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