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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 : 89554545 : 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 : : /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
64 : : struct radix_tree_root {
65 : : unsigned int height;
66 : : gfp_t gfp_mask;
67 : : struct radix_tree_node __rcu *rnode;
68 : : };
69 : :
70 : : #define RADIX_TREE_INIT(mask) { \
71 : : .height = 0, \
72 : : .gfp_mask = (mask), \
73 : : .rnode = NULL, \
74 : : }
75 : :
76 : : #define RADIX_TREE(name, mask) \
77 : : struct radix_tree_root name = RADIX_TREE_INIT(mask)
78 : :
79 : : #define INIT_RADIX_TREE(root, mask) \
80 : : do { \
81 : : (root)->height = 0; \
82 : : (root)->gfp_mask = (mask); \
83 : : (root)->rnode = NULL; \
84 : : } while (0)
85 : :
86 : : /**
87 : : * Radix-tree synchronization
88 : : *
89 : : * The radix-tree API requires that users provide all synchronisation (with
90 : : * specific exceptions, noted below).
91 : : *
92 : : * Synchronization of access to the data items being stored in the tree, and
93 : : * management of their lifetimes must be completely managed by API users.
94 : : *
95 : : * For API usage, in general,
96 : : * - any function _modifying_ the tree or tags (inserting or deleting
97 : : * items, setting or clearing tags) must exclude other modifications, and
98 : : * exclude any functions reading the tree.
99 : : * - any function _reading_ the tree or tags (looking up items or tags,
100 : : * gang lookups) must exclude modifications to the tree, but may occur
101 : : * concurrently with other readers.
102 : : *
103 : : * The notable exceptions to this rule are the following functions:
104 : : * radix_tree_lookup
105 : : * radix_tree_lookup_slot
106 : : * radix_tree_tag_get
107 : : * radix_tree_gang_lookup
108 : : * radix_tree_gang_lookup_slot
109 : : * radix_tree_gang_lookup_tag
110 : : * radix_tree_gang_lookup_tag_slot
111 : : * radix_tree_tagged
112 : : *
113 : : * The first 7 functions are able to be called locklessly, using RCU. The
114 : : * caller must ensure calls to these functions are made within rcu_read_lock()
115 : : * regions. Other readers (lock-free or otherwise) and modifications may be
116 : : * running concurrently.
117 : : *
118 : : * It is still required that the caller manage the synchronization and lifetimes
119 : : * of the items. So if RCU lock-free lookups are used, typically this would mean
120 : : * that the items have their own locks, or are amenable to lock-free access; and
121 : : * that the items are freed by RCU (or only freed after having been deleted from
122 : : * the radix tree *and* a synchronize_rcu() grace period).
123 : : *
124 : : * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
125 : : * access to data items when inserting into or looking up from the radix tree)
126 : : *
127 : : * Note that the value returned by radix_tree_tag_get() may not be relied upon
128 : : * if only the RCU read lock is held. Functions to set/clear tags and to
129 : : * delete nodes running concurrently with it may affect its result such that
130 : : * two consecutive reads in the same locked section may return different
131 : : * values. If reliability is required, modification functions must also be
132 : : * excluded from concurrency.
133 : : *
134 : : * radix_tree_tagged is able to be called without locking or RCU.
135 : : */
136 : :
137 : : /**
138 : : * radix_tree_deref_slot - dereference a slot
139 : : * @pslot: pointer to slot, returned by radix_tree_lookup_slot
140 : : * Returns: item that was stored in that slot with any direct pointer flag
141 : : * removed.
142 : : *
143 : : * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
144 : : * locked across slot lookup and dereference. Not required if write lock is
145 : : * held (ie. items cannot be concurrently inserted).
146 : : *
147 : : * radix_tree_deref_retry must be used to confirm validity of the pointer if
148 : : * only the read lock is held.
149 : : */
150 : : static inline void *radix_tree_deref_slot(void **pslot)
151 : : {
152 : 72364403 : return rcu_dereference(*pslot);
153 : : }
154 : :
155 : : /**
156 : : * radix_tree_deref_slot_protected - dereference a slot without RCU lock but with tree lock held
157 : : * @pslot: pointer to slot, returned by radix_tree_lookup_slot
158 : : * Returns: item that was stored in that slot with any direct pointer flag
159 : : * removed.
160 : : *
161 : : * Similar to radix_tree_deref_slot but only used during migration when a pages
162 : : * mapping is being moved. The caller does not hold the RCU read lock but it
163 : : * must hold the tree lock to prevent parallel updates.
164 : : */
165 : : static inline void *radix_tree_deref_slot_protected(void **pslot,
166 : : spinlock_t *treelock)
167 : : {
168 : : return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
169 : : }
170 : :
171 : : /**
172 : : * radix_tree_deref_retry - check radix_tree_deref_slot
173 : : * @arg: pointer returned by radix_tree_deref_slot
174 : : * Returns: 0 if retry is not required, otherwise retry is required
175 : : *
176 : : * radix_tree_deref_retry must be used with radix_tree_deref_slot.
177 : : */
178 : : static inline int radix_tree_deref_retry(void *arg)
179 : : {
180 : 0 : return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
181 : : }
182 : :
183 : : /**
184 : : * radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry?
185 : : * @arg: value returned by radix_tree_deref_slot
186 : : * Returns: 0 if well-aligned pointer, non-0 if exceptional entry.
187 : : */
188 : : static inline int radix_tree_exceptional_entry(void *arg)
189 : : {
190 : : /* Not unlikely because radix_tree_exception often tested first */
191 : 268943 : return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY;
192 : : }
193 : :
194 : : /**
195 : : * radix_tree_exception - radix_tree_deref_slot returned either exception?
196 : : * @arg: value returned by radix_tree_deref_slot
197 : : * Returns: 0 if well-aligned pointer, non-0 if either kind of exception.
198 : : */
199 : : static inline int radix_tree_exception(void *arg)
200 : : {
201 : 78438759 : return unlikely((unsigned long)arg &
202 : : (RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY));
203 : : }
204 : :
205 : : /**
206 : : * radix_tree_replace_slot - replace item in a slot
207 : : * @pslot: pointer to slot, returned by radix_tree_lookup_slot
208 : : * @item: new item to store in the slot.
209 : : *
210 : : * For use with radix_tree_lookup_slot(). Caller must hold tree write locked
211 : : * across slot lookup and replacement.
212 : : */
213 : : static inline void radix_tree_replace_slot(void **pslot, void *item)
214 : : {
215 [ # # ][ # # ]: 0 : BUG_ON(radix_tree_is_indirect_ptr(item));
216 : 0 : rcu_assign_pointer(*pslot, item);
217 : : }
218 : :
219 : : int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
220 : : void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
221 : : void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
222 : : void *radix_tree_delete(struct radix_tree_root *, unsigned long);
223 : : unsigned int
224 : : radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
225 : : unsigned long first_index, unsigned int max_items);
226 : : unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root,
227 : : void ***results, unsigned long *indices,
228 : : unsigned long first_index, unsigned int max_items);
229 : : unsigned long radix_tree_next_hole(struct radix_tree_root *root,
230 : : unsigned long index, unsigned long max_scan);
231 : : unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
232 : : unsigned long index, unsigned long max_scan);
233 : : int radix_tree_preload(gfp_t gfp_mask);
234 : : int radix_tree_maybe_preload(gfp_t gfp_mask);
235 : : void radix_tree_init(void);
236 : : void *radix_tree_tag_set(struct radix_tree_root *root,
237 : : unsigned long index, unsigned int tag);
238 : : void *radix_tree_tag_clear(struct radix_tree_root *root,
239 : : unsigned long index, unsigned int tag);
240 : : int radix_tree_tag_get(struct radix_tree_root *root,
241 : : unsigned long index, unsigned int tag);
242 : : unsigned int
243 : : radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
244 : : unsigned long first_index, unsigned int max_items,
245 : : unsigned int tag);
246 : : unsigned int
247 : : radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
248 : : unsigned long first_index, unsigned int max_items,
249 : : unsigned int tag);
250 : : unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
251 : : unsigned long *first_indexp, unsigned long last_index,
252 : : unsigned long nr_to_tag,
253 : : unsigned int fromtag, unsigned int totag);
254 : : int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
255 : : unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item);
256 : :
257 : : static inline void radix_tree_preload_end(void)
258 : : {
259 : 2194753 : preempt_enable();
260 : : }
261 : :
262 : : /**
263 : : * struct radix_tree_iter - radix tree iterator state
264 : : *
265 : : * @index: index of current slot
266 : : * @next_index: next-to-last index for this chunk
267 : : * @tags: bit-mask for tag-iterating
268 : : *
269 : : * This radix tree iterator works in terms of "chunks" of slots. A chunk is a
270 : : * subinterval of slots contained within one radix tree leaf node. It is
271 : : * described by a pointer to its first slot and a struct radix_tree_iter
272 : : * which holds the chunk's position in the tree and its size. For tagged
273 : : * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
274 : : * radix tree tag.
275 : : */
276 : : struct radix_tree_iter {
277 : : unsigned long index;
278 : : unsigned long next_index;
279 : : unsigned long tags;
280 : : };
281 : :
282 : : #define RADIX_TREE_ITER_TAG_MASK 0x00FF /* tag index in lower byte */
283 : : #define RADIX_TREE_ITER_TAGGED 0x0100 /* lookup tagged slots */
284 : : #define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */
285 : :
286 : : /**
287 : : * radix_tree_iter_init - initialize radix tree iterator
288 : : *
289 : : * @iter: pointer to iterator state
290 : : * @start: iteration starting index
291 : : * Returns: NULL
292 : : */
293 : : static __always_inline void **
294 : : radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
295 : : {
296 : : /*
297 : : * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
298 : : * in the case of a successful tagged chunk lookup. If the lookup was
299 : : * unsuccessful or non-tagged then nobody cares about ->tags.
300 : : *
301 : : * Set index to zero to bypass next_index overflow protection.
302 : : * See the comment in radix_tree_next_chunk() for details.
303 : : */
304 : 4541823 : iter->index = 0;
305 : 4541823 : iter->next_index = start;
306 : : return NULL;
307 : : }
308 : :
309 : : /**
310 : : * radix_tree_next_chunk - find next chunk of slots for iteration
311 : : *
312 : : * @root: radix tree root
313 : : * @iter: iterator state
314 : : * @flags: RADIX_TREE_ITER_* flags and tag index
315 : : * Returns: pointer to chunk first slot, or NULL if there no more left
316 : : *
317 : : * This function looks up the next chunk in the radix tree starting from
318 : : * @iter->next_index. It returns a pointer to the chunk's first slot.
319 : : * Also it fills @iter with data about chunk: position in the tree (index),
320 : : * its end (next_index), and constructs a bit mask for tagged iterating (tags).
321 : : */
322 : : void **radix_tree_next_chunk(struct radix_tree_root *root,
323 : : struct radix_tree_iter *iter, unsigned flags);
324 : :
325 : : /**
326 : : * radix_tree_chunk_size - get current chunk size
327 : : *
328 : : * @iter: pointer to radix tree iterator
329 : : * Returns: current chunk size
330 : : */
331 : : static __always_inline unsigned
332 : : radix_tree_chunk_size(struct radix_tree_iter *iter)
333 : : {
334 : 3290536 : return iter->next_index - iter->index;
335 : : }
336 : :
337 : : /**
338 : : * radix_tree_next_slot - find next slot in chunk
339 : : *
340 : : * @slot: pointer to current slot
341 : : * @iter: pointer to interator state
342 : : * @flags: RADIX_TREE_ITER_*, should be constant
343 : : * Returns: pointer to next slot, or NULL if there no more left
344 : : *
345 : : * This function updates @iter->index in the case of a successful lookup.
346 : : * For tagged lookup it also eats @iter->tags.
347 : : */
348 : : static __always_inline void **
349 : 3290536 : radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags)
350 : : {
351 : : if (flags & RADIX_TREE_ITER_TAGGED) {
352 : 4144034 : iter->tags >>= 1;
353 [ + + ][ # # ]: 4144034 : if (likely(iter->tags & 1ul)) {
354 : 1116856 : iter->index++;
355 : 1116856 : return slot + 1;
356 : : }
357 [ + + ][ # # ]: 3027178 : if (!(flags & RADIX_TREE_ITER_CONTIG) && likely(iter->tags)) {
358 : 821886 : unsigned offset = __ffs(iter->tags);
359 : :
360 : 410943 : iter->tags >>= offset;
361 : 410943 : iter->index += offset + 1;
362 : 1912886 : return slot + offset + 1;
363 : : }
364 : : } else {
365 : 3290536 : unsigned size = radix_tree_chunk_size(iter) - 1;
366 : :
367 [ + + ][ # # ]: 13435423 : while (size--) {
[ + + ]
368 : 10144887 : slot++;
369 : 10144887 : iter->index++;
370 [ + + ][ + + ]: 10144887 : if (likely(*slot))
371 : : return slot;
372 : : if (flags & RADIX_TREE_ITER_CONTIG) {
373 : : /* forbid switching to the next chunk */
374 : 0 : iter->next_index = 0;
375 : : break;
376 : : }
377 : : }
378 : : }
379 : : return NULL;
380 : : }
381 : :
382 : : /**
383 : : * radix_tree_for_each_chunk - iterate over chunks
384 : : *
385 : : * @slot: the void** variable for pointer to chunk first slot
386 : : * @root: the struct radix_tree_root pointer
387 : : * @iter: the struct radix_tree_iter pointer
388 : : * @start: iteration starting index
389 : : * @flags: RADIX_TREE_ITER_* and tag index
390 : : *
391 : : * Locks can be released and reacquired between iterations.
392 : : */
393 : : #define radix_tree_for_each_chunk(slot, root, iter, start, flags) \
394 : : for (slot = radix_tree_iter_init(iter, start) ; \
395 : : (slot = radix_tree_next_chunk(root, iter, flags)) ;)
396 : :
397 : : /**
398 : : * radix_tree_for_each_chunk_slot - iterate over slots in one chunk
399 : : *
400 : : * @slot: the void** variable, at the beginning points to chunk first slot
401 : : * @iter: the struct radix_tree_iter pointer
402 : : * @flags: RADIX_TREE_ITER_*, should be constant
403 : : *
404 : : * This macro is designed to be nested inside radix_tree_for_each_chunk().
405 : : * @slot points to the radix tree slot, @iter->index contains its index.
406 : : */
407 : : #define radix_tree_for_each_chunk_slot(slot, iter, flags) \
408 : : for (; slot ; slot = radix_tree_next_slot(slot, iter, flags))
409 : :
410 : : /**
411 : : * radix_tree_for_each_slot - iterate over non-empty slots
412 : : *
413 : : * @slot: the void** variable for pointer to slot
414 : : * @root: the struct radix_tree_root pointer
415 : : * @iter: the struct radix_tree_iter pointer
416 : : * @start: iteration starting index
417 : : *
418 : : * @slot points to radix tree slot, @iter->index contains its index.
419 : : */
420 : : #define radix_tree_for_each_slot(slot, root, iter, start) \
421 : : for (slot = radix_tree_iter_init(iter, start) ; \
422 : : slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \
423 : : slot = radix_tree_next_slot(slot, iter, 0))
424 : :
425 : : /**
426 : : * radix_tree_for_each_contig - iterate over contiguous slots
427 : : *
428 : : * @slot: the void** variable for pointer to slot
429 : : * @root: the struct radix_tree_root pointer
430 : : * @iter: the struct radix_tree_iter pointer
431 : : * @start: iteration starting index
432 : : *
433 : : * @slot points to radix tree slot, @iter->index contains its index.
434 : : */
435 : : #define radix_tree_for_each_contig(slot, root, iter, start) \
436 : : for (slot = radix_tree_iter_init(iter, start) ; \
437 : : slot || (slot = radix_tree_next_chunk(root, iter, \
438 : : RADIX_TREE_ITER_CONTIG)) ; \
439 : : slot = radix_tree_next_slot(slot, iter, \
440 : : RADIX_TREE_ITER_CONTIG))
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))
459 : :
460 : : #endif /* _LINUX_RADIX_TREE_H */
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