Line data Source code
1 : /*
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
6 : *
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.
11 : *
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.
16 : *
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.
20 : */
21 : #ifndef _LINUX_RADIX_TREE_H
22 : #define _LINUX_RADIX_TREE_H
23 :
24 : #include <linux/preempt.h>
25 : #include <linux/types.h>
26 : #include <linux/bug.h>
27 : #include <linux/kernel.h>
28 : #include <linux/rcupdate.h>
29 :
30 : /*
31 : * An indirect pointer (root->rnode pointing to a radix_tree_node, rather
32 : * than a data item) is signalled by the low bit set in the root->rnode
33 : * pointer.
34 : *
35 : * In this case root->height is > 0, but the indirect pointer tests are
36 : * needed for RCU lookups (because root->height is unreliable). The only
37 : * time callers need worry about this is when doing a lookup_slot under
38 : * RCU.
39 : *
40 : * Indirect pointer in fact is also used to tag the last pointer of a node
41 : * when it is shrunk, before we rcu free the node. See shrink code for
42 : * details.
43 : */
44 : #define RADIX_TREE_INDIRECT_PTR 1
45 : /*
46 : * A common use of the radix tree is to store pointers to struct pages;
47 : * but shmem/tmpfs needs also to store swap entries in the same tree:
48 : * those are marked as exceptional entries to distinguish them.
49 : * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
50 : */
51 : #define RADIX_TREE_EXCEPTIONAL_ENTRY 2
52 : #define RADIX_TREE_EXCEPTIONAL_SHIFT 2
53 :
54 : static inline int radix_tree_is_indirect_ptr(void *ptr)
55 : {
56 : return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
57 : }
58 :
59 : /*** radix-tree API starts here ***/
60 :
61 : #define RADIX_TREE_MAX_TAGS 3
62 :
63 : #ifdef __KERNEL__
64 : #define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
65 : #else
66 : #define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */
67 : #endif
68 :
69 : #define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
70 : #define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
71 :
72 : #define RADIX_TREE_TAG_LONGS \
73 : ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
74 :
75 : #define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
76 : #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
77 : RADIX_TREE_MAP_SHIFT))
78 :
79 : /* Height component in node->path */
80 : #define RADIX_TREE_HEIGHT_SHIFT (RADIX_TREE_MAX_PATH + 1)
81 : #define RADIX_TREE_HEIGHT_MASK ((1UL << RADIX_TREE_HEIGHT_SHIFT) - 1)
82 :
83 : /* Internally used bits of node->count */
84 : #define RADIX_TREE_COUNT_SHIFT (RADIX_TREE_MAP_SHIFT + 1)
85 : #define RADIX_TREE_COUNT_MASK ((1UL << RADIX_TREE_COUNT_SHIFT) - 1)
86 :
87 : struct radix_tree_node {
88 : unsigned int path; /* Offset in parent & height from the bottom */
89 : unsigned int count;
90 : union {
91 : struct {
92 : /* Used when ascending tree */
93 : struct radix_tree_node *parent;
94 : /* For tree user */
95 : void *private_data;
96 : };
97 : /* Used when freeing node */
98 : struct rcu_head rcu_head;
99 : };
100 : /* For tree user */
101 : struct list_head private_list;
102 : void __rcu *slots[RADIX_TREE_MAP_SIZE];
103 : unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
104 : };
105 :
106 : /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
107 : struct radix_tree_root {
108 : unsigned int height;
109 : gfp_t gfp_mask;
110 : struct radix_tree_node __rcu *rnode;
111 : };
112 :
113 : #define RADIX_TREE_INIT(mask) { \
114 : .height = 0, \
115 : .gfp_mask = (mask), \
116 : .rnode = NULL, \
117 : }
118 :
119 : #define RADIX_TREE(name, mask) \
120 : struct radix_tree_root name = RADIX_TREE_INIT(mask)
121 :
122 : #define INIT_RADIX_TREE(root, mask) \
123 : do { \
124 : (root)->height = 0; \
125 : (root)->gfp_mask = (mask); \
126 : (root)->rnode = NULL; \
127 : } while (0)
128 :
129 : /**
130 : * Radix-tree synchronization
131 : *
132 : * The radix-tree API requires that users provide all synchronisation (with
133 : * specific exceptions, noted below).
134 : *
135 : * Synchronization of access to the data items being stored in the tree, and
136 : * management of their lifetimes must be completely managed by API users.
137 : *
138 : * For API usage, in general,
139 : * - any function _modifying_ the tree or tags (inserting or deleting
140 : * items, setting or clearing tags) must exclude other modifications, and
141 : * exclude any functions reading the tree.
142 : * - any function _reading_ the tree or tags (looking up items or tags,
143 : * gang lookups) must exclude modifications to the tree, but may occur
144 : * concurrently with other readers.
145 : *
146 : * The notable exceptions to this rule are the following functions:
147 : * __radix_tree_lookup
148 : * radix_tree_lookup
149 : * radix_tree_lookup_slot
150 : * radix_tree_tag_get
151 : * radix_tree_gang_lookup
152 : * radix_tree_gang_lookup_slot
153 : * radix_tree_gang_lookup_tag
154 : * radix_tree_gang_lookup_tag_slot
155 : * radix_tree_tagged
156 : *
157 : * The first 7 functions are able to be called locklessly, using RCU. The
158 : * caller must ensure calls to these functions are made within rcu_read_lock()
159 : * regions. Other readers (lock-free or otherwise) and modifications may be
160 : * running concurrently.
161 : *
162 : * It is still required that the caller manage the synchronization and lifetimes
163 : * of the items. So if RCU lock-free lookups are used, typically this would mean
164 : * that the items have their own locks, or are amenable to lock-free access; and
165 : * that the items are freed by RCU (or only freed after having been deleted from
166 : * the radix tree *and* a synchronize_rcu() grace period).
167 : *
168 : * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
169 : * access to data items when inserting into or looking up from the radix tree)
170 : *
171 : * Note that the value returned by radix_tree_tag_get() may not be relied upon
172 : * if only the RCU read lock is held. Functions to set/clear tags and to
173 : * delete nodes running concurrently with it may affect its result such that
174 : * two consecutive reads in the same locked section may return different
175 : * values. If reliability is required, modification functions must also be
176 : * excluded from concurrency.
177 : *
178 : * radix_tree_tagged is able to be called without locking or RCU.
179 : */
180 :
181 : /**
182 : * radix_tree_deref_slot - dereference a slot
183 : * @pslot: pointer to slot, returned by radix_tree_lookup_slot
184 : * Returns: item that was stored in that slot with any direct pointer flag
185 : * removed.
186 : *
187 : * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
188 : * locked across slot lookup and dereference. Not required if write lock is
189 : * held (ie. items cannot be concurrently inserted).
190 : *
191 : * radix_tree_deref_retry must be used to confirm validity of the pointer if
192 : * only the read lock is held.
193 : */
194 : static inline void *radix_tree_deref_slot(void **pslot)
195 : {
196 34 : return rcu_dereference(*pslot);
197 : }
198 :
199 : /**
200 : * radix_tree_deref_slot_protected - dereference a slot without RCU lock but with tree lock held
201 : * @pslot: pointer to slot, returned by radix_tree_lookup_slot
202 : * Returns: item that was stored in that slot with any direct pointer flag
203 : * removed.
204 : *
205 : * Similar to radix_tree_deref_slot but only used during migration when a pages
206 : * mapping is being moved. The caller does not hold the RCU read lock but it
207 : * must hold the tree lock to prevent parallel updates.
208 : */
209 : static inline void *radix_tree_deref_slot_protected(void **pslot,
210 : spinlock_t *treelock)
211 : {
212 : return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
213 : }
214 :
215 : /**
216 : * radix_tree_deref_retry - check radix_tree_deref_slot
217 : * @arg: pointer returned by radix_tree_deref_slot
218 : * Returns: 0 if retry is not required, otherwise retry is required
219 : *
220 : * radix_tree_deref_retry must be used with radix_tree_deref_slot.
221 : */
222 : static inline int radix_tree_deref_retry(void *arg)
223 : {
224 0 : return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
225 : }
226 :
227 : /**
228 : * radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry?
229 : * @arg: value returned by radix_tree_deref_slot
230 : * Returns: 0 if well-aligned pointer, non-0 if exceptional entry.
231 : */
232 : static inline int radix_tree_exceptional_entry(void *arg)
233 : {
234 : /* Not unlikely because radix_tree_exception often tested first */
235 0 : return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
236 : }
237 :
238 : /**
239 : * radix_tree_exception - radix_tree_deref_slot returned either exception?
240 : * @arg: value returned by radix_tree_deref_slot
241 : * Returns: 0 if well-aligned pointer, non-0 if either kind of exception.
242 : */
243 : static inline int radix_tree_exception(void *arg)
244 : {
245 34 : return unlikely((unsigned long)arg &
246 : (RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY));
247 : }
248 :
249 : /**
250 : * radix_tree_replace_slot - replace item in a slot
251 : * @pslot: pointer to slot, returned by radix_tree_lookup_slot
252 : * @item: new item to store in the slot.
253 : *
254 : * For use with radix_tree_lookup_slot(). Caller must hold tree write locked
255 : * across slot lookup and replacement.
256 : */
257 : static inline void radix_tree_replace_slot(void **pslot, void *item)
258 : {
259 : BUG_ON(radix_tree_is_indirect_ptr(item));
260 : rcu_assign_pointer(*pslot, item);
261 : }
262 :
263 : int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
264 : struct radix_tree_node **nodep, void ***slotp);
265 : int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
266 : void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
267 : struct radix_tree_node **nodep, void ***slotp);
268 : void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
269 : void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
270 : bool __radix_tree_delete_node(struct radix_tree_root *root,
271 : struct radix_tree_node *node);
272 : void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
273 : void *radix_tree_delete(struct radix_tree_root *, unsigned long);
274 : unsigned int
275 : radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
276 : unsigned long first_index, unsigned int max_items);
277 : unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root,
278 : void ***results, unsigned long *indices,
279 : unsigned long first_index, unsigned int max_items);
280 : int radix_tree_preload(gfp_t gfp_mask);
281 : int radix_tree_maybe_preload(gfp_t gfp_mask);
282 : void radix_tree_init(void);
283 : void *radix_tree_tag_set(struct radix_tree_root *root,
284 : unsigned long index, unsigned int tag);
285 : void *radix_tree_tag_clear(struct radix_tree_root *root,
286 : unsigned long index, unsigned int tag);
287 : int radix_tree_tag_get(struct radix_tree_root *root,
288 : unsigned long index, unsigned int tag);
289 : unsigned int
290 : radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
291 : unsigned long first_index, unsigned int max_items,
292 : unsigned int tag);
293 : unsigned int
294 : radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
295 : unsigned long first_index, unsigned int max_items,
296 : unsigned int tag);
297 : unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
298 : unsigned long *first_indexp, unsigned long last_index,
299 : unsigned long nr_to_tag,
300 : unsigned int fromtag, unsigned int totag);
301 : int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
302 : unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item);
303 :
304 : static inline void radix_tree_preload_end(void)
305 : {
306 84048 : preempt_enable();
307 : }
308 :
309 : /**
310 : * struct radix_tree_iter - radix tree iterator state
311 : *
312 : * @index: index of current slot
313 : * @next_index: next-to-last index for this chunk
314 : * @tags: bit-mask for tag-iterating
315 : *
316 : * This radix tree iterator works in terms of "chunks" of slots. A chunk is a
317 : * subinterval of slots contained within one radix tree leaf node. It is
318 : * described by a pointer to its first slot and a struct radix_tree_iter
319 : * which holds the chunk's position in the tree and its size. For tagged
320 : * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
321 : * radix tree tag.
322 : */
323 : struct radix_tree_iter {
324 : unsigned long index;
325 : unsigned long next_index;
326 : unsigned long tags;
327 : };
328 :
329 : #define RADIX_TREE_ITER_TAG_MASK 0x00FF /* tag index in lower byte */
330 : #define RADIX_TREE_ITER_TAGGED 0x0100 /* lookup tagged slots */
331 : #define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */
332 :
333 : /**
334 : * radix_tree_iter_init - initialize radix tree iterator
335 : *
336 : * @iter: pointer to iterator state
337 : * @start: iteration starting index
338 : * Returns: NULL
339 : */
340 : static __always_inline void **
341 : radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
342 : {
343 : /*
344 : * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
345 : * in the case of a successful tagged chunk lookup. If the lookup was
346 : * unsuccessful or non-tagged then nobody cares about ->tags.
347 : *
348 : * Set index to zero to bypass next_index overflow protection.
349 : * See the comment in radix_tree_next_chunk() for details.
350 : */
351 : iter->index = 0;
352 : iter->next_index = start;
353 : return NULL;
354 : }
355 :
356 : /**
357 : * radix_tree_next_chunk - find next chunk of slots for iteration
358 : *
359 : * @root: radix tree root
360 : * @iter: iterator state
361 : * @flags: RADIX_TREE_ITER_* flags and tag index
362 : * Returns: pointer to chunk first slot, or NULL if there no more left
363 : *
364 : * This function looks up the next chunk in the radix tree starting from
365 : * @iter->next_index. It returns a pointer to the chunk's first slot.
366 : * Also it fills @iter with data about chunk: position in the tree (index),
367 : * its end (next_index), and constructs a bit mask for tagged iterating (tags).
368 : */
369 : void **radix_tree_next_chunk(struct radix_tree_root *root,
370 : struct radix_tree_iter *iter, unsigned flags);
371 :
372 : /**
373 : * radix_tree_chunk_size - get current chunk size
374 : *
375 : * @iter: pointer to radix tree iterator
376 : * Returns: current chunk size
377 : */
378 : static __always_inline unsigned
379 : radix_tree_chunk_size(struct radix_tree_iter *iter)
380 : {
381 : return iter->next_index - iter->index;
382 : }
383 :
384 : /**
385 : * radix_tree_next_slot - find next slot in chunk
386 : *
387 : * @slot: pointer to current slot
388 : * @iter: pointer to interator state
389 : * @flags: RADIX_TREE_ITER_*, should be constant
390 : * Returns: pointer to next slot, or NULL if there no more left
391 : *
392 : * This function updates @iter->index in the case of a successful lookup.
393 : * For tagged lookup it also eats @iter->tags.
394 : */
395 : static __always_inline void **
396 : radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags)
397 : {
398 : if (flags & RADIX_TREE_ITER_TAGGED) {
399 : iter->tags >>= 1;
400 : if (likely(iter->tags & 1ul)) {
401 : iter->index++;
402 : return slot + 1;
403 : }
404 : if (!(flags & RADIX_TREE_ITER_CONTIG) && likely(iter->tags)) {
405 : unsigned offset = __ffs(iter->tags);
406 :
407 : iter->tags >>= offset;
408 : iter->index += offset + 1;
409 : return slot + offset + 1;
410 : }
411 : } else {
412 : unsigned size = radix_tree_chunk_size(iter) - 1;
413 :
414 : while (size--) {
415 : slot++;
416 : iter->index++;
417 : if (likely(*slot))
418 : return slot;
419 : if (flags & RADIX_TREE_ITER_CONTIG) {
420 : /* forbid switching to the next chunk */
421 : iter->next_index = 0;
422 : break;
423 : }
424 : }
425 : }
426 : return NULL;
427 : }
428 :
429 : /**
430 : * radix_tree_for_each_chunk - iterate over chunks
431 : *
432 : * @slot: the void** variable for pointer to chunk first slot
433 : * @root: the struct radix_tree_root pointer
434 : * @iter: the struct radix_tree_iter pointer
435 : * @start: iteration starting index
436 : * @flags: RADIX_TREE_ITER_* and tag index
437 : *
438 : * Locks can be released and reacquired between iterations.
439 : */
440 : #define radix_tree_for_each_chunk(slot, root, iter, start, flags) \
441 : for (slot = radix_tree_iter_init(iter, start) ; \
442 : (slot = radix_tree_next_chunk(root, iter, flags)) ;)
443 :
444 : /**
445 : * radix_tree_for_each_chunk_slot - iterate over slots in one chunk
446 : *
447 : * @slot: the void** variable, at the beginning points to chunk first slot
448 : * @iter: the struct radix_tree_iter pointer
449 : * @flags: RADIX_TREE_ITER_*, should be constant
450 : *
451 : * This macro is designed to be nested inside radix_tree_for_each_chunk().
452 : * @slot points to the radix tree slot, @iter->index contains its index.
453 : */
454 : #define radix_tree_for_each_chunk_slot(slot, iter, flags) \
455 : for (; slot ; slot = radix_tree_next_slot(slot, iter, flags))
456 :
457 : /**
458 : * radix_tree_for_each_slot - iterate over non-empty slots
459 : *
460 : * @slot: the void** variable for pointer to slot
461 : * @root: the struct radix_tree_root pointer
462 : * @iter: the struct radix_tree_iter pointer
463 : * @start: iteration starting index
464 : *
465 : * @slot points to radix tree slot, @iter->index contains its index.
466 : */
467 : #define radix_tree_for_each_slot(slot, root, iter, start) \
468 : for (slot = radix_tree_iter_init(iter, start) ; \
469 : slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \
470 : slot = radix_tree_next_slot(slot, iter, 0))
471 :
472 : /**
473 : * radix_tree_for_each_contig - iterate over contiguous slots
474 : *
475 : * @slot: the void** variable for pointer to slot
476 : * @root: the struct radix_tree_root pointer
477 : * @iter: the struct radix_tree_iter pointer
478 : * @start: iteration starting index
479 : *
480 : * @slot points to radix tree slot, @iter->index contains its index.
481 : */
482 : #define radix_tree_for_each_contig(slot, root, iter, start) \
483 : for (slot = radix_tree_iter_init(iter, start) ; \
484 : slot || (slot = radix_tree_next_chunk(root, iter, \
485 : RADIX_TREE_ITER_CONTIG)) ; \
486 : slot = radix_tree_next_slot(slot, iter, \
487 : RADIX_TREE_ITER_CONTIG))
488 :
489 : /**
490 : * radix_tree_for_each_tagged - iterate over tagged slots
491 : *
492 : * @slot: the void** variable for pointer to slot
493 : * @root: the struct radix_tree_root pointer
494 : * @iter: the struct radix_tree_iter pointer
495 : * @start: iteration starting index
496 : * @tag: tag index
497 : *
498 : * @slot points to radix tree slot, @iter->index contains its index.
499 : */
500 : #define radix_tree_for_each_tagged(slot, root, iter, start, tag) \
501 : for (slot = radix_tree_iter_init(iter, start) ; \
502 : slot || (slot = radix_tree_next_chunk(root, iter, \
503 : RADIX_TREE_ITER_TAGGED | tag)) ; \
504 : slot = radix_tree_next_slot(slot, iter, \
505 : RADIX_TREE_ITER_TAGGED))
506 :
507 : #endif /* _LINUX_RADIX_TREE_H */
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