur_index = next_index;
 580         }
 581         return ret;
 582 }
 583 EXPORT_SYMBOL(radix_tree_gang_lookup);
 584
 585 /*
 586  * FIXME: the two tag_get()s here should use find_next_bit() instead of
 587  * open-coding the search.
 588  */
 589 static unsigned int
 590 __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
 591         unsigned int max_items, unsigned long *next_index, int tag)
 592 {
 593         unsigned int nr_found = 0;
 594         unsigned int shift;
 595         unsigned int height = root->height;
 596         struct radix_tree_node *slot;
 597
 598         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 599         slot = root->rnode;
 600
 601         while (height > 0) {
 602                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
 603
 604                 for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
 605                         if (tag_get(slot, tag, i)) {
 606                                 BUG_ON(slot->slots[i] == NULL);
 607                                 break;
 608                         }
 609                         index &= ~((1UL << shift) - 1);
 610                         index += 1UL << shift;
 611                         if (index == 0)
 612                                 goto out;       /* 32-bit wraparound */
 613                 }
 614                 if (i == RADIX_TREE_MAP_SIZE)
 615                         goto out;
 616                 height--;
 617                 if (height == 0) {      /* Bottom level: grab some items */
 618                         unsigned long j = index & RADIX_TREE_MAP_MASK;
 619
 620                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
 621                                 index++;
 622                                 if (tag_get(slot, tag, j)) {
 623                                         BUG_ON(slot->slots[j] == NULL);
 624                                         results[nr_found++] = slot->slots[j];
 625                                         if (nr_found == max_items)
 626                                                 goto out;
 627                                 }
 628                         }
 629                 }
 630                 shift -= RADIX_TREE_MAP_SHIFT;
 631                 slot = slot->slots[i];
 632         }
 633 out:
 634         *next_index = index;
 635         return nr_found;
 636 }
 637
 638 /**
 639  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
 640  *                                   based on a tag
 641  *      @root:          radix tree root
 642  *      @results:       where the results of the lookup are placed
 643  *      @first_index:   start the lookup from this key
 644  *      @max_items:     place up to this many items at *results
 645  *      @tag:           the tag index
 646  *
 647  *      Performs an index-ascending scan of the tree for present items which
 648  *      have the tag indexed by @tag set.  Places the items at *@results and
 649  *      returns the number of items which were placed at *@results.
 650  */
 651 unsigned int
 652 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
 653                 unsigned long first_index, unsigned int max_items, int tag)
 654 {
 655         const unsigned long max_index = radix_tree_maxindex(root->height);
 656         unsigned long cur_index = first_index;
 657         unsigned int ret = 0;
 658
 659         while (ret < max_items) {
 660                 unsigned int nr_found;
 661                 unsigned long next_index;       /* Index of next search */
 662
 663                 if (cur_index > max_index)
 664                         break;
 665                 nr_found = __lookup_tag(root, results + ret, cur_index,
 666                                         max_items - ret, &next_index, tag);
 667                 ret += nr_found;
 668                 if (next_index == 0)
 669                         break;
 670                 cur_index = next_index;
 671         }
 672         return ret;
 673 }
 674 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
 675
 676 /**
 677  *      radix_tree_delete    -    delete an item from a radix tree
 678  *      @root:          radix tree root
 679  *      @index:         index key
 680  *
 681  *      Remove the item at @index from the radix tree rooted at @root.
 682  *
 683  *      Returns the address of the deleted item, or NULL if it was not present.
 684  */
 685 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 686 {
 687         struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
 688         struct radix_tree_path *orig_pathp;
 689         struct radix_tree_node *slot;
 690         unsigned int height, shift;
 691         void *ret = NULL;
 692         char tags[RADIX_TREE_TAGS];
 693         int nr_cleared_tags;
 694
 695         height = root->height;
 696         if (index > radix_tree_maxindex(height))
 697                 goto out;
 698
 699         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 700         pathp->node = NULL;
 701         slot = root->rnode;
 702
 703         for ( ; height > 0; height--) {
 704                 int offset;
 705
 706                 if (slot == NULL)
 707                         goto out;
 708
 709                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 710                 pathp[1].offset = offset;
 711                 pathp[1].node = slot;
 712                 slot = slot->slots[offset];
 713                 pathp++;
 714                 shift -= RADIX_TREE_MAP_SHIFT;
 715         }
 716
 717         ret = slot;
 718         if (ret == NULL)
 719                 goto out;
 720
 721         orig_pathp = pathp;
 722
 723         /*
 724          * Clear all tags associated with the just-deleted item
 725          */
 726         memset(tags, 0, sizeof(tags));
 727         do {
 728                 int tag;
 729
 730                 nr_cleared_tags = RADIX_TREE_TAGS;
 731                 for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
 732                         int idx;
 733
 734                         if (tags[tag])
 735                                 continue;
 736
 737                         tag_clear(pathp->node, tag, pathp->offset);
 738
 739                         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 740                                 if (pathp->node->tags[tag][idx]) {
 741                                         tags[tag] = 1;
 742                                         nr_cleared_tags--;
 743                                         break;
 744                                 }
 745                         }
 746                 }
 747                 pathp--;
 748         } while (pathp->node && nr_cleared_tags);
 749
 750         /* Now free the nodes we do not need anymore */
 751         for (pathp = orig_pathp; pathp->node; pathp--) {
 752                 pathp->node->slots[pathp->offset] = NULL;
 753                 if (--pathp->node->count)
 754                         goto out;
 755
 756                 /* Node with zero slots in use so free it */
 757                 radix_tree_node_free(pathp->node);
 758         }
 759         root->rnode = NULL;
 760         root->height = 0;
 761 out:
 762         return ret;
 763 }
 764 EXPORT_SYMBOL(radix_tree_delete);
 765
 766 /**
 767  *      radix_tree_tagged - test whether any items in the tree are tagged
 768  *      @root:          radix tree root
 769  *      @tag:           tag to test
 770  */
 771 int radix_tree_tagged(struct radix_tree_root *root, int tag)
 772 {
 773         int idx;
 774
 775         if (!root->rnode)
 776                 return 0;
 777         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 778                 if (root->rnode->tags[tag][idx])
 779                         return 1;
 780         }
 781         return 0;
 782 }
 783 EXPORT_SYMBOL(radix_tree_tagged);
 784
 785 static void
 786 radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
 787 {
 788         memset(node, 0, sizeof(struct radix_tree_node));
 789 }
 790
 791 static __init unsigned long __maxindex(unsigned int height)
 792 {
 793         unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
 794         unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
 795
 796         if (tmp >= RADIX_TREE_INDEX_BITS)
 797                 index = ~0UL;
 798         return index;
 799 }
 800
 801 static __init void radix_tree_init_maxindex(void)
 802 {
 803         unsigned int i;
 804
 805         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
 806                 height_to_maxindex[i] = __maxindex(i);
 807 }
 808
 809 #ifdef CONFIG_HOTPLUG_CPU
 810 static int radix_tree_callback(struct notifier_block *nfb,
 811                             unsigned long action,
 812                             void *hcpu)
 813 {
 814        int cpu = (long)hcpu;
 815        struct radix_tree_preload *rtp;
 816
 817        /* Free per-cpu pool of perloaded nodes */
 818        if (action == CPU_DEAD) {
 819                rtp = &per_cpu(radix_tree_preloads, cpu);
 820                while (rtp->nr) {
 821                        kmem_cache_free(radix_tree_node_cachep,
 822                                        rtp->nodes[rtp->nr-1]);
 823                        rtp->nodes[rtp->nr-1] = NULL;
 824                        rtp->nr--;
 825                }
 826        }
 827        return NOTIFY_OK;
 828 }
 829 #endif /* CONFIG_HOTPLUG_CPU */
 830
 831 void __init radix_tree_init(void)
 832 {
 833         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
 834                         sizeof(struct radix_tree_node), 0,
 835                         SLAB_PANIC, radix_tree_node_ctor, NULL);
 836         radix_tree_init_maxindex();
 837         hotcpu_notifier(radix_tree_callback, 0);
 838 }