Line data Source code
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 41579 : 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 9625 : iter->index = 0;
292 9625 : 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, index);
327 : return radix_tree_next_chunk(root, iter, 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 0 : iter->next_index = iter->index;
343 0 : 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 0 : 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 0 : 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 0 : iter->tags >>= 1;
402 0 : if (unlikely(!iter->tags))
403 : return NULL;
404 0 : if (likely(iter->tags & 1ul)) {
405 0 : iter->index = __radix_tree_iter_add(iter, 1);
406 0 : slot++;
407 : goto found;
408 : }
409 0 : if (!(flags & RADIX_TREE_ITER_CONTIG)) {
410 0 : unsigned offset = __ffs(iter->tags);
411 :
412 0 : iter->tags >>= offset++;
413 0 : iter->index = __radix_tree_iter_add(iter, offset);
414 0 : slot += offset;
415 : goto found;
416 : }
417 : } else {
418 0 : long count = radix_tree_chunk_size(iter);
419 :
420 0 : while (--count > 0) {
421 0 : slot++;
422 0 : iter->index = __radix_tree_iter_add(iter, 1);
423 :
424 0 : 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 */
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