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
  41 #define RADIX_TREE_MAP_SIZE     (1UL << RADIX_TREE_MAP_SHIFT)
  42 #define RADIX_TREE_MAP_MASK     (RADIX_TREE_MAP_SIZE-1)
  43
  44 #define RADIX_TREE_TAG_LONGS    \
  45         ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
  46
  47 struct radix_tree_node {
  48         unsigned int    count;
  49         void            *slots[RADIX_TREE_MAP_SIZE];
  50         unsigned long   tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
  51 };
  52
  53 struct radix_tree_path {
  54         struct radix_tree_node *node;
  55         int offset;
  56 };
  57
  58 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
  59 #define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
  60
  61 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH] __read_mostly;
  62
  63 /*
  64  * Radix tree node cache.
  65  */
  66 static kmem_cache_t *radix_tree_node_cachep;
  67
  68 /*
  69  * Per-cpu pool of preloaded nodes
  70  */
  71 struct radix_tree_preload {
  72         int nr;
  73         struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
  74 };
  75 DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
  76
  77 /*
  78  * This assumes that the caller has performed appropriate preallocation, and
  79  * that the caller has pinned this thread of control to the current CPU.
  80  */
  81 static struct radix_tree_node *
  82 radix_tree_node_alloc(struct radix_tree_root *root)
  83 {
  84         struct radix_tree_node *ret;
  85
  86         ret = kmem_cache_alloc(radix_tree_node_cachep, root->gfp_mask);
  87         if (ret == NULL && !(root->gfp_mask & __GFP_WAIT)) {
  88                 struct radix_tree_preload *rtp;
  89
  90                 rtp = &__get_cpu_var(radix_tree_preloads);
  91                 if (rtp->nr) {
  92                         ret = rtp->nodes[rtp->nr - 1];
  93                         rtp->nodes[rtp->nr - 1] = NULL;
  94                         rtp->nr--;
  95                 }
  96         }
  97         return ret;
  98 }
  99
 100 static inline void
 101 radix_tree_node_free(struct radix_tree_node *node)
 102 {
 103         kmem_cache_free(radix_tree_node_cachep, node);
 104 }
 105
 106 /*
 107  * Load up this CPU's radix_tree_node buffer with sufficient objects to
 108  * ensure that the addition of a single element in the tree cannot fail.  On
 109  * success, return zero, with preemption disabled.  On error, return -ENOMEM
 110  * with preemption not disabled.
 111  */
 112 int radix_tree_preload(gfp_t gfp_mask)
 113 {
 114         struct radix_tree_preload *rtp;
 115         struct radix_tree_node *node;
 116         int ret = -ENOMEM;
 117
 118         preempt_disable();
 119         rtp = &__get_cpu_var(radix_tree_preloads);
 120         while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
 121                 preempt_enable();
 122                 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 123                 if (node == NULL)
 124                         goto out;
 125                 preempt_disable();
 126                 rtp = &__get_cpu_var(radix_tree_preloads);
 127                 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
 128                         rtp->nodes[rtp->nr++] = node;
 129                 else
 130                         kmem_cache_free(radix_tree_node_cachep, node);
 131         }
 132         ret = 0;
 133 out:
 134         return ret;
 135 }
 136
 137 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
 138                 int offset)
 139 {
 140         __set_bit(offset, node->tags[tag]);
 141 }
 142
 143 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
 144                 int offset)
 145 {
 146         __clear_bit(offset, node->tags[tag]);
 147 }
 148
 149 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
 150                 int offset)
 151 {
 152         return test_bit(offset, node->tags[tag]);
 153 }
 154
 155 /*
 156  * Returns 1 if any slot in the node has this tag set.
 157  * Otherwise returns 0.
 158  */
 159 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
 160 {
 161         int idx;
 162         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 163                 if (node->tags[tag][idx])
 164                         return 1;
 165         }
 166         return 0;
 167 }
 168
 169 /*
 170  *      Return the maximum key which can be store into a
 171  *      radix tree with height HEIGHT.
 172  */
 173 static inline unsigned long radix_tree_maxindex(unsigned int height)
 174 {
 175         return height_to_maxindex[height];
 176 }
 177
 178 /*
 179  *      Extend a radix tree so it can store key @index.
 180  */
 181 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 182 {
 183         struct radix_tree_node *node;
 184         unsigned int height;
 185         char tags[RADIX_TREE_MAX_TAGS];
 186         int tag;
 187
 188         /* Figure out what the height should be.  */
 189         height = root->height + 1;
 190         while (index > radix_tree_maxindex(height))
 191                 height++;
 192
 193         if (root->rnode == NULL) {
 194                 root->height = height;
 195                 goto out;
 196         }
 197
 198         /*
 199          * Prepare the tag status of the top-level node for propagation
 200          * into the newly-pushed top-level node(s)
 201          */
 202         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 203                 tags[tag] = 0;
 204                 if (any_tag_set(root->rnode, tag))
 205                         tags[tag] = 1;
 206         }
 207
 208         do {
 209                 if (!(node = radix_tree_node_alloc(root)))
 210                         return -ENOMEM;
 211
 212                 /* Increase the height.  */
 213                 node->slots[0] = root->rnode;
 214
 215                 /* Propagate the aggregated tag info into the new root */
 216                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 217                         if (tags[tag])
 218                                 tag_set(node, tag, 0);
 219                 }
 220
 221                 node->count = 1;
 222                 root->rnode = node;
 223                 root->height++;
 224         } while (height > root->height);
 225 out:
 226         return 0;
 227 }
 228
 229 /**
 230  *      radix_tree_insert    -    insert into a radix tree
 231  *      @root:          radix tree root
 232  *      @index:         index key
 233  *      @item:          item to insert
 234  *
 235  *      Insert an item into the radix tree at position @index.
 236  */
 237 int radix_tree_insert(struct radix_tree_root *root,
 238                         unsigned long index, void *item)
 239 {
 240         struct radix_tree_node *node = NULL, *slot;
 241         unsigned int height, shift;
 242         int offset;
 243         int error;
 244
 245         /* Make sure the tree is high enough.  */
 246         if ((!index && !root->rnode) ||
 247                         index > radix_tree_maxindex(root->height)) {
 248                 error = radix_tree_extend(root, index);
 249                 if (error)
 250                         return error;
 251         }
 252
 253         slot = root->rnode;
 254         height = root->height;
 255         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 256
 257         offset = 0;                     /* uninitialised var warning */
 258         do {
 259                 if (slot == NULL) {
 260                         /* Have to add a child node.  */
 261                         if (!(slot = radix_tree_node_alloc(root)))
 262                                 return -ENOMEM;
 263                         if (node) {
 264                                 node->slots[offset] = slot;
 265                                 node->count++;
 266                         } else
 267                                 root->rnode = slot;
 268                 }
 269
 270                 /* Go a level down */
 271                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 272                 node = slot;
 273                 slot = node->slots[offset];
 274                 shift -= RADIX_TREE_MAP_SHIFT;
 275                 height--;
 276         } while (height > 0);
 277
 278         if (slot != NULL)
 279                 return -EEXIST;
 280
 281         BUG_ON(!node);
 282         node->count++;
 283         node->slots[offset] = item;
 284         BUG_ON(tag_get(node, 0, offset));
 285         BUG_ON(tag_get(node, 1, offset));
 286
 287         return 0;
 288 }
 289 EXPORT_SYMBOL(radix_tree_insert);
 290
 291 static inline void **__lookup_slot(struct radix_tree_root *root,
 292                                    unsigned long index)
 293 {
 294         unsigned int height, shift;
 295         struct radix_tree_node **slot;
 296
 297         height = root->height;
 298         if (index > radix_tree_maxindex(height))
 299                 return NULL;
 300
 301         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 302         slot = &root->rnode;
 303
 304         while (height > 0) {
 305                 if (*slot == NULL)
 306                         return NULL;
 307
 308                 slot = (struct radix_tree_node **)
 309                         ((*slot)->slots +
 310                                 ((index >> shift) & RADIX_TREE_MAP_MASK));
 311                 shift -= RADIX_TREE_MAP_SHIFT;
 312                 height--;
 313         }
 314
 315         return (void **)slot;
 316 }
 317
 318 /**
 319  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
 320  *      @root:          radix tree root
 321  *      @index:         index key
 322  *
 323  *      Lookup the slot corresponding to the position @index in the radix tree
 324  *      @root. This is useful for update-if-exists operations.
 325  */
 326 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
 327 {
 328         return __lookup_slot(root, index);
 329 }
 330 EXPORT_SYMBOL(radix_tree_lookup_slot);
 331
 332 /**
 333  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 334  *      @root:          radix tree root
 335  *      @index:         index key
 336  *
 337  *      Lookup the item at the position @index in the radix tree @root.
 338  */
 339 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 340 {
 341         void **slot;
 342
 343         slot = __lookup_slot(root, index);
 344         return slot != NULL ? *slot : NULL;
 345 }
 346 EXPORT_SYMBOL(radix_tree_lookup);
 347
 348 /**
 349  *      radix_tree_tag_set - set a tag on a radix tree node
 350  *      @root:          radix tree root
 351  *      @index:         index key
 352  *      @tag:           tag index
 353  *
 354  *      Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
 355  *      corresponding to @index in the radix tree.  From
 356  *      the root all the way down to the leaf node.
 357  *
 358  *      Returns the address of the tagged item.   Setting a tag on a not-present
 359  *      item is a bug.
 360  */
 361 void *radix_tree_tag_set(struct radix_tree_root *root,
 362                         unsigned long index, unsigned int tag)
 363 {
 364         unsigned int height, shift;
 365         struct radix_tree_node *slot;
 366
 367         height = root->height;
 368         if (index > radix_tree_maxindex(height))
 369                 return NULL;
 370
 371         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 372         slot = root->rnode;
 373
 374         while (height > 0) {
 375                 int offset;
 376
 377                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 378                 if (!tag_get(slot, tag, offset))
 379                         tag_set(slot, tag, offset);
 380                 slot = slot->slots[offset];
 381                 BUG_ON(slot == NULL);
 382                 shift -= RADIX_TREE_MAP_SHIFT;
 383                 height--;
 384         }
 385
 386         return slot;
 387 }
 388 EXPORT_SYMBOL(radix_tree_tag_set);
 389
 390 /**
 391  *      radix_tree_tag_clear - clear a tag on a radix tree node
 392  *      @root:          radix tree root
 393  *      @index:         index key
 394  *      @tag:           tag index
 395  *
 396  *      Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
 397  *      corresponding to @index in the radix tree.  If
 398  *      this causes the leaf node to have no tags set then clear the tag in the
 399  *      next-to-leaf node, etc.
 400  *
 401  *      Returns the address of the tagged item on success, else NULL.  ie:
 402  *      has the same return value and semantics as radix_tree_lookup().
 403  */
 404 void *radix_tree_tag_clear(struct radix_tree_root *root,
 405                         unsigned long index, unsigned int tag)
 406 {
 407         struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
 408         struct radix_tree_node *slot;
 409         unsigned int height, shift;
 410         void *ret = NULL;
 411
 412         height = root->height;
 413         if (index > radix_tree_maxindex(height))
 414                 goto out;
 415
 416         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 417         pathp->node = NULL;
 418         slot = root->rnode;
 419
 420         while (height > 0) {
 421                 int offset;
 422
 423                 if (slot == NULL)
 424                         goto out;
 425
 426                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 427                 pathp[1].offset = offset;
 428                 pathp[1].node = slot;
 429                 slot = slot->slots[offset];
 430                 pathp++;
 431                 shift -= RADIX_TREE_MAP_SHIFT;
 432                 height--;
 433         }
 434
 435         ret = slot;
 436         if (ret == NULL)
 437                 goto out;
 438
 439         do {
 440                 if (!tag_get(pathp->node, tag, pathp->offset))
 441                         goto out;
 442                 tag_clear(pathp->node, tag, pathp->offset);
 443                 if (any_tag_set(pathp->node, tag))
 444                         goto out;
 445                 pathp--;
 446         } while (pathp->node);
 447 out:
 448         return ret;
 449 }
 450 EXPORT_SYMBOL(radix_tree_tag_clear);
 451
 452 #ifndef __KERNEL__      /* Only the test harness uses this at present */
 453 /**
 454  * radix_tree_tag_get - get a tag on a radix tree node
 455  * @root:               radix tree root
 456  * @index:              index key
 457  * @tag:                tag index (< RADIX_TREE_MAX_TAGS)
 458  *
 459  * Return values:
 460  *
 461  *  0: tag not present
 462  *  1: tag present, set
 463  * -1: tag present, unset
 464  */
 465 int radix_tree_tag_get(struct radix_tree_root *root,
 466                         unsigned long index, unsigned int tag)
 467 {
 468         unsigned int height, shift;
 469         struct radix_tree_node *slot;
 470         int saw_unset_tag = 0;
 471
 472         height = root->height;
 473         if (index > radix_tree_maxindex(height))
 474                 return 0;
 475
 476         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 477         slot = root->rnode;
 478
 479         for ( ; ; ) {
 480                 int offset;
 481
 482                 if (slot == NULL)
 483                         return 0;
 484
 485                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 486
 487                 /*
 488                  * This is just a debug check.  Later, we can bale as soon as
 489                  * we see an unset tag.
 490                  */
 491                 if (!tag_get(slot, tag, offset))
 492                         saw_unset_tag = 1;
 493                 if (height == 1) {
 494                         int ret = tag_get(slot, tag, offset);
 495
 496                         BUG_ON(ret && saw_unset_tag);
 497                         return ret ? 1 : -1;
 498                 }
 499                 slot = slot->slots[offset];
 500                 shift -= RADIX_TREE_MAP_SHIFT;
 501                 height--;
 502         }
 503 }
 504 EXPORT_SYMBOL(radix_tree_tag_get);
 505 #endif
 506
 507 static unsigned int
 508 __lookup(struct radix_tree_root *root, void **results, unsigned long index,
 509         unsigned int max_items, unsigned long *next_index)
 510 {
 511         unsigned int nr_found = 0;
 512         unsigned int shift, height;
 513         struct radix_tree_node *slot;
 514         unsigned long i;
 515
 516         height = root->height;
 517         if (height == 0)
 518                 goto out;
 519
 520         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 521         slot = root->rnode;
 522
 523         for ( ; height > 1; height--) {
 524
 525                 for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
 526                                 i < RADIX_TREE_MAP_SIZE; i++) {
 527                         if (slot->slots[i] != NULL)
 528                                 break;
 529                         index &= ~((1UL << shift) - 1);
 530                         index += 1UL << shift;
 531                         if (index == 0)
 532                                 goto out;       /* 32-bit wraparound */
 533                 }
 534                 if (i == RADIX_TREE_MAP_SIZE)
 535                         goto out;
 536
 537                 shift -= RADIX_TREE_MAP_SHIFT;
 538                 slot = slot->slots[i];
 539         }
 540
 541         /* Bottom level: grab some items */
 542         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
 543                 index++;
 544                 if (slot->slots[i]) {
 545                         results[nr_found++] = slot->slots[i];
 546                         if (nr_found == max_items)
 547                                 goto out;
 548                 }
 549         }
 550 out:
 551         *next_index = index;
 552         return nr_found;
 553 }
 554
 555 /**
 556  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
 557  *      @root:          radix tree root
 558  *      @results:       where the results of the lookup are placed
 559  *      @first_index:   start the lookup from this key
 560  *      @max_items:     place up to this many items at *results
 561  *
 562  *      Performs an index-ascending scan of the tree for present items.  Places
 563  *      them at *@results and returns the number of items which were placed at
 564  *      *@results.
 565  *
 566  *      The implementation is naive.
 567  */
 568 unsigned int
 569 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 570                         unsigned long first_index, unsigned int max_items)
 571 {
 572         const unsigned long max_index = radix_tree_maxindex(root->height);
 573         unsigned long cur_index = first_index;
 574         unsigned int ret = 0;
 575
 576         while (ret < max_items) {
 577                 unsigned int nr_found;
 578                 unsigned long next_index;       /* Index of next search */
 579
 580                 if (cur_index > max_index)
 581                         break;
 582                 nr_found = __lookup(root, results + ret, cur_index,
 583                                         max_items - ret, &next_index);
 584                 ret += nr_found;
 585                 if (next_index == 0)
 586                         break;
 587                 cur_index = next_index;
 588         }
 589         return ret;
 590 }
 591 EXPORT_SYMBOL(radix_tree_gang_lookup);
 592
 593 /*
 594  * FIXME: the two tag_get()s here should use find_next_bit() instead of
 595  * open-coding the search.
 596  */
 597 static unsigned int
 598 __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
 599         unsigned int max_items, unsigned long *next_index, unsigned int tag)
 600 {
 601         unsigned int nr_found = 0;
 602         unsigned int shift;
 603         unsigned int height = root->height;
 604         struct radix_tree_node *slot;
 605
 606         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 607         slot = root->rnode;
 608
 609         while (height > 0) {
 610                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
 611
 612                 for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
 613                         if (tag_get(slot, tag, i)) {
 614                                 BUG_ON(slot->slots[i] == NULL);
 615                                 break;
 616                         }
 617                         index &= ~((1UL << shift) - 1);
 618                         index += 1UL << shift;
 619                         if (index == 0)
 620                                 goto out;       /* 32-bit wraparound */
 621                 }
 622                 if (i == RADIX_TREE_MAP_SIZE)
 623                         goto out;
 624                 height--;
 625                 if (height == 0) {      /* Bottom level: grab some items */
 626                         unsigned long j = index & RADIX_TREE_MAP_MASK;
 627
 628                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
 629                                 index++;
 630                                 if (tag_get(slot, tag, j)) {
 631                                         BUG_ON(slot->slots[j] == NULL);
 632                                         results[nr_found++] = slot->slots[j];
 633                                         if (nr_found == max_items)
 634                                                 goto out;
 635                                 }
 636                         }
 637                 }
 638                 shift -= RADIX_TREE_MAP_SHIFT;
 639                 slot = slot->slots[i];
 640         }
 641 out:
 642         *next_index = index;
 643         return nr_found;
 644 }
 645
 646 /**
 647  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
 648  *                                   based on a tag
 649  *      @root:          radix tree root
 650  *      @results:       where the results of the lookup are placed
 651  *      @first_index:   start the lookup from this key
 652  *      @max_items:     place up to this many items at *results
 653  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
 654  *
 655  *      Performs an index-ascending scan of the tree for present items which
 656  *      have the tag indexed by @tag set.  Places the items at *@results and
 657  *      returns the number of items which were placed at *@results.
 658  */
 659 unsigned int
 660 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
 661                 unsigned long first_index, unsigned int max_items,
 662                 unsigned int tag)
 663 {
 664         const unsigned long max_index = radix_tree_maxindex(root->height);
 665         unsigned long cur_index = first_index;
 666         unsigned int ret = 0;
 667
 668         while (ret < max_items) {
 669                 unsigned int nr_found;
 670                 unsigned long next_index;       /* Index of next search */
 671
 672                 if (cur_index > max_index)
 673                         break;
 674                 nr_found = __lookup_tag(root, results + ret, cur_index,
 675                                         max_items - ret, &next_index, tag);
 676                 ret += nr_found;
 677                 if (next_index == 0)
 678                         break;
 679                 cur_index = next_index;
 680         }
 681         return ret;
 682 }
 683 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
 684
 685 /**
 686  *      radix_tree_shrink    -    shrink height of a radix tree to minimal
 687  *      @root           radix tree root
 688  */
 689 static inline void radix_tree_shrink(struct radix_tree_root *root)
 690 {
 691         /* try to shrink tree height */
 692         while (root->height > 1 &&
 693                         root->rnode->count == 1 &&
 694                         root->rnode->slots[0]) {
 695                 struct radix_tree_node *to_free = root->rnode;
 696
 697                 root->rnode = to_free->slots[0];
 698                 root->height--;
 699                 /* must only free zeroed nodes into the slab */
 700                 tag_clear(to_free, 0, 0);
 701                 tag_clear(to_free, 1, 0);
 702                 to_free->slots[0] = NULL;
 703                 to_free->count = 0;
 704                 radix_tree_node_free(to_free);
 705         }
 706 }
 707
 708 /**
 709  *      radix_tree_delete    -    delete an item from a radix tree
 710  *      @root:          radix tree root
 711  *      @index:         index key
 712  *
 713  *      Remove the item at @index from the radix tree rooted at @root.
 714  *
 715  *      Returns the address of the deleted item, or NULL if it was not present.
 716  */
 717 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 718 {
 719         struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
 720         struct radix_tree_path *orig_pathp;
 721         struct radix_tree_node *slot;
 722         unsigned int height, shift;
 723         void *ret = NULL;
 724         char tags[RADIX_TREE_MAX_TAGS];
 725         int nr_cleared_tags;
 726         int tag;
 727         int offset;
 728
 729         height = root->height;
 730         if (index > radix_tree_maxindex(height))
 731                 goto out;
 732
 733         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 734         pathp->node = NULL;
 735         slot = root->rnode;
 736
 737         for ( ; height > 0; height--) {
 738                 if (slot == NULL)
 739                         goto out;
 740
 741                 pathp++;
 742                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 743                 pathp->offset = offset;
 744                 pathp->node = slot;
 745                 slot = slot->slots[offset];
 746                 shift -= RADIX_TREE_MAP_SHIFT;
 747         }
 748
 749         ret = slot;
 750         if (ret == NULL)
 751                 goto out;
 752
 753         orig_pathp = pathp;
 754
 755         /*
 756          * Clear all tags associated with the just-deleted item
 757          */
 758         nr_cleared_tags = 0;
 759         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 760                 tags[tag] = 1;
 761                 if (tag_get(pathp->node, tag, pathp->offset)) {
 762                         tag_clear(pathp->node, tag, pathp->offset);
 763                         if (!any_tag_set(pathp->node, tag)) {
 764                                 tags[tag] = 0;
 765                                 nr_cleared_tags++;
 766                         }
 767                 }
 768         }
 769
 770         for (pathp--; nr_cleared_tags && pathp->node; pathp--) {
 771                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 772                         if (tags[tag])
 773                                 continue;
 774
 775                         tag_clear(pathp->node, tag, pathp->offset);
 776                         if (any_tag_set(pathp->node, tag)) {
 777                                 tags[tag] = 1;
 778                                 nr_cleared_tags--;
 779                         }
 780                 }
 781         }
 782
 783         /* Now free the nodes we do not need anymore */
 784         for (pathp = orig_pathp; pathp->node; pathp--) {
 785                 pathp->node->slots[pathp->offset] = NULL;
 786                 pathp->node->count--;
 787
 788                 if (pathp->node->count) {
 789                         if (pathp->node == root->rnode)
 790                                 radix_tree_shrink(root);
 791                         goto out;
 792                 }
 793
 794                 /* Node with zero slots in use so free it */
 795                 radix_tree_node_free(pathp->node);
 796         }
 797         root->rnode = NULL;
 798         root->height = 0;
 799 out:
 800         return ret;
 801 }
 802 EXPORT_SYMBOL(radix_tree_delete);
 803
 804 /**
 805  *      radix_tree_tagged - test whether any items in the tree are tagged
 806  *      @root:          radix tree root
 807  *      @tag:           tag to test
 808  */
 809 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
 810 {
 811         struct radix_tree_node *rnode;
 812         rnode = root->rnode;
 813         if (!rnode)
 814                 return 0;
 815         return any_tag_set(rnode, tag);
 816 }
 817 EXPORT_SYMBOL(radix_tree_tagged);
 818
 819 static void
 820 radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
 821 {
 822         memset(node, 0, sizeof(struct radix_tree_node));
 823 }
 824
 825 static __init unsigned long __maxindex(unsigned int height)
 826 {
 827         unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
 828         unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
 829
 830         if (tmp >= RADIX_TREE_INDEX_BITS)
 831                 index = ~0UL;
 832         return index;
 833 }
 834
 835 static __init void radix_tree_init_maxindex(void)
 836 {
 837         unsigned int i;
 838
 839         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
 840                 height_to_maxindex[i] = __maxindex(i);
 841 }
 842
 843 #ifdef CONFIG_HOTPLUG_CPU
 844 static int radix_tree_callback(struct notifier_block *nfb,
 845                             unsigned long action,
 846                             void *hcpu)
 847 {
 848        int cpu = (long)hcpu;
 849        struct radix_tree_preload *rtp;
 850
 851        /* Free per-cpu pool of perloaded nodes */
 852        if (action == CPU_DEAD) {
 853                rtp = &per_cpu(radix_tree_preloads, cpu);
 854                while (rtp->nr) {
 855                        kmem_cache_free(radix_tree_node_cachep,
 856                                        rtp->nodes[rtp->nr-1]);
 857                        rtp->nodes[rtp->nr-1] = NULL;
 858                        rtp->nr--;
 859                }
 860        }
 861        return NOTIFY_OK;
 862 }
 863 #endif /* CONFIG_HOTPLUG_CPU */
 864
 865 void __init radix_tree_init(void)
 866 {
 867         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
 868                         sizeof(struct radix_tree_node), 0,
 869                         SLAB_PANIC, radix_tree_node_ctor, NULL);
 870         radix_tree_init_maxindex();
 871         hotcpu_notifier(radix_tree_callback, 0);
 872 }