lib/radix-tree.c

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