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 = NULL;
  99         gfp_t gfp_mask = root_gfp_mask(root);
 100
 101         if (!(gfp_mask & __GFP_WAIT)) {
 102                 struct radix_tree_preload *rtp;
 103
 104                 /*
 105                  * Provided the caller has preloaded here, we will always
 106                  * succeed in getting a node here (and never reach
 107                  * kmem_cache_alloc)
 108                  */
 109                 rtp = &__get_cpu_var(radix_tree_preloads);
 110                 if (rtp->nr) {
 111                         ret = rtp->nodes[rtp->nr - 1];
 112                         rtp->nodes[rtp->nr - 1] = NULL;
 113                         rtp->nr--;
 114                 }
 115         }
 116         if (ret == NULL)
 117                 ret = kmem_cache_alloc(radix_tree_node_cachep,
 118                                 set_migrateflags(gfp_mask, __GFP_RECLAIMABLE));
 119
 120         BUG_ON(radix_tree_is_indirect_ptr(ret));
 121         return ret;
 122 }
 123
 124 static void radix_tree_node_rcu_free(struct rcu_head *head)
 125 {
 126         struct radix_tree_node *node =
 127                         container_of(head, struct radix_tree_node, rcu_head);
 128         kmem_cache_free(radix_tree_node_cachep, node);
 129 }
 130
 131 static inline void
 132 radix_tree_node_free(struct radix_tree_node *node)
 133 {
 134         call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
 135 }
 136
 137 /*
 138  * Load up this CPU's radix_tree_node buffer with sufficient objects to
 139  * ensure that the addition of a single element in the tree cannot fail.  On
 140  * success, return zero, with preemption disabled.  On error, return -ENOMEM
 141  * with preemption not disabled.
 142  */
 143 int radix_tree_preload(gfp_t gfp_mask)
 144 {
 145         struct radix_tree_preload *rtp;
 146         struct radix_tree_node *node;
 147         int ret = -ENOMEM;
 148
 149         preempt_disable();
 150         rtp = &__get_cpu_var(radix_tree_preloads);
 151         while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
 152                 preempt_enable();
 153                 node = kmem_cache_alloc(radix_tree_node_cachep,
 154                                 set_migrateflags(gfp_mask, __GFP_RECLAIMABLE));
 155                 if (node == NULL)
 156                         goto out;
 157                 preempt_disable();
 158                 rtp = &__get_cpu_var(radix_tree_preloads);
 159                 if (rtp->nr < ARRAY_SIZE(rtp->nodes))
 160                         rtp->nodes[rtp->nr++] = node;
 161                 else
 162                         kmem_cache_free(radix_tree_node_cachep, node);
 163         }
 164         ret = 0;
 165 out:
 166         return ret;
 167 }
 168 EXPORT_SYMBOL(radix_tree_preload);
 169
 170 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
 171                 int offset)
 172 {
 173         __set_bit(offset, node->tags[tag]);
 174 }
 175
 176 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
 177                 int offset)
 178 {
 179         __clear_bit(offset, node->tags[tag]);
 180 }
 181
 182 static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
 183                 int offset)
 184 {
 185         return test_bit(offset, node->tags[tag]);
 186 }
 187
 188 static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
 189 {
 190         root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
 191 }
 192
 193
 194 static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
 195 {
 196         root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
 197 }
 198
 199 static inline void root_tag_clear_all(struct radix_tree_root *root)
 200 {
 201         root->gfp_mask &= __GFP_BITS_MASK;
 202 }
 203
 204 static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
 205 {
 206         return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
 207 }
 208
 209 /*
 210  * Returns 1 if any slot in the node has this tag set.
 211  * Otherwise returns 0.
 212  */
 213 static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
 214 {
 215         int idx;
 216         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 217                 if (node->tags[tag][idx])
 218                         return 1;
 219         }
 220         return 0;
 221 }
 222
 223 /*
 224  *      Return the maximum key which can be store into a
 225  *      radix tree with height HEIGHT.
 226  */
 227 static inline unsigned long radix_tree_maxindex(unsigned int height)
 228 {
 229         return height_to_maxindex[height];
 230 }
 231
 232 /*
 233  *      Extend a radix tree so it can store key @index.
 234  */
 235 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 236 {
 237         struct radix_tree_node *node;
 238         unsigned int height;
 239         int tag;
 240
 241         /* Figure out what the height should be.  */
 242         height = root->height + 1;
 243         while (index > radix_tree_maxindex(height))
 244                 height++;
 245
 246         if (root->rnode == NULL) {
 247                 root->height = height;
 248                 goto out;
 249         }
 250
 251         do {
 252                 unsigned int newheight;
 253                 if (!(node = radix_tree_node_alloc(root)))
 254                         return -ENOMEM;
 255
 256                 /* Increase the height.  */
 257                 node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
 258
 259                 /* Propagate the aggregated tag info into the new root */
 260                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 261                         if (root_tag_get(root, tag))
 262                                 tag_set(node, tag, 0);
 263                 }
 264
 265                 newheight = root->height+1;
 266                 node->height = newheight;
 267                 node->count = 1;
 268                 node = radix_tree_ptr_to_indirect(node);
 269                 rcu_assign_pointer(root->rnode, node);
 270                 root->height = newheight;
 271         } while (height > root->height);
 272 out:
 273         return 0;
 274 }
 275
 276 /**
 277  *      radix_tree_insert    -    insert into a radix tree
 278  *      @root:          radix tree root
 279  *      @index:         index key
 280  *      @item:          item to insert
 281  *
 282  *      Insert an item into the radix tree at position @index.
 283  */
 284 int radix_tree_insert(struct radix_tree_root *root,
 285                         unsigned long index, void *item)
 286 {
 287         struct radix_tree_node *node = NULL, *slot;
 288         unsigned int height, shift;
 289         int offset;
 290         int error;
 291
 292         BUG_ON(radix_tree_is_indirect_ptr(item));
 293
 294         /* Make sure the tree is high enough.  */
 295         if (index > radix_tree_maxindex(root->height)) {
 296                 error = radix_tree_extend(root, index);
 297                 if (error)
 298                         return error;
 299         }
 300
 301         slot = radix_tree_indirect_to_ptr(root->rnode);
 302
 303         height = root->height;
 304         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 305
 306         offset = 0;                     /* uninitialised var warning */
 307         while (height > 0) {
 308                 if (slot == NULL) {
 309                         /* Have to add a child node.  */
 310                         if (!(slot = radix_tree_node_alloc(root)))
 311                                 return -ENOMEM;
 312                         slot->height = height;
 313                         if (node) {
 314                                 rcu_assign_pointer(node->slots[offset], slot);
 315                                 node->count++;
 316                         } else
 317                                 rcu_assign_pointer(root->rnode,
 318                                         radix_tree_ptr_to_indirect(slot));
 319                 }
 320
 321                 /* Go a level down */
 322                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 323                 node = slot;
 324                 slot = node->slots[offset];
 325                 shift -= RADIX_TREE_MAP_SHIFT;
 326                 height--;
 327         }
 328
 329         if (slot != NULL)
 330                 return -EEXIST;
 331
 332         if (node) {
 333                 node->count++;
 334                 rcu_assign_pointer(node->slots[offset], item);
 335                 BUG_ON(tag_get(node, 0, offset));
 336                 BUG_ON(tag_get(node, 1, offset));
 337         } else {
 338                 rcu_assign_pointer(root->rnode, item);
 339                 BUG_ON(root_tag_get(root, 0));
 340                 BUG_ON(root_tag_get(root, 1));
 341         }
 342
 343         return 0;
 344 }
 345 EXPORT_SYMBOL(radix_tree_insert);
 346
 347 /**
 348  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
 349  *      @root:          radix tree root
 350  *      @index:         index key
 351  *
 352  *      Returns:  the slot corresponding to the position @index in the
 353  *      radix tree @root. This is useful for update-if-exists operations.
 354  *
 355  *      This function cannot be called under rcu_read_lock, it must be
 356  *      excluded from writers, as must the returned slot for subsequent
 357  *      use by radix_tree_deref_slot() and radix_tree_replace slot.
 358  *      Caller must hold tree write locked across slot lookup and
 359  *      replace.
 360  */
 361 void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
 362 {
 363         unsigned int height, shift;
 364         struct radix_tree_node *node, **slot;
 365
 366         node = root->rnode;
 367         if (node == NULL)
 368                 return NULL;
 369
 370         if (!radix_tree_is_indirect_ptr(node)) {
 371                 if (index > 0)
 372                         return NULL;
 373                 return (void **)&root->rnode;
 374         }
 375         node = radix_tree_indirect_to_ptr(node);
 376
 377         height = node->height;
 378         if (index > radix_tree_maxindex(height))
 379                 return NULL;
 380
 381         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 382
 383         do {
 384                 slot = (struct radix_tree_node **)
 385                         (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
 386                 node = *slot;
 387                 if (node == NULL)
 388                         return NULL;
 389
 390                 shift -= RADIX_TREE_MAP_SHIFT;
 391                 height--;
 392         } while (height > 0);
 393
 394         return (void **)slot;
 395 }
 396 EXPORT_SYMBOL(radix_tree_lookup_slot);
 397
 398 /**
 399  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 400  *      @root:          radix tree root
 401  *      @index:         index key
 402  *
 403  *      Lookup the item at the position @index in the radix tree @root.
 404  *
 405  *      This function can be called under rcu_read_lock, however the caller
 406  *      must manage lifetimes of leaf nodes (eg. RCU may also be used to free
 407  *      them safely). No RCU barriers are required to access or modify the
 408  *      returned item, however.
 409  */
 410 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 411 {
 412         unsigned int height, shift;
 413         struct radix_tree_node *node, **slot;
 414
 415         node = rcu_dereference(root->rnode);
 416         if (node == NULL)
 417                 return NULL;
 418
 419         if (!radix_tree_is_indirect_ptr(node)) {
 420                 if (index > 0)
 421                         return NULL;
 422                 return node;
 423         }
 424         node = radix_tree_indirect_to_ptr(node);
 425
 426         height = node->height;
 427         if (index > radix_tree_maxindex(height))
 428                 return NULL;
 429
 430         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 431
 432         do {
 433                 slot = (struct radix_tree_node **)
 434                         (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
 435                 node = rcu_dereference(*slot);
 436                 if (node == NULL)
 437                         return NULL;
 438
 439                 shift -= RADIX_TREE_MAP_SHIFT;
 440                 height--;
 441         } while (height > 0);
 442
 443         return node;
 444 }
 445 EXPORT_SYMBOL(radix_tree_lookup);
 446
 447 /**
 448  *      radix_tree_tag_set - set a tag on a radix tree node
 449  *      @root:          radix tree root
 450  *      @index:         index key
 451  *      @tag:           tag index
 452  *
 453  *      Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
 454  *      corresponding to @index in the radix tree.  From
 455  *      the root all the way down to the leaf node.
 456  *
 457  *      Returns the address of the tagged item.   Setting a tag on a not-present
 458  *      item is a bug.
 459  */
 460 void *radix_tree_tag_set(struct radix_tree_root *root,
 461                         unsigned long index, unsigned int tag)
 462 {
 463         unsigned int height, shift;
 464         struct radix_tree_node *slot;
 465
 466         height = root->height;
 467         BUG_ON(index > radix_tree_maxindex(height));
 468
 469         slot = radix_tree_indirect_to_ptr(root->rnode);
 470         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 471
 472         while (height > 0) {
 473                 int offset;
 474
 475                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 476                 if (!tag_get(slot, tag, offset))
 477                         tag_set(slot, tag, offset);
 478                 slot = slot->slots[offset];
 479                 BUG_ON(slot == NULL);
 480                 shift -= RADIX_TREE_MAP_SHIFT;
 481                 height--;
 482         }
 483
 484         /* set the root's tag bit */
 485         if (slot && !root_tag_get(root, tag))
 486                 root_tag_set(root, tag);
 487
 488         return slot;
 489 }
 490 EXPORT_SYMBOL(radix_tree_tag_set);
 491
 492 /**
 493  *      radix_tree_tag_clear - clear a tag on a radix tree node
 494  *      @root:          radix tree root
 495  *      @index:         index key
 496  *      @tag:           tag index
 497  *
 498  *      Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
 499  *      corresponding to @index in the radix tree.  If
 500  *      this causes the leaf node to have no tags set then clear the tag in the
 501  *      next-to-leaf node, etc.
 502  *
 503  *      Returns the address of the tagged item on success, else NULL.  ie:
 504  *      has the same return value and semantics as radix_tree_lookup().
 505  */
 506 void *radix_tree_tag_clear(struct radix_tree_root *root,
 507                         unsigned long index, unsigned int tag)
 508 {
 509         /*
 510          * The radix tree path needs to be one longer than the maximum path
 511          * since the "list" is null terminated.
 512          */
 513         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
 514         struct radix_tree_node *slot = NULL;
 515         unsigned int height, shift;
 516
 517         height = root->height;
 518         if (index > radix_tree_maxindex(height))
 519                 goto out;
 520
 521         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 522         pathp->node = NULL;
 523         slot = radix_tree_indirect_to_ptr(root->rnode);
 524
 525         while (height > 0) {
 526                 int offset;
 527
 528                 if (slot == NULL)
 529                         goto out;
 530
 531                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 532                 pathp[1].offset = offset;
 533                 pathp[1].node = slot;
 534                 slot = slot->slots[offset];
 535                 pathp++;
 536                 shift -= RADIX_TREE_MAP_SHIFT;
 537                 height--;
 538         }
 539
 540         if (slot == NULL)
 541                 goto out;
 542
 543         while (pathp->node) {
 544                 if (!tag_get(pathp->node, tag, pathp->offset))
 545                         goto out;
 546                 tag_clear(pathp->node, tag, pathp->offset);
 547                 if (any_tag_set(pathp->node, tag))
 548                         goto out;
 549                 pathp--;
 550         }
 551
 552         /* clear the root's tag bit */
 553         if (root_tag_get(root, tag))
 554                 root_tag_clear(root, tag);
 555
 556 out:
 557         return slot;
 558 }
 559 EXPORT_SYMBOL(radix_tree_tag_clear);
 560
 561 #ifndef __KERNEL__      /* Only the test harness uses this at present */
 562 /**
 563  * radix_tree_tag_get - get a tag on a radix tree node
 564  * @root:               radix tree root
 565  * @index:              index key
 566  * @tag:                tag index (< RADIX_TREE_MAX_TAGS)
 567  *
 568  * Return values:
 569  *
 570  *  0: tag not present or not set
 571  *  1: tag set
 572  */
 573 int radix_tree_tag_get(struct radix_tree_root *root,
 574                         unsigned long index, unsigned int tag)
 575 {
 576         unsigned int height, shift;
 577         struct radix_tree_node *node;
 578         int saw_unset_tag = 0;
 579
 580         /* check the root's tag bit */
 581         if (!root_tag_get(root, tag))
 582                 return 0;
 583
 584         node = rcu_dereference(root->rnode);
 585         if (node == NULL)
 586                 return 0;
 587
 588         if (!radix_tree_is_indirect_ptr(node))
 589                 return (index == 0);
 590         node = radix_tree_indirect_to_ptr(node);
 591
 592         height = node->height;
 593         if (index > radix_tree_maxindex(height))
 594                 return 0;
 595
 596         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 597
 598         for ( ; ; ) {
 599                 int offset;
 600
 601                 if (node == NULL)
 602                         return 0;
 603
 604                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 605
 606                 /*
 607                  * This is just a debug check.  Later, we can bale as soon as
 608                  * we see an unset tag.
 609                  */
 610                 if (!tag_get(node, tag, offset))
 611                         saw_unset_tag = 1;
 612                 if (height == 1) {
 613                         int ret = tag_get(node, tag, offset);
 614
 615                         BUG_ON(ret && saw_unset_tag);
 616                         return !!ret;
 617                 }
 618                 node = rcu_dereference(node->slots[offset]);
 619                 shift -= RADIX_TREE_MAP_SHIFT;
 620                 height--;
 621         }
 622 }
 623 EXPORT_SYMBOL(radix_tree_tag_get);
 624 #endif
 625
 626 /**
 627  *      radix_tree_next_hole    -    find the next hole (not-present entry)
 628  *      @root:          tree root
 629  *      @index:         index key
 630  *      @max_scan:      maximum range to search
 631  *
 632  *      Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
 633  *      indexed hole.
 634  *
 635  *      Returns: the index of the hole if found, otherwise returns an index
 636  *      outside of the set specified (in which case 'return - index >= max_scan'
 637  *      will be true).
 638  *
 639  *      radix_tree_next_hole may be called under rcu_read_lock. However, like
 640  *      radix_tree_gang_lookup, this will not atomically search a snapshot of the
 641  *      tree at a single point in time. For example, if a hole is created at index
 642  *      5, then subsequently a hole is created at index 10, radix_tree_next_hole
 643  *      covering both indexes may return 10 if called under rcu_read_lock.
 644  */
 645 unsigned long radix_tree_next_hole(struct radix_tree_root *root,
 646                                 unsigned long index, unsigned long max_scan)
 647 {
 648         unsigned long i;
 649
 650         for (i = 0; i < max_scan; i++) {
 651                 if (!radix_tree_lookup(root, index))
 652                         break;
 653                 index++;
 654                 if (index == 0)
 655                         break;
 656         }
 657
 658         return index;
 659 }
 660 EXPORT_SYMBOL(radix_tree_next_hole);
 661
 662 static unsigned int
 663 __lookup(struct radix_tree_node *slot, void **results, unsigned long index,
 664         unsigned int max_items, unsigned long *next_index)
 665 {
 666         unsigned int nr_found = 0;
 667         unsigned int shift, height;
 668         unsigned long i;
 669
 670         height = slot->height;
 671         if (height == 0)
 672                 goto out;
 673         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 674
 675         for ( ; height > 1; height--) {
 676                 i = (index >> shift) & RADIX_TREE_MAP_MASK;
 677                 for (;;) {
 678                         if (slot->slots[i] != NULL)
 679                                 break;
 680                         index &= ~((1UL << shift) - 1);
 681                         index += 1UL << shift;
 682                         if (index == 0)
 683                                 goto out;       /* 32-bit wraparound */
 684                         i++;
 685                         if (i == RADIX_TREE_MAP_SIZE)
 686                                 goto out;
 687                 }
 688
 689                 shift -= RADIX_TREE_MAP_SHIFT;
 690                 slot = rcu_dereference(slot->slots[i]);
 691                 if (slot == NULL)
 692                         goto out;
 693         }
 694
 695         /* Bottom level: grab some items */
 696         for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
 697                 struct radix_tree_node *node;
 698                 index++;
 699                 node = slot->slots[i];
 700                 if (node) {
 701                         results[nr_found++] = rcu_dereference(node);
 702                         if (nr_found == max_items)
 703                                 goto out;
 704                 }
 705         }
 706 out:
 707         *next_index = index;
 708         return nr_found;
 709 }
 710
 711 /**
 712  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
 713  *      @root:          radix tree root
 714  *      @results:       where the results of the lookup are placed
 715  *      @first_index:   start the lookup from this key
 716  *      @max_items:     place up to this many items at *results
 717  *
 718  *      Performs an index-ascending scan of the tree for present items.  Places
 719  *      them at *@results and returns the number of items which were placed at
 720  *      *@results.
 721  *
 722  *      The implementation is naive.
 723  *
 724  *      Like radix_tree_lookup, radix_tree_gang_lookup may be called under
 725  *      rcu_read_lock. In this case, rather than the returned results being
 726  *      an atomic snapshot of the tree at a single point in time, the semantics
 727  *      of an RCU protected gang lookup are as though multiple radix_tree_lookups
 728  *      have been issued in individual locks, and results stored in 'results'.
 729  */
 730 unsigned int
 731 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 732                         unsigned long first_index, unsigned int max_items)
 733 {
 734         unsigned long max_index;
 735         struct radix_tree_node *node;
 736         unsigned long cur_index = first_index;
 737         unsigned int ret;
 738
 739         node = rcu_dereference(root->rnode);
 740         if (!node)
 741                 return 0;
 742
 743         if (!radix_tree_is_indirect_ptr(node)) {
 744                 if (first_index > 0)
 745                         return 0;
 746                 results[0] = node;
 747                 return 1;
 748         }
 749         node = radix_tree_indirect_to_ptr(node);
 750
 751         max_index = radix_tree_maxindex(node->height);
 752
 753         ret = 0;
 754         while (ret < max_items) {
 755                 unsigned int nr_found;
 756                 unsigned long next_index;       /* Index of next search */
 757
 758                 if (cur_index > max_index)
 759                         break;
 760                 nr_found = __lookup(node, results + ret, cur_index,
 761                                         max_items - ret, &next_index);
 762                 ret += nr_found;
 763                 if (next_index == 0)
 764                         break;
 765                 cur_index = next_index;
 766         }
 767
 768         return ret;
 769 }
 770 EXPORT_SYMBOL(radix_tree_gang_lookup);
 771
 772 /*
 773  * FIXME: the two tag_get()s here should use find_next_bit() instead of
 774  * open-coding the search.
 775  */
 776 static unsigned int
 777 __lookup_tag(struct radix_tree_node *slot, void **results, unsigned long index,
 778         unsigned int max_items, unsigned long *next_index, unsigned int tag)
 779 {
 780         unsigned int nr_found = 0;
 781         unsigned int shift, height;
 782
 783         height = slot->height;
 784         if (height == 0)
 785                 goto out;
 786         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 787
 788         while (height > 0) {
 789                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
 790
 791                 for (;;) {
 792                         if (tag_get(slot, tag, i))
 793                                 break;
 794                         index &= ~((1UL << shift) - 1);
 795                         index += 1UL << shift;
 796                         if (index == 0)
 797                                 goto out;       /* 32-bit wraparound */
 798                         i++;
 799                         if (i == RADIX_TREE_MAP_SIZE)
 800                                 goto out;
 801                 }
 802                 height--;
 803                 if (height == 0) {      /* Bottom level: grab some items */
 804                         unsigned long j = index & RADIX_TREE_MAP_MASK;
 805
 806                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
 807                                 struct radix_tree_node *node;
 808                                 index++;
 809                                 if (!tag_get(slot, tag, j))
 810                                         continue;
 811                                 node = slot->slots[j];
 812                                 /*
 813                                  * Even though the tag was found set, we need to
 814                                  * recheck that we have a non-NULL node, because
 815                                  * if this lookup is lockless, it may have been
 816                                  * subsequently deleted.
 817                                  *
 818                                  * Similar care must be taken in any place that
 819                                  * lookup ->slots[x] without a lock (ie. can't
 820                                  * rely on its value remaining the same).
 821                                  */
 822                                 if (node) {
 823                                         node = rcu_dereference(node);
 824                                         results[nr_found++] = node;
 825                                         if (nr_found == max_items)
 826                                                 goto out;
 827                                 }
 828                         }
 829                 }
 830                 shift -= RADIX_TREE_MAP_SHIFT;
 831                 slot = rcu_dereference(slot->slots[i]);
 832                 if (slot == NULL)
 833                         break;
 834         }
 835 out:
 836         *next_index = index;
 837         return nr_found;
 838 }
 839
 840 /**
 841  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
 842  *                                   based on a tag
 843  *      @root:          radix tree root
 844  *      @results:       where the results of the lookup are placed
 845  *      @first_index:   start the lookup from this key
 846  *      @max_items:     place up to this many items at *results
 847  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
 848  *
 849  *      Performs an index-ascending scan of the tree for present items which
 850  *      have the tag indexed by @tag set.  Places the items at *@results and
 851  *      returns the number of items which were placed at *@results.
 852  */
 853 unsigned int
 854 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
 855                 unsigned long first_index, unsigned int max_items,
 856                 unsigned int tag)
 857 {
 858         struct radix_tree_node *node;
 859         unsigned long max_index;
 860         unsigned long cur_index = first_index;
 861         unsigned int ret;
 862
 863         /* check the root's tag bit */
 864         if (!root_tag_get(root, tag))
 865                 return 0;
 866
 867         node = rcu_dereference(root->rnode);
 868         if (!node)
 869                 return 0;
 870
 871         if (!radix_tree_is_indirect_ptr(node)) {
 872                 if (first_index > 0)
 873                         return 0;
 874                 results[0] = node;
 875                 return 1;
 876         }
 877         node = radix_tree_indirect_to_ptr(node);
 878
 879         max_index = radix_tree_maxindex(node->height);
 880
 881         ret = 0;
 882         while (ret < max_items) {
 883                 unsigned int nr_found;
 884                 unsigned long next_index;       /* Index of next search */
 885
 886                 if (cur_index > max_index)
 887                         break;
 888                 nr_found = __lookup_tag(node, results + ret, cur_index,
 889                                         max_items - ret, &next_index, tag);
 890                 ret += nr_found;
 891                 if (next_index == 0)
 892                         break;
 893                 cur_index = next_index;
 894         }
 895
 896         return ret;
 897 }
 898 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
 899
 900 /**
 901  *      radix_tree_shrink    -    shrink height of a radix tree to minimal
 902  *      @root           radix tree root
 903  */
 904 static inline void radix_tree_shrink(struct radix_tree_root *root)
 905 {
 906         /* try to shrink tree height */
 907         while (root->height > 0) {
 908                 struct radix_tree_node *to_free = root->rnode;
 909                 void *newptr;
 910
 911                 BUG_ON(!radix_tree_is_indirect_ptr(to_free));
 912                 to_free = radix_tree_indirect_to_ptr(to_free);
 913
 914                 /*
 915                  * The candidate node has more than one child, or its child
 916                  * is not at the leftmost slot, we cannot shrink.
 917                  */
 918                 if (to_free->count != 1)
 919                         break;
 920                 if (!to_free->slots[0])
 921                         break;
 922
 923                 /*
 924                  * We don't need rcu_assign_pointer(), since we are simply
 925                  * moving the node from one part of the tree to another. If
 926                  * it was safe to dereference the old pointer to it
 927                  * (to_free->slots[0]), it will be safe to dereference the new
 928                  * one (root->rnode).
 929                  */
 930                 newptr = to_free->slots[0];
 931                 if (root->height > 1)
 932                         newptr = radix_tree_ptr_to_indirect(newptr);
 933                 root->rnode = newptr;
 934                 root->height--;
 935                 /* must only free zeroed nodes into the slab */
 936                 tag_clear(to_free, 0, 0);
 937                 tag_clear(to_free, 1, 0);
 938                 to_free->slots[0] = NULL;
 939                 to_free->count = 0;
 940                 radix_tree_node_free(to_free);
 941         }
 942 }
 943
 944 /**
 945  *      radix_tree_delete    -    delete an item from a radix tree
 946  *      @root:          radix tree root
 947  *      @index:         index key
 948  *
 949  *      Remove the item at @index from the radix tree rooted at @root.
 950  *
 951  *      Returns the address of the deleted item, or NULL if it was not present.
 952  */
 953 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 954 {
 955         /*
 956          * The radix tree path needs to be one longer than the maximum path
 957          * since the "list" is null terminated.
 958          */
 959         struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
 960         struct radix_tree_node *slot = NULL;
 961         struct radix_tree_node *to_free;
 962         unsigned int height, shift;
 963         int tag;
 964         int offset;
 965
 966         height = root->height;
 967         if (index > radix_tree_maxindex(height))
 968                 goto out;
 969
 970         slot = root->rnode;
 971         if (height == 0) {
 972                 root_tag_clear_all(root);
 973                 root->rnode = NULL;
 974                 goto out;
 975         }
 976         slot = radix_tree_indirect_to_ptr(slot);
 977
 978         shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 979         pathp->node = NULL;
 980
 981         do {
 982                 if (slot == NULL)
 983                         goto out;
 984
 985                 pathp++;
 986                 offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 987                 pathp->offset = offset;
 988                 pathp->node = slot;
 989                 slot = slot->slots[offset];
 990                 shift -= RADIX_TREE_MAP_SHIFT;
 991                 height--;
 992         } while (height > 0);
 993
 994         if (slot == NULL)
 995                 goto out;
 996
 997         /*
 998          * Clear all tags associated with the just-deleted item
 999          */
1000         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
1001                 if (tag_get(pathp->node, tag, pathp->offset))
1002                         radix_tree_tag_clear(root, index, tag);
1003         }
1004
1005         to_free = NULL;
1006         /* Now free the nodes we do not need anymore */
1007         while (pathp->node) {
1008                 pathp->node->slots[pathp->offset] = NULL;
1009                 pathp->node->count--;
1010                 /*
1011                  * Queue the node for deferred freeing after the
1012                  * last reference to it disappears (set NULL, above).
1013                  */
1014                 if (to_free)
1015                         radix_tree_node_free(to_free);
1016
1017                 if (pathp->node->count) {
1018                         if (pathp->node ==
1019                                         radix_tree_indirect_to_ptr(root->rnode))
1020                                 radix_tree_shrink(root);
1021                         goto out;
1022                 }
1023
1024                 /* Node with zero slots in use so free it */
1025                 to_free = pathp->node;
1026                 pathp--;
1027
1028         }
1029         root_tag_clear_all(root);
1030         root->height = 0;
1031         root->rnode = NULL;
1032         if (to_free)
1033                 radix_tree_node_free(to_free);
1034
1035 out:
1036         return slot;
1037 }
1038 EXPORT_SYMBOL(radix_tree_delete);
1039
1040 /**
1041  *      radix_tree_tagged - test whether any items in the tree are tagged
1042  *      @root:          radix tree root
1043  *      @tag:           tag to test
1044  */
1045 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
1046 {
1047         return root_tag_get(root, tag);
1048 }
1049 EXPORT_SYMBOL(radix_tree_tagged);
1050
1051 static void
1052 radix_tree_node_ctor(struct kmem_cache *cachep, void *node)
1053 {
1054         memset(node, 0, sizeof(struct radix_tree_node));
1055 }
1056
1057 static __init unsigned long __maxindex(unsigned int height)
1058 {
1059         unsigned int width = height * RADIX_TREE_MAP_SHIFT;
1060         int shift = RADIX_TREE_INDEX_BITS - width;
1061
1062         if (shift < 0)
1063                 return ~0UL;
1064         if (shift >= BITS_PER_LONG)
1065                 return 0UL;
1066         return ~0UL >> shift;
1067 }
1068
1069 static __init void radix_tree_init_maxindex(void)
1070 {
1071         unsigned int i;
1072
1073         for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
1074                 height_to_maxindex[i] = __maxindex(i);
1075 }
1076
1077 static int radix_tree_callback(struct notifier_block *nfb,
1078                             unsigned long action,
1079                             void *hcpu)
1080 {
1081        int cpu = (long)hcpu;
1082        struct radix_tree_preload *rtp;
1083
1084        /* Free per-cpu pool of perloaded nodes */
1085        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
1086                rtp = &per_cpu(radix_tree_preloads, cpu);
1087                while (rtp->nr) {
1088                        kmem_cache_free(radix_tree_node_cachep,
1089                                        rtp->nodes[rtp->nr-1]);
1090                        rtp->nodes[rtp->nr-1] = NULL;
1091                        rtp->nr--;
1092                }
1093        }
1094        return NOTIFY_OK;
1095 }
1096
1097 void __init radix_tree_init(void)
1098 {
1099         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1100                         sizeof(struct radix_tree_node), 0,
1101                         SLAB_PANIC, radix_tree_node_ctor);
1102         radix_tree_init_maxindex();
1103         hotcpu_notifier(radix_tree_callback, 0);
1104 }