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