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