1/* 2 * Copyright (C) 2001 Momchil Velikov 3 * Portions Copyright (C) 2001 Christoph Hellwig 4 * Copyright (C) 2006 Nick Piggin 5 * Copyright (C) 2012 Konstantin Khlebnikov 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License as 9 * published by the Free Software Foundation; either version 2, or (at 10 * your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, but 13 * WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 20 */ 21#ifndef _LINUX_RADIX_TREE_H 22#define _LINUX_RADIX_TREE_H 23 24#include <linux/preempt.h> 25#include <linux/types.h> 26#include <linux/bug.h> 27#include <linux/kernel.h> 28#include <linux/rcupdate.h> 29 30/* 31 * An indirect pointer (root->rnode pointing to a radix_tree_node, rather 32 * than a data item) is signalled by the low bit set in the root->rnode 33 * pointer. 34 * 35 * In this case root->height is > 0, but the indirect pointer tests are 36 * needed for RCU lookups (because root->height is unreliable). The only 37 * time callers need worry about this is when doing a lookup_slot under 38 * RCU. 39 * 40 * Indirect pointer in fact is also used to tag the last pointer of a node 41 * when it is shrunk, before we rcu free the node. See shrink code for 42 * details. 43 */ 44#define RADIX_TREE_INDIRECT_PTR 1 45/* 46 * A common use of the radix tree is to store pointers to struct pages; 47 * but shmem/tmpfs needs also to store swap entries in the same tree: 48 * those are marked as exceptional entries to distinguish them. 49 * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it. 50 */ 51#define RADIX_TREE_EXCEPTIONAL_ENTRY 2 52#define RADIX_TREE_EXCEPTIONAL_SHIFT 2 53 54static inline int radix_tree_is_indirect_ptr(void *ptr) 55{ 56 return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); 57} 58 59/*** radix-tree API starts here ***/ 60 61#define RADIX_TREE_MAX_TAGS 3 62 63/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */ 64struct radix_tree_root { 65 unsigned int height; 66 gfp_t gfp_mask; 67 struct radix_tree_node __rcu *rnode; 68}; 69 70#define RADIX_TREE_INIT(mask) { \ 71 .height = 0, \ 72 .gfp_mask = (mask), \ 73 .rnode = NULL, \ 74} 75 76#define RADIX_TREE(name, mask) \ 77 struct radix_tree_root name = RADIX_TREE_INIT(mask) 78 79#define INIT_RADIX_TREE(root, mask) \ 80do { \ 81 (root)->height = 0; \ 82 (root)->gfp_mask = (mask); \ 83 (root)->rnode = NULL; \ 84} while (0) 85 86/** 87 * Radix-tree synchronization 88 * 89 * The radix-tree API requires that users provide all synchronisation (with 90 * specific exceptions, noted below). 91 * 92 * Synchronization of access to the data items being stored in the tree, and 93 * management of their lifetimes must be completely managed by API users. 94 * 95 * For API usage, in general, 96 * - any function _modifying_ the tree or tags (inserting or deleting 97 * items, setting or clearing tags) must exclude other modifications, and 98 * exclude any functions reading the tree. 99 * - any function _reading_ the tree or tags (looking up items or tags, 100 * gang lookups) must exclude modifications to the tree, but may occur 101 * concurrently with other readers. 102 * 103 * The notable exceptions to this rule are the following functions: 104 * radix_tree_lookup 105 * radix_tree_lookup_slot 106 * radix_tree_tag_get 107 * radix_tree_gang_lookup 108 * radix_tree_gang_lookup_slot 109 * radix_tree_gang_lookup_tag 110 * radix_tree_gang_lookup_tag_slot 111 * radix_tree_tagged 112 * 113 * The first 7 functions are able to be called locklessly, using RCU. The 114 * caller must ensure calls to these functions are made within rcu_read_lock() 115 * regions. Other readers (lock-free or otherwise) and modifications may be 116 * running concurrently. 117 * 118 * It is still required that the caller manage the synchronization and lifetimes 119 * of the items. So if RCU lock-free lookups are used, typically this would mean 120 * that the items have their own locks, or are amenable to lock-free access; and 121 * that the items are freed by RCU (or only freed after having been deleted from 122 * the radix tree *and* a synchronize_rcu() grace period). 123 * 124 * (Note, rcu_assign_pointer and rcu_dereference are not needed to control 125 * access to data items when inserting into or looking up from the radix tree) 126 * 127 * Note that the value returned by radix_tree_tag_get() may not be relied upon 128 * if only the RCU read lock is held. Functions to set/clear tags and to 129 * delete nodes running concurrently with it may affect its result such that 130 * two consecutive reads in the same locked section may return different 131 * values. If reliability is required, modification functions must also be 132 * excluded from concurrency. 133 * 134 * radix_tree_tagged is able to be called without locking or RCU. 135 */ 136 137/** 138 * radix_tree_deref_slot - dereference a slot 139 * @pslot: pointer to slot, returned by radix_tree_lookup_slot 140 * Returns: item that was stored in that slot with any direct pointer flag 141 * removed. 142 * 143 * For use with radix_tree_lookup_slot(). Caller must hold tree at least read 144 * locked across slot lookup and dereference. Not required if write lock is 145 * held (ie. items cannot be concurrently inserted). 146 * 147 * radix_tree_deref_retry must be used to confirm validity of the pointer if 148 * only the read lock is held. 149 */ 150static inline void *radix_tree_deref_slot(void **pslot) 151{ 152 return rcu_dereference(*pslot); 153} 154 155/** 156 * radix_tree_deref_slot_protected - dereference a slot without RCU lock but with tree lock held 157 * @pslot: pointer to slot, returned by radix_tree_lookup_slot 158 * Returns: item that was stored in that slot with any direct pointer flag 159 * removed. 160 * 161 * Similar to radix_tree_deref_slot but only used during migration when a pages 162 * mapping is being moved. The caller does not hold the RCU read lock but it 163 * must hold the tree lock to prevent parallel updates. 164 */ 165static inline void *radix_tree_deref_slot_protected(void **pslot, 166 spinlock_t *treelock) 167{ 168 return rcu_dereference_protected(*pslot, lockdep_is_held(treelock)); 169} 170 171/** 172 * radix_tree_deref_retry - check radix_tree_deref_slot 173 * @arg: pointer returned by radix_tree_deref_slot 174 * Returns: 0 if retry is not required, otherwise retry is required 175 * 176 * radix_tree_deref_retry must be used with radix_tree_deref_slot. 177 */ 178static inline int radix_tree_deref_retry(void *arg) 179{ 180 return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR); 181} 182 183/** 184 * radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry? 185 * @arg: value returned by radix_tree_deref_slot 186 * Returns: 0 if well-aligned pointer, non-0 if exceptional entry. 187 */ 188static inline int radix_tree_exceptional_entry(void *arg) 189{ 190 /* Not unlikely because radix_tree_exception often tested first */ 191 return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY; 192} 193 194/** 195 * radix_tree_exception - radix_tree_deref_slot returned either exception? 196 * @arg: value returned by radix_tree_deref_slot 197 * Returns: 0 if well-aligned pointer, non-0 if either kind of exception. 198 */ 199static inline int radix_tree_exception(void *arg) 200{ 201 return unlikely((unsigned long)arg & 202 (RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY)); 203} 204 205/** 206 * radix_tree_replace_slot - replace item in a slot 207 * @pslot: pointer to slot, returned by radix_tree_lookup_slot 208 * @item: new item to store in the slot. 209 * 210 * For use with radix_tree_lookup_slot(). Caller must hold tree write locked 211 * across slot lookup and replacement. 212 */ 213static inline void radix_tree_replace_slot(void **pslot, void *item) 214{ 215 BUG_ON(radix_tree_is_indirect_ptr(item)); 216 rcu_assign_pointer(*pslot, item); 217} 218 219int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); 220void *radix_tree_lookup(struct radix_tree_root *, unsigned long); 221void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long); 222void *radix_tree_delete(struct radix_tree_root *, unsigned long); 223unsigned int 224radix_tree_gang_lookup(struct radix_tree_root *root, void **results, 225 unsigned long first_index, unsigned int max_items); 226unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root, 227 void ***results, unsigned long *indices, 228 unsigned long first_index, unsigned int max_items); 229unsigned long radix_tree_next_hole(struct radix_tree_root *root, 230 unsigned long index, unsigned long max_scan); 231unsigned long radix_tree_prev_hole(struct radix_tree_root *root, 232 unsigned long index, unsigned long max_scan); 233int radix_tree_preload(gfp_t gfp_mask); 234void radix_tree_init(void); 235void *radix_tree_tag_set(struct radix_tree_root *root, 236 unsigned long index, unsigned int tag); 237void *radix_tree_tag_clear(struct radix_tree_root *root, 238 unsigned long index, unsigned int tag); 239int radix_tree_tag_get(struct radix_tree_root *root, 240 unsigned long index, unsigned int tag); 241unsigned int 242radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results, 243 unsigned long first_index, unsigned int max_items, 244 unsigned int tag); 245unsigned int 246radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results, 247 unsigned long first_index, unsigned int max_items, 248 unsigned int tag); 249unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, 250 unsigned long *first_indexp, unsigned long last_index, 251 unsigned long nr_to_tag, 252 unsigned int fromtag, unsigned int totag); 253int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag); 254unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item); 255 256static inline void radix_tree_preload_end(void) 257{ 258 preempt_enable(); 259} 260 261/** 262 * struct radix_tree_iter - radix tree iterator state 263 * 264 * @index: index of current slot 265 * @next_index: next-to-last index for this chunk 266 * @tags: bit-mask for tag-iterating 267 * 268 * This radix tree iterator works in terms of "chunks" of slots. A chunk is a 269 * subinterval of slots contained within one radix tree leaf node. It is 270 * described by a pointer to its first slot and a struct radix_tree_iter 271 * which holds the chunk's position in the tree and its size. For tagged 272 * iteration radix_tree_iter also holds the slots' bit-mask for one chosen 273 * radix tree tag. 274 */ 275struct radix_tree_iter { 276 unsigned long index; 277 unsigned long next_index; 278 unsigned long tags; 279}; 280 281#define RADIX_TREE_ITER_TAG_MASK 0x00FF /* tag index in lower byte */ 282#define RADIX_TREE_ITER_TAGGED 0x0100 /* lookup tagged slots */ 283#define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */ 284 285/** 286 * radix_tree_iter_init - initialize radix tree iterator 287 * 288 * @iter: pointer to iterator state 289 * @start: iteration starting index 290 * Returns: NULL 291 */ 292static __always_inline void ** 293radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start) 294{ 295 /* 296 * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it 297 * in the case of a successful tagged chunk lookup. If the lookup was 298 * unsuccessful or non-tagged then nobody cares about ->tags. 299 * 300 * Set index to zero to bypass next_index overflow protection. 301 * See the comment in radix_tree_next_chunk() for details. 302 */ 303 iter->index = 0; 304 iter->next_index = start; 305 return NULL; 306} 307 308/** 309 * radix_tree_next_chunk - find next chunk of slots for iteration 310 * 311 * @root: radix tree root 312 * @iter: iterator state 313 * @flags: RADIX_TREE_ITER_* flags and tag index 314 * Returns: pointer to chunk first slot, or NULL if there no more left 315 * 316 * This function looks up the next chunk in the radix tree starting from 317 * @iter->next_index. It returns a pointer to the chunk's first slot. 318 * Also it fills @iter with data about chunk: position in the tree (index), 319 * its end (next_index), and constructs a bit mask for tagged iterating (tags). 320 */ 321void **radix_tree_next_chunk(struct radix_tree_root *root, 322 struct radix_tree_iter *iter, unsigned flags); 323 324/** 325 * radix_tree_chunk_size - get current chunk size 326 * 327 * @iter: pointer to radix tree iterator 328 * Returns: current chunk size 329 */ 330static __always_inline unsigned 331radix_tree_chunk_size(struct radix_tree_iter *iter) 332{ 333 return iter->next_index - iter->index; 334} 335 336/** 337 * radix_tree_next_slot - find next slot in chunk 338 * 339 * @slot: pointer to current slot 340 * @iter: pointer to interator state 341 * @flags: RADIX_TREE_ITER_*, should be constant 342 * Returns: pointer to next slot, or NULL if there no more left 343 * 344 * This function updates @iter->index in the case of a successful lookup. 345 * For tagged lookup it also eats @iter->tags. 346 */ 347static __always_inline void ** 348radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags) 349{ 350 if (flags & RADIX_TREE_ITER_TAGGED) { 351 iter->tags >>= 1; 352 if (likely(iter->tags & 1ul)) { 353 iter->index++; 354 return slot + 1; 355 } 356 if (!(flags & RADIX_TREE_ITER_CONTIG) && likely(iter->tags)) { 357 unsigned offset = __ffs(iter->tags); 358 359 iter->tags >>= offset; 360 iter->index += offset + 1; 361 return slot + offset + 1; 362 } 363 } else { 364 unsigned size = radix_tree_chunk_size(iter) - 1; 365 366 while (size--) { 367 slot++; 368 iter->index++; 369 if (likely(*slot)) 370 return slot; 371 if (flags & RADIX_TREE_ITER_CONTIG) { 372 /* forbid switching to the next chunk */ 373 iter->next_index = 0; 374 break; 375 } 376 } 377 } 378 return NULL; 379} 380 381/** 382 * radix_tree_for_each_chunk - iterate over chunks 383 * 384 * @slot: the void** variable for pointer to chunk first slot 385 * @root: the struct radix_tree_root pointer 386 * @iter: the struct radix_tree_iter pointer 387 * @start: iteration starting index 388 * @flags: RADIX_TREE_ITER_* and tag index 389 * 390 * Locks can be released and reacquired between iterations. 391 */ 392#define radix_tree_for_each_chunk(slot, root, iter, start, flags) \ 393 for (slot = radix_tree_iter_init(iter, start) ; \ 394 (slot = radix_tree_next_chunk(root, iter, flags)) ;) 395 396/** 397 * radix_tree_for_each_chunk_slot - iterate over slots in one chunk 398 * 399 * @slot: the void** variable, at the beginning points to chunk first slot 400 * @iter: the struct radix_tree_iter pointer 401 * @flags: RADIX_TREE_ITER_*, should be constant 402 * 403 * This macro is designed to be nested inside radix_tree_for_each_chunk(). 404 * @slot points to the radix tree slot, @iter->index contains its index. 405 */ 406#define radix_tree_for_each_chunk_slot(slot, iter, flags) \ 407 for (; slot ; slot = radix_tree_next_slot(slot, iter, flags)) 408 409/** 410 * radix_tree_for_each_slot - iterate over non-empty slots 411 * 412 * @slot: the void** variable for pointer to slot 413 * @root: the struct radix_tree_root pointer 414 * @iter: the struct radix_tree_iter pointer 415 * @start: iteration starting index 416 * 417 * @slot points to radix tree slot, @iter->index contains its index. 418 */ 419#define radix_tree_for_each_slot(slot, root, iter, start) \ 420 for (slot = radix_tree_iter_init(iter, start) ; \ 421 slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \ 422 slot = radix_tree_next_slot(slot, iter, 0)) 423 424/** 425 * radix_tree_for_each_contig - iterate over contiguous slots 426 * 427 * @slot: the void** variable for pointer to slot 428 * @root: the struct radix_tree_root pointer 429 * @iter: the struct radix_tree_iter pointer 430 * @start: iteration starting index 431 * 432 * @slot points to radix tree slot, @iter->index contains its index. 433 */ 434#define radix_tree_for_each_contig(slot, root, iter, start) \ 435 for (slot = radix_tree_iter_init(iter, start) ; \ 436 slot || (slot = radix_tree_next_chunk(root, iter, \ 437 RADIX_TREE_ITER_CONTIG)) ; \ 438 slot = radix_tree_next_slot(slot, iter, \ 439 RADIX_TREE_ITER_CONTIG)) 440 441/** 442 * radix_tree_for_each_tagged - iterate over tagged slots 443 * 444 * @slot: the void** variable for pointer to slot 445 * @root: the struct radix_tree_root pointer 446 * @iter: the struct radix_tree_iter pointer 447 * @start: iteration starting index 448 * @tag: tag index 449 * 450 * @slot points to radix tree slot, @iter->index contains its index. 451 */ 452#define radix_tree_for_each_tagged(slot, root, iter, start, tag) \ 453 for (slot = radix_tree_iter_init(iter, start) ; \ 454 slot || (slot = radix_tree_next_chunk(root, iter, \ 455 RADIX_TREE_ITER_TAGGED | tag)) ; \ 456 slot = radix_tree_next_slot(slot, iter, \ 457 RADIX_TREE_ITER_TAGGED)) 458 459#endif /* _LINUX_RADIX_TREE_H */ 460