lib/radix-tree.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
entry_to_node
node_to_entry
get_slot_offset
radix_tree_descend
root_gfp_mask
tag_set
tag_clear
tag_get
root_tag_set
root_tag_clear
root_tag_clear_all
root_tag_get
root_tags_get
is_idr
any_tag_set
all_tag_set
radix_tree_find_next_bit
iter_offset
shift_maxindex
node_maxindex
next_index
radix_tree_node_alloc
radix_tree_node_rcu_free
radix_tree_node_free
__radix_tree_preload
radix_tree_preload
radix_tree_maybe_preload
radix_tree_load_root
radix_tree_extend
radix_tree_shrink
delete_node
__radix_tree_create
radix_tree_free_nodes
insert_entries
radix_tree_insert
__radix_tree_lookup
radix_tree_lookup_slot
radix_tree_lookup
replace_slot
node_tag_get
calculate_count
__radix_tree_replace
radix_tree_replace_slot
radix_tree_iter_replace
node_tag_set
radix_tree_tag_set
node_tag_clear
radix_tree_tag_clear
radix_tree_iter_tag_clear
radix_tree_tag_get
set_iter_tags
radix_tree_iter_resume
radix_tree_next_chunk
radix_tree_gang_lookup
radix_tree_gang_lookup_tag
radix_tree_gang_lookup_tag_slot
__radix_tree_delete
radix_tree_iter_delete
radix_tree_delete_item
radix_tree_delete
radix_tree_tagged
idr_preload
idr_get_free
idr_destroy
radix_tree_node_ctor
radix_tree_cpu_dead
radix_tree_init
   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2001 Momchil Velikov
   4  * Portions Copyright (C) 2001 Christoph Hellwig
   5  * Copyright (C) 2005 SGI, Christoph Lameter
   6  * Copyright (C) 2006 Nick Piggin
   7  * Copyright (C) 2012 Konstantin Khlebnikov
   8  * Copyright (C) 2016 Intel, Matthew Wilcox
   9  * Copyright (C) 2016 Intel, Ross Zwisler
  10  */
  11 
  12 #include <linux/bitmap.h>
  13 #include <linux/bitops.h>
  14 #include <linux/bug.h>
  15 #include <linux/cpu.h>
  16 #include <linux/errno.h>
  17 #include <linux/export.h>
  18 #include <linux/idr.h>
  19 #include <linux/init.h>
  20 #include <linux/kernel.h>
  21 #include <linux/kmemleak.h>
  22 #include <linux/percpu.h>
  23 #include <linux/preempt.h>              /* in_interrupt() */
  24 #include <linux/radix-tree.h>
  25 #include <linux/rcupdate.h>
  26 #include <linux/slab.h>
  27 #include <linux/string.h>
  28 #include <linux/xarray.h>
  29 
  30 
  31 /*
  32  * Radix tree node cache.
  33  */
  34 struct kmem_cache *radix_tree_node_cachep;
  35 
  36 /*
  37  * The radix tree is variable-height, so an insert operation not only has
  38  * to build the branch to its corresponding item, it also has to build the
  39  * branch to existing items if the size has to be increased (by
  40  * radix_tree_extend).
  41  *
  42  * The worst case is a zero height tree with just a single item at index 0,
  43  * and then inserting an item at index ULONG_MAX. This requires 2 new branches
  44  * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
  45  * Hence:
  46  */
  47 #define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
  48 
  49 /*
  50  * The IDR does not have to be as high as the radix tree since it uses
  51  * signed integers, not unsigned longs.
  52  */
  53 #define IDR_INDEX_BITS          (8 /* CHAR_BIT */ * sizeof(int) - 1)
  54 #define IDR_MAX_PATH            (DIV_ROUND_UP(IDR_INDEX_BITS, \
  55                                                 RADIX_TREE_MAP_SHIFT))
  56 #define IDR_PRELOAD_SIZE        (IDR_MAX_PATH * 2 - 1)
  57 
  58 /*
  59  * The IDA is even shorter since it uses a bitmap at the last level.
  60  */
  61 #define IDA_INDEX_BITS          (8 * sizeof(int) - 1 - ilog2(IDA_BITMAP_BITS))
  62 #define IDA_MAX_PATH            (DIV_ROUND_UP(IDA_INDEX_BITS, \
  63                                                 RADIX_TREE_MAP_SHIFT))
  64 #define IDA_PRELOAD_SIZE        (IDA_MAX_PATH * 2 - 1)
  65 
  66 /*
  67  * Per-cpu pool of preloaded nodes
  68  */
  69 struct radix_tree_preload {
  70         unsigned nr;
  71         /* nodes->parent points to next preallocated node */
  72         struct radix_tree_node *nodes;
  73 };
  74 static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
  75 
  76 static inline struct radix_tree_node *entry_to_node(void *ptr)
  77 {
  78         return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
  79 }
  80 
  81 static inline void *node_to_entry(void *ptr)
  82 {
  83         return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
  84 }
  85 
  86 #define RADIX_TREE_RETRY        XA_RETRY_ENTRY
  87 
  88 static inline unsigned long
  89 get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
  90 {
  91         return parent ? slot - parent->slots : 0;
  92 }
  93 
  94 static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
  95                         struct radix_tree_node **nodep, unsigned long index)
  96 {
  97         unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
  98         void __rcu **entry = rcu_dereference_raw(parent->slots[offset]);
  99 
 100         *nodep = (void *)entry;
 101         return offset;
 102 }
 103 
 104 static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
 105 {
 106         return root->xa_flags & (__GFP_BITS_MASK & ~GFP_ZONEMASK);
 107 }
 108 
 109 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
 110                 int offset)
 111 {
 112         __set_bit(offset, node->tags[tag]);
 113 }
 114 
 115 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
 116                 int offset)
 117 {
 118         __clear_bit(offset, node->tags[tag]);
 119 }
 120 
 121 static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
 122                 int offset)
 123 {
 124         return test_bit(offset, node->tags[tag]);
 125 }
 126 
 127 static inline void root_tag_set(struct radix_tree_root *root, unsigned tag)
 128 {
 129         root->xa_flags |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT));
 130 }
 131 
 132 static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
 133 {
 134         root->xa_flags &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT));
 135 }
 136 
 137 static inline void root_tag_clear_all(struct radix_tree_root *root)
 138 {
 139         root->xa_flags &= (__force gfp_t)((1 << ROOT_TAG_SHIFT) - 1);
 140 }
 141 
 142 static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag)
 143 {
 144         return (__force int)root->xa_flags & (1 << (tag + ROOT_TAG_SHIFT));
 145 }
 146 
 147 static inline unsigned root_tags_get(const struct radix_tree_root *root)
 148 {
 149         return (__force unsigned)root->xa_flags >> ROOT_TAG_SHIFT;
 150 }
 151 
 152 static inline bool is_idr(const struct radix_tree_root *root)
 153 {
 154         return !!(root->xa_flags & ROOT_IS_IDR);
 155 }
 156 
 157 /*
 158  * Returns 1 if any slot in the node has this tag set.
 159  * Otherwise returns 0.
 160  */
 161 static inline int any_tag_set(const struct radix_tree_node *node,
 162                                                         unsigned int tag)
 163 {
 164         unsigned idx;
 165         for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
 166                 if (node->tags[tag][idx])
 167                         return 1;
 168         }
 169         return 0;
 170 }
 171 
 172 static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag)
 173 {
 174         bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE);
 175 }
 176 
 177 /**
 178  * radix_tree_find_next_bit - find the next set bit in a memory region
 179  *
 180  * @addr: The address to base the search on
 181  * @size: The bitmap size in bits
 182  * @offset: The bitnumber to start searching at
 183  *
 184  * Unrollable variant of find_next_bit() for constant size arrays.
 185  * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
 186  * Returns next bit offset, or size if nothing found.
 187  */
 188 static __always_inline unsigned long
 189 radix_tree_find_next_bit(struct radix_tree_node *node, unsigned int tag,
 190                          unsigned long offset)
 191 {
 192         const unsigned long *addr = node->tags[tag];
 193 
 194         if (offset < RADIX_TREE_MAP_SIZE) {
 195                 unsigned long tmp;
 196 
 197                 addr += offset / BITS_PER_LONG;
 198                 tmp = *addr >> (offset % BITS_PER_LONG);
 199                 if (tmp)
 200                         return __ffs(tmp) + offset;
 201                 offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
 202                 while (offset < RADIX_TREE_MAP_SIZE) {
 203                         tmp = *++addr;
 204                         if (tmp)
 205                                 return __ffs(tmp) + offset;
 206                         offset += BITS_PER_LONG;
 207                 }
 208         }
 209         return RADIX_TREE_MAP_SIZE;
 210 }
 211 
 212 static unsigned int iter_offset(const struct radix_tree_iter *iter)
 213 {
 214         return iter->index & RADIX_TREE_MAP_MASK;
 215 }
 216 
 217 /*
 218  * The maximum index which can be stored in a radix tree
 219  */
 220 static inline unsigned long shift_maxindex(unsigned int shift)
 221 {
 222         return (RADIX_TREE_MAP_SIZE << shift) - 1;
 223 }
 224 
 225 static inline unsigned long node_maxindex(const struct radix_tree_node *node)
 226 {
 227         return shift_maxindex(node->shift);
 228 }
 229 
 230 static unsigned long next_index(unsigned long index,
 231                                 const struct radix_tree_node *node,
 232                                 unsigned long offset)
 233 {
 234         return (index & ~node_maxindex(node)) + (offset << node->shift);
 235 }
 236 
 237 /*
 238  * This assumes that the caller has performed appropriate preallocation, and
 239  * that the caller has pinned this thread of control to the current CPU.
 240  */
 241 static struct radix_tree_node *
 242 radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
 243                         struct radix_tree_root *root,
 244                         unsigned int shift, unsigned int offset,
 245                         unsigned int count, unsigned int nr_values)
 246 {
 247         struct radix_tree_node *ret = NULL;
 248 
 249         /*
 250          * Preload code isn't irq safe and it doesn't make sense to use
 251          * preloading during an interrupt anyway as all the allocations have
 252          * to be atomic. So just do normal allocation when in interrupt.
 253          */
 254         if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
 255                 struct radix_tree_preload *rtp;
 256 
 257                 /*
 258                  * Even if the caller has preloaded, try to allocate from the
 259                  * cache first for the new node to get accounted to the memory
 260                  * cgroup.
 261                  */
 262                 ret = kmem_cache_alloc(radix_tree_node_cachep,
 263                                        gfp_mask | __GFP_NOWARN);
 264                 if (ret)
 265                         goto out;
 266 
 267                 /*
 268                  * Provided the caller has preloaded here, we will always
 269                  * succeed in getting a node here (and never reach
 270                  * kmem_cache_alloc)
 271                  */
 272                 rtp = this_cpu_ptr(&radix_tree_preloads);
 273                 if (rtp->nr) {
 274                         ret = rtp->nodes;
 275                         rtp->nodes = ret->parent;
 276                         rtp->nr--;
 277                 }
 278                 /*
 279                  * Update the allocation stack trace as this is more useful
 280                  * for debugging.
 281                  */
 282                 kmemleak_update_trace(ret);
 283                 goto out;
 284         }
 285         ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 286 out:
 287         BUG_ON(radix_tree_is_internal_node(ret));
 288         if (ret) {
 289                 ret->shift = shift;
 290                 ret->offset = offset;
 291                 ret->count = count;
 292                 ret->nr_values = nr_values;
 293                 ret->parent = parent;
 294                 ret->array = root;
 295         }
 296         return ret;
 297 }
 298 
 299 void radix_tree_node_rcu_free(struct rcu_head *head)
 300 {
 301         struct radix_tree_node *node =
 302                         container_of(head, struct radix_tree_node, rcu_head);
 303 
 304         /*
 305          * Must only free zeroed nodes into the slab.  We can be left with
 306          * non-NULL entries by radix_tree_free_nodes, so clear the entries
 307          * and tags here.
 308          */
 309         memset(node->slots, 0, sizeof(node->slots));
 310         memset(node->tags, 0, sizeof(node->tags));
 311         INIT_LIST_HEAD(&node->private_list);
 312 
 313         kmem_cache_free(radix_tree_node_cachep, node);
 314 }
 315 
 316 static inline void
 317 radix_tree_node_free(struct radix_tree_node *node)
 318 {
 319         call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
 320 }
 321 
 322 /*
 323  * Load up this CPU's radix_tree_node buffer with sufficient objects to
 324  * ensure that the addition of a single element in the tree cannot fail.  On
 325  * success, return zero, with preemption disabled.  On error, return -ENOMEM
 326  * with preemption not disabled.
 327  *
 328  * To make use of this facility, the radix tree must be initialised without
 329  * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
 330  */
 331 static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
 332 {
 333         struct radix_tree_preload *rtp;
 334         struct radix_tree_node *node;
 335         int ret = -ENOMEM;
 336 
 337         /*
 338          * Nodes preloaded by one cgroup can be be used by another cgroup, so
 339          * they should never be accounted to any particular memory cgroup.
 340          */
 341         gfp_mask &= ~__GFP_ACCOUNT;
 342 
 343         preempt_disable();
 344         rtp = this_cpu_ptr(&radix_tree_preloads);
 345         while (rtp->nr < nr) {
 346                 preempt_enable();
 347                 node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 348                 if (node == NULL)
 349                         goto out;
 350                 preempt_disable();
 351                 rtp = this_cpu_ptr(&radix_tree_preloads);
 352                 if (rtp->nr < nr) {
 353                         node->parent = rtp->nodes;
 354                         rtp->nodes = node;
 355                         rtp->nr++;
 356                 } else {
 357                         kmem_cache_free(radix_tree_node_cachep, node);
 358                 }
 359         }
 360         ret = 0;
 361 out:
 362         return ret;
 363 }
 364 
 365 /*
 366  * Load up this CPU's radix_tree_node buffer with sufficient objects to
 367  * ensure that the addition of a single element in the tree cannot fail.  On
 368  * success, return zero, with preemption disabled.  On error, return -ENOMEM
 369  * with preemption not disabled.
 370  *
 371  * To make use of this facility, the radix tree must be initialised without
 372  * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
 373  */
 374 int radix_tree_preload(gfp_t gfp_mask)
 375 {
 376         /* Warn on non-sensical use... */
 377         WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
 378         return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
 379 }
 380 EXPORT_SYMBOL(radix_tree_preload);
 381 
 382 /*
 383  * The same as above function, except we don't guarantee preloading happens.
 384  * We do it, if we decide it helps. On success, return zero with preemption
 385  * disabled. On error, return -ENOMEM with preemption not disabled.
 386  */
 387 int radix_tree_maybe_preload(gfp_t gfp_mask)
 388 {
 389         if (gfpflags_allow_blocking(gfp_mask))
 390                 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
 391         /* Preloading doesn't help anything with this gfp mask, skip it */
 392         preempt_disable();
 393         return 0;
 394 }
 395 EXPORT_SYMBOL(radix_tree_maybe_preload);
 396 
 397 static unsigned radix_tree_load_root(const struct radix_tree_root *root,
 398                 struct radix_tree_node **nodep, unsigned long *maxindex)
 399 {
 400         struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
 401 
 402         *nodep = node;
 403 
 404         if (likely(radix_tree_is_internal_node(node))) {
 405                 node = entry_to_node(node);
 406                 *maxindex = node_maxindex(node);
 407                 return node->shift + RADIX_TREE_MAP_SHIFT;
 408         }
 409 
 410         *maxindex = 0;
 411         return 0;
 412 }
 413 
 414 /*
 415  *      Extend a radix tree so it can store key @index.
 416  */
 417 static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
 418                                 unsigned long index, unsigned int shift)
 419 {
 420         void *entry;
 421         unsigned int maxshift;
 422         int tag;
 423 
 424         /* Figure out what the shift should be.  */
 425         maxshift = shift;
 426         while (index > shift_maxindex(maxshift))
 427                 maxshift += RADIX_TREE_MAP_SHIFT;
 428 
 429         entry = rcu_dereference_raw(root->xa_head);
 430         if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE)))
 431                 goto out;
 432 
 433         do {
 434                 struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
 435                                                         root, shift, 0, 1, 0);
 436                 if (!node)
 437                         return -ENOMEM;
 438 
 439                 if (is_idr(root)) {
 440                         all_tag_set(node, IDR_FREE);
 441                         if (!root_tag_get(root, IDR_FREE)) {
 442                                 tag_clear(node, IDR_FREE, 0);
 443                                 root_tag_set(root, IDR_FREE);
 444                         }
 445                 } else {
 446                         /* Propagate the aggregated tag info to the new child */
 447                         for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
 448                                 if (root_tag_get(root, tag))
 449                                         tag_set(node, tag, 0);
 450                         }
 451                 }
 452 
 453                 BUG_ON(shift > BITS_PER_LONG);
 454                 if (radix_tree_is_internal_node(entry)) {
 455                         entry_to_node(entry)->parent = node;
 456                 } else if (xa_is_value(entry)) {
 457                         /* Moving a value entry root->xa_head to a node */
 458                         node->nr_values = 1;
 459                 }
 460                 /*
 461                  * entry was already in the radix tree, so we do not need
 462                  * rcu_assign_pointer here
 463                  */
 464                 node->slots[0] = (void __rcu *)entry;
 465                 entry = node_to_entry(node);
 466                 rcu_assign_pointer(root->xa_head, entry);
 467                 shift += RADIX_TREE_MAP_SHIFT;
 468         } while (shift <= maxshift);
 469 out:
 470         return maxshift + RADIX_TREE_MAP_SHIFT;
 471 }
 472 
 473 /**
 474  *      radix_tree_shrink    -    shrink radix tree to minimum height
 475  *      @root           radix tree root
 476  */
 477 static inline bool radix_tree_shrink(struct radix_tree_root *root)
 478 {
 479         bool shrunk = false;
 480 
 481         for (;;) {
 482                 struct radix_tree_node *node = rcu_dereference_raw(root->xa_head);
 483                 struct radix_tree_node *child;
 484 
 485                 if (!radix_tree_is_internal_node(node))
 486                         break;
 487                 node = entry_to_node(node);
 488 
 489                 /*
 490                  * The candidate node has more than one child, or its child
 491                  * is not at the leftmost slot, we cannot shrink.
 492                  */
 493                 if (node->count != 1)
 494                         break;
 495                 child = rcu_dereference_raw(node->slots[0]);
 496                 if (!child)
 497                         break;
 498 
 499                 /*
 500                  * For an IDR, we must not shrink entry 0 into the root in
 501                  * case somebody calls idr_replace() with a pointer that
 502                  * appears to be an internal entry
 503                  */
 504                 if (!node->shift && is_idr(root))
 505                         break;
 506 
 507                 if (radix_tree_is_internal_node(child))
 508                         entry_to_node(child)->parent = NULL;
 509 
 510                 /*
 511                  * We don't need rcu_assign_pointer(), since we are simply
 512                  * moving the node from one part of the tree to another: if it
 513                  * was safe to dereference the old pointer to it
 514                  * (node->slots[0]), it will be safe to dereference the new
 515                  * one (root->xa_head) as far as dependent read barriers go.
 516                  */
 517                 root->xa_head = (void __rcu *)child;
 518                 if (is_idr(root) && !tag_get(node, IDR_FREE, 0))
 519                         root_tag_clear(root, IDR_FREE);
 520 
 521                 /*
 522                  * We have a dilemma here. The node's slot[0] must not be
 523                  * NULLed in case there are concurrent lookups expecting to
 524                  * find the item. However if this was a bottom-level node,
 525                  * then it may be subject to the slot pointer being visible
 526                  * to callers dereferencing it. If item corresponding to
 527                  * slot[0] is subsequently deleted, these callers would expect
 528                  * their slot to become empty sooner or later.
 529                  *
 530                  * For example, lockless pagecache will look up a slot, deref
 531                  * the page pointer, and if the page has 0 refcount it means it
 532                  * was concurrently deleted from pagecache so try the deref
 533                  * again. Fortunately there is already a requirement for logic
 534                  * to retry the entire slot lookup -- the indirect pointer
 535                  * problem (replacing direct root node with an indirect pointer
 536                  * also results in a stale slot). So tag the slot as indirect
 537                  * to force callers to retry.
 538                  */
 539                 node->count = 0;
 540                 if (!radix_tree_is_internal_node(child)) {
 541                         node->slots[0] = (void __rcu *)RADIX_TREE_RETRY;
 542                 }
 543 
 544                 WARN_ON_ONCE(!list_empty(&node->private_list));
 545                 radix_tree_node_free(node);
 546                 shrunk = true;
 547         }
 548 
 549         return shrunk;
 550 }
 551 
 552 static bool delete_node(struct radix_tree_root *root,
 553                         struct radix_tree_node *node)
 554 {
 555         bool deleted = false;
 556 
 557         do {
 558                 struct radix_tree_node *parent;
 559 
 560                 if (node->count) {
 561                         if (node_to_entry(node) ==
 562                                         rcu_dereference_raw(root->xa_head))
 563                                 deleted |= radix_tree_shrink(root);
 564                         return deleted;
 565                 }
 566 
 567                 parent = node->parent;
 568                 if (parent) {
 569                         parent->slots[node->offset] = NULL;
 570                         parent->count--;
 571                 } else {
 572                         /*
 573                          * Shouldn't the tags already have all been cleared
 574                          * by the caller?
 575                          */
 576                         if (!is_idr(root))
 577                                 root_tag_clear_all(root);
 578                         root->xa_head = NULL;
 579                 }
 580 
 581                 WARN_ON_ONCE(!list_empty(&node->private_list));
 582                 radix_tree_node_free(node);
 583                 deleted = true;
 584 
 585                 node = parent;
 586         } while (node);
 587 
 588         return deleted;
 589 }
 590 
 591 /**
 592  *      __radix_tree_create     -       create a slot in a radix tree
 593  *      @root:          radix tree root
 594  *      @index:         index key
 595  *      @nodep:         returns node
 596  *      @slotp:         returns slot
 597  *
 598  *      Create, if necessary, and return the node and slot for an item
 599  *      at position @index in the radix tree @root.
 600  *
 601  *      Until there is more than one item in the tree, no nodes are
 602  *      allocated and @root->xa_head is used as a direct slot instead of
 603  *      pointing to a node, in which case *@nodep will be NULL.
 604  *
 605  *      Returns -ENOMEM, or 0 for success.
 606  */
 607 static int __radix_tree_create(struct radix_tree_root *root,
 608                 unsigned long index, struct radix_tree_node **nodep,
 609                 void __rcu ***slotp)
 610 {
 611         struct radix_tree_node *node = NULL, *child;
 612         void __rcu **slot = (void __rcu **)&root->xa_head;
 613         unsigned long maxindex;
 614         unsigned int shift, offset = 0;
 615         unsigned long max = index;
 616         gfp_t gfp = root_gfp_mask(root);
 617 
 618         shift = radix_tree_load_root(root, &child, &maxindex);
 619 
 620         /* Make sure the tree is high enough.  */
 621         if (max > maxindex) {
 622                 int error = radix_tree_extend(root, gfp, max, shift);
 623                 if (error < 0)
 624                         return error;
 625                 shift = error;
 626                 child = rcu_dereference_raw(root->xa_head);
 627         }
 628 
 629         while (shift > 0) {
 630                 shift -= RADIX_TREE_MAP_SHIFT;
 631                 if (child == NULL) {
 632                         /* Have to add a child node.  */
 633                         child = radix_tree_node_alloc(gfp, node, root, shift,
 634                                                         offset, 0, 0);
 635                         if (!child)
 636                                 return -ENOMEM;
 637                         rcu_assign_pointer(*slot, node_to_entry(child));
 638                         if (node)
 639                                 node->count++;
 640                 } else if (!radix_tree_is_internal_node(child))
 641                         break;
 642 
 643                 /* Go a level down */
 644                 node = entry_to_node(child);
 645                 offset = radix_tree_descend(node, &child, index);
 646                 slot = &node->slots[offset];
 647         }
 648 
 649         if (nodep)
 650                 *nodep = node;
 651         if (slotp)
 652                 *slotp = slot;
 653         return 0;
 654 }
 655 
 656 /*
 657  * Free any nodes below this node.  The tree is presumed to not need
 658  * shrinking, and any user data in the tree is presumed to not need a
 659  * destructor called on it.  If we need to add a destructor, we can
 660  * add that functionality later.  Note that we may not clear tags or
 661  * slots from the tree as an RCU walker may still have a pointer into
 662  * this subtree.  We could replace the entries with RADIX_TREE_RETRY,
 663  * but we'll still have to clear those in rcu_free.
 664  */
 665 static void radix_tree_free_nodes(struct radix_tree_node *node)
 666 {
 667         unsigned offset = 0;
 668         struct radix_tree_node *child = entry_to_node(node);
 669 
 670         for (;;) {
 671                 void *entry = rcu_dereference_raw(child->slots[offset]);
 672                 if (xa_is_node(entry) && child->shift) {
 673                         child = entry_to_node(entry);
 674                         offset = 0;
 675                         continue;
 676                 }
 677                 offset++;
 678                 while (offset == RADIX_TREE_MAP_SIZE) {
 679                         struct radix_tree_node *old = child;
 680                         offset = child->offset + 1;
 681                         child = child->parent;
 682                         WARN_ON_ONCE(!list_empty(&old->private_list));
 683                         radix_tree_node_free(old);
 684                         if (old == entry_to_node(node))
 685                                 return;
 686                 }
 687         }
 688 }
 689 
 690 static inline int insert_entries(struct radix_tree_node *node,
 691                 void __rcu **slot, void *item, bool replace)
 692 {
 693         if (*slot)
 694                 return -EEXIST;
 695         rcu_assign_pointer(*slot, item);
 696         if (node) {
 697                 node->count++;
 698                 if (xa_is_value(item))
 699                         node->nr_values++;
 700         }
 701         return 1;
 702 }
 703 
 704 /**
 705  *      __radix_tree_insert    -    insert into a radix tree
 706  *      @root:          radix tree root
 707  *      @index:         index key
 708  *      @item:          item to insert
 709  *
 710  *      Insert an item into the radix tree at position @index.
 711  */
 712 int radix_tree_insert(struct radix_tree_root *root, unsigned long index,
 713                         void *item)
 714 {
 715         struct radix_tree_node *node;
 716         void __rcu **slot;
 717         int error;
 718 
 719         BUG_ON(radix_tree_is_internal_node(item));
 720 
 721         error = __radix_tree_create(root, index, &node, &slot);
 722         if (error)
 723                 return error;
 724 
 725         error = insert_entries(node, slot, item, false);
 726         if (error < 0)
 727                 return error;
 728 
 729         if (node) {
 730                 unsigned offset = get_slot_offset(node, slot);
 731                 BUG_ON(tag_get(node, 0, offset));
 732                 BUG_ON(tag_get(node, 1, offset));
 733                 BUG_ON(tag_get(node, 2, offset));
 734         } else {
 735                 BUG_ON(root_tags_get(root));
 736         }
 737 
 738         return 0;
 739 }
 740 EXPORT_SYMBOL(radix_tree_insert);
 741 
 742 /**
 743  *      __radix_tree_lookup     -       lookup an item in a radix tree
 744  *      @root:          radix tree root
 745  *      @index:         index key
 746  *      @nodep:         returns node
 747  *      @slotp:         returns slot
 748  *
 749  *      Lookup and return the item at position @index in the radix
 750  *      tree @root.
 751  *
 752  *      Until there is more than one item in the tree, no nodes are
 753  *      allocated and @root->xa_head is used as a direct slot instead of
 754  *      pointing to a node, in which case *@nodep will be NULL.
 755  */
 756 void *__radix_tree_lookup(const struct radix_tree_root *root,
 757                           unsigned long index, struct radix_tree_node **nodep,
 758                           void __rcu ***slotp)
 759 {
 760         struct radix_tree_node *node, *parent;
 761         unsigned long maxindex;
 762         void __rcu **slot;
 763 
 764  restart:
 765         parent = NULL;
 766         slot = (void __rcu **)&root->xa_head;
 767         radix_tree_load_root(root, &node, &maxindex);
 768         if (index > maxindex)
 769                 return NULL;
 770 
 771         while (radix_tree_is_internal_node(node)) {
 772                 unsigned offset;
 773 
 774                 parent = entry_to_node(node);
 775                 offset = radix_tree_descend(parent, &node, index);
 776                 slot = parent->slots + offset;
 777                 if (node == RADIX_TREE_RETRY)
 778                         goto restart;
 779                 if (parent->shift == 0)
 780                         break;
 781         }
 782 
 783         if (nodep)
 784                 *nodep = parent;
 785         if (slotp)
 786                 *slotp = slot;
 787         return node;
 788 }
 789 
 790 /**
 791  *      radix_tree_lookup_slot    -    lookup a slot in a radix tree
 792  *      @root:          radix tree root
 793  *      @index:         index key
 794  *
 795  *      Returns:  the slot corresponding to the position @index in the
 796  *      radix tree @root. This is useful for update-if-exists operations.
 797  *
 798  *      This function can be called under rcu_read_lock iff the slot is not
 799  *      modified by radix_tree_replace_slot, otherwise it must be called
 800  *      exclusive from other writers. Any dereference of the slot must be done
 801  *      using radix_tree_deref_slot.
 802  */
 803 void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *root,
 804                                 unsigned long index)
 805 {
 806         void __rcu **slot;
 807 
 808         if (!__radix_tree_lookup(root, index, NULL, &slot))
 809                 return NULL;
 810         return slot;
 811 }
 812 EXPORT_SYMBOL(radix_tree_lookup_slot);
 813 
 814 /**
 815  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 816  *      @root:          radix tree root
 817  *      @index:         index key
 818  *
 819  *      Lookup the item at the position @index in the radix tree @root.
 820  *
 821  *      This function can be called under rcu_read_lock, however the caller
 822  *      must manage lifetimes of leaf nodes (eg. RCU may also be used to free
 823  *      them safely). No RCU barriers are required to access or modify the
 824  *      returned item, however.
 825  */
 826 void *radix_tree_lookup(const struct radix_tree_root *root, unsigned long index)
 827 {
 828         return __radix_tree_lookup(root, index, NULL, NULL);
 829 }
 830 EXPORT_SYMBOL(radix_tree_lookup);
 831 
 832 static void replace_slot(void __rcu **slot, void *item,
 833                 struct radix_tree_node *node, int count, int values)
 834 {
 835         if (node && (count || values)) {
 836                 node->count += count;
 837                 node->nr_values += values;
 838         }
 839 
 840         rcu_assign_pointer(*slot, item);
 841 }
 842 
 843 static bool node_tag_get(const struct radix_tree_root *root,
 844                                 const struct radix_tree_node *node,
 845                                 unsigned int tag, unsigned int offset)
 846 {
 847         if (node)
 848                 return tag_get(node, tag, offset);
 849         return root_tag_get(root, tag);
 850 }
 851 
 852 /*
 853  * IDR users want to be able to store NULL in the tree, so if the slot isn't
 854  * free, don't adjust the count, even if it's transitioning between NULL and
 855  * non-NULL.  For the IDA, we mark slots as being IDR_FREE while they still
 856  * have empty bits, but it only stores NULL in slots when they're being
 857  * deleted.
 858  */
 859 static int calculate_count(struct radix_tree_root *root,
 860                                 struct radix_tree_node *node, void __rcu **slot,
 861                                 void *item, void *old)
 862 {
 863         if (is_idr(root)) {
 864                 unsigned offset = get_slot_offset(node, slot);
 865                 bool free = node_tag_get(root, node, IDR_FREE, offset);
 866                 if (!free)
 867                         return 0;
 868                 if (!old)
 869                         return 1;
 870         }
 871         return !!item - !!old;
 872 }
 873 
 874 /**
 875  * __radix_tree_replace         - replace item in a slot
 876  * @root:               radix tree root
 877  * @node:               pointer to tree node
 878  * @slot:               pointer to slot in @node
 879  * @item:               new item to store in the slot.
 880  *
 881  * For use with __radix_tree_lookup().  Caller must hold tree write locked
 882  * across slot lookup and replacement.
 883  */
 884 void __radix_tree_replace(struct radix_tree_root *root,
 885                           struct radix_tree_node *node,
 886                           void __rcu **slot, void *item)
 887 {
 888         void *old = rcu_dereference_raw(*slot);
 889         int values = !!xa_is_value(item) - !!xa_is_value(old);
 890         int count = calculate_count(root, node, slot, item, old);
 891 
 892         /*
 893          * This function supports replacing value entries and
 894          * deleting entries, but that needs accounting against the
 895          * node unless the slot is root->xa_head.
 896          */
 897         WARN_ON_ONCE(!node && (slot != (void __rcu **)&root->xa_head) &&
 898                         (count || values));
 899         replace_slot(slot, item, node, count, values);
 900 
 901         if (!node)
 902                 return;
 903 
 904         delete_node(root, node);
 905 }
 906 
 907 /**
 908  * radix_tree_replace_slot      - replace item in a slot
 909  * @root:       radix tree root
 910  * @slot:       pointer to slot
 911  * @item:       new item to store in the slot.
 912  *
 913  * For use with radix_tree_lookup_slot() and
 914  * radix_tree_gang_lookup_tag_slot().  Caller must hold tree write locked
 915  * across slot lookup and replacement.
 916  *
 917  * NOTE: This cannot be used to switch between non-entries (empty slots),
 918  * regular entries, and value entries, as that requires accounting
 919  * inside the radix tree node. When switching from one type of entry or
 920  * deleting, use __radix_tree_lookup() and __radix_tree_replace() or
 921  * radix_tree_iter_replace().
 922  */
 923 void radix_tree_replace_slot(struct radix_tree_root *root,
 924                              void __rcu **slot, void *item)
 925 {
 926         __radix_tree_replace(root, NULL, slot, item);
 927 }
 928 EXPORT_SYMBOL(radix_tree_replace_slot);
 929 
 930 /**
 931  * radix_tree_iter_replace - replace item in a slot
 932  * @root:       radix tree root
 933  * @slot:       pointer to slot
 934  * @item:       new item to store in the slot.
 935  *
 936  * For use with radix_tree_for_each_slot().
 937  * Caller must hold tree write locked.
 938  */
 939 void radix_tree_iter_replace(struct radix_tree_root *root,
 940                                 const struct radix_tree_iter *iter,
 941                                 void __rcu **slot, void *item)
 942 {
 943         __radix_tree_replace(root, iter->node, slot, item);
 944 }
 945 
 946 static void node_tag_set(struct radix_tree_root *root,
 947                                 struct radix_tree_node *node,
 948                                 unsigned int tag, unsigned int offset)
 949 {
 950         while (node) {
 951                 if (tag_get(node, tag, offset))
 952                         return;
 953                 tag_set(node, tag, offset);
 954                 offset = node->offset;
 955                 node = node->parent;
 956         }
 957 
 958         if (!root_tag_get(root, tag))
 959                 root_tag_set(root, tag);
 960 }
 961 
 962 /**
 963  *      radix_tree_tag_set - set a tag on a radix tree node
 964  *      @root:          radix tree root
 965  *      @index:         index key
 966  *      @tag:           tag index
 967  *
 968  *      Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
 969  *      corresponding to @index in the radix tree.  From
 970  *      the root all the way down to the leaf node.
 971  *
 972  *      Returns the address of the tagged item.  Setting a tag on a not-present
 973  *      item is a bug.
 974  */
 975 void *radix_tree_tag_set(struct radix_tree_root *root,
 976                         unsigned long index, unsigned int tag)
 977 {
 978         struct radix_tree_node *node, *parent;
 979         unsigned long maxindex;
 980 
 981         radix_tree_load_root(root, &node, &maxindex);
 982         BUG_ON(index > maxindex);
 983 
 984         while (radix_tree_is_internal_node(node)) {
 985                 unsigned offset;
 986 
 987                 parent = entry_to_node(node);
 988                 offset = radix_tree_descend(parent, &node, index);
 989                 BUG_ON(!node);
 990 
 991                 if (!tag_get(parent, tag, offset))
 992                         tag_set(parent, tag, offset);
 993         }
 994 
 995         /* set the root's tag bit */
 996         if (!root_tag_get(root, tag))
 997                 root_tag_set(root, tag);
 998 
 999         return node;
1000 }
1001 EXPORT_SYMBOL(radix_tree_tag_set);
1002 
1003 static void node_tag_clear(struct radix_tree_root *root,
1004                                 struct radix_tree_node *node,
1005                                 unsigned int tag, unsigned int offset)
1006 {
1007         while (node) {
1008                 if (!tag_get(node, tag, offset))
1009                         return;
1010                 tag_clear(node, tag, offset);
1011                 if (any_tag_set(node, tag))
1012                         return;
1013 
1014                 offset = node->offset;
1015                 node = node->parent;
1016         }
1017 
1018         /* clear the root's tag bit */
1019         if (root_tag_get(root, tag))
1020                 root_tag_clear(root, tag);
1021 }
1022 
1023 /**
1024  *      radix_tree_tag_clear - clear a tag on a radix tree node
1025  *      @root:          radix tree root
1026  *      @index:         index key
1027  *      @tag:           tag index
1028  *
1029  *      Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
1030  *      corresponding to @index in the radix tree.  If this causes
1031  *      the leaf node to have no tags set then clear the tag in the
1032  *      next-to-leaf node, etc.
1033  *
1034  *      Returns the address of the tagged item on success, else NULL.  ie:
1035  *      has the same return value and semantics as radix_tree_lookup().
1036  */
1037 void *radix_tree_tag_clear(struct radix_tree_root *root,
1038                         unsigned long index, unsigned int tag)
1039 {
1040         struct radix_tree_node *node, *parent;
1041         unsigned long maxindex;
1042         int uninitialized_var(offset);
1043 
1044         radix_tree_load_root(root, &node, &maxindex);
1045         if (index > maxindex)
1046                 return NULL;
1047 
1048         parent = NULL;
1049 
1050         while (radix_tree_is_internal_node(node)) {
1051                 parent = entry_to_node(node);
1052                 offset = radix_tree_descend(parent, &node, index);
1053         }
1054 
1055         if (node)
1056                 node_tag_clear(root, parent, tag, offset);
1057 
1058         return node;
1059 }
1060 EXPORT_SYMBOL(radix_tree_tag_clear);
1061 
1062 /**
1063   * radix_tree_iter_tag_clear - clear a tag on the current iterator entry
1064   * @root: radix tree root
1065   * @iter: iterator state
1066   * @tag: tag to clear
1067   */
1068 void radix_tree_iter_tag_clear(struct radix_tree_root *root,
1069                         const struct radix_tree_iter *iter, unsigned int tag)
1070 {
1071         node_tag_clear(root, iter->node, tag, iter_offset(iter));
1072 }
1073 
1074 /**
1075  * radix_tree_tag_get - get a tag on a radix tree node
1076  * @root:               radix tree root
1077  * @index:              index key
1078  * @tag:                tag index (< RADIX_TREE_MAX_TAGS)
1079  *
1080  * Return values:
1081  *
1082  *  0: tag not present or not set
1083  *  1: tag set
1084  *
1085  * Note that the return value of this function may not be relied on, even if
1086  * the RCU lock is held, unless tag modification and node deletion are excluded
1087  * from concurrency.
1088  */
1089 int radix_tree_tag_get(const struct radix_tree_root *root,
1090                         unsigned long index, unsigned int tag)
1091 {
1092         struct radix_tree_node *node, *parent;
1093         unsigned long maxindex;
1094 
1095         if (!root_tag_get(root, tag))
1096                 return 0;
1097 
1098         radix_tree_load_root(root, &node, &maxindex);
1099         if (index > maxindex)
1100                 return 0;
1101 
1102         while (radix_tree_is_internal_node(node)) {
1103                 unsigned offset;
1104 
1105                 parent = entry_to_node(node);
1106                 offset = radix_tree_descend(parent, &node, index);
1107 
1108                 if (!tag_get(parent, tag, offset))
1109                         return 0;
1110                 if (node == RADIX_TREE_RETRY)
1111                         break;
1112         }
1113 
1114         return 1;
1115 }
1116 EXPORT_SYMBOL(radix_tree_tag_get);
1117 
1118 /* Construct iter->tags bit-mask from node->tags[tag] array */
1119 static void set_iter_tags(struct radix_tree_iter *iter,
1120                                 struct radix_tree_node *node, unsigned offset,
1121                                 unsigned tag)
1122 {
1123         unsigned tag_long = offset / BITS_PER_LONG;
1124         unsigned tag_bit  = offset % BITS_PER_LONG;
1125 
1126         if (!node) {
1127                 iter->tags = 1;
1128                 return;
1129         }
1130 
1131         iter->tags = node->tags[tag][tag_long] >> tag_bit;
1132 
1133         /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
1134         if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
1135                 /* Pick tags from next element */
1136                 if (tag_bit)
1137                         iter->tags |= node->tags[tag][tag_long + 1] <<
1138                                                 (BITS_PER_LONG - tag_bit);
1139                 /* Clip chunk size, here only BITS_PER_LONG tags */
1140                 iter->next_index = __radix_tree_iter_add(iter, BITS_PER_LONG);
1141         }
1142 }
1143 
1144 void __rcu **radix_tree_iter_resume(void __rcu **slot,
1145                                         struct radix_tree_iter *iter)
1146 {
1147         slot++;
1148         iter->index = __radix_tree_iter_add(iter, 1);
1149         iter->next_index = iter->index;
1150         iter->tags = 0;
1151         return NULL;
1152 }
1153 EXPORT_SYMBOL(radix_tree_iter_resume);
1154 
1155 /**
1156  * radix_tree_next_chunk - find next chunk of slots for iteration
1157  *
1158  * @root:       radix tree root
1159  * @iter:       iterator state
1160  * @flags:      RADIX_TREE_ITER_* flags and tag index
1161  * Returns:     pointer to chunk first slot, or NULL if iteration is over
1162  */
1163 void __rcu **radix_tree_next_chunk(const struct radix_tree_root *root,
1164                              struct radix_tree_iter *iter, unsigned flags)
1165 {
1166         unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
1167         struct radix_tree_node *node, *child;
1168         unsigned long index, offset, maxindex;
1169 
1170         if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
1171                 return NULL;
1172 
1173         /*
1174          * Catch next_index overflow after ~0UL. iter->index never overflows
1175          * during iterating; it can be zero only at the beginning.
1176          * And we cannot overflow iter->next_index in a single step,
1177          * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
1178          *
1179          * This condition also used by radix_tree_next_slot() to stop
1180          * contiguous iterating, and forbid switching to the next chunk.
1181          */
1182         index = iter->next_index;
1183         if (!index && iter->index)
1184                 return NULL;
1185 
1186  restart:
1187         radix_tree_load_root(root, &child, &maxindex);
1188         if (index > maxindex)
1189                 return NULL;
1190         if (!child)
1191                 return NULL;
1192 
1193         if (!radix_tree_is_internal_node(child)) {
1194                 /* Single-slot tree */
1195                 iter->index = index;
1196                 iter->next_index = maxindex + 1;
1197                 iter->tags = 1;
1198                 iter->node = NULL;
1199                 return (void __rcu **)&root->xa_head;
1200         }
1201 
1202         do {
1203                 node = entry_to_node(child);
1204                 offset = radix_tree_descend(node, &child, index);
1205 
1206                 if ((flags & RADIX_TREE_ITER_TAGGED) ?
1207                                 !tag_get(node, tag, offset) : !child) {
1208                         /* Hole detected */
1209                         if (flags & RADIX_TREE_ITER_CONTIG)
1210                                 return NULL;
1211 
1212                         if (flags & RADIX_TREE_ITER_TAGGED)
1213                                 offset = radix_tree_find_next_bit(node, tag,
1214                                                 offset + 1);
1215                         else
1216                                 while (++offset < RADIX_TREE_MAP_SIZE) {
1217                                         void *slot = rcu_dereference_raw(
1218                                                         node->slots[offset]);
1219                                         if (slot)
1220                                                 break;
1221                                 }
1222                         index &= ~node_maxindex(node);
1223                         index += offset << node->shift;
1224                         /* Overflow after ~0UL */
1225                         if (!index)
1226                                 return NULL;
1227                         if (offset == RADIX_TREE_MAP_SIZE)
1228                                 goto restart;
1229                         child = rcu_dereference_raw(node->slots[offset]);
1230                 }
1231 
1232                 if (!child)
1233                         goto restart;
1234                 if (child == RADIX_TREE_RETRY)
1235                         break;
1236         } while (node->shift && radix_tree_is_internal_node(child));
1237 
1238         /* Update the iterator state */
1239         iter->index = (index &~ node_maxindex(node)) | offset;
1240         iter->next_index = (index | node_maxindex(node)) + 1;
1241         iter->node = node;
1242 
1243         if (flags & RADIX_TREE_ITER_TAGGED)
1244                 set_iter_tags(iter, node, offset, tag);
1245 
1246         return node->slots + offset;
1247 }
1248 EXPORT_SYMBOL(radix_tree_next_chunk);
1249 
1250 /**
1251  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
1252  *      @root:          radix tree root
1253  *      @results:       where the results of the lookup are placed
1254  *      @first_index:   start the lookup from this key
1255  *      @max_items:     place up to this many items at *results
1256  *
1257  *      Performs an index-ascending scan of the tree for present items.  Places
1258  *      them at *@results and returns the number of items which were placed at
1259  *      *@results.
1260  *
1261  *      The implementation is naive.
1262  *
1263  *      Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1264  *      rcu_read_lock. In this case, rather than the returned results being
1265  *      an atomic snapshot of the tree at a single point in time, the
1266  *      semantics of an RCU protected gang lookup are as though multiple
1267  *      radix_tree_lookups have been issued in individual locks, and results
1268  *      stored in 'results'.
1269  */
1270 unsigned int
1271 radix_tree_gang_lookup(const struct radix_tree_root *root, void **results,
1272                         unsigned long first_index, unsigned int max_items)
1273 {
1274         struct radix_tree_iter iter;
1275         void __rcu **slot;
1276         unsigned int ret = 0;
1277 
1278         if (unlikely(!max_items))
1279                 return 0;
1280 
1281         radix_tree_for_each_slot(slot, root, &iter, first_index) {
1282                 results[ret] = rcu_dereference_raw(*slot);
1283                 if (!results[ret])
1284                         continue;
1285                 if (radix_tree_is_internal_node(results[ret])) {
1286                         slot = radix_tree_iter_retry(&iter);
1287                         continue;
1288                 }
1289                 if (++ret == max_items)
1290                         break;
1291         }
1292 
1293         return ret;
1294 }
1295 EXPORT_SYMBOL(radix_tree_gang_lookup);
1296 
1297 /**
1298  *      radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1299  *                                   based on a tag
1300  *      @root:          radix tree root
1301  *      @results:       where the results of the lookup are placed
1302  *      @first_index:   start the lookup from this key
1303  *      @max_items:     place up to this many items at *results
1304  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
1305  *
1306  *      Performs an index-ascending scan of the tree for present items which
1307  *      have the tag indexed by @tag set.  Places the items at *@results and
1308  *      returns the number of items which were placed at *@results.
1309  */
1310 unsigned int
1311 radix_tree_gang_lookup_tag(const struct radix_tree_root *root, void **results,
1312                 unsigned long first_index, unsigned int max_items,
1313                 unsigned int tag)
1314 {
1315         struct radix_tree_iter iter;
1316         void __rcu **slot;
1317         unsigned int ret = 0;
1318 
1319         if (unlikely(!max_items))
1320                 return 0;
1321 
1322         radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1323                 results[ret] = rcu_dereference_raw(*slot);
1324                 if (!results[ret])
1325                         continue;
1326                 if (radix_tree_is_internal_node(results[ret])) {
1327                         slot = radix_tree_iter_retry(&iter);
1328                         continue;
1329                 }
1330                 if (++ret == max_items)
1331                         break;
1332         }
1333 
1334         return ret;
1335 }
1336 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1337 
1338 /**
1339  *      radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1340  *                                        radix tree based on a tag
1341  *      @root:          radix tree root
1342  *      @results:       where the results of the lookup are placed
1343  *      @first_index:   start the lookup from this key
1344  *      @max_items:     place up to this many items at *results
1345  *      @tag:           the tag index (< RADIX_TREE_MAX_TAGS)
1346  *
1347  *      Performs an index-ascending scan of the tree for present items which
1348  *      have the tag indexed by @tag set.  Places the slots at *@results and
1349  *      returns the number of slots which were placed at *@results.
1350  */
1351 unsigned int
1352 radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *root,
1353                 void __rcu ***results, unsigned long first_index,
1354                 unsigned int max_items, unsigned int tag)
1355 {
1356         struct radix_tree_iter iter;
1357         void __rcu **slot;
1358         unsigned int ret = 0;
1359 
1360         if (unlikely(!max_items))
1361                 return 0;
1362 
1363         radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1364                 results[ret] = slot;
1365                 if (++ret == max_items)
1366                         break;
1367         }
1368 
1369         return ret;
1370 }
1371 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1372 
1373 static bool __radix_tree_delete(struct radix_tree_root *root,
1374                                 struct radix_tree_node *node, void __rcu **slot)
1375 {
1376         void *old = rcu_dereference_raw(*slot);
1377         int values = xa_is_value(old) ? -1 : 0;
1378         unsigned offset = get_slot_offset(node, slot);
1379         int tag;
1380 
1381         if (is_idr(root))
1382                 node_tag_set(root, node, IDR_FREE, offset);
1383         else
1384                 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1385                         node_tag_clear(root, node, tag, offset);
1386 
1387         replace_slot(slot, NULL, node, -1, values);
1388         return node && delete_node(root, node);
1389 }
1390 
1391 /**
1392  * radix_tree_iter_delete - delete the entry at this iterator position
1393  * @root: radix tree root
1394  * @iter: iterator state
1395  * @slot: pointer to slot
1396  *
1397  * Delete the entry at the position currently pointed to by the iterator.
1398  * This may result in the current node being freed; if it is, the iterator
1399  * is advanced so that it will not reference the freed memory.  This
1400  * function may be called without any locking if there are no other threads
1401  * which can access this tree.
1402  */
1403 void radix_tree_iter_delete(struct radix_tree_root *root,
1404                                 struct radix_tree_iter *iter, void __rcu **slot)
1405 {
1406         if (__radix_tree_delete(root, iter->node, slot))
1407                 iter->index = iter->next_index;
1408 }
1409 EXPORT_SYMBOL(radix_tree_iter_delete);
1410 
1411 /**
1412  * radix_tree_delete_item - delete an item from a radix tree
1413  * @root: radix tree root
1414  * @index: index key
1415  * @item: expected item
1416  *
1417  * Remove @item at @index from the radix tree rooted at @root.
1418  *
1419  * Return: the deleted entry, or %NULL if it was not present
1420  * or the entry at the given @index was not @item.
1421  */
1422 void *radix_tree_delete_item(struct radix_tree_root *root,
1423                              unsigned long index, void *item)
1424 {
1425         struct radix_tree_node *node = NULL;
1426         void __rcu **slot = NULL;
1427         void *entry;
1428 
1429         entry = __radix_tree_lookup(root, index, &node, &slot);
1430         if (!slot)
1431                 return NULL;
1432         if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,
1433                                                 get_slot_offset(node, slot))))
1434                 return NULL;
1435 
1436         if (item && entry != item)
1437                 return NULL;
1438 
1439         __radix_tree_delete(root, node, slot);
1440 
1441         return entry;
1442 }
1443 EXPORT_SYMBOL(radix_tree_delete_item);
1444 
1445 /**
1446  * radix_tree_delete - delete an entry from a radix tree
1447  * @root: radix tree root
1448  * @index: index key
1449  *
1450  * Remove the entry at @index from the radix tree rooted at @root.
1451  *
1452  * Return: The deleted entry, or %NULL if it was not present.
1453  */
1454 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
1455 {
1456         return radix_tree_delete_item(root, index, NULL);
1457 }
1458 EXPORT_SYMBOL(radix_tree_delete);
1459 
1460 /**
1461  *      radix_tree_tagged - test whether any items in the tree are tagged
1462  *      @root:          radix tree root
1463  *      @tag:           tag to test
1464  */
1465 int radix_tree_tagged(const struct radix_tree_root *root, unsigned int tag)
1466 {
1467         return root_tag_get(root, tag);
1468 }
1469 EXPORT_SYMBOL(radix_tree_tagged);
1470 
1471 /**
1472  * idr_preload - preload for idr_alloc()
1473  * @gfp_mask: allocation mask to use for preloading
1474  *
1475  * Preallocate memory to use for the next call to idr_alloc().  This function
1476  * returns with preemption disabled.  It will be enabled by idr_preload_end().
1477  */
1478 void idr_preload(gfp_t gfp_mask)
1479 {
1480         if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
1481                 preempt_disable();
1482 }
1483 EXPORT_SYMBOL(idr_preload);
1484 
1485 void __rcu **idr_get_free(struct radix_tree_root *root,
1486                               struct radix_tree_iter *iter, gfp_t gfp,
1487                               unsigned long max)
1488 {
1489         struct radix_tree_node *node = NULL, *child;
1490         void __rcu **slot = (void __rcu **)&root->xa_head;
1491         unsigned long maxindex, start = iter->next_index;
1492         unsigned int shift, offset = 0;
1493 
1494  grow:
1495         shift = radix_tree_load_root(root, &child, &maxindex);
1496         if (!radix_tree_tagged(root, IDR_FREE))
1497                 start = max(start, maxindex + 1);
1498         if (start > max)
1499                 return ERR_PTR(-ENOSPC);
1500 
1501         if (start > maxindex) {
1502                 int error = radix_tree_extend(root, gfp, start, shift);
1503                 if (error < 0)
1504                         return ERR_PTR(error);
1505                 shift = error;
1506                 child = rcu_dereference_raw(root->xa_head);
1507         }
1508         if (start == 0 && shift == 0)
1509                 shift = RADIX_TREE_MAP_SHIFT;
1510 
1511         while (shift) {
1512                 shift -= RADIX_TREE_MAP_SHIFT;
1513                 if (child == NULL) {
1514                         /* Have to add a child node.  */
1515                         child = radix_tree_node_alloc(gfp, node, root, shift,
1516                                                         offset, 0, 0);
1517                         if (!child)
1518                                 return ERR_PTR(-ENOMEM);
1519                         all_tag_set(child, IDR_FREE);
1520                         rcu_assign_pointer(*slot, node_to_entry(child));
1521                         if (node)
1522                                 node->count++;
1523                 } else if (!radix_tree_is_internal_node(child))
1524                         break;
1525 
1526                 node = entry_to_node(child);
1527                 offset = radix_tree_descend(node, &child, start);
1528                 if (!tag_get(node, IDR_FREE, offset)) {
1529                         offset = radix_tree_find_next_bit(node, IDR_FREE,
1530                                                         offset + 1);
1531                         start = next_index(start, node, offset);
1532                         if (start > max || start == 0)
1533                                 return ERR_PTR(-ENOSPC);
1534                         while (offset == RADIX_TREE_MAP_SIZE) {
1535                                 offset = node->offset + 1;
1536                                 node = node->parent;
1537                                 if (!node)
1538                                         goto grow;
1539                                 shift = node->shift;
1540                         }
1541                         child = rcu_dereference_raw(node->slots[offset]);
1542                 }
1543                 slot = &node->slots[offset];
1544         }
1545 
1546         iter->index = start;
1547         if (node)
1548                 iter->next_index = 1 + min(max, (start | node_maxindex(node)));
1549         else
1550                 iter->next_index = 1;
1551         iter->node = node;
1552         set_iter_tags(iter, node, offset, IDR_FREE);
1553 
1554         return slot;
1555 }
1556 
1557 /**
1558  * idr_destroy - release all internal memory from an IDR
1559  * @idr: idr handle
1560  *
1561  * After this function is called, the IDR is empty, and may be reused or
1562  * the data structure containing it may be freed.
1563  *
1564  * A typical clean-up sequence for objects stored in an idr tree will use
1565  * idr_for_each() to free all objects, if necessary, then idr_destroy() to
1566  * free the memory used to keep track of those objects.
1567  */
1568 void idr_destroy(struct idr *idr)
1569 {
1570         struct radix_tree_node *node = rcu_dereference_raw(idr->idr_rt.xa_head);
1571         if (radix_tree_is_internal_node(node))
1572                 radix_tree_free_nodes(node);
1573         idr->idr_rt.xa_head = NULL;
1574         root_tag_set(&idr->idr_rt, IDR_FREE);
1575 }
1576 EXPORT_SYMBOL(idr_destroy);
1577 
1578 static void
1579 radix_tree_node_ctor(void *arg)
1580 {
1581         struct radix_tree_node *node = arg;
1582 
1583         memset(node, 0, sizeof(*node));
1584         INIT_LIST_HEAD(&node->private_list);
1585 }
1586 
1587 static int radix_tree_cpu_dead(unsigned int cpu)
1588 {
1589         struct radix_tree_preload *rtp;
1590         struct radix_tree_node *node;
1591 
1592         /* Free per-cpu pool of preloaded nodes */
1593         rtp = &per_cpu(radix_tree_preloads, cpu);
1594         while (rtp->nr) {
1595                 node = rtp->nodes;
1596                 rtp->nodes = node->parent;
1597                 kmem_cache_free(radix_tree_node_cachep, node);
1598                 rtp->nr--;
1599         }
1600         return 0;
1601 }
1602 
1603 void __init radix_tree_init(void)
1604 {
1605         int ret;
1606 
1607         BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
1608         BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK);
1609         BUILD_BUG_ON(XA_CHUNK_SIZE > 255);
1610         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
1611                         sizeof(struct radix_tree_node), 0,
1612                         SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
1613                         radix_tree_node_ctor);
1614         ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
1615                                         NULL, radix_tree_cpu_dead);
1616         WARN_ON(ret < 0);
1617 }
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root/lib/radix-tree.c

DEFINITIONS
