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
28struct 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};
34DECLARE_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
55static 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
86static 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 */
106struct 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 */
177static 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 */
191static 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 */
204static 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 */
214static inline int radix_tree_exception(void *arg)
215{
216 return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK);
217}
218
219int radix_tree_insert(struct radix_tree_root *, unsigned long index,
220 void *);
221void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index,
222 struct radix_tree_node **nodep, void __rcu ***slotp);
223void *radix_tree_lookup(const struct radix_tree_root *, unsigned long);
224void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *,
225 unsigned long index);
226void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,
227 void __rcu **slot, void *entry);
228void radix_tree_iter_replace(struct radix_tree_root *,
229 const struct radix_tree_iter *, void __rcu **slot, void *entry);
230void radix_tree_replace_slot(struct radix_tree_root *,
231 void __rcu **slot, void *entry);
232void radix_tree_iter_delete(struct radix_tree_root *,
233 struct radix_tree_iter *iter, void __rcu **slot);
234void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
235void *radix_tree_delete(struct radix_tree_root *, unsigned long);
236unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,
237 void **results, unsigned long first_index,
238 unsigned int max_items);
239int radix_tree_preload(gfp_t gfp_mask);
240int radix_tree_maybe_preload(gfp_t gfp_mask);
241void radix_tree_init(void);
242void *radix_tree_tag_set(struct radix_tree_root *,
243 unsigned long index, unsigned int tag);
244void *radix_tree_tag_clear(struct radix_tree_root *,
245 unsigned long index, unsigned int tag);
246int radix_tree_tag_get(const struct radix_tree_root *,
247 unsigned long index, unsigned int tag);
248void radix_tree_iter_tag_clear(struct radix_tree_root *,
249 const struct radix_tree_iter *iter, unsigned int tag);
250unsigned 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);
253unsigned 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);
256int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag);
257
258static inline void radix_tree_preload_end(void)
259{
260 local_unlock(&radix_tree_preloads.lock);
261}
262
263void __rcu **idr_get_free(struct radix_tree_root *root,
264 struct radix_tree_iter *iter, gfp_t gfp,
265 unsigned long max);
266
267enum {
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 */
280static __always_inline void __rcu **
281radix_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 */
309void __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 */
322static inline void __rcu **
323radix_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 */
339static inline __must_check
340void __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
347static 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 */
363void __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 */
372static __always_inline long
373radix_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 */
397static __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