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) 2006 Nick Piggin 6 * Copyright (C) 2012 Konstantin Khlebnikov 7 */ 8#ifndef _LINUX_RADIX_TREE_H 9#define _LINUX_RADIX_TREE_H 10 11#include <linux/bitops.h> 12#include <linux/kernel.h> 13#include <linux/list.h> 14#include <linux/percpu.h> 15#include <linux/preempt.h> 16#include <linux/rcupdate.h> 17#include <linux/spinlock.h> 18#include <linux/types.h> 19#include <linux/xarray.h> 20#include <linux/local_lock.h> 21 22/* Keep unconverted code working */ 23#define radix_tree_root xarray 24#define radix_tree_node xa_node 25 26struct radix_tree_preload { 27 local_lock_t lock; 28 unsigned nr; 29 /* nodes->parent points to next preallocated node */ 30 struct radix_tree_node *nodes; 31}; 32DECLARE_PER_CPU(struct radix_tree_preload, radix_tree_preloads); 33 34/* 35 * The bottom two bits of the slot determine how the remaining bits in the 36 * slot are interpreted: 37 * 38 * 00 - data pointer 39 * 10 - internal entry 40 * x1 - value entry 41 * 42 * The internal entry may be a pointer to the next level in the tree, a 43 * sibling entry, or an indicator that the entry in this slot has been moved 44 * to another location in the tree and the lookup should be restarted. While 45 * NULL fits the 'data pointer' pattern, it means that there is no entry in 46 * the tree for this index (no matter what level of the tree it is found at). 47 * This means that storing a NULL entry in the tree is the same as deleting 48 * the entry from the tree. 49 */ 50#define RADIX_TREE_ENTRY_MASK 3UL 51#define RADIX_TREE_INTERNAL_NODE 2UL 52 53static inline bool radix_tree_is_internal_node(void *ptr) 54{ 55 return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) == 56 RADIX_TREE_INTERNAL_NODE; 57} 58 59/*** radix-tree API starts here ***/ 60 61#define RADIX_TREE_MAP_SHIFT XA_CHUNK_SHIFT 62#define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT) 63#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1) 64 65#define RADIX_TREE_MAX_TAGS XA_MAX_MARKS 66#define RADIX_TREE_TAG_LONGS XA_MARK_LONGS 67 68#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long)) 69#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \ 70 RADIX_TREE_MAP_SHIFT)) 71 72/* The IDR tag is stored in the low bits of xa_flags */ 73#define ROOT_IS_IDR ((__force gfp_t)4) 74/* The top bits of xa_flags are used to store the root tags */ 75#define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT) 76 77#define RADIX_TREE_INIT(name, mask) XARRAY_INIT(name, mask) 78 79#define RADIX_TREE(name, mask) \ 80 struct radix_tree_root name = RADIX_TREE_INIT(name, mask) 81 82#define INIT_RADIX_TREE(root, mask) xa_init_flags(root, mask) 83 84static inline bool radix_tree_empty(const struct radix_tree_root *root) 85{ 86 return root->xa_head == NULL; 87} 88 89/** 90 * struct radix_tree_iter - radix tree iterator state 91 * 92 * @index: index of current slot 93 * @next_index: one beyond the last index for this chunk 94 * @tags: bit-mask for tag-iterating 95 * @node: node that contains current slot 96 * 97 * This radix tree iterator works in terms of "chunks" of slots. A chunk is a 98 * subinterval of slots contained within one radix tree leaf node. It is 99 * described by a pointer to its first slot and a struct radix_tree_iter 100 * which holds the chunk's position in the tree and its size. For tagged 101 * iteration radix_tree_iter also holds the slots' bit-mask for one chosen 102 * radix tree tag. 103 */ 104struct radix_tree_iter { 105 unsigned long index; 106 unsigned long next_index; 107 unsigned long tags; 108 struct radix_tree_node *node; 109}; 110 111/** 112 * Radix-tree synchronization 113 * 114 * The radix-tree API requires that users provide all synchronisation (with 115 * specific exceptions, noted below). 116 * 117 * Synchronization of access to the data items being stored in the tree, and 118 * management of their lifetimes must be completely managed by API users. 119 * 120 * For API usage, in general, 121 * - any function _modifying_ the tree or tags (inserting or deleting 122 * items, setting or clearing tags) must exclude other modifications, and 123 * exclude any functions reading the tree. 124 * - any function _reading_ the tree or tags (looking up items or tags, 125 * gang lookups) must exclude modifications to the tree, but may occur 126 * concurrently with other readers. 127 * 128 * The notable exceptions to this rule are the following functions: 129 * __radix_tree_lookup 130 * radix_tree_lookup 131 * radix_tree_lookup_slot 132 * radix_tree_tag_get 133 * radix_tree_gang_lookup 134 * radix_tree_gang_lookup_tag 135 * radix_tree_gang_lookup_tag_slot 136 * radix_tree_tagged 137 * 138 * The first 7 functions are able to be called locklessly, using RCU. The 139 * caller must ensure calls to these functions are made within rcu_read_lock() 140 * regions. Other readers (lock-free or otherwise) and modifications may be 141 * running concurrently. 142 * 143 * It is still required that the caller manage the synchronization and lifetimes 144 * of the items. So if RCU lock-free lookups are used, typically this would mean 145 * that the items have their own locks, or are amenable to lock-free access; and 146 * that the items are freed by RCU (or only freed after having been deleted from 147 * the radix tree *and* a synchronize_rcu() grace period). 148 * 149 * (Note, rcu_assign_pointer and rcu_dereference are not needed to control 150 * access to data items when inserting into or looking up from the radix tree) 151 * 152 * Note that the value returned by radix_tree_tag_get() may not be relied upon 153 * if only the RCU read lock is held. Functions to set/clear tags and to 154 * delete nodes running concurrently with it may affect its result such that 155 * two consecutive reads in the same locked section may return different 156 * values. If reliability is required, modification functions must also be 157 * excluded from concurrency. 158 * 159 * radix_tree_tagged is able to be called without locking or RCU. 160 */ 161 162/** 163 * radix_tree_deref_slot - dereference a slot 164 * @slot: slot pointer, returned by radix_tree_lookup_slot 165 * 166 * For use with radix_tree_lookup_slot(). Caller must hold tree at least read 167 * locked across slot lookup and dereference. Not required if write lock is 168 * held (ie. items cannot be concurrently inserted). 169 * 170 * radix_tree_deref_retry must be used to confirm validity of the pointer if 171 * only the read lock is held. 172 * 173 * Return: entry stored in that slot. 174 */ 175static inline void *radix_tree_deref_slot(void __rcu **slot) 176{ 177 return rcu_dereference(*slot); 178} 179 180/** 181 * radix_tree_deref_slot_protected - dereference a slot with tree lock held 182 * @slot: slot pointer, returned by radix_tree_lookup_slot 183 * 184 * Similar to radix_tree_deref_slot. The caller does not hold the RCU read 185 * lock but it must hold the tree lock to prevent parallel updates. 186 * 187 * Return: entry stored in that slot. 188 */ 189static inline void *radix_tree_deref_slot_protected(void __rcu **slot, 190 spinlock_t *treelock) 191{ 192 return rcu_dereference_protected(*slot, lockdep_is_held(treelock)); 193} 194 195/** 196 * radix_tree_deref_retry - check radix_tree_deref_slot 197 * @arg: pointer returned by radix_tree_deref_slot 198 * Returns: 0 if retry is not required, otherwise retry is required 199 * 200 * radix_tree_deref_retry must be used with radix_tree_deref_slot. 201 */ 202static inline int radix_tree_deref_retry(void *arg) 203{ 204 return unlikely(radix_tree_is_internal_node(arg)); 205} 206 207/** 208 * radix_tree_exception - radix_tree_deref_slot returned either exception? 209 * @arg: value returned by radix_tree_deref_slot 210 * Returns: 0 if well-aligned pointer, non-0 if either kind of exception. 211 */ 212static inline int radix_tree_exception(void *arg) 213{ 214 return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK); 215} 216 217int radix_tree_insert(struct radix_tree_root *, unsigned long index, 218 void *); 219void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index, 220 struct radix_tree_node **nodep, void __rcu ***slotp); 221void *radix_tree_lookup(const struct radix_tree_root *, unsigned long); 222void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *, 223 unsigned long index); 224void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *, 225 void __rcu **slot, void *entry); 226void radix_tree_iter_replace(struct radix_tree_root *, 227 const struct radix_tree_iter *, void __rcu **slot, void *entry); 228void radix_tree_replace_slot(struct radix_tree_root *, 229 void __rcu **slot, void *entry); 230void radix_tree_iter_delete(struct radix_tree_root *, 231 struct radix_tree_iter *iter, void __rcu **slot); 232void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *); 233void *radix_tree_delete(struct radix_tree_root *, unsigned long); 234unsigned int radix_tree_gang_lookup(const struct radix_tree_root *, 235 void **results, unsigned long first_index, 236 unsigned int max_items); 237int radix_tree_preload(gfp_t gfp_mask); 238int radix_tree_maybe_preload(gfp_t gfp_mask); 239void radix_tree_init(void); 240void *radix_tree_tag_set(struct radix_tree_root *, 241 unsigned long index, unsigned int tag); 242void *radix_tree_tag_clear(struct radix_tree_root *, 243 unsigned long index, unsigned int tag); 244int radix_tree_tag_get(const struct radix_tree_root *, 245 unsigned long index, unsigned int tag); 246void radix_tree_iter_tag_clear(struct radix_tree_root *, 247 const struct radix_tree_iter *iter, unsigned int tag); 248unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *, 249 void **results, unsigned long first_index, 250 unsigned int max_items, unsigned int tag); 251unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *, 252 void __rcu ***results, unsigned long first_index, 253 unsigned int max_items, unsigned int tag); 254int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag); 255 256static inline void radix_tree_preload_end(void) 257{ 258 local_unlock(&radix_tree_preloads.lock); 259} 260 261void __rcu **idr_get_free(struct radix_tree_root *root, 262 struct radix_tree_iter *iter, gfp_t gfp, 263 unsigned long max); 264 265enum { 266 RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */ 267 RADIX_TREE_ITER_TAGGED = 0x10, /* lookup tagged slots */ 268 RADIX_TREE_ITER_CONTIG = 0x20, /* stop at first hole */ 269}; 270 271/** 272 * radix_tree_iter_init - initialize radix tree iterator 273 * 274 * @iter: pointer to iterator state 275 * @start: iteration starting index 276 * Returns: NULL 277 */ 278static __always_inline void __rcu ** 279radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start) 280{ 281 /* 282 * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it 283 * in the case of a successful tagged chunk lookup. If the lookup was 284 * unsuccessful or non-tagged then nobody cares about ->tags. 285 * 286 * Set index to zero to bypass next_index overflow protection. 287 * See the comment in radix_tree_next_chunk() for details. 288 */ 289 iter->index = 0; 290 iter->next_index = start; 291 return NULL; 292} 293 294/** 295 * radix_tree_next_chunk - find next chunk of slots for iteration 296 * 297 * @root: radix tree root 298 * @iter: iterator state 299 * @flags: RADIX_TREE_ITER_* flags and tag index 300 * Returns: pointer to chunk first slot, or NULL if there no more left 301 * 302 * This function looks up the next chunk in the radix tree starting from 303 * @iter->next_index. It returns a pointer to the chunk's first slot. 304 * Also it fills @iter with data about chunk: position in the tree (index), 305 * its end (next_index), and constructs a bit mask for tagged iterating (tags). 306 */ 307void __rcu **radix_tree_next_chunk(const struct radix_tree_root *, 308 struct radix_tree_iter *iter, unsigned flags); 309 310/** 311 * radix_tree_iter_lookup - look up an index in the radix tree 312 * @root: radix tree root 313 * @iter: iterator state 314 * @index: key to look up 315 * 316 * If @index is present in the radix tree, this function returns the slot 317 * containing it and updates @iter to describe the entry. If @index is not 318 * present, it returns NULL. 319 */ 320static inline void __rcu ** 321radix_tree_iter_lookup(const struct radix_tree_root *root, 322 struct radix_tree_iter *iter, unsigned long index) 323{ 324 radix_tree_iter_init(iter, index); 325 return radix_tree_next_chunk(root, iter, RADIX_TREE_ITER_CONTIG); 326} 327 328/** 329 * radix_tree_iter_retry - retry this chunk of the iteration 330 * @iter: iterator state 331 * 332 * If we iterate over a tree protected only by the RCU lock, a race 333 * against deletion or creation may result in seeing a slot for which 334 * radix_tree_deref_retry() returns true. If so, call this function 335 * and continue the iteration. 336 */ 337static inline __must_check 338void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter) 339{ 340 iter->next_index = iter->index; 341 iter->tags = 0; 342 return NULL; 343} 344 345static inline unsigned long 346__radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots) 347{ 348 return iter->index + slots; 349} 350 351/** 352 * radix_tree_iter_resume - resume iterating when the chunk may be invalid 353 * @slot: pointer to current slot 354 * @iter: iterator state 355 * Returns: New slot pointer 356 * 357 * If the iterator needs to release then reacquire a lock, the chunk may 358 * have been invalidated by an insertion or deletion. Call this function 359 * before releasing the lock to continue the iteration from the next index. 360 */ 361void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot, 362 struct radix_tree_iter *iter); 363 364/** 365 * radix_tree_chunk_size - get current chunk size 366 * 367 * @iter: pointer to radix tree iterator 368 * Returns: current chunk size 369 */ 370static __always_inline long 371radix_tree_chunk_size(struct radix_tree_iter *iter) 372{ 373 return iter->next_index - iter->index; 374} 375 376/** 377 * radix_tree_next_slot - find next slot in chunk 378 * 379 * @slot: pointer to current slot 380 * @iter: pointer to iterator state 381 * @flags: RADIX_TREE_ITER_*, should be constant 382 * Returns: pointer to next slot, or NULL if there no more left 383 * 384 * This function updates @iter->index in the case of a successful lookup. 385 * For tagged lookup it also eats @iter->tags. 386 * 387 * There are several cases where 'slot' can be passed in as NULL to this 388 * function. These cases result from the use of radix_tree_iter_resume() or 389 * radix_tree_iter_retry(). In these cases we don't end up dereferencing 390 * 'slot' because either: 391 * a) we are doing tagged iteration and iter->tags has been set to 0, or 392 * b) we are doing non-tagged iteration, and iter->index and iter->next_index 393 * have been set up so that radix_tree_chunk_size() returns 1 or 0. 394 */ 395static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot, 396 struct radix_tree_iter *iter, unsigned flags) 397{ 398 if (flags & RADIX_TREE_ITER_TAGGED) { 399 iter->tags >>= 1; 400 if (unlikely(!iter->tags)) 401 return NULL; 402 if (likely(iter->tags & 1ul)) { 403 iter->index = __radix_tree_iter_add(iter, 1); 404 slot++; 405 goto found; 406 } 407 if (!(flags & RADIX_TREE_ITER_CONTIG)) { 408 unsigned offset = __ffs(iter->tags); 409 410 iter->tags >>= offset++; 411 iter->index = __radix_tree_iter_add(iter, offset); 412 slot += offset; 413 goto found; 414 } 415 } else { 416 long count = radix_tree_chunk_size(iter); 417 418 while (--count > 0) { 419 slot++; 420 iter->index = __radix_tree_iter_add(iter, 1); 421 422 if (likely(*slot)) 423 goto found; 424 if (flags & RADIX_TREE_ITER_CONTIG) { 425 /* forbid switching to the next chunk */ 426 iter->next_index = 0; 427 break; 428 } 429 } 430 } 431 return NULL; 432 433 found: 434 return slot; 435} 436 437/** 438 * radix_tree_for_each_slot - iterate over non-empty slots 439 * 440 * @slot: the void** variable for pointer to slot 441 * @root: the struct radix_tree_root pointer 442 * @iter: the struct radix_tree_iter pointer 443 * @start: iteration starting index 444 * 445 * @slot points to radix tree slot, @iter->index contains its index. 446 */ 447#define radix_tree_for_each_slot(slot, root, iter, start) \ 448 for (slot = radix_tree_iter_init(iter, start) ; \ 449 slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \ 450 slot = radix_tree_next_slot(slot, iter, 0)) 451 452/** 453 * radix_tree_for_each_tagged - iterate over tagged slots 454 * 455 * @slot: the void** variable for pointer to slot 456 * @root: the struct radix_tree_root pointer 457 * @iter: the struct radix_tree_iter pointer 458 * @start: iteration starting index 459 * @tag: tag index 460 * 461 * @slot points to radix tree slot, @iter->index contains its index. 462 */ 463#define radix_tree_for_each_tagged(slot, root, iter, start, tag) \ 464 for (slot = radix_tree_iter_init(iter, start) ; \ 465 slot || (slot = radix_tree_next_chunk(root, iter, \ 466 RADIX_TREE_ITER_TAGGED | tag)) ; \ 467 slot = radix_tree_next_slot(slot, iter, \ 468 RADIX_TREE_ITER_TAGGED | tag)) 469 470#endif /* _LINUX_RADIX_TREE_H */ 471