libfrog/radix-tree.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (C) 2001 Momchil Velikov
   4  * Portions Copyright (C) 2001 Christoph Hellwig
   5  * Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
   6  */
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <errno.h>
  10 #include <stdint.h>
  11 #include "platform_defs.h"
  12 #include "radix-tree.h"
  13
  14 #ifndef ARRAY_SIZE
  15 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
  16 #endif
  17
  18 #define RADIX_TREE_MAP_SHIFT    6
  19 #define RADIX_TREE_MAP_SIZE     (1UL << RADIX_TREE_MAP_SHIFT)
  20 #define RADIX_TREE_MAP_MASK     (RADIX_TREE_MAP_SIZE-1)
  21
  22 #ifdef RADIX_TREE_TAGS
  23 #define RADIX_TREE_TAG_LONGS    \
  24         ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
  25 #endif
  26
  27 struct radix_tree_node {
  28         unsigned int    count;
  29         void            *slots[RADIX_TREE_MAP_SIZE];
  30 #ifdef RADIX_TREE_TAGS
  31         unsigned long   tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
  32 #endif
  33 };
  34
  35 struct radix_tree_path {
  36         struct radix_tree_node *node;
  37         int offset;
  38 };
  39
  40 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
  41 #define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
  42
  43 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH];
  44
  45 /*
  46  * Radix tree node cache.
  47  */
  48
  49 #define radix_tree_node_alloc(r)        ((struct radix_tree_node *) \
  50                 calloc(1, sizeof(struct radix_tree_node)))
  51 #define radix_tree_node_free(n)         free(n)
  52
  53 #ifdef RADIX_TREE_TAGS
  54
  55 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
  56                 int offset)
  57 {
  58         *((uint32_t *)node->tags[tag] + (offset >> 5)) |= (1 << (offset & 31));
  59 }
  60
  61 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
  62                 int offset)
  63 {
  64         uint32_t        *p = (uint32_t*)node->tags[tag] + (offset >> 5);
  65         uint32_t        m = 1 << (offset & 31);
  66         *p &= ~m;
  67 }
  68
  69 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
  70                 int offset)
  71 {
  72         return 1 & (((const uint32_t *)node->tags[tag])[offset >> 5] >> (offset & 31));
  73 }
  74
  75 /*
  76  * Returns 1 if any slot in the node has this tag set.
  77  * Otherwise returns 0.
  78  */
  79 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
  80 {
  81         int idx;
  82         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
  83                 if (node->tags[tag][idx])
  84                         return 1;
  85         }
  86         return 0;
  87 }
  88
  89 #endif
  90
  91 /*
  92  *      Return the maximum key which can be store into a
  93  *      radix tree with height HEIGHT.
  94  */
  95 static inline unsigned long radix_tree_maxindex(unsigned int height)
  96 {
  97         return height_to_maxindex[height];
  98 }
  99
 100 /*
 101  *      Extend a radix tree so it can store key @index.
 102  */
 103 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 104 {
 105         struct radix_tree_node *node;
 106         unsigned int height;
 107 #ifdef RADIX_TREE_TAGS
 108         char tags[RADIX_TREE_MAX_TAGS];
 109         int tag;
 110 #endif
 111
 112         /* Figure out what the height should be.  */
 113         height = root->height + 1;
 114         while (index > radix_tree_maxindex(height))
 115                 height++;
 116
 117         if (root->rnode == NULL) {
 118                 root->height = height;
 119                 goto out;
 120         }
 121
 122 #ifdef RADIX_TREE_TAGS
 123         /*
 124          * Prepare the tag status of the top-level node for propagation
 125          * into the newly-pushed top-level node(s)
 126          */
 127         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 128                 tags[tag] = 0;
 129                 if (any_tag_set(root->rnode, tag))
 130                         tags[tag] = 1;
 131         }
 132 #endif
 133         do {
 134                 if (!(node = radix_tree_node_alloc(root)))
 135                         return -ENOMEM;
 136
 137                 /* Increase the height.  */
 138                 node->slots[0] = root->rnode;
 139
 140 #ifdef RADIX_TREE_TAGS
 141                 /* Propagate the aggregated tag info into the new root */
 142                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 143                         if (tags[tag])
 144                                 tag_set(node, tag, 0);
 145                 }
 146 #endif
 147                 node->count = 1;
 148                 root->rnode = node;
 149                 root->height++;
 150         } while (height > root->height);
 151 out:
 152         return 0;
 153 }
 154
 155 /**
 156  *      radix_tree_insert    -    insert into a radix tree
 157  *      @root:          radix tree root
 158  *      @index:         index key
 159  *      @item:          item to insert
 160  *
 161  *      Insert an item into the radix tree at position @index.
 162  */
 163 int radix_tree_insert(struct radix_tree_root *root,
 164                         unsigned long index, void *item)
 165 {
 166         struct radix_tree_node *node = NULL, *slot;
 167         unsigned int height, shift;
 168         int offset;
 169         int error;
 170
 171         /* Make sure the tree is high enough.  */
 172         if ((!index && !root->rnode) ||
 173                         index > radix_tree_maxindex(root->height)) {
 174                 error = radix_tree_extend(root, index);
 175                 if (error)
 176                         return error;
 177         }
 178
 179         slot = root->rnode;
 180         height = root->height;
 181         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 182
 183         offset = 0;                     /* uninitialised var warning */
 184         do {
 185                 if (slot == NULL) {
 186                         /* Have to add a child node.  */
 187                         if (!(slot = radix_tree_node_alloc(root)))
 188                                 return -ENOMEM;
 189                         if (node) {
 190                                 node->slots[offset] = slot;
 191                                 node->count++;
 192                         } else
 193                                 root->rnode = slot;
 194                 }
 195
 196                 /* Go a level down */
 197                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 198                 node = slot;
 199                 slot = node->slots[offset];
 200                 shift -= RADIX_TREE_MAP_SHIFT;
 201                 height--;
 202         } while (height > 0);
 203
 204         if (slot != NULL)
 205                 return -EEXIST;
 206
 207         ASSERT(node);
 208         node->count++;
 209         node->slots[offset] = item;
 210 #ifdef RADIX_TREE_TAGS
 211         ASSERT(!tag_get(node, 0, offset));
 212         ASSERT(!tag_get(node, 1, offset));
 213 #endif
 214         return 0;
 215 }
 216
 217 static inline void **__lookup_slot(struct radix_tree_root *root,
 218                                    unsigned long index)
 219 {
 220         unsigned int height, shift;
 221         struct radix_tree_node **slot;
 222
 223         height = root->height;
 224         if (index > radix_tree_maxindex(height))
 225                 return NULL;
 226
 227         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 228         slot = &root->rnode;
 229
 230         while (height > 0) {
 231                 if (*slot == NULL)
 232                         return NULL;
 233
 234                 slot = (struct radix_tree_node **)
 235                         ((*slot)->slots +
 236                                 ((index >> shift) & RADIX_TREE_MAP_MASK));
 237                 shift -= RADIX_TREE_MAP_SHIFT;
 238                 height--;
 239         }
 240
 241         return (void **)slot;
 242 }
 243
 244 /**
 245  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
 246  *      @root:          radix tree root
 247  *      @index:         index key
 248  *
 249  *      Lookup the slot corresponding to the position @index in the radix tree
 250  *      @root. This is useful for update-if-exists operations.
 251  */
 252 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
 253 {
 254         return __lookup_slot(root, index);
 255 }
 256
 257 /**
 258  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 259  *      @root:          radix tree root
 260  *      @index:         index key
 261  *
 262  *      Lookup the item at the position @index in the radix tree @root.
 263  */
 264 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 265 {
 266         void **slot;
 267
 268         slot = __lookup_slot(root, index);
 269         return slot != NULL ? *slot : NULL;
 270 }
 271
 272 /**
 273  *      raid_tree_first_key - find the first index key in the radix tree
 274  *      @root:          radix tree root
 275  *      @index:         where the first index will be placed
 276  *
 277  *      Returns the first entry and index key in the radix tree @root.
 278  */
 279 void *radix_tree_lookup_first(struct radix_tree_root *root, unsigned long *index)
 280 {
 281         unsigned int height, shift;
 282         struct radix_tree_node *slot;
 283         unsigned long i;
 284
 285         height = root->height;
 286         *index = 0;
 287         if (height == 0)
 288                 return NULL;
 289
 290         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 291         slot = root->rnode;
 292
 293         for (; height > 1; height--) {
 294                 for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
 295                         if (slot->slots[i] != NULL)
 296                                 break;
 297                 }
 298                 ASSERT(i < RADIX_TREE_MAP_SIZE);
 299
 300                 *index |= (i << shift);
 301                 shift -= RADIX_TREE_MAP_SHIFT;
 302                 slot = slot->slots[i];
 303         }
 304         for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
 305                 if (slot->slots[i] != NULL) {
 306                         *index |= i;
 307                         return slot->slots[i];
 308                 }
 309         }
 310         return NULL;
 311 }
 312
 313 #ifdef RADIX_TREE_TAGS
 314
 315 /**
 316  *      radix_tree_tag_set - set a tag on a radix tree node
 317  *      @root:          radix tree root
 318  *      @index:         index key
 319  *      @tag:           tag index
 320  *
 321  *      Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
 322  *      corresponding to @index in the radix tree.  From
 323  *      the root all the way down to the leaf node.
 324  *
 325  *      Returns the address of the tagged item.   Setting a tag on a not-present
 326  *      item is a bug.
 327  */
 328 void *radix_tree_tag_set(struct radix_tree_root *root,
 329                         unsigned long index, unsigned int tag)
 330 {
 331         unsigned int height, shift;
 332         struct radix_tree_node *slot;
 333
 334         height = root->height;
 335         if (index > radix_tree_maxindex(height))
 336                 return NULL;
 337
 338         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 339         slot = root->rnode;
 340
 341         while (height > 0) {
 342                 int offset;
 343
 344                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 345                 if (!tag_get(slot, tag, offset))
 346                         tag_set(slot, tag, offset);
 347                 slot = slot->slots[offset];
 348                 ASSERT(slot != NULL);
 349                 shift -= RADIX_TREE_MAP_SHIFT;
 350                 height--;
 351         }
 352
 353         return slot;
 354 }
 355
 356 /**
 357  *      radix_tree_tag_clear - clear a tag on a radix tree node
 358  *      @root:          radix tree root
 359  *      @index:         index key
 360  *      @tag:           tag index
 361  *
 362  *      Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
 363  *      corresponding to @index in the radix tree.  If
 364  *      this causes the leaf node to have no tags set then clear the tag in the
 365  *      next-to-leaf node, etc.
 366  *
 367  *      Returns the address of the tagged item on success, else NULL.  ie:
 368  *      has the same return value and semantics as radix_tree_lookup().
 369  */
 370 void *radix_tree_tag_clear(struct radix_tree_root *root,
 371                         unsigned long index, unsigned int tag)
 372 {
 373         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
 374         struct radix_tree_node *slot;
 375         unsigned int height, shift;
 376         void *ret = NULL;
 377
 378         height = root->height;
 379         if (index > radix_tree_maxindex(height))
 380                 goto out;
 381
 382         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 383         pathp->node = NULL;
 384         slot = root->rnode;
 385
 386         while (height > 0) {
 387                 int offset;
 388
 389                 if (slot == NULL)
 390                         goto out;
 391
 392                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 393                 pathp[1].offset = offset;
 394                 pathp[1].node = slot;
 395                 slot = slot->slots[offset];
 396                 pathp++;
 397                 shift -= RADIX_TREE_MAP_SHIFT;
 398                 height--;
 399         }
 400
 401         ret = slot;
 402         if (ret == NULL)
 403                 goto out;
 404
 405         do {
 406                 if (!tag_get(pathp->node, tag, pathp->offset))
 407                         goto out;
 408                 tag_clear(pathp->node, tag, pathp->offset);
 409                 if (any_tag_set(pathp->node, tag))
 410                         goto out;
 411                 pathp--;
 412         } while (pathp->node);
 413 out:
 414         return ret;
 415 }
 416
 417 #endif
 418
 419 static unsigned int
 420 __lookup(struct radix_tree_root *root, void **results, unsigned long index,
 421         unsigned int max_items, unsigned long *next_index)
 422 {
 423         unsigned int nr_found = 0;
 424         unsigned int shift, height;
 425         struct radix_tree_node *slot;
 426         unsigned long i;
 427
 428         height = root->height;
 429         if (height == 0)
 430                 goto out;
 431
 432         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 433         slot = root->rnode;
 434
 435         for ( ; height > 1; height--) {
 436
 437                 for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
 438                                 i < RADIX_TREE_MAP_SIZE; i++) {
 439                         if (slot->slots[i] != NULL)
 440                                 break;
 441                         index &= ~((1UL << shift) - 1);
 442                         index += 1UL << shift;
 443                         if (index == 0)
 444                                 goto out;       /* 32-bit wraparound */
 445                 }
 446                 if (i == RADIX_TREE_MAP_SIZE)
 447                         goto out;
 448
 449                 shift -= RADIX_TREE_MAP_SHIFT;
 450                 slot = slot->slots[i];
 451         }
 452
 453         /* Bottom level: grab some items */
 454         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
 455                 index++;
 456                 if (slot->slots[i]) {
 457                         results[nr_found++] = slot->slots[i];
 458                         if (nr_found == max_items)
 459                                 goto out;
 460                 }
 461         }
 462 out:
 463         *next_index = index;
 464         return nr_found;
 465 }
 466
 467 /**
 468  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
 469  *      @root:          radix tree root
 470  *      @results:       where the results of the lookup are placed
 471  *      @first_index:   start the lookup from this key
 472  *      @max_items:     place up to this many items at *results
 473  *
 474  *      Performs an index-ascending scan of the tree for present items.  Places
 475  *      them at *@results and returns the number of items which were placed at
 476  *      *@results.
 477  *
 478  *      The implementation is naive.
 479  */
 480 unsigned int
 481 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 482                         unsigned long first_index, unsigned int max_items)
 483 {
 484         const unsigned long max_index = radix_tree_maxindex(root->height);
 485         unsigned long cur_index = first_index;
 486         unsigned int ret = 0;
 487
 488         while (ret < max_items) {
 489                 unsigned int nr_found;
 490                 unsigned long next_index;       /* Index of next search */
 491
 492                 if (cur_index > max_index)
 493                         break;
 494                 nr_found = __lookup(root, results + ret, cur_index,
 495                                         max_items - ret, &next_index);
 496                 ret += nr_found;
 497                 if (next_index == 0)
 498                         break;
 499                 cur_index = next_index;
 500         }
 501         return ret;
 502 }
 503
 504 /**
 505  *      radix_tree_gang_lookup_ex - perform multiple lookup on a radix tree
 506  *      @root:          radix tree root
 507  *      @results:       where the results of the lookup are placed
 508  *      @first_index:   start the lookup from this key
 509  *      @last_index:    don't lookup past this key
 510  *      @max_items:     place up to this many items at *results
 511  *
 512  *      Performs an index-ascending scan of the tree for present items starting
 513  *      @first_index until @last_index up to as many as @max_items.  Places
 514  *      them at *@results and returns the number of items which were placed
 515  *      at *@results.
 516  *
 517  *      The implementation is naive.
 518  */
 519 unsigned int
 520 radix_tree_gang_lookup_ex(struct radix_tree_root *root, void **results,
 521                         unsigned long first_index, unsigned long last_index,
 522                         unsigned int max_items)
 523 {
 524         const unsigned long max_index = radix_tree_maxindex(root->height);
 525         unsigned long cur_index = first_index;
 526         unsigned int ret = 0;
 527
 528         while (ret < max_items && cur_index < last_index) {
 529                 unsigned int nr_found;
 530                 unsigned long next_index;       /* Index of next search */
 531
 532                 if (cur_index > max_index)
 533                         break;
 534                 nr_found = __lookup(root, results + ret, cur_index,
 535                                         max_items - ret, &next_index);
 536                 ret += nr_found;
 537                 if (next_index == 0)
 538                         break;
 539                 cur_index = next_index;
 540         }
 541         return ret;
 542 }
 543
 544 #ifdef RADIX_TREE_TAGS
 545
 546 static unsigned int
 547 __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
 548         unsigned int max_items, unsigned long *next_index, unsigned int tag)
 549 {
 550         unsigned int nr_found = 0;
 551         unsigned int shift;
 552         unsigned int height = root->height;
 553         struct radix_tree_node *slot;
 554
 555         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 556         slot = root->rnode;
 557
 558         while (height > 0) {
 559                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
 560
 561                 for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
 562                         if (tag_get(slot, tag, i)) {
 563                                 ASSERT(slot->slots[i] != NULL);
 564                                 break;
 565                         }
 566                         index &= ~((1UL << shift) - 1);
 567                         index += 1UL << shift;
 568                         if (index == 0)
 569                                 goto out;       /* 32-bit wraparound */
 570                 }
 571                 if (i == RADIX_TREE_MAP_SIZE)
 572                         goto out;
 573                 height--;
 574                 if (height == 0) {      /* Bottom level: grab some items */
 575                         unsigned long j = index & RADIX_TREE_MAP_MASK;
 576
 577                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
 578                                 index++;
 579                                 if (tag_get(slot, tag, j)) {
 580                                         ASSERT(slot->slots[j] != NULL);
 581                                         results[nr_found++] = slot->slots[j];
 582                                         if (nr_found == max_items)
 583                                                 goto out;
 584                                 }
 585                         }
 586                 }
 587                 shift -= RADIX_TREE_MAP_SHIFT;
 588                 slot = slot->slots[i];
 589         }
 590 out:
 591         *next_index = index;
 592         return nr_found;
 593 }
 594
 595 /**
 596  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
 597  *                                   based on a tag
 598  *      @root:          radix tree root
 599  *      @results:       where the results of the lookup are placed
 600  *      @first_index:   start the lookup from this key
 601  *      @max_items:     place up to this many items at *results
 602  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
 603  *
 604  *      Performs an index-ascending scan of the tree for present items which
 605  *      have the tag indexed by @tag set.  Places the items at *@results and
 606  *      returns the number of items which were placed at *@results.
 607  */
 608 unsigned int
 609 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
 610                 unsigned long first_index, unsigned int max_items,
 611                 unsigned int tag)
 612 {
 613         const unsigned long max_index = radix_tree_maxindex(root->height);
 614         unsigned long cur_index = first_index;
 615         unsigned int ret = 0;
 616
 617         while (ret < max_items) {
 618                 unsigned int nr_found;
 619                 unsigned long next_index;       /* Index of next search */
 620
 621                 if (cur_index > max_index)
 622                         break;
 623                 nr_found = __lookup_tag(root, results + ret, cur_index,
 624                                         max_items - ret, &next_index, tag);
 625                 ret += nr_found;
 626                 if (next_index == 0)
 627                         break;
 628                 cur_index = next_index;
 629         }
 630         return ret;
 631 }
 632
 633 #endif
 634
 635 /**
 636  *      radix_tree_shrink    -    shrink height of a radix tree to minimal
 637  *      @root           radix tree root
 638  */
 639 static inline void radix_tree_shrink(struct radix_tree_root *root)
 640 {
 641         /* try to shrink tree height */
 642         while (root->height > 1 &&
 643                         root->rnode->count == 1 &&
 644                         root->rnode->slots[0]) {
 645                 struct radix_tree_node *to_free = root->rnode;
 646
 647                 root->rnode = to_free->slots[0];
 648                 root->height--;
 649                 /* must only free zeroed nodes into the slab */
 650 #ifdef RADIX_TREE_TAGS
 651                 tag_clear(to_free, 0, 0);
 652                 tag_clear(to_free, 1, 0);
 653 #endif
 654                 to_free->slots[0] = NULL;
 655                 to_free->count = 0;
 656                 radix_tree_node_free(to_free);
 657         }
 658 }
 659
 660 /**
 661  *      radix_tree_delete    -    delete an item from a radix tree
 662  *      @root:          radix tree root
 663  *      @index:         index key
 664  *
 665  *      Remove the item at @index from the radix tree rooted at @root.
 666  *
 667  *      Returns the address of the deleted item, or NULL if it was not present.
 668  */
 669 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 670 {
 671         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
 672         struct radix_tree_path *orig_pathp;
 673         struct radix_tree_node *slot;
 674         unsigned int height, shift;
 675         void *ret = NULL;
 676 #ifdef RADIX_TREE_TAGS
 677         char tags[RADIX_TREE_MAX_TAGS];
 678         int nr_cleared_tags;
 679         int tag;
 680 #endif
 681         int offset;
 682
 683         height = root->height;
 684         if (index > radix_tree_maxindex(height))
 685                 goto out;
 686
 687         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 688         pathp->node = NULL;
 689         slot = root->rnode;
 690
 691         for ( ; height > 0; height--) {
 692                 if (slot == NULL)
 693                         goto out;
 694
 695                 pathp++;
 696                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 697                 pathp->offset = offset;
 698                 pathp->node = slot;
 699                 slot = slot->slots[offset];
 700                 shift -= RADIX_TREE_MAP_SHIFT;
 701         }
 702
 703         ret = slot;
 704         if (ret == NULL)
 705                 goto out;
 706
 707         orig_pathp = pathp;
 708
 709 #ifdef RADIX_TREE_TAGS
 710         /*
 711          * Clear all tags associated with the just-deleted item
 712          */
 713         nr_cleared_tags = 0;
 714         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 715                 tags[tag] = 1;
 716                 if (tag_get(pathp->node, tag, pathp->offset)) {
 717                         tag_clear(pathp->node, tag, pathp->offset);
 718                         if (!any_tag_set(pathp->node, tag)) {
 719                                 tags[tag] = 0;
 720                                 nr_cleared_tags++;
 721                         }
 722                 }
 723         }
 724
 725         for (pathp--; nr_cleared_tags && pathp->node; pathp--) {
 726                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 727                         if (tags[tag])
 728                                 continue;
 729
 730                         tag_clear(pathp->node, tag, pathp->offset);
 731                         if (any_tag_set(pathp->node, tag)) {
 732                                 tags[tag] = 1;
 733                                 nr_cleared_tags--;
 734                         }
 735                 }
 736         }
 737 #endif
 738         /* Now free the nodes we do not need anymore */
 739         for (pathp = orig_pathp; pathp->node; pathp--) {
 740                 pathp->node->slots[pathp->offset] = NULL;
 741                 pathp->node->count--;
 742
 743                 if (pathp->node->count) {
 744                         if (pathp->node == root->rnode)
 745                                 radix_tree_shrink(root);
 746                         goto out;
 747                 }
 748
 749                 /* Node with zero slots in use so free it */
 750                 radix_tree_node_free(pathp->node);
 751         }
 752         root->rnode = NULL;
 753         root->height = 0;
 754 out:
 755         return ret;
 756 }
 757
 758 #ifdef RADIX_TREE_TAGS
 759 /**
 760  *      radix_tree_tagged - test whether any items in the tree are tagged
 761  *      @root:          radix tree root
 762  *      @tag:           tag to test
 763  */
 764 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
 765 {
 766         struct radix_tree_node *rnode;
 767         rnode = root->rnode;
 768         if (!rnode)
 769                 return 0;
 770         return any_tag_set(rnode, tag);
 771 }
 772 #endif
 773
 774 static unsigned long __maxindex(unsigned int height)
 775 {
 776         unsigned int width = height * RADIX_TREE_MAP_SHIFT;
 777         int shift = RADIX_TREE_INDEX_BITS - width;
 778
 779         if (shift < 0)
 780                 return ~0UL;
 781         if (shift >= BITS_PER_LONG)
 782                 return 0UL;
 783         return ~0UL >> shift;
 784 }
 785
 786 static void radix_tree_init_maxindex(void)
 787 {
 788         unsigned int i;
 789
 790         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
 791                 height_to_maxindex[i] = __maxindex(i);
 792 }
 793
 794 void radix_tree_init(void)
 795 {
 796         radix_tree_init_maxindex();
 797 }