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