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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 : :
20 : : /* Keep unconverted code working */
21 : : #define radix_tree_root xarray
22 : : #define radix_tree_node xa_node
23 : :
24 : : /*
25 : : * The bottom two bits of the slot determine how the remaining bits in the
26 : : * slot are interpreted:
27 : : *
28 : : * 00 - data pointer
29 : : * 10 - internal entry
30 : : * x1 - value entry
31 : : *
32 : : * The internal entry may be a pointer to the next level in the tree, a
33 : : * sibling entry, or an indicator that the entry in this slot has been moved
34 : : * to another location in the tree and the lookup should be restarted. While
35 : : * NULL fits the 'data pointer' pattern, it means that there is no entry in
36 : : * the tree for this index (no matter what level of the tree it is found at).
37 : : * This means that storing a NULL entry in the tree is the same as deleting
38 : : * the entry from the tree.
39 : : */
40 : : #define RADIX_TREE_ENTRY_MASK 3UL
41 : : #define RADIX_TREE_INTERNAL_NODE 2UL
42 : :
43 : : static inline bool radix_tree_is_internal_node(void *ptr)
44 : : {
45 : 911232232 : return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) ==
46 : : RADIX_TREE_INTERNAL_NODE;
47 : : }
48 : :
49 : : /*** radix-tree API starts here ***/
50 : :
51 : : #define RADIX_TREE_MAP_SHIFT XA_CHUNK_SHIFT
52 : : #define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
53 : : #define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
54 : :
55 : : #define RADIX_TREE_MAX_TAGS XA_MAX_MARKS
56 : : #define RADIX_TREE_TAG_LONGS XA_MARK_LONGS
57 : :
58 : : #define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
59 : : #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
60 : : RADIX_TREE_MAP_SHIFT))
61 : :
62 : : /* The IDR tag is stored in the low bits of xa_flags */
63 : : #define ROOT_IS_IDR ((__force gfp_t)4)
64 : : /* The top bits of xa_flags are used to store the root tags */
65 : : #define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT)
66 : :
67 : : #define RADIX_TREE_INIT(name, mask) XARRAY_INIT(name, mask)
68 : :
69 : : #define RADIX_TREE(name, mask) \
70 : : struct radix_tree_root name = RADIX_TREE_INIT(name, mask)
71 : :
72 : : #define INIT_RADIX_TREE(root, mask) xa_init_flags(root, mask)
73 : :
74 : : static inline bool radix_tree_empty(const struct radix_tree_root *root)
75 : : {
76 : 0 : return root->xa_head == NULL;
77 : : }
78 : :
79 : : /**
80 : : * struct radix_tree_iter - radix tree iterator state
81 : : *
82 : : * @index: index of current slot
83 : : * @next_index: one beyond the last index for this chunk
84 : : * @tags: bit-mask for tag-iterating
85 : : * @node: node that contains current slot
86 : : *
87 : : * This radix tree iterator works in terms of "chunks" of slots. A chunk is a
88 : : * subinterval of slots contained within one radix tree leaf node. It is
89 : : * described by a pointer to its first slot and a struct radix_tree_iter
90 : : * which holds the chunk's position in the tree and its size. For tagged
91 : : * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
92 : : * radix tree tag.
93 : : */
94 : : struct radix_tree_iter {
95 : : unsigned long index;
96 : : unsigned long next_index;
97 : : unsigned long tags;
98 : : struct radix_tree_node *node;
99 : : };
100 : :
101 : : /**
102 : : * Radix-tree synchronization
103 : : *
104 : : * The radix-tree API requires that users provide all synchronisation (with
105 : : * specific exceptions, noted below).
106 : : *
107 : : * Synchronization of access to the data items being stored in the tree, and
108 : : * management of their lifetimes must be completely managed by API users.
109 : : *
110 : : * For API usage, in general,
111 : : * - any function _modifying_ the tree or tags (inserting or deleting
112 : : * items, setting or clearing tags) must exclude other modifications, and
113 : : * exclude any functions reading the tree.
114 : : * - any function _reading_ the tree or tags (looking up items or tags,
115 : : * gang lookups) must exclude modifications to the tree, but may occur
116 : : * concurrently with other readers.
117 : : *
118 : : * The notable exceptions to this rule are the following functions:
119 : : * __radix_tree_lookup
120 : : * radix_tree_lookup
121 : : * radix_tree_lookup_slot
122 : : * radix_tree_tag_get
123 : : * radix_tree_gang_lookup
124 : : * radix_tree_gang_lookup_tag
125 : : * radix_tree_gang_lookup_tag_slot
126 : : * radix_tree_tagged
127 : : *
128 : : * The first 7 functions are able to be called locklessly, using RCU. The
129 : : * caller must ensure calls to these functions are made within rcu_read_lock()
130 : : * regions. Other readers (lock-free or otherwise) and modifications may be
131 : : * running concurrently.
132 : : *
133 : : * It is still required that the caller manage the synchronization and lifetimes
134 : : * of the items. So if RCU lock-free lookups are used, typically this would mean
135 : : * that the items have their own locks, or are amenable to lock-free access; and
136 : : * that the items are freed by RCU (or only freed after having been deleted from
137 : : * the radix tree *and* a synchronize_rcu() grace period).
138 : : *
139 : : * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
140 : : * access to data items when inserting into or looking up from the radix tree)
141 : : *
142 : : * Note that the value returned by radix_tree_tag_get() may not be relied upon
143 : : * if only the RCU read lock is held. Functions to set/clear tags and to
144 : : * delete nodes running concurrently with it may affect its result such that
145 : : * two consecutive reads in the same locked section may return different
146 : : * values. If reliability is required, modification functions must also be
147 : : * excluded from concurrency.
148 : : *
149 : : * radix_tree_tagged is able to be called without locking or RCU.
150 : : */
151 : :
152 : : /**
153 : : * radix_tree_deref_slot - dereference a slot
154 : : * @slot: slot pointer, returned by radix_tree_lookup_slot
155 : : *
156 : : * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
157 : : * locked across slot lookup and dereference. Not required if write lock is
158 : : * held (ie. items cannot be concurrently inserted).
159 : : *
160 : : * radix_tree_deref_retry must be used to confirm validity of the pointer if
161 : : * only the read lock is held.
162 : : *
163 : : * Return: entry stored in that slot.
164 : : */
165 : : static inline void *radix_tree_deref_slot(void __rcu **slot)
166 : : {
167 : : return rcu_dereference(*slot);
168 : : }
169 : :
170 : : /**
171 : : * radix_tree_deref_slot_protected - dereference a slot with tree lock held
172 : : * @slot: slot pointer, returned by radix_tree_lookup_slot
173 : : *
174 : : * Similar to radix_tree_deref_slot. The caller does not hold the RCU read
175 : : * lock but it must hold the tree lock to prevent parallel updates.
176 : : *
177 : : * Return: entry stored in that slot.
178 : : */
179 : : static inline void *radix_tree_deref_slot_protected(void __rcu **slot,
180 : : spinlock_t *treelock)
181 : : {
182 : : return rcu_dereference_protected(*slot, lockdep_is_held(treelock));
183 : : }
184 : :
185 : : /**
186 : : * radix_tree_deref_retry - check radix_tree_deref_slot
187 : : * @arg: pointer returned by radix_tree_deref_slot
188 : : * Returns: 0 if retry is not required, otherwise retry is required
189 : : *
190 : : * radix_tree_deref_retry must be used with radix_tree_deref_slot.
191 : : */
192 : : static inline int radix_tree_deref_retry(void *arg)
193 : : {
194 : : return unlikely(radix_tree_is_internal_node(arg));
195 : : }
196 : :
197 : : /**
198 : : * radix_tree_exception - radix_tree_deref_slot returned either exception?
199 : : * @arg: value returned by radix_tree_deref_slot
200 : : * Returns: 0 if well-aligned pointer, non-0 if either kind of exception.
201 : : */
202 : : static inline int radix_tree_exception(void *arg)
203 : : {
204 : : return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK);
205 : : }
206 : :
207 : : int radix_tree_insert(struct radix_tree_root *, unsigned long index,
208 : : void *);
209 : : void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index,
210 : : struct radix_tree_node **nodep, void __rcu ***slotp);
211 : : void *radix_tree_lookup(const struct radix_tree_root *, unsigned long);
212 : : void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *,
213 : : unsigned long index);
214 : : void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,
215 : : void __rcu **slot, void *entry);
216 : : void radix_tree_iter_replace(struct radix_tree_root *,
217 : : const struct radix_tree_iter *, void __rcu **slot, void *entry);
218 : : void radix_tree_replace_slot(struct radix_tree_root *,
219 : : void __rcu **slot, void *entry);
220 : : void radix_tree_iter_delete(struct radix_tree_root *,
221 : : struct radix_tree_iter *iter, void __rcu **slot);
222 : : void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
223 : : void *radix_tree_delete(struct radix_tree_root *, unsigned long);
224 : : unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,
225 : : void **results, unsigned long first_index,
226 : : unsigned int max_items);
227 : : int radix_tree_preload(gfp_t gfp_mask);
228 : : int radix_tree_maybe_preload(gfp_t gfp_mask);
229 : : void radix_tree_init(void);
230 : : void *radix_tree_tag_set(struct radix_tree_root *,
231 : : unsigned long index, unsigned int tag);
232 : : void *radix_tree_tag_clear(struct radix_tree_root *,
233 : : unsigned long index, unsigned int tag);
234 : : int radix_tree_tag_get(const struct radix_tree_root *,
235 : : unsigned long index, unsigned int tag);
236 : : void radix_tree_iter_tag_clear(struct radix_tree_root *,
237 : : const struct radix_tree_iter *iter, unsigned int tag);
238 : : unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *,
239 : : void **results, unsigned long first_index,
240 : : unsigned int max_items, unsigned int tag);
241 : : unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *,
242 : : void __rcu ***results, unsigned long first_index,
243 : : unsigned int max_items, unsigned int tag);
244 : : int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag);
245 : :
246 : : static inline void radix_tree_preload_end(void)
247 : : {
248 : 10100 : preempt_enable();
249 : : }
250 : :
251 : : void __rcu **idr_get_free(struct radix_tree_root *root,
252 : : struct radix_tree_iter *iter, gfp_t gfp,
253 : : unsigned long max);
254 : :
255 : : enum {
256 : : RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */
257 : : RADIX_TREE_ITER_TAGGED = 0x10, /* lookup tagged slots */
258 : : RADIX_TREE_ITER_CONTIG = 0x20, /* stop at first hole */
259 : : };
260 : :
261 : : /**
262 : : * radix_tree_iter_init - initialize radix tree iterator
263 : : *
264 : : * @iter: pointer to iterator state
265 : : * @start: iteration starting index
266 : : * Returns: NULL
267 : : */
268 : : static __always_inline void __rcu **
269 : : radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
270 : : {
271 : : /*
272 : : * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
273 : : * in the case of a successful tagged chunk lookup. If the lookup was
274 : : * unsuccessful or non-tagged then nobody cares about ->tags.
275 : : *
276 : : * Set index to zero to bypass next_index overflow protection.
277 : : * See the comment in radix_tree_next_chunk() for details.
278 : : */
279 : 10395210 : iter->index = 0;
280 : 10395210 : iter->next_index = start;
281 : : return NULL;
282 : : }
283 : :
284 : : /**
285 : : * radix_tree_next_chunk - find next chunk of slots for iteration
286 : : *
287 : : * @root: radix tree root
288 : : * @iter: iterator state
289 : : * @flags: RADIX_TREE_ITER_* flags and tag index
290 : : * Returns: pointer to chunk first slot, or NULL if there no more left
291 : : *
292 : : * This function looks up the next chunk in the radix tree starting from
293 : : * @iter->next_index. It returns a pointer to the chunk's first slot.
294 : : * Also it fills @iter with data about chunk: position in the tree (index),
295 : : * its end (next_index), and constructs a bit mask for tagged iterating (tags).
296 : : */
297 : : void __rcu **radix_tree_next_chunk(const struct radix_tree_root *,
298 : : struct radix_tree_iter *iter, unsigned flags);
299 : :
300 : : /**
301 : : * radix_tree_iter_lookup - look up an index in the radix tree
302 : : * @root: radix tree root
303 : : * @iter: iterator state
304 : : * @index: key to look up
305 : : *
306 : : * If @index is present in the radix tree, this function returns the slot
307 : : * containing it and updates @iter to describe the entry. If @index is not
308 : : * present, it returns NULL.
309 : : */
310 : : static inline void __rcu **
311 : : radix_tree_iter_lookup(const struct radix_tree_root *root,
312 : : struct radix_tree_iter *iter, unsigned long index)
313 : : {
314 : : radix_tree_iter_init(iter, index);
315 : : return radix_tree_next_chunk(root, iter, RADIX_TREE_ITER_CONTIG);
316 : : }
317 : :
318 : : /**
319 : : * radix_tree_iter_retry - retry this chunk of the iteration
320 : : * @iter: iterator state
321 : : *
322 : : * If we iterate over a tree protected only by the RCU lock, a race
323 : : * against deletion or creation may result in seeing a slot for which
324 : : * radix_tree_deref_retry() returns true. If so, call this function
325 : : * and continue the iteration.
326 : : */
327 : : static inline __must_check
328 : : void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter)
329 : : {
330 : 0 : iter->next_index = iter->index;
331 : 0 : iter->tags = 0;
332 : : return NULL;
333 : : }
334 : :
335 : : static inline unsigned long
336 : 0 : __radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
337 : : {
338 : 5208300 : return iter->index + slots;
339 : : }
340 : :
341 : : /**
342 : : * radix_tree_iter_resume - resume iterating when the chunk may be invalid
343 : : * @slot: pointer to current slot
344 : : * @iter: iterator state
345 : : * Returns: New slot pointer
346 : : *
347 : : * If the iterator needs to release then reacquire a lock, the chunk may
348 : : * have been invalidated by an insertion or deletion. Call this function
349 : : * before releasing the lock to continue the iteration from the next index.
350 : : */
351 : : void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot,
352 : : struct radix_tree_iter *iter);
353 : :
354 : : /**
355 : : * radix_tree_chunk_size - get current chunk size
356 : : *
357 : : * @iter: pointer to radix tree iterator
358 : : * Returns: current chunk size
359 : : */
360 : : static __always_inline long
361 : : radix_tree_chunk_size(struct radix_tree_iter *iter)
362 : : {
363 : 0 : return iter->next_index - iter->index;
364 : : }
365 : :
366 : : /**
367 : : * radix_tree_next_slot - find next slot in chunk
368 : : *
369 : : * @slot: pointer to current slot
370 : : * @iter: pointer to interator state
371 : : * @flags: RADIX_TREE_ITER_*, should be constant
372 : : * Returns: pointer to next slot, or NULL if there no more left
373 : : *
374 : : * This function updates @iter->index in the case of a successful lookup.
375 : : * For tagged lookup it also eats @iter->tags.
376 : : *
377 : : * There are several cases where 'slot' can be passed in as NULL to this
378 : : * function. These cases result from the use of radix_tree_iter_resume() or
379 : : * radix_tree_iter_retry(). In these cases we don't end up dereferencing
380 : : * 'slot' because either:
381 : : * a) we are doing tagged iteration and iter->tags has been set to 0, or
382 : : * b) we are doing non-tagged iteration, and iter->index and iter->next_index
383 : : * have been set up so that radix_tree_chunk_size() returns 1 or 0.
384 : : */
385 : : static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot,
386 : : struct radix_tree_iter *iter, unsigned flags)
387 : : {
388 : : if (flags & RADIX_TREE_ITER_TAGGED) {
389 : 0 : iter->tags >>= 1;
390 [ # # # # ]: 0 : if (unlikely(!iter->tags))
391 : : return NULL;
392 [ # # # # ]: 0 : if (likely(iter->tags & 1ul)) {
393 : 0 : iter->index = __radix_tree_iter_add(iter, 1);
394 : 0 : slot++;
395 : : goto found;
396 : : }
397 [ # # # # ]: 0 : if (!(flags & RADIX_TREE_ITER_CONTIG)) {
398 : : unsigned offset = __ffs(iter->tags);
399 : :
400 : 0 : iter->tags >>= offset++;
401 : 0 : iter->index = __radix_tree_iter_add(iter, offset);
402 : 0 : slot += offset;
403 : : goto found;
404 : : }
405 : : } else {
406 : : long count = radix_tree_chunk_size(iter);
407 : :
408 [ # # # # ]: 0 : while (--count > 0) {
409 : 0 : slot++;
410 : 0 : iter->index = __radix_tree_iter_add(iter, 1);
411 : :
412 [ # # # # ]: 0 : if (likely(*slot))
413 : : goto found;
414 : : if (flags & RADIX_TREE_ITER_CONTIG) {
415 : : /* forbid switching to the next chunk */
416 : : iter->next_index = 0;
417 : : break;
418 : : }
419 : : }
420 : : }
421 : : return NULL;
422 : :
423 : : found:
424 : : return slot;
425 : : }
426 : :
427 : : /**
428 : : * radix_tree_for_each_slot - iterate over non-empty slots
429 : : *
430 : : * @slot: the void** variable for pointer to slot
431 : : * @root: the struct radix_tree_root pointer
432 : : * @iter: the struct radix_tree_iter pointer
433 : : * @start: iteration starting index
434 : : *
435 : : * @slot points to radix tree slot, @iter->index contains its index.
436 : : */
437 : : #define radix_tree_for_each_slot(slot, root, iter, start) \
438 : : for (slot = radix_tree_iter_init(iter, start) ; \
439 : : slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \
440 : : slot = radix_tree_next_slot(slot, iter, 0))
441 : :
442 : : /**
443 : : * radix_tree_for_each_tagged - iterate over tagged slots
444 : : *
445 : : * @slot: the void** variable for pointer to slot
446 : : * @root: the struct radix_tree_root pointer
447 : : * @iter: the struct radix_tree_iter pointer
448 : : * @start: iteration starting index
449 : : * @tag: tag index
450 : : *
451 : : * @slot points to radix tree slot, @iter->index contains its index.
452 : : */
453 : : #define radix_tree_for_each_tagged(slot, root, iter, start, tag) \
454 : : for (slot = radix_tree_iter_init(iter, start) ; \
455 : : slot || (slot = radix_tree_next_chunk(root, iter, \
456 : : RADIX_TREE_ITER_TAGGED | tag)) ; \
457 : : slot = radix_tree_next_slot(slot, iter, \
458 : : RADIX_TREE_ITER_TAGGED | tag))
459 : :
460 : : #endif /* _LINUX_RADIX_TREE_H */
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