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/gfp_types.h> |
13 | #include <linux/list.h> |
14 | #include <linux/lockdep.h> |
15 | #include <linux/math.h> |
16 | #include <linux/percpu.h> |
17 | #include <linux/preempt.h> |
18 | #include <linux/rcupdate.h> |
19 | #include <linux/spinlock.h> |
20 | #include <linux/types.h> |
21 | #include <linux/xarray.h> |
22 | #include <linux/local_lock.h> |
23 | |
24 | /* Keep unconverted code working */ |
25 | #define radix_tree_root xarray |
26 | #define radix_tree_node xa_node |
27 | |
28 | struct radix_tree_preload { |
29 | local_lock_t lock; |
30 | unsigned nr; |
31 | /* nodes->parent points to next preallocated node */ |
32 | struct radix_tree_node *nodes; |
33 | }; |
34 | DECLARE_PER_CPU(struct radix_tree_preload, radix_tree_preloads); |
35 | |
36 | /* |
37 | * The bottom two bits of the slot determine how the remaining bits in the |
38 | * slot are interpreted: |
39 | * |
40 | * 00 - data pointer |
41 | * 10 - internal entry |
42 | * x1 - value entry |
43 | * |
44 | * The internal entry may be a pointer to the next level in the tree, a |
45 | * sibling entry, or an indicator that the entry in this slot has been moved |
46 | * to another location in the tree and the lookup should be restarted. While |
47 | * NULL fits the 'data pointer' pattern, it means that there is no entry in |
48 | * the tree for this index (no matter what level of the tree it is found at). |
49 | * This means that storing a NULL entry in the tree is the same as deleting |
50 | * the entry from the tree. |
51 | */ |
52 | #define RADIX_TREE_ENTRY_MASK 3UL |
53 | #define RADIX_TREE_INTERNAL_NODE 2UL |
54 | |
55 | static inline bool radix_tree_is_internal_node(void *ptr) |
56 | { |
57 | return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) == |
58 | RADIX_TREE_INTERNAL_NODE; |
59 | } |
60 | |
61 | /*** radix-tree API starts here ***/ |
62 | |
63 | #define RADIX_TREE_MAP_SHIFT XA_CHUNK_SHIFT |
64 | #define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT) |
65 | #define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1) |
66 | |
67 | #define RADIX_TREE_MAX_TAGS XA_MAX_MARKS |
68 | #define RADIX_TREE_TAG_LONGS XA_MARK_LONGS |
69 | |
70 | #define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long)) |
71 | #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \ |
72 | RADIX_TREE_MAP_SHIFT)) |
73 | |
74 | /* The IDR tag is stored in the low bits of xa_flags */ |
75 | #define ROOT_IS_IDR ((__force gfp_t)4) |
76 | /* The top bits of xa_flags are used to store the root tags */ |
77 | #define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT) |
78 | |
79 | #define RADIX_TREE_INIT(name, mask) XARRAY_INIT(name, mask) |
80 | |
81 | #define RADIX_TREE(name, mask) \ |
82 | struct radix_tree_root name = RADIX_TREE_INIT(name, mask) |
83 | |
84 | #define INIT_RADIX_TREE(root, mask) xa_init_flags(root, mask) |
85 | |
86 | static inline bool radix_tree_empty(const struct radix_tree_root *root) |
87 | { |
88 | return root->xa_head == NULL; |
89 | } |
90 | |
91 | /** |
92 | * struct radix_tree_iter - radix tree iterator state |
93 | * |
94 | * @index: index of current slot |
95 | * @next_index: one beyond the last index for this chunk |
96 | * @tags: bit-mask for tag-iterating |
97 | * @node: node that contains current slot |
98 | * |
99 | * This radix tree iterator works in terms of "chunks" of slots. A chunk is a |
100 | * subinterval of slots contained within one radix tree leaf node. It is |
101 | * described by a pointer to its first slot and a struct radix_tree_iter |
102 | * which holds the chunk's position in the tree and its size. For tagged |
103 | * iteration radix_tree_iter also holds the slots' bit-mask for one chosen |
104 | * radix tree tag. |
105 | */ |
106 | struct radix_tree_iter { |
107 | unsigned long index; |
108 | unsigned long next_index; |
109 | unsigned long tags; |
110 | struct radix_tree_node *node; |
111 | }; |
112 | |
113 | /** |
114 | * Radix-tree synchronization |
115 | * |
116 | * The radix-tree API requires that users provide all synchronisation (with |
117 | * specific exceptions, noted below). |
118 | * |
119 | * Synchronization of access to the data items being stored in the tree, and |
120 | * management of their lifetimes must be completely managed by API users. |
121 | * |
122 | * For API usage, in general, |
123 | * - any function _modifying_ the tree or tags (inserting or deleting |
124 | * items, setting or clearing tags) must exclude other modifications, and |
125 | * exclude any functions reading the tree. |
126 | * - any function _reading_ the tree or tags (looking up items or tags, |
127 | * gang lookups) must exclude modifications to the tree, but may occur |
128 | * concurrently with other readers. |
129 | * |
130 | * The notable exceptions to this rule are the following functions: |
131 | * __radix_tree_lookup |
132 | * radix_tree_lookup |
133 | * radix_tree_lookup_slot |
134 | * radix_tree_tag_get |
135 | * radix_tree_gang_lookup |
136 | * radix_tree_gang_lookup_tag |
137 | * radix_tree_gang_lookup_tag_slot |
138 | * radix_tree_tagged |
139 | * |
140 | * The first 7 functions are able to be called locklessly, using RCU. The |
141 | * caller must ensure calls to these functions are made within rcu_read_lock() |
142 | * regions. Other readers (lock-free or otherwise) and modifications may be |
143 | * running concurrently. |
144 | * |
145 | * It is still required that the caller manage the synchronization and lifetimes |
146 | * of the items. So if RCU lock-free lookups are used, typically this would mean |
147 | * that the items have their own locks, or are amenable to lock-free access; and |
148 | * that the items are freed by RCU (or only freed after having been deleted from |
149 | * the radix tree *and* a synchronize_rcu() grace period). |
150 | * |
151 | * (Note, rcu_assign_pointer and rcu_dereference are not needed to control |
152 | * access to data items when inserting into or looking up from the radix tree) |
153 | * |
154 | * Note that the value returned by radix_tree_tag_get() may not be relied upon |
155 | * if only the RCU read lock is held. Functions to set/clear tags and to |
156 | * delete nodes running concurrently with it may affect its result such that |
157 | * two consecutive reads in the same locked section may return different |
158 | * values. If reliability is required, modification functions must also be |
159 | * excluded from concurrency. |
160 | * |
161 | * radix_tree_tagged is able to be called without locking or RCU. |
162 | */ |
163 | |
164 | /** |
165 | * radix_tree_deref_slot - dereference a slot |
166 | * @slot: slot pointer, returned by radix_tree_lookup_slot |
167 | * |
168 | * For use with radix_tree_lookup_slot(). Caller must hold tree at least read |
169 | * locked across slot lookup and dereference. Not required if write lock is |
170 | * held (ie. items cannot be concurrently inserted). |
171 | * |
172 | * radix_tree_deref_retry must be used to confirm validity of the pointer if |
173 | * only the read lock is held. |
174 | * |
175 | * Return: entry stored in that slot. |
176 | */ |
177 | static inline void *radix_tree_deref_slot(void __rcu **slot) |
178 | { |
179 | return rcu_dereference(*slot); |
180 | } |
181 | |
182 | /** |
183 | * radix_tree_deref_slot_protected - dereference a slot with tree lock held |
184 | * @slot: slot pointer, returned by radix_tree_lookup_slot |
185 | * |
186 | * Similar to radix_tree_deref_slot. The caller does not hold the RCU read |
187 | * lock but it must hold the tree lock to prevent parallel updates. |
188 | * |
189 | * Return: entry stored in that slot. |
190 | */ |
191 | static inline void *radix_tree_deref_slot_protected(void __rcu **slot, |
192 | spinlock_t *treelock) |
193 | { |
194 | return rcu_dereference_protected(*slot, lockdep_is_held(treelock)); |
195 | } |
196 | |
197 | /** |
198 | * radix_tree_deref_retry - check radix_tree_deref_slot |
199 | * @arg: pointer returned by radix_tree_deref_slot |
200 | * Returns: 0 if retry is not required, otherwise retry is required |
201 | * |
202 | * radix_tree_deref_retry must be used with radix_tree_deref_slot. |
203 | */ |
204 | static inline int radix_tree_deref_retry(void *arg) |
205 | { |
206 | return unlikely(radix_tree_is_internal_node(arg)); |
207 | } |
208 | |
209 | /** |
210 | * radix_tree_exception - radix_tree_deref_slot returned either exception? |
211 | * @arg: value returned by radix_tree_deref_slot |
212 | * Returns: 0 if well-aligned pointer, non-0 if either kind of exception. |
213 | */ |
214 | static inline int radix_tree_exception(void *arg) |
215 | { |
216 | return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK); |
217 | } |
218 | |
219 | int radix_tree_insert(struct radix_tree_root *, unsigned long index, |
220 | void *); |
221 | void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index, |
222 | struct radix_tree_node **nodep, void __rcu ***slotp); |
223 | void *radix_tree_lookup(const struct radix_tree_root *, unsigned long); |
224 | void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *, |
225 | unsigned long index); |
226 | void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *, |
227 | void __rcu **slot, void *entry); |
228 | void radix_tree_iter_replace(struct radix_tree_root *, |
229 | const struct radix_tree_iter *, void __rcu **slot, void *entry); |
230 | void radix_tree_replace_slot(struct radix_tree_root *, |
231 | void __rcu **slot, void *entry); |
232 | void radix_tree_iter_delete(struct radix_tree_root *, |
233 | struct radix_tree_iter *iter, void __rcu **slot); |
234 | void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *); |
235 | void *radix_tree_delete(struct radix_tree_root *, unsigned long); |
236 | unsigned int radix_tree_gang_lookup(const struct radix_tree_root *, |
237 | void **results, unsigned long first_index, |
238 | unsigned int max_items); |
239 | int radix_tree_preload(gfp_t gfp_mask); |
240 | int radix_tree_maybe_preload(gfp_t gfp_mask); |
241 | void radix_tree_init(void); |
242 | void *radix_tree_tag_set(struct radix_tree_root *, |
243 | unsigned long index, unsigned int tag); |
244 | void *radix_tree_tag_clear(struct radix_tree_root *, |
245 | unsigned long index, unsigned int tag); |
246 | int radix_tree_tag_get(const struct radix_tree_root *, |
247 | unsigned long index, unsigned int tag); |
248 | void radix_tree_iter_tag_clear(struct radix_tree_root *, |
249 | const struct radix_tree_iter *iter, unsigned int tag); |
250 | unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *, |
251 | void **results, unsigned long first_index, |
252 | unsigned int max_items, unsigned int tag); |
253 | unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *, |
254 | void __rcu ***results, unsigned long first_index, |
255 | unsigned int max_items, unsigned int tag); |
256 | int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag); |
257 | |
258 | static inline void radix_tree_preload_end(void) |
259 | { |
260 | local_unlock(&radix_tree_preloads.lock); |
261 | } |
262 | |
263 | void __rcu **idr_get_free(struct radix_tree_root *root, |
264 | struct radix_tree_iter *iter, gfp_t gfp, |
265 | unsigned long max); |
266 | |
267 | enum { |
268 | RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */ |
269 | RADIX_TREE_ITER_TAGGED = 0x10, /* lookup tagged slots */ |
270 | RADIX_TREE_ITER_CONTIG = 0x20, /* stop at first hole */ |
271 | }; |
272 | |
273 | /** |
274 | * radix_tree_iter_init - initialize radix tree iterator |
275 | * |
276 | * @iter: pointer to iterator state |
277 | * @start: iteration starting index |
278 | * Returns: NULL |
279 | */ |
280 | static __always_inline void __rcu ** |
281 | radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start) |
282 | { |
283 | /* |
284 | * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it |
285 | * in the case of a successful tagged chunk lookup. If the lookup was |
286 | * unsuccessful or non-tagged then nobody cares about ->tags. |
287 | * |
288 | * Set index to zero to bypass next_index overflow protection. |
289 | * See the comment in radix_tree_next_chunk() for details. |
290 | */ |
291 | iter->index = 0; |
292 | iter->next_index = start; |
293 | return NULL; |
294 | } |
295 | |
296 | /** |
297 | * radix_tree_next_chunk - find next chunk of slots for iteration |
298 | * |
299 | * @root: radix tree root |
300 | * @iter: iterator state |
301 | * @flags: RADIX_TREE_ITER_* flags and tag index |
302 | * Returns: pointer to chunk first slot, or NULL if there no more left |
303 | * |
304 | * This function looks up the next chunk in the radix tree starting from |
305 | * @iter->next_index. It returns a pointer to the chunk's first slot. |
306 | * Also it fills @iter with data about chunk: position in the tree (index), |
307 | * its end (next_index), and constructs a bit mask for tagged iterating (tags). |
308 | */ |
309 | void __rcu **radix_tree_next_chunk(const struct radix_tree_root *, |
310 | struct radix_tree_iter *iter, unsigned flags); |
311 | |
312 | /** |
313 | * radix_tree_iter_lookup - look up an index in the radix tree |
314 | * @root: radix tree root |
315 | * @iter: iterator state |
316 | * @index: key to look up |
317 | * |
318 | * If @index is present in the radix tree, this function returns the slot |
319 | * containing it and updates @iter to describe the entry. If @index is not |
320 | * present, it returns NULL. |
321 | */ |
322 | static inline void __rcu ** |
323 | radix_tree_iter_lookup(const struct radix_tree_root *root, |
324 | struct radix_tree_iter *iter, unsigned long index) |
325 | { |
326 | radix_tree_iter_init(iter, start: index); |
327 | return radix_tree_next_chunk(root, iter, flags: RADIX_TREE_ITER_CONTIG); |
328 | } |
329 | |
330 | /** |
331 | * radix_tree_iter_retry - retry this chunk of the iteration |
332 | * @iter: iterator state |
333 | * |
334 | * If we iterate over a tree protected only by the RCU lock, a race |
335 | * against deletion or creation may result in seeing a slot for which |
336 | * radix_tree_deref_retry() returns true. If so, call this function |
337 | * and continue the iteration. |
338 | */ |
339 | static inline __must_check |
340 | void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter) |
341 | { |
342 | iter->next_index = iter->index; |
343 | iter->tags = 0; |
344 | return NULL; |
345 | } |
346 | |
347 | static inline unsigned long |
348 | __radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots) |
349 | { |
350 | return iter->index + slots; |
351 | } |
352 | |
353 | /** |
354 | * radix_tree_iter_resume - resume iterating when the chunk may be invalid |
355 | * @slot: pointer to current slot |
356 | * @iter: iterator state |
357 | * Returns: New slot pointer |
358 | * |
359 | * If the iterator needs to release then reacquire a lock, the chunk may |
360 | * have been invalidated by an insertion or deletion. Call this function |
361 | * before releasing the lock to continue the iteration from the next index. |
362 | */ |
363 | void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot, |
364 | struct radix_tree_iter *iter); |
365 | |
366 | /** |
367 | * radix_tree_chunk_size - get current chunk size |
368 | * |
369 | * @iter: pointer to radix tree iterator |
370 | * Returns: current chunk size |
371 | */ |
372 | static __always_inline long |
373 | radix_tree_chunk_size(struct radix_tree_iter *iter) |
374 | { |
375 | return iter->next_index - iter->index; |
376 | } |
377 | |
378 | /** |
379 | * radix_tree_next_slot - find next slot in chunk |
380 | * |
381 | * @slot: pointer to current slot |
382 | * @iter: pointer to iterator state |
383 | * @flags: RADIX_TREE_ITER_*, should be constant |
384 | * Returns: pointer to next slot, or NULL if there no more left |
385 | * |
386 | * This function updates @iter->index in the case of a successful lookup. |
387 | * For tagged lookup it also eats @iter->tags. |
388 | * |
389 | * There are several cases where 'slot' can be passed in as NULL to this |
390 | * function. These cases result from the use of radix_tree_iter_resume() or |
391 | * radix_tree_iter_retry(). In these cases we don't end up dereferencing |
392 | * 'slot' because either: |
393 | * a) we are doing tagged iteration and iter->tags has been set to 0, or |
394 | * b) we are doing non-tagged iteration, and iter->index and iter->next_index |
395 | * have been set up so that radix_tree_chunk_size() returns 1 or 0. |
396 | */ |
397 | static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot, |
398 | struct radix_tree_iter *iter, unsigned flags) |
399 | { |
400 | if (flags & RADIX_TREE_ITER_TAGGED) { |
401 | iter->tags >>= 1; |
402 | if (unlikely(!iter->tags)) |
403 | return NULL; |
404 | if (likely(iter->tags & 1ul)) { |
405 | iter->index = __radix_tree_iter_add(iter, slots: 1); |
406 | slot++; |
407 | goto found; |
408 | } |
409 | if (!(flags & RADIX_TREE_ITER_CONTIG)) { |
410 | unsigned offset = __ffs(iter->tags); |
411 | |
412 | iter->tags >>= offset++; |
413 | iter->index = __radix_tree_iter_add(iter, slots: offset); |
414 | slot += offset; |
415 | goto found; |
416 | } |
417 | } else { |
418 | long count = radix_tree_chunk_size(iter); |
419 | |
420 | while (--count > 0) { |
421 | slot++; |
422 | iter->index = __radix_tree_iter_add(iter, slots: 1); |
423 | |
424 | if (likely(*slot)) |
425 | goto found; |
426 | if (flags & RADIX_TREE_ITER_CONTIG) { |
427 | /* forbid switching to the next chunk */ |
428 | iter->next_index = 0; |
429 | break; |
430 | } |
431 | } |
432 | } |
433 | return NULL; |
434 | |
435 | found: |
436 | return slot; |
437 | } |
438 | |
439 | /** |
440 | * radix_tree_for_each_slot - iterate over non-empty slots |
441 | * |
442 | * @slot: the void** variable for pointer to slot |
443 | * @root: the struct radix_tree_root pointer |
444 | * @iter: the struct radix_tree_iter pointer |
445 | * @start: iteration starting index |
446 | * |
447 | * @slot points to radix tree slot, @iter->index contains its index. |
448 | */ |
449 | #define radix_tree_for_each_slot(slot, root, iter, start) \ |
450 | for (slot = radix_tree_iter_init(iter, start) ; \ |
451 | slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \ |
452 | slot = radix_tree_next_slot(slot, iter, 0)) |
453 | |
454 | /** |
455 | * radix_tree_for_each_tagged - iterate over tagged slots |
456 | * |
457 | * @slot: the void** variable for pointer to slot |
458 | * @root: the struct radix_tree_root pointer |
459 | * @iter: the struct radix_tree_iter pointer |
460 | * @start: iteration starting index |
461 | * @tag: tag index |
462 | * |
463 | * @slot points to radix tree slot, @iter->index contains its index. |
464 | */ |
465 | #define radix_tree_for_each_tagged(slot, root, iter, start, tag) \ |
466 | for (slot = radix_tree_iter_init(iter, start) ; \ |
467 | slot || (slot = radix_tree_next_chunk(root, iter, \ |
468 | RADIX_TREE_ITER_TAGGED | tag)) ; \ |
469 | slot = radix_tree_next_slot(slot, iter, \ |
470 | RADIX_TREE_ITER_TAGGED | tag)) |
471 | |
472 | #endif /* _LINUX_RADIX_TREE_H */ |
473 | |