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,
 102                                 set_migrateflags(gfp_mask, __GFP_RECLAIMABLE));
 103         if (ret == NULL && !(gfp_mask & __GFP_WAIT)) {
 104                 struct radix_tree_preload *rtp;
 105
 106                 rtp = &__get_cpu_var(radix_tree_preloads);
 107                 if (rtp->nr) {
 108                         ret = rtp->nodes[rtp->nr - 1];
 109                         rtp->nodes[rtp->nr - 1] = NULL;
 110                         rtp->nr--;
 111                 }
 112         }
 113         BUG_ON(radix_tree_is_indirect_ptr(ret));
 114         return ret;
 115 }
 116
 117 static void radix_tree_node_rcu_free(struct rcu_head *head)
 118 {
 119         struct radix_tree_node *node =
 120                         container_of(head, struct radix_tree_node, rcu_head);
 121         kmem_cache_free(radix_tree_node_cachep, node);
 122 }
 123
 124 static inline void
 125 radix_tree_node_free(struct radix_tree_node *node)
 126 {
 127         call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
 128 }
 129
 130 /*
 131  * Load up this CPU's radix_tree_node buffer with sufficient objects to
 132  * ensure that the addition of a single element in the tree cannot fail.  On
 133  * success, return zero, with preemption disabled.  On error, return -ENOMEM
 134  * with preemption not disabled.
 135  */
 136 int radix_tree_preload(gfp_t gfp_mask)
 137 {
 138         struct radix_tree_preload *rtp;
 139         struct radix_tree_node *node;
 140         int ret = -ENOMEM;
 141
 142         preempt_disable();
 143         rtp = &__get_cpu_var(radix_tree_preloads);
 144         while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
 145                 preempt_enable();
 146                 node = kmem_cache_alloc(radix_tree_node_cachep,
 147                                 set_migrateflags(gfp_mask, __GFP_RECLAIMABLE));
 148                 if (node == NULL)
 149                         goto out;
 150                 preempt_disable();
 151                 rtp = &__get_cpu_var(radix_tree_preloads);
 152                 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
 153                         rtp->nodes[rtp->nr++] = node;
 154                 else
 155                         kmem_cache_free(radix_tree_node_cachep, node);
 156         }
 157         ret = 0;
 158 out:
 159         return ret;
 160 }
 161 EXPORT_SYMBOL(radix_tree_preload);
 162
 163 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
 164                 int offset)
 165 {
 166         __set_bit(offset, node->tags[tag]);
 167 }
 168
 169 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
 170                 int offset)
 171 {
 172         __clear_bit(offset, node->tags[tag]);
 173 }
 174
 175 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
 176                 int offset)
 177 {
 178         return test_bit(offset, node->tags[tag]);
 179 }
 180
 181 static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
 182 {
 183         root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
 184 }
 185
 186
 187 static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
 188 {
 189         root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
 190 }
 191
 192 static inline void root_tag_clear_all(struct radix_tree_root *root)
 193 {
 194         root->gfp_mask &= __GFP_BITS_MASK;
 195 }
 196
 197 static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
 198 {
 199         return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
 200 }
 201
 202 /*
 203  * Returns 1 if any slot in the node has this tag set.
 204  * Otherwise returns 0.
 205  */
 206 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
 207 {
 208         int idx;
 209         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 210                 if (node->tags[tag][idx])
 211                         return 1;
 212         }
 213         return 0;
 214 }
 215
 216 /*
 217  *      Return the maximum key which can be store into a
 218  *      radix tree with height HEIGHT.
 219  */
 220 static inline unsigned long radix_tree_maxindex(unsigned int height)
 221 {
 222         return height_to_maxindex[height];
 223 }
 224
 225 /*
 226  *      Extend a radix tree so it can store key @index.
 227  */
 228 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 229 {
 230         struct radix_tree_node *node;
 231         unsigned int height;
 232         int tag;
 233
 234         /* Figure out what the height should be.  */
 235         height = root->height + 1;
 236         while (index > radix_tree_maxindex(height))
 237                 height++;
 238
 239         if (root->rnode == NULL) {
 240                 root->height = height;
 241                 goto out;
 242         }
 243
 244         do {
 245                 unsigned int newheight;
 246                 if (!(node = radix_tree_node_alloc(root)))
 247                         return -ENOMEM;
 248
 249                 /* Increase the height.  */
 250                 node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
 251
 252                 /* Propagate the aggregated tag info into the new root */
 253                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 254                         if (root_tag_get(root, tag))
 255                                 tag_set(node, tag, 0);
 256                 }
 257
 258                 newheight = root->height+1;
 259                 node->height = newheight;
 260                 node->count = 1;
 261                 node = radix_tree_ptr_to_indirect(node);
 262                 rcu_assign_pointer(root->rnode, node);
 263                 root->height = newheight;
 264         } while (height > root->height);
 265 out:
 266         return 0;
 267 }
 268
 269 /**
 270  *      radix_tree_insert    -    insert into a radix tree
 271  *      @root:          radix tree root
 272  *      @index:         index key
 273  *      @item:          item to insert
 274  *
 275  *      Insert an item into the radix tree at position @index.
 276  */
 277 int radix_tree_insert(struct radix_tree_root *root,
 278                         unsigned long index, void *item)
 279 {
 280         struct radix_tree_node *node = NULL, *slot;
 281         unsigned int height, shift;
 282         int offset;
 283         int error;
 284
 285         BUG_ON(radix_tree_is_indirect_ptr(item));
 286
 287         /* Make sure the tree is high enough.  */
 288         if (index > radix_tree_maxindex(root->height)) {
 289                 error = radix_tree_extend(root, index);
 290                 if (error)
 291                         return error;
 292         }
 293
 294         slot = radix_tree_indirect_to_ptr(root->rnode);
 295
 296         height = root->height;
 297         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 298
 299         offset = 0;                     /* uninitialised var warning */
 300         while (height > 0) {
 301                 if (slot == NULL) {
 302                         /* Have to add a child node.  */
 303                         if (!(slot = radix_tree_node_alloc(root)))
 304                                 return -ENOMEM;
 305                         slot->height = height;
 306                         if (node) {
 307                                 rcu_assign_pointer(node->slots[offset], slot);
 308                                 node->count++;
 309                         } else
 310                                 rcu_assign_pointer(root->rnode,
 311                                         radix_tree_ptr_to_indirect(slot));
 312                 }
 313
 314                 /* Go a level down */
 315                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 316                 node = slot;
 317                 slot = node->slots[offset];
 318                 shift -= RADIX_TREE_MAP_SHIFT;
 319                 height--;
 320         }
 321
 322         if (slot != NULL)
 323                 return -EEXIST;
 324
 325         if (node) {
 326                 node->count++;
 327                 rcu_assign_pointer(node->slots[offset], item);
 328                 BUG_ON(tag_get(node, 0, offset));
 329                 BUG_ON(tag_get(node, 1, offset));
 330         } else {
 331                 rcu_assign_pointer(root->rnode, item);
 332                 BUG_ON(root_tag_get(root, 0));
 333                 BUG_ON(root_tag_get(root, 1));
 334         }
 335
 336         return 0;
 337 }
 338 EXPORT_SYMBOL(radix_tree_insert);
 339
 340 /**
 341  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
 342  *      @root:          radix tree root
 343  *      @index:         index key
 344  *
 345  *      Returns:  the slot corresponding to the position @index in the
 346  *      radix tree @root. This is useful for update-if-exists operations.
 347  *
 348  *      This function cannot be called under rcu_read_lock, it must be
 349  *      excluded from writers, as must the returned slot for subsequent
 350  *      use by radix_tree_deref_slot() and radix_tree_replace slot.
 351  *      Caller must hold tree write locked across slot lookup and
 352  *      replace.
 353  */
 354 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
 355 {
 356         unsigned int height, shift;
 357         struct radix_tree_node *node, **slot;
 358
 359         node = root->rnode;
 360         if (node == NULL)
 361                 return NULL;
 362
 363         if (!radix_tree_is_indirect_ptr(node)) {
 364                 if (index > 0)
 365                         return NULL;
 366                 return (void **)&root->rnode;
 367         }
 368         node = radix_tree_indirect_to_ptr(node);
 369
 370         height = node->height;
 371         if (index > radix_tree_maxindex(height))
 372                 return NULL;
 373
 374         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 375
 376         do {
 377                 slot = (struct radix_tree_node **)
 378                         (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
 379                 node = *slot;
 380                 if (node == NULL)
 381                         return NULL;
 382
 383                 shift -= RADIX_TREE_MAP_SHIFT;
 384                 height--;
 385         } while (height > 0);
 386
 387         return (void **)slot;
 388 }
 389 EXPORT_SYMBOL(radix_tree_lookup_slot);
 390
 391 /**
 392  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 393  *      @root:          radix tree root
 394  *      @index:         index key
 395  *
 396  *      Lookup the item at the position @index in the radix tree @root.
 397  *
 398  *      This function can be called under rcu_read_lock, however the caller
 399  *      must manage lifetimes of leaf nodes (eg. RCU may also be used to free
 400  *      them safely). No RCU barriers are required to access or modify the
 401  *      returned item, however.
 402  */
 403 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 404 {
 405         unsigned int height, shift;
 406         struct radix_tree_node *node, **slot;
 407
 408         node = rcu_dereference(root->rnode);
 409         if (node == NULL)
 410                 return NULL;
 411
 412         if (!radix_tree_is_indirect_ptr(node)) {
 413                 if (index > 0)
 414                         return NULL;
 415                 return node;
 416         }
 417         node = radix_tree_indirect_to_ptr(node);
 418
 419         height = node->height;
 420         if (index > radix_tree_maxindex(height))
 421                 return NULL;
 422
 423         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 424
 425         do {
 426                 slot = (struct radix_tree_node **)
 427                         (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
 428                 node = rcu_dereference(*slot);
 429                 if (node == NULL)
 430                         return NULL;
 431
 432                 shift -= RADIX_TREE_MAP_SHIFT;
 433                 height--;
 434         } while (height > 0);
 435
 436         return node;
 437 }
 438 EXPORT_SYMBOL(radix_tree_lookup);
 439
 440 /**
 441  *      radix_tree_tag_set - set a tag on a radix tree node
 442  *      @root:          radix tree root
 443  *      @index:         index key
 444  *      @tag:           tag index
 445  *
 446  *      Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
 447  *      corresponding to @index in the radix tree.  From
 448  *      the root all the way down to the leaf node.
 449  *
 450  *      Returns the address of the tagged item.   Setting a tag on a not-present
 451  *      item is a bug.
 452  */
 453 void *radix_tree_tag_set(struct radix_tree_root *root,
 454                         unsigned long index, unsigned int tag)
 455 {
 456         unsigned int height, shift;
 457         struct radix_tree_node *slot;
 458
 459         height = root->height;
 460         BUG_ON(index > radix_tree_maxindex(height));
 461
 462         slot = radix_tree_indirect_to_ptr(root->rnode);
 463         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 464
 465         while (height > 0) {
 466                 int offset;
 467
 468                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 469                 if (!tag_get(slot, tag, offset))
 470                         tag_set(slot, tag, offset);
 471                 slot = slot->slots[offset];
 472                 BUG_ON(slot == NULL);
 473                 shift -= RADIX_TREE_MAP_SHIFT;
 474                 height--;
 475         }
 476
 477         /* set the root's tag bit */
 478         if (slot && !root_tag_get(root, tag))
 479                 root_tag_set(root, tag);
 480
 481         return slot;
 482 }
 483 EXPORT_SYMBOL(radix_tree_tag_set);
 484
 485 /**
 486  *      radix_tree_tag_clear - clear a tag on a radix tree node
 487  *      @root:          radix tree root
 488  *      @index:         index key
 489  *      @tag:           tag index
 490  *
 491  *      Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
 492  *      corresponding to @index in the radix tree.  If
 493  *      this causes the leaf node to have no tags set then clear the tag in the
 494  *      next-to-leaf node, etc.
 495  *
 496  *      Returns the address of the tagged item on success, else NULL.  ie:
 497  *      has the same return value and semantics as radix_tree_lookup().
 498  */
 499 void *radix_tree_tag_clear(struct radix_tree_root *root,
 500                         unsigned long index, unsigned int tag)
 501 {
 502         /*
 503          * The radix tree path needs to be one longer than the maximum path
 504          * since the "list" is null terminated.
 505          */
 506         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
 507         struct radix_tree_node *slot = NULL;
 508         unsigned int height, shift;
 509
 510         height = root->height;
 511         if (index > radix_tree_maxindex(height))
 512                 goto out;
 513
 514         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 515         pathp->node = NULL;
 516         slot = radix_tree_indirect_to_ptr(root->rnode);
 517
 518         while (height > 0) {
 519                 int offset;
 520
 521                 if (slot == NULL)
 522                         goto out;
 523
 524                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 525                 pathp[1].offset = offset;
 526                 pathp[1].node = slot;
 527                 slot = slot->slots[offset];
 528                 pathp++;
 529                 shift -= RADIX_TREE_MAP_SHIFT;
 530                 height--;
 531         }
 532
 533         if (slot == NULL)
 534                 goto out;
 535
 536         while (pathp->node) {
 537                 if (!tag_get(pathp->node, tag, pathp->offset))
 538                         goto out;
 539                 tag_clear(pathp->node, tag, pathp->offset);
 540                 if (any_tag_set(pathp->node, tag))
 541                         goto out;
 542                 pathp--;
 543         }
 544
 545         /* clear the root's tag bit */
 546         if (root_tag_get(root, tag))
 547                 root_tag_clear(root, tag);
 548
 549 out:
 550         return slot;
 551 }
 552 EXPORT_SYMBOL(radix_tree_tag_clear);
 553
 554 #ifndef __KERNEL__      /* Only the test harness uses this at present */
 555 /**
 556  * radix_tree_tag_get - get a tag on a radix tree node
 557  * @root:               radix tree root
 558  * @index:              index key
 559  * @tag:                tag index (< RADIX_TREE_MAX_TAGS)
 560  *
 561  * Return values:
 562  *
 563  *  0: tag not present or not set
 564  *  1: tag set
 565  */
 566 int radix_tree_tag_get(struct radix_tree_root *root,
 567                         unsigned long index, unsigned int tag)
 568 {
 569         unsigned int height, shift;
 570         struct radix_tree_node *node;
 571         int saw_unset_tag = 0;
 572
 573         /* check the root's tag bit */
 574         if (!root_tag_get(root, tag))
 575                 return 0;
 576
 577         node = rcu_dereference(root->rnode);
 578         if (node == NULL)
 579                 return 0;
 580
 581         if (!radix_tree_is_indirect_ptr(node))
 582                 return (index == 0);
 583         node = radix_tree_indirect_to_ptr(node);
 584
 585         height = node->height;
 586         if (index > radix_tree_maxindex(height))
 587                 return 0;
 588
 589         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 590
 591         for ( ; ; ) {
 592                 int offset;
 593
 594                 if (node == NULL)
 595                         return 0;
 596
 597                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 598
 599                 /*
 600                  * This is just a debug check.  Later, we can bale as soon as
 601                  * we see an unset tag.
 602                  */
 603                 if (!tag_get(node, tag, offset))
 604                         saw_unset_tag = 1;
 605                 if (height == 1) {
 606                         int ret = tag_get(node, tag, offset);
 607
 608                         BUG_ON(ret && saw_unset_tag);
 609                         return !!ret;
 610                 }
 611                 node = rcu_dereference(node->slots[offset]);
 612                 shift -= RADIX_TREE_MAP_SHIFT;
 613                 height--;
 614         }
 615 }
 616 EXPORT_SYMBOL(radix_tree_tag_get);
 617 #endif
 618
 619 /**
 620  *      radix_tree_next_hole    -    find the next hole (not-present entry)
 621  *      @root:          tree root
 622  *      @index:         index key
 623  *      @max_scan:      maximum range to search
 624  *
 625  *      Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
 626  *      indexed hole.
 627  *
 628  *      Returns: the index of the hole if found, otherwise returns an index
 629  *      outside of the set specified (in which case 'return - index >= max_scan'
 630  *      will be true).
 631  *
 632  *      radix_tree_next_hole may be called under rcu_read_lock. However, like
 633  *      radix_tree_gang_lookup, this will not atomically search a snapshot of the
 634  *      tree at a single point in time. For example, if a hole is created at index
 635  *      5, then subsequently a hole is created at index 10, radix_tree_next_hole
 636  *      covering both indexes may return 10 if called under rcu_read_lock.
 637  */
 638 unsigned long radix_tree_next_hole(struct radix_tree_root *root,
 639                                 unsigned long index, unsigned long max_scan)
 640 {
 641         unsigned long i;
 642
 643         for (i = 0; i < max_scan; i++) {
 644                 if (!radix_tree_lookup(root, index))
 645                         break;
 646                 index++;
 647                 if (index == 0)
 648                         break;
 649         }
 650
 651         return index;
 652 }
 653 EXPORT_SYMBOL(radix_tree_next_hole);
 654
 655 static unsigned int
 656 __lookup(struct radix_tree_node *slot, void **results, unsigned long index,
 657         unsigned int max_items, unsigned long *next_index)
 658 {
 659         unsigned int nr_found = 0;
 660         unsigned int shift, height;
 661         unsigned long i;
 662
 663         height = slot->height;
 664         if (height == 0)
 665                 goto out;
 666         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 667
 668         for ( ; height > 1; height--) {
 669                 i = (index >> shift) & RADIX_TREE_MAP_MASK;
 670                 for (;;) {
 671                         if (slot->slots[i] != NULL)
 672                                 break;
 673                         index &= ~((1UL << shift) - 1);
 674                         index += 1UL << shift;
 675                         if (index == 0)
 676                                 goto out;       /* 32-bit wraparound */
 677                         i++;
 678                         if (i == RADIX_TREE_MAP_SIZE)
 679                                 goto out;
 680                 }
 681
 682                 shift -= RADIX_TREE_MAP_SHIFT;
 683                 slot = rcu_dereference(slot->slots[i]);
 684                 if (slot == NULL)
 685                         goto out;
 686         }
 687
 688         /* Bottom level: grab some items */
 689         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
 690                 struct radix_tree_node *node;
 691                 index++;
 692                 node = slot->slots[i];
 693                 if (node) {
 694                         results[nr_found++] = rcu_dereference(node);
 695                         if (nr_found == max_items)
 696                                 goto out;
 697                 }
 698         }
 699 out:
 700         *next_index = index;
 701         return nr_found;
 702 }
 703
 704 /**
 705  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
 706  *      @root:          radix tree root
 707  *      @results:       where the results of the lookup are placed
 708  *      @first_index:   start the lookup from this key
 709  *      @max_items:     place up to this many items at *results
 710  *
 711  *      Performs an index-ascending scan of the tree for present items.  Places
 712  *      them at *@results and returns the number of items which were placed at
 713  *      *@results.
 714  *
 715  *      The implementation is naive.
 716  *
 717  *      Like radix_tree_lookup, radix_tree_gang_lookup may be called under
 718  *      rcu_read_lock. In this case, rather than the returned results being
 719  *      an atomic snapshot of the tree at a single point in time, the semantics
 720  *      of an RCU protected gang lookup are as though multiple radix_tree_lookups
 721  *      have been issued in individual locks, and results stored in 'results'.
 722  */
 723 unsigned int
 724 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 725                         unsigned long first_index, unsigned int max_items)
 726 {
 727         unsigned long max_index;
 728         struct radix_tree_node *node;
 729         unsigned long cur_index = first_index;
 730         unsigned int ret;
 731
 732         node = rcu_dereference(root->rnode);
 733         if (!node)
 734                 return 0;
 735
 736         if (!radix_tree_is_indirect_ptr(node)) {
 737                 if (first_index > 0)
 738                         return 0;
 739                 results[0] = node;
 740                 return 1;
 741         }
 742         node = radix_tree_indirect_to_ptr(node);
 743
 744         max_index = radix_tree_maxindex(node->height);
 745
 746         ret = 0;
 747         while (ret < max_items) {
 748                 unsigned int nr_found;
 749                 unsigned long next_index;       /* Index of next search */
 750
 751                 if (cur_index > max_index)
 752                         break;
 753                 nr_found = __lookup(node, results + ret, cur_index,
 754                                         max_items - ret, &next_index);
 755                 ret += nr_found;
 756                 if (next_index == 0)
 757                         break;
 758                 cur_index = next_index;
 759         }
 760
 761         return ret;
 762 }
 763 EXPORT_SYMBOL(radix_tree_gang_lookup);
 764
 765 /*
 766  * FIXME: the two tag_get()s here should use find_next_bit() instead of
 767  * open-coding the search.
 768  */
 769 static unsigned int
 770 __lookup_tag(struct radix_tree_node *slot, void **results, unsigned long index,
 771         unsigned int max_items, unsigned long *next_index, unsigned int tag)
 772 {
 773         unsigned int nr_found = 0;
 774         unsigned int shift, height;
 775
 776         height = slot->height;
 777         if (height == 0)
 778                 goto out;
 779         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 780
 781         while (height > 0) {
 782                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
 783
 784                 for (;;) {
 785                         if (tag_get(slot, tag, i))
 786                                 break;
 787                         index &= ~((1UL << shift) - 1);
 788                         index += 1UL << shift;
 789                         if (index == 0)
 790                                 goto out;       /* 32-bit wraparound */
 791                         i++;
 792                         if (i == RADIX_TREE_MAP_SIZE)
 793                                 goto out;
 794                 }
 795                 height--;
 796                 if (height == 0) {      /* Bottom level: grab some items */
 797                         unsigned long j = index & RADIX_TREE_MAP_MASK;
 798
 799                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
 800                                 struct radix_tree_node *node;
 801                                 index++;
 802                                 if (!tag_get(slot, tag, j))
 803                                         continue;
 804                                 node = slot->slots[j];
 805                                 /*
 806                                  * Even though the tag was found set, we need to
 807                                  * recheck that we have a non-NULL node, because
 808                                  * if this lookup is lockless, it may have been
 809                                  * subsequently deleted.
 810                                  *
 811                                  * Similar care must be taken in any place that
 812                                  * lookup ->slots[x] without a lock (ie. can't
 813                                  * rely on its value remaining the same).
 814                                  */
 815                                 if (node) {
 816                                         node = rcu_dereference(node);
 817                                         results[nr_found++] = node;
 818                                         if (nr_found == max_items)
 819                                                 goto out;
 820                                 }
 821                         }
 822                 }
 823                 shift -= RADIX_TREE_MAP_SHIFT;
 824                 slot = rcu_dereference(slot->slots[i]);
 825                 if (slot == NULL)
 826                         break;
 827         }
 828 out:
 829         *next_index = index;
 830         return nr_found;
 831 }
 832
 833 /**
 834  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
 835  *                                   based on a tag
 836  *      @root:          radix tree root
 837  *      @results:       where the results of the lookup are placed
 838  *      @first_index:   start the lookup from this key
 839  *      @max_items:     place up to this many items at *results
 840  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
 841  *
 842  *      Performs an index-ascending scan of the tree for present items which
 843  *      have the tag indexed by @tag set.  Places the items at *@results and
 844  *      returns the number of items which were placed at *@results.
 845  */
 846 unsigned int
 847 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
 848                 unsigned long first_index, unsigned int max_items,
 849                 unsigned int tag)
 850 {
 851         struct radix_tree_node *node;
 852         unsigned long max_index;
 853         unsigned long cur_index = first_index;
 854         unsigned int ret;
 855
 856         /* check the root's tag bit */
 857         if (!root_tag_get(root, tag))
 858                 return 0;
 859
 860         node = rcu_dereference(root->rnode);
 861         if (!node)
 862                 return 0;
 863
 864         if (!radix_tree_is_indirect_ptr(node)) {
 865                 if (first_index > 0)
 866                         return 0;
 867                 results[0] = node;
 868                 return 1;
 869         }
 870         node = radix_tree_indirect_to_ptr(node);
 871
 872         max_index = radix_tree_maxindex(node->height);
 873
 874         ret = 0;
 875         while (ret < max_items) {
 876                 unsigned int nr_found;
 877                 unsigned long next_index;       /* Index of next search */
 878
 879                 if (cur_index > max_index)
 880                         break;
 881                 nr_found = __lookup_tag(node, results + ret, cur_index,
 882                                         max_items - ret, &next_index, tag);
 883                 ret += nr_found;
 884                 if (next_index == 0)
 885                         break;
 886                 cur_index = next_index;
 887         }
 888
 889         return ret;
 890 }
 891 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
 892
 893 /**
 894  *      radix_tree_shrink    -    shrink height of a radix tree to minimal
 895  *      @root           radix tree root
 896  */
 897 static inline void radix_tree_shrink(struct radix_tree_root *root)
 898 {
 899         /* try to shrink tree height */
 900         while (root->height > 0) {
 901                 struct radix_tree_node *to_free = root->rnode;
 902                 void *newptr;
 903
 904                 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
 905                 to_free = radix_tree_indirect_to_ptr(to_free);
 906
 907                 /*
 908                  * The candidate node has more than one child, or its child
 909                  * is not at the leftmost slot, we cannot shrink.
 910                  */
 911                 if (to_free->count != 1)
 912                         break;
 913                 if (!to_free->slots[0])
 914                         break;
 915
 916                 /*
 917                  * We don't need rcu_assign_pointer(), since we are simply
 918                  * moving the node from one part of the tree to another. If
 919                  * it was safe to dereference the old pointer to it
 920                  * (to_free->slots[0]), it will be safe to dereference the new
 921                  * one (root->rnode).
 922                  */
 923                 newptr = to_free->slots[0];
 924                 if (root->height > 1)
 925                         newptr = radix_tree_ptr_to_indirect(newptr);
 926                 root->rnode = newptr;
 927                 root->height--;
 928                 /* must only free zeroed nodes into the slab */
 929                 tag_clear(to_free, 0, 0);
 930                 tag_clear(to_free, 1, 0);
 931                 to_free->slots[0] = NULL;
 932                 to_free->count = 0;
 933                 radix_tree_node_free(to_free);
 934         }
 935 }
 936
 937 /**
 938  *      radix_tree_delete    -    delete an item from a radix tree
 939  *      @root:          radix tree root
 940  *      @index:         index key
 941  *
 942  *      Remove the item at @index from the radix tree rooted at @root.
 943  *
 944  *      Returns the address of the deleted item, or NULL if it was not present.
 945  */
 946 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 947 {
 948         /*
 949          * The radix tree path needs to be one longer than the maximum path
 950          * since the "list" is null terminated.
 951          */
 952         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
 953         struct radix_tree_node *slot = NULL;
 954         struct radix_tree_node *to_free;
 955         unsigned int height, shift;
 956         int tag;
 957         int offset;
 958
 959         height = root->height;
 960         if (index > radix_tree_maxindex(height))
 961                 goto out;
 962
 963         slot = root->rnode;
 964         if (height == 0) {
 965                 root_tag_clear_all(root);
 966                 root->rnode = NULL;
 967                 goto out;
 968         }
 969         slot = radix_tree_indirect_to_ptr(slot);
 970
 971         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 972         pathp->node = NULL;
 973
 974         do {
 975                 if (slot == NULL)
 976                         goto out;
 977
 978                 pathp++;
 979                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 980                 pathp->offset = offset;
 981                 pathp->node = slot;
 982                 slot = slot->slots[offset];
 983                 shift -= RADIX_TREE_MAP_SHIFT;
 984                 height--;
 985         } while (height > 0);
 986
 987         if (slot == NULL)
 988                 goto out;
 989
 990         /*
 991          * Clear all tags associated with the just-deleted item
 992          */
 993         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 994                 if (tag_get(pathp->node, tag, pathp->offset))
 995                         radix_tree_tag_clear(root, index, tag);
 996         }
 997
 998         to_free = NULL;
 999         /* Now free the nodes we do not need anymore */
1000         while (pathp->node) {
1001                 pathp->node->slots[pathp->offset] = NULL;
1002                 pathp->node->count--;
1003                 /*
1004                  * Queue the node for deferred freeing after the
1005                  * last reference to it disappears (set NULL, above).
1006                  */
1007                 if (to_free)
1008                         radix_tree_node_free(to_free);
1009
1010                 if (pathp->node->count) {
1011                         if (pathp->node ==
1012                                         radix_tree_indirect_to_ptr(root->rnode))
1013                                 radix_tree_shrink(root);
1014                         goto out;
1015                 }
1016
1017                 /* Node with zero slots in use so free it */
1018                 to_free = pathp->node;
1019                 pathp--;
1020
1021         }
1022         root_tag_clear_all(root);
1023         root->height = 0;
1024         root->rnode = NULL;
1025         if (to_free)
1026                 radix_tree_node_free(to_free);
1027
1028 out:
1029         return slot;
1030 }
1031 EXPORT_SYMBOL(radix_tree_delete);
1032
1033 /**
1034  *      radix_tree_tagged - test whether any items in the tree are tagged
1035  *      @root:          radix tree root
1036  *      @tag:           tag to test
1037  */
1038 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1039 {
1040         return root_tag_get(root, tag);
1041 }
1042 EXPORT_SYMBOL(radix_tree_tagged);
1043
1044 static void
1045 radix_tree_node_ctor(struct kmem_cache *cachep, void *node)
1046 {
1047         memset(node, 0, sizeof(struct radix_tree_node));
1048 }
1049
1050 static __init unsigned long __maxindex(unsigned int height)
1051 {
1052         unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1053         int shift = RADIX_TREE_INDEX_BITS - width;
1054
1055         if (shift < 0)
1056                 return ~0UL;
1057         if (shift >= BITS_PER_LONG)
1058                 return 0UL;
1059         return ~0UL >> shift;
1060 }
1061
1062 static __init void radix_tree_init_maxindex(void)
1063 {
1064         unsigned int i;
1065
1066         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1067                 height_to_maxindex[i] = __maxindex(i);
1068 }
1069
1070 static int radix_tree_callback(struct notifier_block *nfb,
1071                             unsigned long action,
1072                             void *hcpu)
1073 {
1074        int cpu = (long)hcpu;
1075        struct radix_tree_preload *rtp;
1076
1077        /* Free per-cpu pool of perloaded nodes */
1078        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1079                rtp = &per_cpu(radix_tree_preloads, cpu);
1080                while (rtp->nr) {
1081                        kmem_cache_free(radix_tree_node_cachep,
1082                                        rtp->nodes[rtp->nr-1]);
1083                        rtp->nodes[rtp->nr-1] = NULL;
1084                        rtp->nr--;
1085                }
1086        }
1087        return NOTIFY_OK;
1088 }
1089
1090 void __init radix_tree_init(void)
1091 {
1092         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1093                         sizeof(struct radix_tree_node), 0,
1094                         SLAB_PANIC, radix_tree_node_ctor);
1095         radix_tree_init_maxindex();
1096         hotcpu_notifier(radix_tree_callback, 0);
1097 }