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  * Copyright (C) 2006 Nick Piggin
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation; either version 2, or (at
  10  * your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <linux/errno.h>
  23 #include <linux/init.h>
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/radix-tree.h>
  27 #include <linux/percpu.h>
  28 #include <linux/slab.h>
  29 #include <linux/notifier.h>
  30 #include <linux/cpu.h>
  31 #include <linux/gfp.h>
  32 #include <linux/string.h>
  33 #include <linux/bitops.h>
  34 #include <linux/rcupdate.h>
  35
  36
  37 #ifdef __KERNEL__
  38 #define RADIX_TREE_MAP_SHIFT    (CONFIG_BASE_SMALL ? 4 : 6)
  39 #else
  40 #define RADIX_TREE_MAP_SHIFT    3       /* For more stressful testing */
  41 #endif
  42
  43 #define RADIX_TREE_MAP_SIZE     (1UL << RADIX_TREE_MAP_SHIFT)
  44 #define RADIX_TREE_MAP_MASK     (RADIX_TREE_MAP_SIZE-1)
  45
  46 #define RADIX_TREE_TAG_LONGS    \
  47         ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
  48
  49 struct radix_tree_node {
  50         unsigned int    height;         /* Height from the bottom */
  51         unsigned int    count;
  52         struct rcu_head rcu_head;
  53         void            *slots[RADIX_TREE_MAP_SIZE];
  54         unsigned long   tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
  55 };
  56
  57 struct radix_tree_path {
  58         struct radix_tree_node *node;
  59         int offset;
  60 };
  61
  62 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
  63 #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
  64                                           RADIX_TREE_MAP_SHIFT))
  65
  66 /*
  67  * The height_to_maxindex array needs to be one deeper than the maximum
  68  * path as height 0 holds only 1 entry.
  69  */
  70 static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
  71
  72 /*
  73  * Radix tree node cache.
  74  */
  75 static struct kmem_cache *radix_tree_node_cachep;
  76
  77 /*
  78  * Per-cpu pool of preloaded nodes
  79  */
  80 struct radix_tree_preload {
  81         int nr;
  82         struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
  83 };
  84 DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
  85
  86 static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
  87 {
  88         return root->gfp_mask & __GFP_BITS_MASK;
  89 }
  90
  91 /*
  92  * This assumes that the caller has performed appropriate preallocation, and
  93  * that the caller has pinned this thread of control to the current CPU.
  94  */
  95 static struct radix_tree_node *
  96 radix_tree_node_alloc(struct radix_tree_root *root)
  97 {
  98         struct radix_tree_node *ret;
  99         gfp_t gfp_mask = root_gfp_mask(root);
 100
 101         ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 102         if (ret == NULL && !(gfp_mask & __GFP_WAIT)) {
 103                 struct radix_tree_preload *rtp;
 104
 105                 rtp = &__get_cpu_var(radix_tree_preloads);
 106                 if (rtp->nr) {
 107                         ret = rtp->nodes[rtp->nr - 1];
 108                         rtp->nodes[rtp->nr - 1] = NULL;
 109                         rtp->nr--;
 110                 }
 111         }
 112         BUG_ON(radix_tree_is_indirect_ptr(ret));
 113         return ret;
 114 }
 115
 116 static void radix_tree_node_rcu_free(struct rcu_head *head)
 117 {
 118         struct radix_tree_node *node =
 119                         container_of(head, struct radix_tree_node, rcu_head);
 120         kmem_cache_free(radix_tree_node_cachep, node);
 121 }
 122
 123 static inline void
 124 radix_tree_node_free(struct radix_tree_node *node)
 125 {
 126         call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
 127 }
 128
 129 /*
 130  * Load up this CPU's radix_tree_node buffer with sufficient objects to
 131  * ensure that the addition of a single element in the tree cannot fail.  On
 132  * success, return zero, with preemption disabled.  On error, return -ENOMEM
 133  * with preemption not disabled.
 134  */
 135 int radix_tree_preload(gfp_t gfp_mask)
 136 {
 137         struct radix_tree_preload *rtp;
 138         struct radix_tree_node *node;
 139         int ret = -ENOMEM;
 140
 141         preempt_disable();
 142         rtp = &__get_cpu_var(radix_tree_preloads);
 143         while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
 144                 preempt_enable();
 145                 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 146                 if (node == NULL)
 147                         goto out;
 148                 preempt_disable();
 149                 rtp = &__get_cpu_var(radix_tree_preloads);
 150                 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
 151                         rtp->nodes[rtp->nr++] = node;
 152                 else
 153                         kmem_cache_free(radix_tree_node_cachep, node);
 154         }
 155         ret = 0;
 156 out:
 157         return ret;
 158 }
 159 EXPORT_SYMBOL(radix_tree_preload);
 160
 161 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
 162                 int offset)
 163 {
 164         __set_bit(offset, node->tags[tag]);
 165 }
 166
 167 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
 168                 int offset)
 169 {
 170         __clear_bit(offset, node->tags[tag]);
 171 }
 172
 173 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
 174                 int offset)
 175 {
 176         return test_bit(offset, node->tags[tag]);
 177 }
 178
 179 static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
 180 {
 181         root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
 182 }
 183
 184
 185 static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
 186 {
 187         root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
 188 }
 189
 190 static inline void root_tag_clear_all(struct radix_tree_root *root)
 191 {
 192         root->gfp_mask &= __GFP_BITS_MASK;
 193 }
 194
 195 static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
 196 {
 197         return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
 198 }
 199
 200 /*
 201  * Returns 1 if any slot in the node has this tag set.
 202  * Otherwise returns 0.
 203  */
 204 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
 205 {
 206         int idx;
 207         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 208                 if (node->tags[tag][idx])
 209                         return 1;
 210         }
 211         return 0;
 212 }
 213
 214 /*
 215  *      Return the maximum key which can be store into a
 216  *      radix tree with height HEIGHT.
 217  */
 218 static inline unsigned long radix_tree_maxindex(unsigned int height)
 219 {
 220         return height_to_maxindex[height];
 221 }
 222
 223 /*
 224  *      Extend a radix tree so it can store key @index.
 225  */
 226 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 227 {
 228         struct radix_tree_node *node;
 229         unsigned int height;
 230         int tag;
 231
 232         /* Figure out what the height should be.  */
 233         height = root->height + 1;
 234         while (index > radix_tree_maxindex(height))
 235                 height++;
 236
 237         if (root->rnode == NULL) {
 238                 root->height = height;
 239                 goto out;
 240         }
 241
 242         do {
 243                 unsigned int newheight;
 244                 if (!(node = radix_tree_node_alloc(root)))
 245                         return -ENOMEM;
 246
 247                 /* Increase the height.  */
 248                 node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
 249
 250                 /* Propagate the aggregated tag info into the new root */
 251                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 252                         if (root_tag_get(root, tag))
 253                                 tag_set(node, tag, 0);
 254                 }
 255
 256                 newheight = root->height+1;
 257                 node->height = newheight;
 258                 node->count = 1;
 259                 node = radix_tree_ptr_to_indirect(node);
 260                 rcu_assign_pointer(root->rnode, node);
 261                 root->height = newheight;
 262         } while (height > root->height);
 263 out:
 264         return 0;
 265 }
 266
 267 /**
 268  *      radix_tree_insert    -    insert into a radix tree
 269  *      @root:          radix tree root
 270  *      @index:         index key
 271  *      @item:          item to insert
 272  *
 273  *      Insert an item into the radix tree at position @index.
 274  */
 275 int radix_tree_insert(struct radix_tree_root *root,
 276                         unsigned long index, void *item)
 277 {
 278         struct radix_tree_node *node = NULL, *slot;
 279         unsigned int height, shift;
 280         int offset;
 281         int error;
 282
 283         BUG_ON(radix_tree_is_indirect_ptr(item));
 284
 285         /* Make sure the tree is high enough.  */
 286         if (index > radix_tree_maxindex(root->height)) {
 287                 error = radix_tree_extend(root, index);
 288                 if (error)
 289                         return error;
 290         }
 291
 292         slot = radix_tree_indirect_to_ptr(root->rnode);
 293
 294         height = root->height;
 295         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 296
 297         offset = 0;                     /* uninitialised var warning */
 298         while (height > 0) {
 299                 if (slot == NULL) {
 300                         /* Have to add a child node.  */
 301                         if (!(slot = radix_tree_node_alloc(root)))
 302                                 return -ENOMEM;
 303                         slot->height = height;
 304                         if (node) {
 305                                 rcu_assign_pointer(node->slots[offset], slot);
 306                                 node->count++;
 307                         } else
 308                                 rcu_assign_pointer(root->rnode,
 309                                         radix_tree_ptr_to_indirect(slot));
 310                 }
 311
 312                 /* Go a level down */
 313                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 314                 node = slot;
 315                 slot = node->slots[offset];
 316                 shift -= RADIX_TREE_MAP_SHIFT;
 317                 height--;
 318         }
 319
 320         if (slot != NULL)
 321                 return -EEXIST;
 322
 323         if (node) {
 324                 node->count++;
 325                 rcu_assign_pointer(node->slots[offset], item);
 326                 BUG_ON(tag_get(node, 0, offset));
 327                 BUG_ON(tag_get(node, 1, offset));
 328         } else {
 329                 rcu_assign_pointer(root->rnode, item);
 330                 BUG_ON(root_tag_get(root, 0));
 331                 BUG_ON(root_tag_get(root, 1));
 332         }
 333
 334         return 0;
 335 }
 336 EXPORT_SYMBOL(radix_tree_insert);
 337
 338 /**
 339  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
 340  *      @root:          radix tree root
 341  *      @index:         index key
 342  *
 343  *      Returns:  the slot corresponding to the position @index in the
 344  *      radix tree @root. This is useful for update-if-exists operations.
 345  *
 346  *      This function cannot be called under rcu_read_lock, it must be
 347  *      excluded from writers, as must the returned slot for subsequent
 348  *      use by radix_tree_deref_slot() and radix_tree_replace slot.
 349  *      Caller must hold tree write locked across slot lookup and
 350  *      replace.
 351  */
 352 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
 353 {
 354         unsigned int height, shift;
 355         struct radix_tree_node *node, **slot;
 356
 357         node = root->rnode;
 358         if (node == NULL)
 359                 return NULL;
 360
 361         if (!radix_tree_is_indirect_ptr(node)) {
 362                 if (index > 0)
 363                         return NULL;
 364                 return (void **)&root->rnode;
 365         }
 366         node = radix_tree_indirect_to_ptr(node);
 367
 368         height = node->height;
 369         if (index > radix_tree_maxindex(height))
 370                 return NULL;
 371
 372         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 373
 374         do {
 375                 slot = (struct radix_tree_node **)
 376                         (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
 377                 node = *slot;
 378                 if (node == NULL)
 379                         return NULL;
 380
 381                 shift -= RADIX_TREE_MAP_SHIFT;
 382                 height--;
 383         } while (height > 0);
 384
 385         return (void **)slot;
 386 }
 387 EXPORT_SYMBOL(radix_tree_lookup_slot);
 388
 389 /**
 390  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 391  *      @root:          radix tree root
 392  *      @index:         index key
 393  *
 394  *      Lookup the item at the position @index in the radix tree @root.
 395  *
 396  *      This function can be called under rcu_read_lock, however the caller
 397  *      must manage lifetimes of leaf nodes (eg. RCU may also be used to free
 398  *      them safely). No RCU barriers are required to access or modify the
 399  *      returned item, however.
 400  */
 401 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 402 {
 403         unsigned int height, shift;
 404         struct radix_tree_node *node, **slot;
 405
 406         node = rcu_dereference(root->rnode);
 407         if (node == NULL)
 408                 return NULL;
 409
 410         if (!radix_tree_is_indirect_ptr(node)) {
 411                 if (index > 0)
 412                         return NULL;
 413                 return node;
 414         }
 415         node = radix_tree_indirect_to_ptr(node);
 416
 417         height = node->height;
 418         if (index > radix_tree_maxindex(height))
 419                 return NULL;
 420
 421         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 422
 423         do {
 424                 slot = (struct radix_tree_node **)
 425                         (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
 426                 node = rcu_dereference(*slot);
 427                 if (node == NULL)
 428                         return NULL;
 429
 430                 shift -= RADIX_TREE_MAP_SHIFT;
 431                 height--;
 432         } while (height > 0);
 433
 434         return node;
 435 }
 436 EXPORT_SYMBOL(radix_tree_lookup);
 437
 438 /**
 439  *      radix_tree_tag_set - set a tag on a radix tree node
 440  *      @root:          radix tree root
 441  *      @index:         index key
 442  *      @tag:           tag index
 443  *
 444  *      Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
 445  *      corresponding to @index in the radix tree.  From
 446  *      the root all the way down to the leaf node.
 447  *
 448  *      Returns the address of the tagged item.   Setting a tag on a not-present
 449  *      item is a bug.
 450  */
 451 void *radix_tree_tag_set(struct radix_tree_root *root,
 452                         unsigned long index, unsigned int tag)
 453 {
 454         unsigned int height, shift;
 455         struct radix_tree_node *slot;
 456
 457         height = root->height;
 458         BUG_ON(index > radix_tree_maxindex(height));
 459
 460         slot = radix_tree_indirect_to_ptr(root->rnode);
 461         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 462
 463         while (height > 0) {
 464                 int offset;
 465
 466                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 467                 if (!tag_get(slot, tag, offset))
 468                         tag_set(slot, tag, offset);
 469                 slot = slot->slots[offset];
 470                 BUG_ON(slot == NULL);
 471                 shift -= RADIX_TREE_MAP_SHIFT;
 472                 height--;
 473         }
 474
 475         /* set the root's tag bit */
 476         if (slot && !root_tag_get(root, tag))
 477                 root_tag_set(root, tag);
 478
 479         return slot;
 480 }
 481 EXPORT_SYMBOL(radix_tree_tag_set);
 482
 483 /**
 484  *      radix_tree_tag_clear - clear a tag on a radix tree node
 485  *      @root:          radix tree root
 486  *      @index:         index key
 487  *      @tag:           tag index
 488  *
 489  *      Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
 490  *      corresponding to @index in the radix tree.  If
 491  *      this causes the leaf node to have no tags set then clear the tag in the
 492  *      next-to-leaf node, etc.
 493  *
 494  *      Returns the address of the tagged item on success, else NULL.  ie:
 495  *      has the same return value and semantics as radix_tree_lookup().
 496  */
 497 void *radix_tree_tag_clear(struct radix_tree_root *root,
 498                         unsigned long index, unsigned int tag)
 499 {
 500         /*
 501          * The radix tree path needs to be one longer than the maximum path
 502          * since the "list" is null terminated.
 503          */
 504         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
 505         struct radix_tree_node *slot = NULL;
 506         unsigned int height, shift;
 507
 508         height = root->height;
 509         if (index > radix_tree_maxindex(height))
 510                 goto out;
 511
 512         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 513         pathp->node = NULL;
 514         slot = radix_tree_indirect_to_ptr(root->rnode);
 515
 516         while (height > 0) {
 517                 int offset;
 518
 519                 if (slot == NULL)
 520                         goto out;
 521
 522                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 523                 pathp[1].offset = offset;
 524                 pathp[1].node = slot;
 525                 slot = slot->slots[offset];
 526                 pathp++;
 527                 shift -= RADIX_TREE_MAP_SHIFT;
 528                 height--;
 529         }
 530
 531         if (slot == NULL)
 532                 goto out;
 533
 534         while (pathp->node) {
 535                 if (!tag_get(pathp->node, tag, pathp->offset))
 536                         goto out;
 537                 tag_clear(pathp->node, tag, pathp->offset);
 538                 if (any_tag_set(pathp->node, tag))
 539                         goto out;
 540                 pathp--;
 541         }
 542
 543         /* clear the root's tag bit */
 544         if (root_tag_get(root, tag))
 545                 root_tag_clear(root, tag);
 546
 547 out:
 548         return slot;
 549 }
 550 EXPORT_SYMBOL(radix_tree_tag_clear);
 551
 552 #ifndef __KERNEL__      /* Only the test harness uses this at present */
 553 /**
 554  * radix_tree_tag_get - get a tag on a radix tree node
 555  * @root:               radix tree root
 556  * @index:              index key
 557  * @tag:                tag index (< RADIX_TREE_MAX_TAGS)
 558  *
 559  * Return values:
 560  *
 561  *  0: tag not present or not set
 562  *  1: tag set
 563  */
 564 int radix_tree_tag_get(struct radix_tree_root *root,
 565                         unsigned long index, unsigned int tag)
 566 {
 567         unsigned int height, shift;
 568         struct radix_tree_node *node;
 569         int saw_unset_tag = 0;
 570
 571         /* check the root's tag bit */
 572         if (!root_tag_get(root, tag))
 573                 return 0;
 574
 575         node = rcu_dereference(root->rnode);
 576         if (node == NULL)
 577                 return 0;
 578
 579         if (!radix_tree_is_indirect_ptr(node))
 580                 return (index == 0);
 581         node = radix_tree_indirect_to_ptr(node);
 582
 583         height = node->height;
 584         if (index > radix_tree_maxindex(height))
 585                 return 0;
 586
 587         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 588
 589         for ( ; ; ) {
 590                 int offset;
 591
 592                 if (node == NULL)
 593                         return 0;
 594
 595                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 596
 597                 /*
 598                  * This is just a debug check.  Later, we can bale as soon as
 599                  * we see an unset tag.
 600                  */
 601                 if (!tag_get(node, tag, offset))
 602                         saw_unset_tag = 1;
 603                 if (height == 1) {
 604                         int ret = tag_get(node, tag, offset);
 605
 606                         BUG_ON(ret && saw_unset_tag);
 607                         return !!ret;
 608                 }
 609                 node = rcu_dereference(node->slots[offset]);
 610                 shift -= RADIX_TREE_MAP_SHIFT;
 611                 height--;
 612         }
 613 }
 614 EXPORT_SYMBOL(radix_tree_tag_get);
 615 #endif
 616
 617 /**
 618  *      radix_tree_next_hole    -    find the next hole (not-present entry)
 619  *      @root:          tree root
 620  *      @index:         index key
 621  *      @max_scan:      maximum range to search
 622  *
 623  *      Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
 624  *      indexed hole.
 625  *
 626  *      Returns: the index of the hole if found, otherwise returns an index
 627  *      outside of the set specified (in which case 'return - index >= max_scan'
 628  *      will be true).
 629  *
 630  *      radix_tree_next_hole may be called under rcu_read_lock. However, like
 631  *      radix_tree_gang_lookup, this will not atomically search a snapshot of the
 632  *      tree at a single point in time. For example, if a hole is created at index
 633  *      5, then subsequently a hole is created at index 10, radix_tree_next_hole
 634  *      covering both indexes may return 10 if called under rcu_read_lock.
 635  */
 636 unsigned long radix_tree_next_hole(struct radix_tree_root *root,
 637                                 unsigned long index, unsigned long max_scan)
 638 {
 639         unsigned long i;
 640
 641         for (i = 0; i < max_scan; i++) {
 642                 if (!radix_tree_lookup(root, index))
 643                         break;
 644                 index++;
 645                 if (index == 0)
 646                         break;
 647         }
 648
 649         return index;
 650 }
 651 EXPORT_SYMBOL(radix_tree_next_hole);
 652
 653 static unsigned int
 654 __lookup(struct radix_tree_node *slot, void **results, unsigned long index,
 655         unsigned int max_items, unsigned long *next_index)
 656 {
 657         unsigned int nr_found = 0;
 658         unsigned int shift, height;
 659         unsigned long i;
 660
 661         height = slot->height;
 662         if (height == 0)
 663                 goto out;
 664         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 665
 666         for ( ; height > 1; height--) {
 667                 i = (index >> shift) & RADIX_TREE_MAP_MASK;
 668                 for (;;) {
 669                         if (slot->slots[i] != NULL)
 670                                 break;
 671                         index &= ~((1UL << shift) - 1);
 672                         index += 1UL << shift;
 673                         if (index == 0)
 674                                 goto out;       /* 32-bit wraparound */
 675                         i++;
 676                         if (i == RADIX_TREE_MAP_SIZE)
 677                                 goto out;
 678                 }
 679
 680                 shift -= RADIX_TREE_MAP_SHIFT;
 681                 slot = rcu_dereference(slot->slots[i]);
 682                 if (slot == NULL)
 683                         goto out;
 684         }
 685
 686         /* Bottom level: grab some items */
 687         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
 688                 struct radix_tree_node *node;
 689                 index++;
 690                 node = slot->slots[i];
 691                 if (node) {
 692                         results[nr_found++] = rcu_dereference(node);
 693                         if (nr_found == max_items)
 694                                 goto out;
 695                 }
 696         }
 697 out:
 698         *next_index = index;
 699         return nr_found;
 700 }
 701
 702 /**
 703  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
 704  *      @root:          radix tree root
 705  *      @results:       where the results of the lookup are placed
 706  *      @first_index:   start the lookup from this key
 707  *      @max_items:     place up to this many items at *results
 708  *
 709  *      Performs an index-ascending scan of the tree for present items.  Places
 710  *      them at *@results and returns the number of items which were placed at
 711  *      *@results.
 712  *
 713  *      The implementation is naive.
 714  *
 715  *      Like radix_tree_lookup, radix_tree_gang_lookup may be called under
 716  *      rcu_read_lock. In this case, rather than the returned results being
 717  *      an atomic snapshot of the tree at a single point in time, the semantics
 718  *      of an RCU protected gang lookup are as though multiple radix_tree_lookups
 719  *      have been issued in individual locks, and results stored in 'results'.
 720  */
 721 unsigned int
 722 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 723                         unsigned long first_index, unsigned int max_items)
 724 {
 725         unsigned long max_index;
 726         struct radix_tree_node *node;
 727         unsigned long cur_index = first_index;
 728         unsigned int ret;
 729
 730         node = rcu_dereference(root->rnode);
 731         if (!node)
 732                 return 0;
 733
 734         if (!radix_tree_is_indirect_ptr(node)) {
 735                 if (first_index > 0)
 736                         return 0;
 737                 results[0] = node;
 738                 return 1;
 739         }
 740         node = radix_tree_indirect_to_ptr(node);
 741
 742         max_index = radix_tree_maxindex(node->height);
 743
 744         ret = 0;
 745         while (ret < max_items) {
 746                 unsigned int nr_found;
 747                 unsigned long next_index;       /* Index of next search */
 748
 749                 if (cur_index > max_index)
 750                         break;
 751                 nr_found = __lookup(node, results + ret, cur_index,
 752                                         max_items - ret, &next_index);
 753                 ret += nr_found;
 754                 if (next_index == 0)
 755                         break;
 756                 cur_index = next_index;
 757         }
 758
 759         return ret;
 760 }
 761 EXPORT_SYMBOL(radix_tree_gang_lookup);
 762
 763 /*
 764  * FIXME: the two tag_get()s here should use find_next_bit() instead of
 765  * open-coding the search.
 766  */
 767 static unsigned int
 768 __lookup_tag(struct radix_tree_node *slot, void **results, unsigned long index,
 769         unsigned int max_items, unsigned long *next_index, unsigned int tag)
 770 {
 771         unsigned int nr_found = 0;
 772         unsigned int shift, height;
 773
 774         height = slot->height;
 775         if (height == 0)
 776                 goto out;
 777         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 778
 779         while (height > 0) {
 780                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
 781
 782                 for (;;) {
 783                         if (tag_get(slot, tag, i))
 784                                 break;
 785                         index &= ~((1UL << shift) - 1);
 786                         index += 1UL << shift;
 787                         if (index == 0)
 788                                 goto out;       /* 32-bit wraparound */
 789                         i++;
 790                         if (i == RADIX_TREE_MAP_SIZE)
 791                                 goto out;
 792                 }
 793                 height--;
 794                 if (height == 0) {      /* Bottom level: grab some items */
 795                         unsigned long j = index & RADIX_TREE_MAP_MASK;
 796
 797                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
 798                                 struct radix_tree_node *node;
 799                                 index++;
 800                                 if (!tag_get(slot, tag, j))
 801                                         continue;
 802                                 node = slot->slots[j];
 803                                 /*
 804                                  * Even though the tag was found set, we need to
 805                                  * recheck that we have a non-NULL node, because
 806                                  * if this lookup is lockless, it may have been
 807                                  * subsequently deleted.
 808                                  *
 809                                  * Similar care must be taken in any place that
 810                                  * lookup ->slots[x] without a lock (ie. can't
 811                                  * rely on its value remaining the same).
 812                                  */
 813                                 if (node) {
 814                                         node = rcu_dereference(node);
 815                                         results[nr_found++] = node;
 816                                         if (nr_found == max_items)
 817                                                 goto out;
 818                                 }
 819                         }
 820                 }
 821                 shift -= RADIX_TREE_MAP_SHIFT;
 822                 slot = rcu_dereference(slot->slots[i]);
 823                 if (slot == NULL)
 824                         break;
 825         }
 826 out:
 827         *next_index = index;
 828         return nr_found;
 829 }
 830
 831 /**
 832  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
 833  *                                   based on a tag
 834  *      @root:          radix tree root
 835  *      @results:       where the results of the lookup are placed
 836  *      @first_index:   start the lookup from this key
 837  *      @max_items:     place up to this many items at *results
 838  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
 839  *
 840  *      Performs an index-ascending scan of the tree for present items which
 841  *      have the tag indexed by @tag set.  Places the items at *@results and
 842  *      returns the number of items which were placed at *@results.
 843  */
 844 unsigned int
 845 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
 846                 unsigned long first_index, unsigned int max_items,
 847                 unsigned int tag)
 848 {
 849         struct radix_tree_node *node;
 850         unsigned long max_index;
 851         unsigned long cur_index = first_index;
 852         unsigned int ret;
 853
 854         /* check the root's tag bit */
 855         if (!root_tag_get(root, tag))
 856                 return 0;
 857
 858         node = rcu_dereference(root->rnode);
 859         if (!node)
 860                 return 0;
 861
 862         if (!radix_tree_is_indirect_ptr(node)) {
 863                 if (first_index > 0)
 864                         return 0;
 865                 results[0] = node;
 866                 return 1;
 867         }
 868         node = radix_tree_indirect_to_ptr(node);
 869
 870         max_index = radix_tree_maxindex(node->height);
 871
 872         ret = 0;
 873         while (ret < max_items) {
 874                 unsigned int nr_found;
 875                 unsigned long next_index;       /* Index of next search */
 876
 877                 if (cur_index > max_index)
 878                         break;
 879                 nr_found = __lookup_tag(node, results + ret, cur_index,
 880                                         max_items - ret, &next_index, tag);
 881                 ret += nr_found;
 882                 if (next_index == 0)
 883                         break;
 884                 cur_index = next_index;
 885         }
 886
 887         return ret;
 888 }
 889 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
 890
 891 /**
 892  *      radix_tree_shrink    -    shrink height of a radix tree to minimal
 893  *      @root           radix tree root
 894  */
 895 static inline void radix_tree_shrink(struct radix_tree_root *root)
 896 {
 897         /* try to shrink tree height */
 898         while (root->height > 0) {
 899                 struct radix_tree_node *to_free = root->rnode;
 900                 void *newptr;
 901
 902                 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
 903                 to_free = radix_tree_indirect_to_ptr(to_free);
 904
 905                 /*
 906                  * The candidate node has more than one child, or its child
 907                  * is not at the leftmost slot, we cannot shrink.
 908                  */
 909                 if (to_free->count != 1)
 910                         break;
 911                 if (!to_free->slots[0])
 912                         break;
 913
 914                 /*
 915                  * We don't need rcu_assign_pointer(), since we are simply
 916                  * moving the node from one part of the tree to another. If
 917                  * it was safe to dereference the old pointer to it
 918                  * (to_free->slots[0]), it will be safe to dereference the new
 919                  * one (root->rnode).
 920                  */
 921                 newptr = to_free->slots[0];
 922                 if (root->height > 1)
 923                         newptr = radix_tree_ptr_to_indirect(newptr);
 924                 root->rnode = newptr;
 925                 root->height--;
 926                 /* must only free zeroed nodes into the slab */
 927                 tag_clear(to_free, 0, 0);
 928                 tag_clear(to_free, 1, 0);
 929                 to_free->slots[0] = NULL;
 930                 to_free->count = 0;
 931                 radix_tree_node_free(to_free);
 932         }
 933 }
 934
 935 /**
 936  *      radix_tree_delete    -    delete an item from a radix tree
 937  *      @root:          radix tree root
 938  *      @index:         index key
 939  *
 940  *      Remove the item at @index from the radix tree rooted at @root.
 941  *
 942  *      Returns the address of the deleted item, or NULL if it was not present.
 943  */
 944 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 945 {
 946         /*
 947          * The radix tree path needs to be one longer than the maximum path
 948          * since the "list" is null terminated.
 949          */
 950         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
 951         struct radix_tree_node *slot = NULL;
 952         struct radix_tree_node *to_free;
 953         unsigned int height, shift;
 954         int tag;
 955         int offset;
 956
 957         height = root->height;
 958         if (index > radix_tree_maxindex(height))
 959                 goto out;
 960
 961         slot = root->rnode;
 962         if (height == 0) {
 963                 root_tag_clear_all(root);
 964                 root->rnode = NULL;
 965                 goto out;
 966         }
 967         slot = radix_tree_indirect_to_ptr(slot);
 968
 969         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 970         pathp->node = NULL;
 971
 972         do {
 973                 if (slot == NULL)
 974                         goto out;
 975
 976                 pathp++;
 977                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 978                 pathp->offset = offset;
 979                 pathp->node = slot;
 980                 slot = slot->slots[offset];
 981                 shift -= RADIX_TREE_MAP_SHIFT;
 982                 height--;
 983         } while (height > 0);
 984
 985         if (slot == NULL)
 986                 goto out;
 987
 988         /*
 989          * Clear all tags associated with the just-deleted item
 990          */
 991         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 992                 if (tag_get(pathp->node, tag, pathp->offset))
 993                         radix_tree_tag_clear(root, index, tag);
 994         }
 995
 996         to_free = NULL;
 997         /* Now free the nodes we do not need anymore */
 998         while (pathp->node) {
 999                 pathp->node->slots[pathp->offset] = NULL;
1000                 pathp->node->count--;
1001                 /*
1002                  * Queue the node for deferred freeing after the
1003                  * last reference to it disappears (set NULL, above).
1004                  */
1005                 if (to_free)
1006                         radix_tree_node_free(to_free);
1007
1008                 if (pathp->node->count) {
1009                         if (pathp->node ==
1010                                         radix_tree_indirect_to_ptr(root->rnode))
1011                                 radix_tree_shrink(root);
1012                         goto out;
1013                 }
1014
1015                 /* Node with zero slots in use so free it */
1016                 to_free = pathp->node;
1017                 pathp--;
1018
1019         }
1020         root_tag_clear_all(root);
1021         root->height = 0;
1022         root->rnode = NULL;
1023         if (to_free)
1024                 radix_tree_node_free(to_free);
1025
1026 out:
1027         return slot;
1028 }
1029 EXPORT_SYMBOL(radix_tree_delete);
1030
1031 /**
1032  *      radix_tree_tagged - test whether any items in the tree are tagged
1033  *      @root:          radix tree root
1034  *      @tag:           tag to test
1035  */
1036 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1037 {
1038         return root_tag_get(root, tag);
1039 }
1040 EXPORT_SYMBOL(radix_tree_tagged);
1041
1042 static void
1043 radix_tree_node_ctor(void *node, struct kmem_cache *cachep, unsigned long flags)
1044 {
1045         memset(node, 0, sizeof(struct radix_tree_node));
1046 }
1047
1048 static __init unsigned long __maxindex(unsigned int height)
1049 {
1050         unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
1051         unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
1052
1053         if (tmp >= RADIX_TREE_INDEX_BITS)
1054                 index = ~0UL;
1055         return index;
1056 }
1057
1058 static __init void radix_tree_init_maxindex(void)
1059 {
1060         unsigned int i;
1061
1062         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1063                 height_to_maxindex[i] = __maxindex(i);
1064 }
1065
1066 static int radix_tree_callback(struct notifier_block *nfb,
1067                             unsigned long action,
1068                             void *hcpu)
1069 {
1070        int cpu = (long)hcpu;
1071        struct radix_tree_preload *rtp;
1072
1073        /* Free per-cpu pool of perloaded nodes */
1074        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1075                rtp = &per_cpu(radix_tree_preloads, cpu);
1076                while (rtp->nr) {
1077                        kmem_cache_free(radix_tree_node_cachep,
1078                                        rtp->nodes[rtp->nr-1]);
1079                        rtp->nodes[rtp->nr-1] = NULL;
1080                        rtp->nr--;
1081                }
1082        }
1083        return NOTIFY_OK;
1084 }
1085
1086 void __init radix_tree_init(void)
1087 {
1088         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1089                         sizeof(struct radix_tree_node), 0,
1090                         SLAB_PANIC, radix_tree_node_ctor);
1091         radix_tree_init_maxindex();
1092         hotcpu_notifier(radix_tree_callback, 0);
1093 }