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
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.
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.
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.
21 #ifndef _LINUX_RADIX_TREE_H
22 #define _LINUX_RADIX_TREE_H
24 #include <linux/bitops.h>
25 #include <linux/kernel.h>
26 #include <linux/list.h>
27 #include <linux/preempt.h>
28 #include <linux/rcupdate.h>
29 #include <linux/spinlock.h>
30 #include <linux/types.h>
33 * The bottom two bits of the slot determine how the remaining bits in the
34 * slot are interpreted:
38 * 10 - exceptional entry
39 * 11 - this bit combination is currently unused/reserved
41 * The internal entry may be a pointer to the next level in the tree, a
42 * sibling entry, or an indicator that the entry in this slot has been moved
43 * to another location in the tree and the lookup should be restarted. While
44 * NULL fits the 'data pointer' pattern, it means that there is no entry in
45 * the tree for this index (no matter what level of the tree it is found at).
46 * This means that you cannot store NULL in the tree as a value for the index.
48 #define RADIX_TREE_ENTRY_MASK 3UL
49 #define RADIX_TREE_INTERNAL_NODE 1UL
52 * Most users of the radix tree store pointers but shmem/tmpfs stores swap
53 * entries in the same tree. They are marked as exceptional entries to
54 * distinguish them from pointers to struct page.
55 * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
57 #define RADIX_TREE_EXCEPTIONAL_ENTRY 2
58 #define RADIX_TREE_EXCEPTIONAL_SHIFT 2
60 static inline bool radix_tree_is_internal_node(void *ptr)
62 return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) ==
63 RADIX_TREE_INTERNAL_NODE;
66 /*** radix-tree API starts here ***/
68 #define RADIX_TREE_MAX_TAGS 3
70 #ifndef RADIX_TREE_MAP_SHIFT
71 #define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
74 #define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
75 #define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
77 #define RADIX_TREE_TAG_LONGS \
78 ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
80 #define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
81 #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
82 RADIX_TREE_MAP_SHIFT))
85 * @count is the count of every non-NULL element in the ->slots array
86 * whether that is an exceptional entry, a retry entry, a user pointer,
87 * a sibling entry or a pointer to the next level of the tree.
88 * @exceptional is the count of every element in ->slots which is
89 * either radix_tree_exceptional_entry() or is a sibling entry for an
92 struct radix_tree_node {
93 unsigned char shift; /* Bits remaining in each slot */
94 unsigned char offset; /* Slot offset in parent */
95 unsigned char count; /* Total entry count */
96 unsigned char exceptional; /* Exceptional entry count */
97 struct radix_tree_node *parent; /* Used when ascending tree */
98 struct radix_tree_root *root; /* The tree we belong to */
100 struct list_head private_list; /* For tree user */
101 struct rcu_head rcu_head; /* Used when freeing node */
103 void __rcu *slots[RADIX_TREE_MAP_SIZE];
104 unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
107 /* The top bits of gfp_mask are used to store the root tags and the IDR flag */
108 #define ROOT_IS_IDR ((__force gfp_t)(1 << __GFP_BITS_SHIFT))
109 #define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT + 1)
111 struct radix_tree_root {
113 struct radix_tree_node __rcu *rnode;
116 #define RADIX_TREE_INIT(mask) { \
117 .gfp_mask = (mask), \
121 #define RADIX_TREE(name, mask) \
122 struct radix_tree_root name = RADIX_TREE_INIT(mask)
124 #define INIT_RADIX_TREE(root, mask) \
126 (root)->gfp_mask = (mask); \
127 (root)->rnode = NULL; \
130 static inline bool radix_tree_empty(const struct radix_tree_root *root)
132 return root->rnode == NULL;
136 * struct radix_tree_iter - radix tree iterator state
138 * @index: index of current slot
139 * @next_index: one beyond the last index for this chunk
140 * @tags: bit-mask for tag-iterating
141 * @node: node that contains current slot
142 * @shift: shift for the node that holds our slots
144 * This radix tree iterator works in terms of "chunks" of slots. A chunk is a
145 * subinterval of slots contained within one radix tree leaf node. It is
146 * described by a pointer to its first slot and a struct radix_tree_iter
147 * which holds the chunk's position in the tree and its size. For tagged
148 * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
151 struct radix_tree_iter {
153 unsigned long next_index;
155 struct radix_tree_node *node;
156 #ifdef CONFIG_RADIX_TREE_MULTIORDER
161 static inline unsigned int iter_shift(const struct radix_tree_iter *iter)
163 #ifdef CONFIG_RADIX_TREE_MULTIORDER
171 * Radix-tree synchronization
173 * The radix-tree API requires that users provide all synchronisation (with
174 * specific exceptions, noted below).
176 * Synchronization of access to the data items being stored in the tree, and
177 * management of their lifetimes must be completely managed by API users.
179 * For API usage, in general,
180 * - any function _modifying_ the tree or tags (inserting or deleting
181 * items, setting or clearing tags) must exclude other modifications, and
182 * exclude any functions reading the tree.
183 * - any function _reading_ the tree or tags (looking up items or tags,
184 * gang lookups) must exclude modifications to the tree, but may occur
185 * concurrently with other readers.
187 * The notable exceptions to this rule are the following functions:
188 * __radix_tree_lookup
190 * radix_tree_lookup_slot
192 * radix_tree_gang_lookup
193 * radix_tree_gang_lookup_slot
194 * radix_tree_gang_lookup_tag
195 * radix_tree_gang_lookup_tag_slot
198 * The first 8 functions are able to be called locklessly, using RCU. The
199 * caller must ensure calls to these functions are made within rcu_read_lock()
200 * regions. Other readers (lock-free or otherwise) and modifications may be
201 * running concurrently.
203 * It is still required that the caller manage the synchronization and lifetimes
204 * of the items. So if RCU lock-free lookups are used, typically this would mean
205 * that the items have their own locks, or are amenable to lock-free access; and
206 * that the items are freed by RCU (or only freed after having been deleted from
207 * the radix tree *and* a synchronize_rcu() grace period).
209 * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
210 * access to data items when inserting into or looking up from the radix tree)
212 * Note that the value returned by radix_tree_tag_get() may not be relied upon
213 * if only the RCU read lock is held. Functions to set/clear tags and to
214 * delete nodes running concurrently with it may affect its result such that
215 * two consecutive reads in the same locked section may return different
216 * values. If reliability is required, modification functions must also be
217 * excluded from concurrency.
219 * radix_tree_tagged is able to be called without locking or RCU.
223 * radix_tree_deref_slot - dereference a slot
224 * @slot: slot pointer, returned by radix_tree_lookup_slot
226 * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
227 * locked across slot lookup and dereference. Not required if write lock is
228 * held (ie. items cannot be concurrently inserted).
230 * radix_tree_deref_retry must be used to confirm validity of the pointer if
231 * only the read lock is held.
233 * Return: entry stored in that slot.
235 static inline void *radix_tree_deref_slot(void __rcu **slot)
237 return rcu_dereference(*slot);
241 * radix_tree_deref_slot_protected - dereference a slot with tree lock held
242 * @slot: slot pointer, returned by radix_tree_lookup_slot
244 * Similar to radix_tree_deref_slot. The caller does not hold the RCU read
245 * lock but it must hold the tree lock to prevent parallel updates.
247 * Return: entry stored in that slot.
249 static inline void *radix_tree_deref_slot_protected(void __rcu **slot,
250 spinlock_t *treelock)
252 return rcu_dereference_protected(*slot, lockdep_is_held(treelock));
256 * radix_tree_deref_retry - check radix_tree_deref_slot
257 * @arg: pointer returned by radix_tree_deref_slot
258 * Returns: 0 if retry is not required, otherwise retry is required
260 * radix_tree_deref_retry must be used with radix_tree_deref_slot.
262 static inline int radix_tree_deref_retry(void *arg)
264 return unlikely(radix_tree_is_internal_node(arg));
268 * radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry?
269 * @arg: value returned by radix_tree_deref_slot
270 * Returns: 0 if well-aligned pointer, non-0 if exceptional entry.
272 static inline int radix_tree_exceptional_entry(void *arg)
274 /* Not unlikely because radix_tree_exception often tested first */
275 return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
279 * radix_tree_exception - radix_tree_deref_slot returned either exception?
280 * @arg: value returned by radix_tree_deref_slot
281 * Returns: 0 if well-aligned pointer, non-0 if either kind of exception.
283 static inline int radix_tree_exception(void *arg)
285 return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK);
288 int __radix_tree_create(struct radix_tree_root *, unsigned long index,
289 unsigned order, struct radix_tree_node **nodep,
290 void __rcu ***slotp);
291 int __radix_tree_insert(struct radix_tree_root *, unsigned long index,
292 unsigned order, void *);
293 static inline int radix_tree_insert(struct radix_tree_root *root,
294 unsigned long index, void *entry)
296 return __radix_tree_insert(root, index, 0, entry);
298 void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index,
299 struct radix_tree_node **nodep, void __rcu ***slotp);
300 void *radix_tree_lookup(const struct radix_tree_root *, unsigned long);
301 void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *,
302 unsigned long index);
303 typedef void (*radix_tree_update_node_t)(struct radix_tree_node *);
304 void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,
305 void __rcu **slot, void *entry,
306 radix_tree_update_node_t update_node);
307 void radix_tree_iter_replace(struct radix_tree_root *,
308 const struct radix_tree_iter *, void __rcu **slot, void *entry);
309 void radix_tree_replace_slot(struct radix_tree_root *,
310 void __rcu **slot, void *entry);
311 void __radix_tree_delete_node(struct radix_tree_root *,
312 struct radix_tree_node *,
313 radix_tree_update_node_t update_node);
314 void radix_tree_iter_delete(struct radix_tree_root *,
315 struct radix_tree_iter *iter, void __rcu **slot);
316 void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
317 void *radix_tree_delete(struct radix_tree_root *, unsigned long);
318 void radix_tree_clear_tags(struct radix_tree_root *, struct radix_tree_node *,
320 unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,
321 void **results, unsigned long first_index,
322 unsigned int max_items);
323 unsigned int radix_tree_gang_lookup_slot(const struct radix_tree_root *,
324 void __rcu ***results, unsigned long *indices,
325 unsigned long first_index, unsigned int max_items);
326 int radix_tree_preload(gfp_t gfp_mask);
327 int radix_tree_maybe_preload(gfp_t gfp_mask);
328 int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order);
329 void radix_tree_init(void);
330 void *radix_tree_tag_set(struct radix_tree_root *,
331 unsigned long index, unsigned int tag);
332 void *radix_tree_tag_clear(struct radix_tree_root *,
333 unsigned long index, unsigned int tag);
334 int radix_tree_tag_get(const struct radix_tree_root *,
335 unsigned long index, unsigned int tag);
336 void radix_tree_iter_tag_set(struct radix_tree_root *,
337 const struct radix_tree_iter *iter, unsigned int tag);
338 void radix_tree_iter_tag_clear(struct radix_tree_root *,
339 const struct radix_tree_iter *iter, unsigned int tag);
340 unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *,
341 void **results, unsigned long first_index,
342 unsigned int max_items, unsigned int tag);
343 unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *,
344 void __rcu ***results, unsigned long first_index,
345 unsigned int max_items, unsigned int tag);
346 int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag);
348 static inline void radix_tree_preload_end(void)
353 int radix_tree_split_preload(unsigned old_order, unsigned new_order, gfp_t);
354 int radix_tree_split(struct radix_tree_root *, unsigned long index,
356 int radix_tree_join(struct radix_tree_root *, unsigned long index,
357 unsigned new_order, void *);
359 void __rcu **idr_get_free_cmn(struct radix_tree_root *root,
360 struct radix_tree_iter *iter, gfp_t gfp,
362 static inline void __rcu **idr_get_free(struct radix_tree_root *root,
363 struct radix_tree_iter *iter,
367 return idr_get_free_cmn(root, iter, gfp, end > 0 ? end - 1 : INT_MAX);
370 static inline void __rcu **idr_get_free_ext(struct radix_tree_root *root,
371 struct radix_tree_iter *iter,
375 return idr_get_free_cmn(root, iter, gfp, end - 1);
379 RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */
380 RADIX_TREE_ITER_TAGGED = 0x10, /* lookup tagged slots */
381 RADIX_TREE_ITER_CONTIG = 0x20, /* stop at first hole */
385 * radix_tree_iter_init - initialize radix tree iterator
387 * @iter: pointer to iterator state
388 * @start: iteration starting index
391 static __always_inline void __rcu **
392 radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
395 * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
396 * in the case of a successful tagged chunk lookup. If the lookup was
397 * unsuccessful or non-tagged then nobody cares about ->tags.
399 * Set index to zero to bypass next_index overflow protection.
400 * See the comment in radix_tree_next_chunk() for details.
403 iter->next_index = start;
408 * radix_tree_next_chunk - find next chunk of slots for iteration
410 * @root: radix tree root
411 * @iter: iterator state
412 * @flags: RADIX_TREE_ITER_* flags and tag index
413 * Returns: pointer to chunk first slot, or NULL if there no more left
415 * This function looks up the next chunk in the radix tree starting from
416 * @iter->next_index. It returns a pointer to the chunk's first slot.
417 * Also it fills @iter with data about chunk: position in the tree (index),
418 * its end (next_index), and constructs a bit mask for tagged iterating (tags).
420 void __rcu **radix_tree_next_chunk(const struct radix_tree_root *,
421 struct radix_tree_iter *iter, unsigned flags);
424 * radix_tree_iter_lookup - look up an index in the radix tree
425 * @root: radix tree root
426 * @iter: iterator state
427 * @index: key to look up
429 * If @index is present in the radix tree, this function returns the slot
430 * containing it and updates @iter to describe the entry. If @index is not
431 * present, it returns NULL.
433 static inline void __rcu **
434 radix_tree_iter_lookup(const struct radix_tree_root *root,
435 struct radix_tree_iter *iter, unsigned long index)
437 radix_tree_iter_init(iter, index);
438 return radix_tree_next_chunk(root, iter, RADIX_TREE_ITER_CONTIG);
442 * radix_tree_iter_find - find a present entry
443 * @root: radix tree root
444 * @iter: iterator state
445 * @index: start location
447 * This function returns the slot containing the entry with the lowest index
448 * which is at least @index. If @index is larger than any present entry, this
449 * function returns NULL. The @iter is updated to describe the entry found.
451 static inline void __rcu **
452 radix_tree_iter_find(const struct radix_tree_root *root,
453 struct radix_tree_iter *iter, unsigned long index)
455 radix_tree_iter_init(iter, index);
456 return radix_tree_next_chunk(root, iter, 0);
460 * radix_tree_iter_retry - retry this chunk of the iteration
461 * @iter: iterator state
463 * If we iterate over a tree protected only by the RCU lock, a race
464 * against deletion or creation may result in seeing a slot for which
465 * radix_tree_deref_retry() returns true. If so, call this function
466 * and continue the iteration.
468 static inline __must_check
469 void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter)
471 iter->next_index = iter->index;
476 static inline unsigned long
477 __radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
479 return iter->index + (slots << iter_shift(iter));
483 * radix_tree_iter_resume - resume iterating when the chunk may be invalid
484 * @slot: pointer to current slot
485 * @iter: iterator state
486 * Returns: New slot pointer
488 * If the iterator needs to release then reacquire a lock, the chunk may
489 * have been invalidated by an insertion or deletion. Call this function
490 * before releasing the lock to continue the iteration from the next index.
492 void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot,
493 struct radix_tree_iter *iter);
496 * radix_tree_chunk_size - get current chunk size
498 * @iter: pointer to radix tree iterator
499 * Returns: current chunk size
501 static __always_inline long
502 radix_tree_chunk_size(struct radix_tree_iter *iter)
504 return (iter->next_index - iter->index) >> iter_shift(iter);
507 #ifdef CONFIG_RADIX_TREE_MULTIORDER
508 void __rcu **__radix_tree_next_slot(void __rcu **slot,
509 struct radix_tree_iter *iter, unsigned flags);
511 /* Can't happen without sibling entries, but the compiler can't tell that */
512 static inline void __rcu **__radix_tree_next_slot(void __rcu **slot,
513 struct radix_tree_iter *iter, unsigned flags)
520 * radix_tree_next_slot - find next slot in chunk
522 * @slot: pointer to current slot
523 * @iter: pointer to interator state
524 * @flags: RADIX_TREE_ITER_*, should be constant
525 * Returns: pointer to next slot, or NULL if there no more left
527 * This function updates @iter->index in the case of a successful lookup.
528 * For tagged lookup it also eats @iter->tags.
530 * There are several cases where 'slot' can be passed in as NULL to this
531 * function. These cases result from the use of radix_tree_iter_resume() or
532 * radix_tree_iter_retry(). In these cases we don't end up dereferencing
533 * 'slot' because either:
534 * a) we are doing tagged iteration and iter->tags has been set to 0, or
535 * b) we are doing non-tagged iteration, and iter->index and iter->next_index
536 * have been set up so that radix_tree_chunk_size() returns 1 or 0.
538 static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot,
539 struct radix_tree_iter *iter, unsigned flags)
541 if (flags & RADIX_TREE_ITER_TAGGED) {
543 if (unlikely(!iter->tags))
545 if (likely(iter->tags & 1ul)) {
546 iter->index = __radix_tree_iter_add(iter, 1);
550 if (!(flags & RADIX_TREE_ITER_CONTIG)) {
551 unsigned offset = __ffs(iter->tags);
553 iter->tags >>= offset++;
554 iter->index = __radix_tree_iter_add(iter, offset);
559 long count = radix_tree_chunk_size(iter);
561 while (--count > 0) {
563 iter->index = __radix_tree_iter_add(iter, 1);
567 if (flags & RADIX_TREE_ITER_CONTIG) {
568 /* forbid switching to the next chunk */
569 iter->next_index = 0;
577 if (unlikely(radix_tree_is_internal_node(rcu_dereference_raw(*slot))))
578 return __radix_tree_next_slot(slot, iter, flags);
583 * radix_tree_for_each_slot - iterate over non-empty slots
585 * @slot: the void** variable for pointer to slot
586 * @root: the struct radix_tree_root pointer
587 * @iter: the struct radix_tree_iter pointer
588 * @start: iteration starting index
590 * @slot points to radix tree slot, @iter->index contains its index.
592 #define radix_tree_for_each_slot(slot, root, iter, start) \
593 for (slot = radix_tree_iter_init(iter, start) ; \
594 slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \
595 slot = radix_tree_next_slot(slot, iter, 0))
598 * radix_tree_for_each_contig - iterate over contiguous slots
600 * @slot: the void** variable for pointer to slot
601 * @root: the struct radix_tree_root pointer
602 * @iter: the struct radix_tree_iter pointer
603 * @start: iteration starting index
605 * @slot points to radix tree slot, @iter->index contains its index.
607 #define radix_tree_for_each_contig(slot, root, iter, start) \
608 for (slot = radix_tree_iter_init(iter, start) ; \
609 slot || (slot = radix_tree_next_chunk(root, iter, \
610 RADIX_TREE_ITER_CONTIG)) ; \
611 slot = radix_tree_next_slot(slot, iter, \
612 RADIX_TREE_ITER_CONTIG))
615 * radix_tree_for_each_tagged - iterate over tagged slots
617 * @slot: the void** variable for pointer to slot
618 * @root: the struct radix_tree_root pointer
619 * @iter: the struct radix_tree_iter pointer
620 * @start: iteration starting index
623 * @slot points to radix tree slot, @iter->index contains its index.
625 #define radix_tree_for_each_tagged(slot, root, iter, start, tag) \
626 for (slot = radix_tree_iter_init(iter, start) ; \
627 slot || (slot = radix_tree_next_chunk(root, iter, \
628 RADIX_TREE_ITER_TAGGED | tag)) ; \
629 slot = radix_tree_next_slot(slot, iter, \
630 RADIX_TREE_ITER_TAGGED | tag))
632 #endif /* _LINUX_RADIX_TREE_H */