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1 | /* | |
2 | * Copyright (C) 2001 Momchil Velikov | |
3 | * Portions Copyright (C) 2001 Christoph Hellwig | |
4 | * Copyright (C) 2005 SGI, Christoph Lameter | |
5 | * Copyright (C) 2006 Nick Piggin | |
6 | * Copyright (C) 2012 Konstantin Khlebnikov | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU General Public License as | |
10 | * published by the Free Software Foundation; either version 2, or (at | |
11 | * your option) any later version. | |
12 | * | |
13 | * This program is distributed in the hope that it will be useful, but | |
14 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | * General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU General Public License | |
19 | * along with this program; if not, write to the Free Software | |
20 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | |
21 | */ | |
22 | ||
23 | #include <linux/errno.h> | |
24 | #include <linux/init.h> | |
25 | #include <linux/kernel.h> | |
26 | #include <linux/export.h> | |
27 | #include <linux/radix-tree.h> | |
28 | #include <linux/percpu.h> | |
29 | #include <linux/slab.h> | |
30 | #include <linux/notifier.h> | |
31 | #include <linux/cpu.h> | |
32 | #include <linux/string.h> | |
33 | #include <linux/bitops.h> | |
34 | #include <linux/rcupdate.h> | |
35 | ||
36 | ||
37 | #ifdef __KERNEL__ | |
38 | #define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6) | |
39 | #else | |
40 | #define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */ | |
41 | #endif | |
42 | ||
43 | #define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT) | |
44 | #define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1) | |
45 | ||
46 | #define RADIX_TREE_TAG_LONGS \ | |
47 | ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG) | |
48 | ||
49 | struct radix_tree_node { | |
50 | unsigned int height; /* Height from the bottom */ | |
51 | unsigned int count; | |
52 | union { | |
53 | struct radix_tree_node *parent; /* Used when ascending tree */ | |
54 | struct rcu_head rcu_head; /* Used when freeing node */ | |
55 | }; | |
56 | void __rcu *slots[RADIX_TREE_MAP_SIZE]; | |
57 | unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS]; | |
58 | }; | |
59 | ||
60 | #define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long)) | |
61 | #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \ | |
62 | RADIX_TREE_MAP_SHIFT)) | |
63 | ||
64 | /* | |
65 | * The height_to_maxindex array needs to be one deeper than the maximum | |
66 | * path as height 0 holds only 1 entry. | |
67 | */ | |
68 | static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly; | |
69 | ||
70 | /* | |
71 | * Radix tree node cache. | |
72 | */ | |
73 | static struct kmem_cache *radix_tree_node_cachep; | |
74 | ||
75 | /* | |
76 | * Per-cpu pool of preloaded nodes | |
77 | */ | |
78 | struct radix_tree_preload { | |
79 | int nr; | |
80 | struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH]; | |
81 | }; | |
82 | static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, }; | |
83 | ||
84 | static inline void *ptr_to_indirect(void *ptr) | |
85 | { | |
86 | return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR); | |
87 | } | |
88 | ||
89 | static inline void *indirect_to_ptr(void *ptr) | |
90 | { | |
91 | return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR); | |
92 | } | |
93 | ||
94 | static inline gfp_t root_gfp_mask(struct radix_tree_root *root) | |
95 | { | |
96 | return root->gfp_mask & __GFP_BITS_MASK; | |
97 | } | |
98 | ||
99 | static inline void tag_set(struct radix_tree_node *node, unsigned int tag, | |
100 | int offset) | |
101 | { | |
102 | __set_bit(offset, node->tags[tag]); | |
103 | } | |
104 | ||
105 | static inline void tag_clear(struct radix_tree_node *node, unsigned int tag, | |
106 | int offset) | |
107 | { | |
108 | __clear_bit(offset, node->tags[tag]); | |
109 | } | |
110 | ||
111 | static inline int tag_get(struct radix_tree_node *node, unsigned int tag, | |
112 | int offset) | |
113 | { | |
114 | return test_bit(offset, node->tags[tag]); | |
115 | } | |
116 | ||
117 | static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag) | |
118 | { | |
119 | root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT)); | |
120 | } | |
121 | ||
122 | static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag) | |
123 | { | |
124 | root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT)); | |
125 | } | |
126 | ||
127 | static inline void root_tag_clear_all(struct radix_tree_root *root) | |
128 | { | |
129 | root->gfp_mask &= __GFP_BITS_MASK; | |
130 | } | |
131 | ||
132 | static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag) | |
133 | { | |
134 | return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT)); | |
135 | } | |
136 | ||
137 | /* | |
138 | * Returns 1 if any slot in the node has this tag set. | |
139 | * Otherwise returns 0. | |
140 | */ | |
141 | static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag) | |
142 | { | |
143 | int idx; | |
144 | for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) { | |
145 | if (node->tags[tag][idx]) | |
146 | return 1; | |
147 | } | |
148 | return 0; | |
149 | } | |
150 | ||
151 | /** | |
152 | * radix_tree_find_next_bit - find the next set bit in a memory region | |
153 | * | |
154 | * @addr: The address to base the search on | |
155 | * @size: The bitmap size in bits | |
156 | * @offset: The bitnumber to start searching at | |
157 | * | |
158 | * Unrollable variant of find_next_bit() for constant size arrays. | |
159 | * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero. | |
160 | * Returns next bit offset, or size if nothing found. | |
161 | */ | |
162 | static __always_inline unsigned long | |
163 | radix_tree_find_next_bit(const unsigned long *addr, | |
164 | unsigned long size, unsigned long offset) | |
165 | { | |
166 | if (!__builtin_constant_p(size)) | |
167 | return find_next_bit(addr, size, offset); | |
168 | ||
169 | if (offset < size) { | |
170 | unsigned long tmp; | |
171 | ||
172 | addr += offset / BITS_PER_LONG; | |
173 | tmp = *addr >> (offset % BITS_PER_LONG); | |
174 | if (tmp) | |
175 | return __ffs(tmp) + offset; | |
176 | offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1); | |
177 | while (offset < size) { | |
178 | tmp = *++addr; | |
179 | if (tmp) | |
180 | return __ffs(tmp) + offset; | |
181 | offset += BITS_PER_LONG; | |
182 | } | |
183 | } | |
184 | return size; | |
185 | } | |
186 | ||
187 | /* | |
188 | * This assumes that the caller has performed appropriate preallocation, and | |
189 | * that the caller has pinned this thread of control to the current CPU. | |
190 | */ | |
191 | static struct radix_tree_node * | |
192 | radix_tree_node_alloc(struct radix_tree_root *root) | |
193 | { | |
194 | struct radix_tree_node *ret = NULL; | |
195 | gfp_t gfp_mask = root_gfp_mask(root); | |
196 | ||
197 | if (!(gfp_mask & __GFP_WAIT)) { | |
198 | struct radix_tree_preload *rtp; | |
199 | ||
200 | /* | |
201 | * Provided the caller has preloaded here, we will always | |
202 | * succeed in getting a node here (and never reach | |
203 | * kmem_cache_alloc) | |
204 | */ | |
205 | rtp = &__get_cpu_var(radix_tree_preloads); | |
206 | if (rtp->nr) { | |
207 | ret = rtp->nodes[rtp->nr - 1]; | |
208 | rtp->nodes[rtp->nr - 1] = NULL; | |
209 | rtp->nr--; | |
210 | } | |
211 | } | |
212 | if (ret == NULL) | |
213 | ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); | |
214 | ||
215 | BUG_ON(radix_tree_is_indirect_ptr(ret)); | |
216 | return ret; | |
217 | } | |
218 | ||
219 | static void radix_tree_node_rcu_free(struct rcu_head *head) | |
220 | { | |
221 | struct radix_tree_node *node = | |
222 | container_of(head, struct radix_tree_node, rcu_head); | |
223 | int i; | |
224 | ||
225 | /* | |
226 | * must only free zeroed nodes into the slab. radix_tree_shrink | |
227 | * can leave us with a non-NULL entry in the first slot, so clear | |
228 | * that here to make sure. | |
229 | */ | |
230 | for (i = 0; i < RADIX_TREE_MAX_TAGS; i++) | |
231 | tag_clear(node, i, 0); | |
232 | ||
233 | node->slots[0] = NULL; | |
234 | node->count = 0; | |
235 | ||
236 | kmem_cache_free(radix_tree_node_cachep, node); | |
237 | } | |
238 | ||
239 | static inline void | |
240 | radix_tree_node_free(struct radix_tree_node *node) | |
241 | { | |
242 | call_rcu(&node->rcu_head, radix_tree_node_rcu_free); | |
243 | } | |
244 | ||
245 | /* | |
246 | * Load up this CPU's radix_tree_node buffer with sufficient objects to | |
247 | * ensure that the addition of a single element in the tree cannot fail. On | |
248 | * success, return zero, with preemption disabled. On error, return -ENOMEM | |
249 | * with preemption not disabled. | |
250 | * | |
251 | * To make use of this facility, the radix tree must be initialised without | |
252 | * __GFP_WAIT being passed to INIT_RADIX_TREE(). | |
253 | */ | |
254 | int radix_tree_preload(gfp_t gfp_mask) | |
255 | { | |
256 | struct radix_tree_preload *rtp; | |
257 | struct radix_tree_node *node; | |
258 | int ret = -ENOMEM; | |
259 | ||
260 | preempt_disable(); | |
261 | rtp = &__get_cpu_var(radix_tree_preloads); | |
262 | while (rtp->nr < ARRAY_SIZE(rtp->nodes)) { | |
263 | preempt_enable(); | |
264 | node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); | |
265 | if (node == NULL) | |
266 | goto out; | |
267 | preempt_disable(); | |
268 | rtp = &__get_cpu_var(radix_tree_preloads); | |
269 | if (rtp->nr < ARRAY_SIZE(rtp->nodes)) | |
270 | rtp->nodes[rtp->nr++] = node; | |
271 | else | |
272 | kmem_cache_free(radix_tree_node_cachep, node); | |
273 | } | |
274 | ret = 0; | |
275 | out: | |
276 | return ret; | |
277 | } | |
278 | EXPORT_SYMBOL(radix_tree_preload); | |
279 | ||
280 | /* | |
281 | * Return the maximum key which can be store into a | |
282 | * radix tree with height HEIGHT. | |
283 | */ | |
284 | static inline unsigned long radix_tree_maxindex(unsigned int height) | |
285 | { | |
286 | return height_to_maxindex[height]; | |
287 | } | |
288 | ||
289 | /* | |
290 | * Extend a radix tree so it can store key @index. | |
291 | */ | |
292 | static int radix_tree_extend(struct radix_tree_root *root, unsigned long index) | |
293 | { | |
294 | struct radix_tree_node *node; | |
295 | struct radix_tree_node *slot; | |
296 | unsigned int height; | |
297 | int tag; | |
298 | ||
299 | /* Figure out what the height should be. */ | |
300 | height = root->height + 1; | |
301 | while (index > radix_tree_maxindex(height)) | |
302 | height++; | |
303 | ||
304 | if (root->rnode == NULL) { | |
305 | root->height = height; | |
306 | goto out; | |
307 | } | |
308 | ||
309 | do { | |
310 | unsigned int newheight; | |
311 | if (!(node = radix_tree_node_alloc(root))) | |
312 | return -ENOMEM; | |
313 | ||
314 | /* Propagate the aggregated tag info into the new root */ | |
315 | for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { | |
316 | if (root_tag_get(root, tag)) | |
317 | tag_set(node, tag, 0); | |
318 | } | |
319 | ||
320 | /* Increase the height. */ | |
321 | newheight = root->height+1; | |
322 | node->height = newheight; | |
323 | node->count = 1; | |
324 | node->parent = NULL; | |
325 | slot = root->rnode; | |
326 | if (newheight > 1) { | |
327 | slot = indirect_to_ptr(slot); | |
328 | slot->parent = node; | |
329 | } | |
330 | node->slots[0] = slot; | |
331 | node = ptr_to_indirect(node); | |
332 | rcu_assign_pointer(root->rnode, node); | |
333 | root->height = newheight; | |
334 | } while (height > root->height); | |
335 | out: | |
336 | return 0; | |
337 | } | |
338 | ||
339 | /** | |
340 | * radix_tree_insert - insert into a radix tree | |
341 | * @root: radix tree root | |
342 | * @index: index key | |
343 | * @item: item to insert | |
344 | * | |
345 | * Insert an item into the radix tree at position @index. | |
346 | */ | |
347 | int radix_tree_insert(struct radix_tree_root *root, | |
348 | unsigned long index, void *item) | |
349 | { | |
350 | struct radix_tree_node *node = NULL, *slot; | |
351 | unsigned int height, shift; | |
352 | int offset; | |
353 | int error; | |
354 | ||
355 | BUG_ON(radix_tree_is_indirect_ptr(item)); | |
356 | ||
357 | /* Make sure the tree is high enough. */ | |
358 | if (index > radix_tree_maxindex(root->height)) { | |
359 | error = radix_tree_extend(root, index); | |
360 | if (error) | |
361 | return error; | |
362 | } | |
363 | ||
364 | slot = indirect_to_ptr(root->rnode); | |
365 | ||
366 | height = root->height; | |
367 | shift = (height-1) * RADIX_TREE_MAP_SHIFT; | |
368 | ||
369 | offset = 0; /* uninitialised var warning */ | |
370 | while (height > 0) { | |
371 | if (slot == NULL) { | |
372 | /* Have to add a child node. */ | |
373 | if (!(slot = radix_tree_node_alloc(root))) | |
374 | return -ENOMEM; | |
375 | slot->height = height; | |
376 | slot->parent = node; | |
377 | if (node) { | |
378 | rcu_assign_pointer(node->slots[offset], slot); | |
379 | node->count++; | |
380 | } else | |
381 | rcu_assign_pointer(root->rnode, ptr_to_indirect(slot)); | |
382 | } | |
383 | ||
384 | /* Go a level down */ | |
385 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; | |
386 | node = slot; | |
387 | slot = node->slots[offset]; | |
388 | shift -= RADIX_TREE_MAP_SHIFT; | |
389 | height--; | |
390 | } | |
391 | ||
392 | if (slot != NULL) | |
393 | return -EEXIST; | |
394 | ||
395 | if (node) { | |
396 | node->count++; | |
397 | rcu_assign_pointer(node->slots[offset], item); | |
398 | BUG_ON(tag_get(node, 0, offset)); | |
399 | BUG_ON(tag_get(node, 1, offset)); | |
400 | } else { | |
401 | rcu_assign_pointer(root->rnode, item); | |
402 | BUG_ON(root_tag_get(root, 0)); | |
403 | BUG_ON(root_tag_get(root, 1)); | |
404 | } | |
405 | ||
406 | return 0; | |
407 | } | |
408 | EXPORT_SYMBOL(radix_tree_insert); | |
409 | ||
410 | /* | |
411 | * is_slot == 1 : search for the slot. | |
412 | * is_slot == 0 : search for the node. | |
413 | */ | |
414 | static void *radix_tree_lookup_element(struct radix_tree_root *root, | |
415 | unsigned long index, int is_slot) | |
416 | { | |
417 | unsigned int height, shift; | |
418 | struct radix_tree_node *node, **slot; | |
419 | ||
420 | node = rcu_dereference_raw(root->rnode); | |
421 | if (node == NULL) | |
422 | return NULL; | |
423 | ||
424 | if (!radix_tree_is_indirect_ptr(node)) { | |
425 | if (index > 0) | |
426 | return NULL; | |
427 | return is_slot ? (void *)&root->rnode : node; | |
428 | } | |
429 | node = indirect_to_ptr(node); | |
430 | ||
431 | height = node->height; | |
432 | if (index > radix_tree_maxindex(height)) | |
433 | return NULL; | |
434 | ||
435 | shift = (height-1) * RADIX_TREE_MAP_SHIFT; | |
436 | ||
437 | do { | |
438 | slot = (struct radix_tree_node **) | |
439 | (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK)); | |
440 | node = rcu_dereference_raw(*slot); | |
441 | if (node == NULL) | |
442 | return NULL; | |
443 | ||
444 | shift -= RADIX_TREE_MAP_SHIFT; | |
445 | height--; | |
446 | } while (height > 0); | |
447 | ||
448 | return is_slot ? (void *)slot : indirect_to_ptr(node); | |
449 | } | |
450 | ||
451 | /** | |
452 | * radix_tree_lookup_slot - lookup a slot in a radix tree | |
453 | * @root: radix tree root | |
454 | * @index: index key | |
455 | * | |
456 | * Returns: the slot corresponding to the position @index in the | |
457 | * radix tree @root. This is useful for update-if-exists operations. | |
458 | * | |
459 | * This function can be called under rcu_read_lock iff the slot is not | |
460 | * modified by radix_tree_replace_slot, otherwise it must be called | |
461 | * exclusive from other writers. Any dereference of the slot must be done | |
462 | * using radix_tree_deref_slot. | |
463 | */ | |
464 | void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index) | |
465 | { | |
466 | return (void **)radix_tree_lookup_element(root, index, 1); | |
467 | } | |
468 | EXPORT_SYMBOL(radix_tree_lookup_slot); | |
469 | ||
470 | /** | |
471 | * radix_tree_lookup - perform lookup operation on a radix tree | |
472 | * @root: radix tree root | |
473 | * @index: index key | |
474 | * | |
475 | * Lookup the item at the position @index in the radix tree @root. | |
476 | * | |
477 | * This function can be called under rcu_read_lock, however the caller | |
478 | * must manage lifetimes of leaf nodes (eg. RCU may also be used to free | |
479 | * them safely). No RCU barriers are required to access or modify the | |
480 | * returned item, however. | |
481 | */ | |
482 | void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index) | |
483 | { | |
484 | return radix_tree_lookup_element(root, index, 0); | |
485 | } | |
486 | EXPORT_SYMBOL(radix_tree_lookup); | |
487 | ||
488 | /** | |
489 | * radix_tree_tag_set - set a tag on a radix tree node | |
490 | * @root: radix tree root | |
491 | * @index: index key | |
492 | * @tag: tag index | |
493 | * | |
494 | * Set the search tag (which must be < RADIX_TREE_MAX_TAGS) | |
495 | * corresponding to @index in the radix tree. From | |
496 | * the root all the way down to the leaf node. | |
497 | * | |
498 | * Returns the address of the tagged item. Setting a tag on a not-present | |
499 | * item is a bug. | |
500 | */ | |
501 | void *radix_tree_tag_set(struct radix_tree_root *root, | |
502 | unsigned long index, unsigned int tag) | |
503 | { | |
504 | unsigned int height, shift; | |
505 | struct radix_tree_node *slot; | |
506 | ||
507 | height = root->height; | |
508 | BUG_ON(index > radix_tree_maxindex(height)); | |
509 | ||
510 | slot = indirect_to_ptr(root->rnode); | |
511 | shift = (height - 1) * RADIX_TREE_MAP_SHIFT; | |
512 | ||
513 | while (height > 0) { | |
514 | int offset; | |
515 | ||
516 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; | |
517 | if (!tag_get(slot, tag, offset)) | |
518 | tag_set(slot, tag, offset); | |
519 | slot = slot->slots[offset]; | |
520 | BUG_ON(slot == NULL); | |
521 | shift -= RADIX_TREE_MAP_SHIFT; | |
522 | height--; | |
523 | } | |
524 | ||
525 | /* set the root's tag bit */ | |
526 | if (slot && !root_tag_get(root, tag)) | |
527 | root_tag_set(root, tag); | |
528 | ||
529 | return slot; | |
530 | } | |
531 | EXPORT_SYMBOL(radix_tree_tag_set); | |
532 | ||
533 | /** | |
534 | * radix_tree_tag_clear - clear a tag on a radix tree node | |
535 | * @root: radix tree root | |
536 | * @index: index key | |
537 | * @tag: tag index | |
538 | * | |
539 | * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS) | |
540 | * corresponding to @index in the radix tree. If | |
541 | * this causes the leaf node to have no tags set then clear the tag in the | |
542 | * next-to-leaf node, etc. | |
543 | * | |
544 | * Returns the address of the tagged item on success, else NULL. ie: | |
545 | * has the same return value and semantics as radix_tree_lookup(). | |
546 | */ | |
547 | void *radix_tree_tag_clear(struct radix_tree_root *root, | |
548 | unsigned long index, unsigned int tag) | |
549 | { | |
550 | struct radix_tree_node *node = NULL; | |
551 | struct radix_tree_node *slot = NULL; | |
552 | unsigned int height, shift; | |
553 | int uninitialized_var(offset); | |
554 | ||
555 | height = root->height; | |
556 | if (index > radix_tree_maxindex(height)) | |
557 | goto out; | |
558 | ||
559 | shift = height * RADIX_TREE_MAP_SHIFT; | |
560 | slot = indirect_to_ptr(root->rnode); | |
561 | ||
562 | while (shift) { | |
563 | if (slot == NULL) | |
564 | goto out; | |
565 | ||
566 | shift -= RADIX_TREE_MAP_SHIFT; | |
567 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; | |
568 | node = slot; | |
569 | slot = slot->slots[offset]; | |
570 | } | |
571 | ||
572 | if (slot == NULL) | |
573 | goto out; | |
574 | ||
575 | while (node) { | |
576 | if (!tag_get(node, tag, offset)) | |
577 | goto out; | |
578 | tag_clear(node, tag, offset); | |
579 | if (any_tag_set(node, tag)) | |
580 | goto out; | |
581 | ||
582 | index >>= RADIX_TREE_MAP_SHIFT; | |
583 | offset = index & RADIX_TREE_MAP_MASK; | |
584 | node = node->parent; | |
585 | } | |
586 | ||
587 | /* clear the root's tag bit */ | |
588 | if (root_tag_get(root, tag)) | |
589 | root_tag_clear(root, tag); | |
590 | ||
591 | out: | |
592 | return slot; | |
593 | } | |
594 | EXPORT_SYMBOL(radix_tree_tag_clear); | |
595 | ||
596 | /** | |
597 | * radix_tree_tag_get - get a tag on a radix tree node | |
598 | * @root: radix tree root | |
599 | * @index: index key | |
600 | * @tag: tag index (< RADIX_TREE_MAX_TAGS) | |
601 | * | |
602 | * Return values: | |
603 | * | |
604 | * 0: tag not present or not set | |
605 | * 1: tag set | |
606 | * | |
607 | * Note that the return value of this function may not be relied on, even if | |
608 | * the RCU lock is held, unless tag modification and node deletion are excluded | |
609 | * from concurrency. | |
610 | */ | |
611 | int radix_tree_tag_get(struct radix_tree_root *root, | |
612 | unsigned long index, unsigned int tag) | |
613 | { | |
614 | unsigned int height, shift; | |
615 | struct radix_tree_node *node; | |
616 | ||
617 | /* check the root's tag bit */ | |
618 | if (!root_tag_get(root, tag)) | |
619 | return 0; | |
620 | ||
621 | node = rcu_dereference_raw(root->rnode); | |
622 | if (node == NULL) | |
623 | return 0; | |
624 | ||
625 | if (!radix_tree_is_indirect_ptr(node)) | |
626 | return (index == 0); | |
627 | node = indirect_to_ptr(node); | |
628 | ||
629 | height = node->height; | |
630 | if (index > radix_tree_maxindex(height)) | |
631 | return 0; | |
632 | ||
633 | shift = (height - 1) * RADIX_TREE_MAP_SHIFT; | |
634 | ||
635 | for ( ; ; ) { | |
636 | int offset; | |
637 | ||
638 | if (node == NULL) | |
639 | return 0; | |
640 | ||
641 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; | |
642 | if (!tag_get(node, tag, offset)) | |
643 | return 0; | |
644 | if (height == 1) | |
645 | return 1; | |
646 | node = rcu_dereference_raw(node->slots[offset]); | |
647 | shift -= RADIX_TREE_MAP_SHIFT; | |
648 | height--; | |
649 | } | |
650 | } | |
651 | EXPORT_SYMBOL(radix_tree_tag_get); | |
652 | ||
653 | /** | |
654 | * radix_tree_next_chunk - find next chunk of slots for iteration | |
655 | * | |
656 | * @root: radix tree root | |
657 | * @iter: iterator state | |
658 | * @flags: RADIX_TREE_ITER_* flags and tag index | |
659 | * Returns: pointer to chunk first slot, or NULL if iteration is over | |
660 | */ | |
661 | void **radix_tree_next_chunk(struct radix_tree_root *root, | |
662 | struct radix_tree_iter *iter, unsigned flags) | |
663 | { | |
664 | unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK; | |
665 | struct radix_tree_node *rnode, *node; | |
666 | unsigned long index, offset; | |
667 | ||
668 | if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag)) | |
669 | return NULL; | |
670 | ||
671 | /* | |
672 | * Catch next_index overflow after ~0UL. iter->index never overflows | |
673 | * during iterating; it can be zero only at the beginning. | |
674 | * And we cannot overflow iter->next_index in a single step, | |
675 | * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG. | |
676 | */ | |
677 | index = iter->next_index; | |
678 | if (!index && iter->index) | |
679 | return NULL; | |
680 | ||
681 | rnode = rcu_dereference_raw(root->rnode); | |
682 | if (radix_tree_is_indirect_ptr(rnode)) { | |
683 | rnode = indirect_to_ptr(rnode); | |
684 | } else if (rnode && !index) { | |
685 | /* Single-slot tree */ | |
686 | iter->index = 0; | |
687 | iter->next_index = 1; | |
688 | iter->tags = 1; | |
689 | return (void **)&root->rnode; | |
690 | } else | |
691 | return NULL; | |
692 | ||
693 | restart: | |
694 | shift = (rnode->height - 1) * RADIX_TREE_MAP_SHIFT; | |
695 | offset = index >> shift; | |
696 | ||
697 | /* Index outside of the tree */ | |
698 | if (offset >= RADIX_TREE_MAP_SIZE) | |
699 | return NULL; | |
700 | ||
701 | node = rnode; | |
702 | while (1) { | |
703 | if ((flags & RADIX_TREE_ITER_TAGGED) ? | |
704 | !test_bit(offset, node->tags[tag]) : | |
705 | !node->slots[offset]) { | |
706 | /* Hole detected */ | |
707 | if (flags & RADIX_TREE_ITER_CONTIG) | |
708 | return NULL; | |
709 | ||
710 | if (flags & RADIX_TREE_ITER_TAGGED) | |
711 | offset = radix_tree_find_next_bit( | |
712 | node->tags[tag], | |
713 | RADIX_TREE_MAP_SIZE, | |
714 | offset + 1); | |
715 | else | |
716 | while (++offset < RADIX_TREE_MAP_SIZE) { | |
717 | if (node->slots[offset]) | |
718 | break; | |
719 | } | |
720 | index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1); | |
721 | index += offset << shift; | |
722 | /* Overflow after ~0UL */ | |
723 | if (!index) | |
724 | return NULL; | |
725 | if (offset == RADIX_TREE_MAP_SIZE) | |
726 | goto restart; | |
727 | } | |
728 | ||
729 | /* This is leaf-node */ | |
730 | if (!shift) | |
731 | break; | |
732 | ||
733 | node = rcu_dereference_raw(node->slots[offset]); | |
734 | if (node == NULL) | |
735 | goto restart; | |
736 | shift -= RADIX_TREE_MAP_SHIFT; | |
737 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; | |
738 | } | |
739 | ||
740 | /* Update the iterator state */ | |
741 | iter->index = index; | |
742 | iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1; | |
743 | ||
744 | /* Construct iter->tags bit-mask from node->tags[tag] array */ | |
745 | if (flags & RADIX_TREE_ITER_TAGGED) { | |
746 | unsigned tag_long, tag_bit; | |
747 | ||
748 | tag_long = offset / BITS_PER_LONG; | |
749 | tag_bit = offset % BITS_PER_LONG; | |
750 | iter->tags = node->tags[tag][tag_long] >> tag_bit; | |
751 | /* This never happens if RADIX_TREE_TAG_LONGS == 1 */ | |
752 | if (tag_long < RADIX_TREE_TAG_LONGS - 1) { | |
753 | /* Pick tags from next element */ | |
754 | if (tag_bit) | |
755 | iter->tags |= node->tags[tag][tag_long + 1] << | |
756 | (BITS_PER_LONG - tag_bit); | |
757 | /* Clip chunk size, here only BITS_PER_LONG tags */ | |
758 | iter->next_index = index + BITS_PER_LONG; | |
759 | } | |
760 | } | |
761 | ||
762 | return node->slots + offset; | |
763 | } | |
764 | EXPORT_SYMBOL(radix_tree_next_chunk); | |
765 | ||
766 | /** | |
767 | * radix_tree_range_tag_if_tagged - for each item in given range set given | |
768 | * tag if item has another tag set | |
769 | * @root: radix tree root | |
770 | * @first_indexp: pointer to a starting index of a range to scan | |
771 | * @last_index: last index of a range to scan | |
772 | * @nr_to_tag: maximum number items to tag | |
773 | * @iftag: tag index to test | |
774 | * @settag: tag index to set if tested tag is set | |
775 | * | |
776 | * This function scans range of radix tree from first_index to last_index | |
777 | * (inclusive). For each item in the range if iftag is set, the function sets | |
778 | * also settag. The function stops either after tagging nr_to_tag items or | |
779 | * after reaching last_index. | |
780 | * | |
781 | * The tags must be set from the leaf level only and propagated back up the | |
782 | * path to the root. We must do this so that we resolve the full path before | |
783 | * setting any tags on intermediate nodes. If we set tags as we descend, then | |
784 | * we can get to the leaf node and find that the index that has the iftag | |
785 | * set is outside the range we are scanning. This reults in dangling tags and | |
786 | * can lead to problems with later tag operations (e.g. livelocks on lookups). | |
787 | * | |
788 | * The function returns number of leaves where the tag was set and sets | |
789 | * *first_indexp to the first unscanned index. | |
790 | * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must | |
791 | * be prepared to handle that. | |
792 | */ | |
793 | unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, | |
794 | unsigned long *first_indexp, unsigned long last_index, | |
795 | unsigned long nr_to_tag, | |
796 | unsigned int iftag, unsigned int settag) | |
797 | { | |
798 | unsigned int height = root->height; | |
799 | struct radix_tree_node *node = NULL; | |
800 | struct radix_tree_node *slot; | |
801 | unsigned int shift; | |
802 | unsigned long tagged = 0; | |
803 | unsigned long index = *first_indexp; | |
804 | ||
805 | last_index = min(last_index, radix_tree_maxindex(height)); | |
806 | if (index > last_index) | |
807 | return 0; | |
808 | if (!nr_to_tag) | |
809 | return 0; | |
810 | if (!root_tag_get(root, iftag)) { | |
811 | *first_indexp = last_index + 1; | |
812 | return 0; | |
813 | } | |
814 | if (height == 0) { | |
815 | *first_indexp = last_index + 1; | |
816 | root_tag_set(root, settag); | |
817 | return 1; | |
818 | } | |
819 | ||
820 | shift = (height - 1) * RADIX_TREE_MAP_SHIFT; | |
821 | slot = indirect_to_ptr(root->rnode); | |
822 | ||
823 | for (;;) { | |
824 | unsigned long upindex; | |
825 | int offset; | |
826 | ||
827 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; | |
828 | if (!slot->slots[offset]) | |
829 | goto next; | |
830 | if (!tag_get(slot, iftag, offset)) | |
831 | goto next; | |
832 | if (shift) { | |
833 | /* Go down one level */ | |
834 | shift -= RADIX_TREE_MAP_SHIFT; | |
835 | node = slot; | |
836 | slot = slot->slots[offset]; | |
837 | continue; | |
838 | } | |
839 | ||
840 | /* tag the leaf */ | |
841 | tagged++; | |
842 | tag_set(slot, settag, offset); | |
843 | ||
844 | /* walk back up the path tagging interior nodes */ | |
845 | upindex = index; | |
846 | while (node) { | |
847 | upindex >>= RADIX_TREE_MAP_SHIFT; | |
848 | offset = upindex & RADIX_TREE_MAP_MASK; | |
849 | ||
850 | /* stop if we find a node with the tag already set */ | |
851 | if (tag_get(node, settag, offset)) | |
852 | break; | |
853 | tag_set(node, settag, offset); | |
854 | node = node->parent; | |
855 | } | |
856 | ||
857 | /* | |
858 | * Small optimization: now clear that node pointer. | |
859 | * Since all of this slot's ancestors now have the tag set | |
860 | * from setting it above, we have no further need to walk | |
861 | * back up the tree setting tags, until we update slot to | |
862 | * point to another radix_tree_node. | |
863 | */ | |
864 | node = NULL; | |
865 | ||
866 | next: | |
867 | /* Go to next item at level determined by 'shift' */ | |
868 | index = ((index >> shift) + 1) << shift; | |
869 | /* Overflow can happen when last_index is ~0UL... */ | |
870 | if (index > last_index || !index) | |
871 | break; | |
872 | if (tagged >= nr_to_tag) | |
873 | break; | |
874 | while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) { | |
875 | /* | |
876 | * We've fully scanned this node. Go up. Because | |
877 | * last_index is guaranteed to be in the tree, what | |
878 | * we do below cannot wander astray. | |
879 | */ | |
880 | slot = slot->parent; | |
881 | shift += RADIX_TREE_MAP_SHIFT; | |
882 | } | |
883 | } | |
884 | /* | |
885 | * We need not to tag the root tag if there is no tag which is set with | |
886 | * settag within the range from *first_indexp to last_index. | |
887 | */ | |
888 | if (tagged > 0) | |
889 | root_tag_set(root, settag); | |
890 | *first_indexp = index; | |
891 | ||
892 | return tagged; | |
893 | } | |
894 | EXPORT_SYMBOL(radix_tree_range_tag_if_tagged); | |
895 | ||
896 | ||
897 | /** | |
898 | * radix_tree_next_hole - find the next hole (not-present entry) | |
899 | * @root: tree root | |
900 | * @index: index key | |
901 | * @max_scan: maximum range to search | |
902 | * | |
903 | * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest | |
904 | * indexed hole. | |
905 | * | |
906 | * Returns: the index of the hole if found, otherwise returns an index | |
907 | * outside of the set specified (in which case 'return - index >= max_scan' | |
908 | * will be true). In rare cases of index wrap-around, 0 will be returned. | |
909 | * | |
910 | * radix_tree_next_hole may be called under rcu_read_lock. However, like | |
911 | * radix_tree_gang_lookup, this will not atomically search a snapshot of | |
912 | * the tree at a single point in time. For example, if a hole is created | |
913 | * at index 5, then subsequently a hole is created at index 10, | |
914 | * radix_tree_next_hole covering both indexes may return 10 if called | |
915 | * under rcu_read_lock. | |
916 | */ | |
917 | unsigned long radix_tree_next_hole(struct radix_tree_root *root, | |
918 | unsigned long index, unsigned long max_scan) | |
919 | { | |
920 | unsigned long i; | |
921 | ||
922 | for (i = 0; i < max_scan; i++) { | |
923 | if (!radix_tree_lookup(root, index)) | |
924 | break; | |
925 | index++; | |
926 | if (index == 0) | |
927 | break; | |
928 | } | |
929 | ||
930 | return index; | |
931 | } | |
932 | EXPORT_SYMBOL(radix_tree_next_hole); | |
933 | ||
934 | /** | |
935 | * radix_tree_prev_hole - find the prev hole (not-present entry) | |
936 | * @root: tree root | |
937 | * @index: index key | |
938 | * @max_scan: maximum range to search | |
939 | * | |
940 | * Search backwards in the range [max(index-max_scan+1, 0), index] | |
941 | * for the first hole. | |
942 | * | |
943 | * Returns: the index of the hole if found, otherwise returns an index | |
944 | * outside of the set specified (in which case 'index - return >= max_scan' | |
945 | * will be true). In rare cases of wrap-around, ULONG_MAX will be returned. | |
946 | * | |
947 | * radix_tree_next_hole may be called under rcu_read_lock. However, like | |
948 | * radix_tree_gang_lookup, this will not atomically search a snapshot of | |
949 | * the tree at a single point in time. For example, if a hole is created | |
950 | * at index 10, then subsequently a hole is created at index 5, | |
951 | * radix_tree_prev_hole covering both indexes may return 5 if called under | |
952 | * rcu_read_lock. | |
953 | */ | |
954 | unsigned long radix_tree_prev_hole(struct radix_tree_root *root, | |
955 | unsigned long index, unsigned long max_scan) | |
956 | { | |
957 | unsigned long i; | |
958 | ||
959 | for (i = 0; i < max_scan; i++) { | |
960 | if (!radix_tree_lookup(root, index)) | |
961 | break; | |
962 | index--; | |
963 | if (index == ULONG_MAX) | |
964 | break; | |
965 | } | |
966 | ||
967 | return index; | |
968 | } | |
969 | EXPORT_SYMBOL(radix_tree_prev_hole); | |
970 | ||
971 | /** | |
972 | * radix_tree_gang_lookup - perform multiple lookup on a radix tree | |
973 | * @root: radix tree root | |
974 | * @results: where the results of the lookup are placed | |
975 | * @first_index: start the lookup from this key | |
976 | * @max_items: place up to this many items at *results | |
977 | * | |
978 | * Performs an index-ascending scan of the tree for present items. Places | |
979 | * them at *@results and returns the number of items which were placed at | |
980 | * *@results. | |
981 | * | |
982 | * The implementation is naive. | |
983 | * | |
984 | * Like radix_tree_lookup, radix_tree_gang_lookup may be called under | |
985 | * rcu_read_lock. In this case, rather than the returned results being | |
986 | * an atomic snapshot of the tree at a single point in time, the semantics | |
987 | * of an RCU protected gang lookup are as though multiple radix_tree_lookups | |
988 | * have been issued in individual locks, and results stored in 'results'. | |
989 | */ | |
990 | unsigned int | |
991 | radix_tree_gang_lookup(struct radix_tree_root *root, void **results, | |
992 | unsigned long first_index, unsigned int max_items) | |
993 | { | |
994 | struct radix_tree_iter iter; | |
995 | void **slot; | |
996 | unsigned int ret = 0; | |
997 | ||
998 | if (unlikely(!max_items)) | |
999 | return 0; | |
1000 | ||
1001 | radix_tree_for_each_slot(slot, root, &iter, first_index) { | |
1002 | results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot)); | |
1003 | if (!results[ret]) | |
1004 | continue; | |
1005 | if (++ret == max_items) | |
1006 | break; | |
1007 | } | |
1008 | ||
1009 | return ret; | |
1010 | } | |
1011 | EXPORT_SYMBOL(radix_tree_gang_lookup); | |
1012 | ||
1013 | /** | |
1014 | * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree | |
1015 | * @root: radix tree root | |
1016 | * @results: where the results of the lookup are placed | |
1017 | * @indices: where their indices should be placed (but usually NULL) | |
1018 | * @first_index: start the lookup from this key | |
1019 | * @max_items: place up to this many items at *results | |
1020 | * | |
1021 | * Performs an index-ascending scan of the tree for present items. Places | |
1022 | * their slots at *@results and returns the number of items which were | |
1023 | * placed at *@results. | |
1024 | * | |
1025 | * The implementation is naive. | |
1026 | * | |
1027 | * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must | |
1028 | * be dereferenced with radix_tree_deref_slot, and if using only RCU | |
1029 | * protection, radix_tree_deref_slot may fail requiring a retry. | |
1030 | */ | |
1031 | unsigned int | |
1032 | radix_tree_gang_lookup_slot(struct radix_tree_root *root, | |
1033 | void ***results, unsigned long *indices, | |
1034 | unsigned long first_index, unsigned int max_items) | |
1035 | { | |
1036 | struct radix_tree_iter iter; | |
1037 | void **slot; | |
1038 | unsigned int ret = 0; | |
1039 | ||
1040 | if (unlikely(!max_items)) | |
1041 | return 0; | |
1042 | ||
1043 | radix_tree_for_each_slot(slot, root, &iter, first_index) { | |
1044 | results[ret] = slot; | |
1045 | if (indices) | |
1046 | indices[ret] = iter.index; | |
1047 | if (++ret == max_items) | |
1048 | break; | |
1049 | } | |
1050 | ||
1051 | return ret; | |
1052 | } | |
1053 | EXPORT_SYMBOL(radix_tree_gang_lookup_slot); | |
1054 | ||
1055 | /** | |
1056 | * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree | |
1057 | * based on a tag | |
1058 | * @root: radix tree root | |
1059 | * @results: where the results of the lookup are placed | |
1060 | * @first_index: start the lookup from this key | |
1061 | * @max_items: place up to this many items at *results | |
1062 | * @tag: the tag index (< RADIX_TREE_MAX_TAGS) | |
1063 | * | |
1064 | * Performs an index-ascending scan of the tree for present items which | |
1065 | * have the tag indexed by @tag set. Places the items at *@results and | |
1066 | * returns the number of items which were placed at *@results. | |
1067 | */ | |
1068 | unsigned int | |
1069 | radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results, | |
1070 | unsigned long first_index, unsigned int max_items, | |
1071 | unsigned int tag) | |
1072 | { | |
1073 | struct radix_tree_iter iter; | |
1074 | void **slot; | |
1075 | unsigned int ret = 0; | |
1076 | ||
1077 | if (unlikely(!max_items)) | |
1078 | return 0; | |
1079 | ||
1080 | radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) { | |
1081 | results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot)); | |
1082 | if (!results[ret]) | |
1083 | continue; | |
1084 | if (++ret == max_items) | |
1085 | break; | |
1086 | } | |
1087 | ||
1088 | return ret; | |
1089 | } | |
1090 | EXPORT_SYMBOL(radix_tree_gang_lookup_tag); | |
1091 | ||
1092 | /** | |
1093 | * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a | |
1094 | * radix tree based on a tag | |
1095 | * @root: radix tree root | |
1096 | * @results: where the results of the lookup are placed | |
1097 | * @first_index: start the lookup from this key | |
1098 | * @max_items: place up to this many items at *results | |
1099 | * @tag: the tag index (< RADIX_TREE_MAX_TAGS) | |
1100 | * | |
1101 | * Performs an index-ascending scan of the tree for present items which | |
1102 | * have the tag indexed by @tag set. Places the slots at *@results and | |
1103 | * returns the number of slots which were placed at *@results. | |
1104 | */ | |
1105 | unsigned int | |
1106 | radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results, | |
1107 | unsigned long first_index, unsigned int max_items, | |
1108 | unsigned int tag) | |
1109 | { | |
1110 | struct radix_tree_iter iter; | |
1111 | void **slot; | |
1112 | unsigned int ret = 0; | |
1113 | ||
1114 | if (unlikely(!max_items)) | |
1115 | return 0; | |
1116 | ||
1117 | radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) { | |
1118 | results[ret] = slot; | |
1119 | if (++ret == max_items) | |
1120 | break; | |
1121 | } | |
1122 | ||
1123 | return ret; | |
1124 | } | |
1125 | EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot); | |
1126 | ||
1127 | #if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP) | |
1128 | #include <linux/sched.h> /* for cond_resched() */ | |
1129 | ||
1130 | /* | |
1131 | * This linear search is at present only useful to shmem_unuse_inode(). | |
1132 | */ | |
1133 | static unsigned long __locate(struct radix_tree_node *slot, void *item, | |
1134 | unsigned long index, unsigned long *found_index) | |
1135 | { | |
1136 | unsigned int shift, height; | |
1137 | unsigned long i; | |
1138 | ||
1139 | height = slot->height; | |
1140 | shift = (height-1) * RADIX_TREE_MAP_SHIFT; | |
1141 | ||
1142 | for ( ; height > 1; height--) { | |
1143 | i = (index >> shift) & RADIX_TREE_MAP_MASK; | |
1144 | for (;;) { | |
1145 | if (slot->slots[i] != NULL) | |
1146 | break; | |
1147 | index &= ~((1UL << shift) - 1); | |
1148 | index += 1UL << shift; | |
1149 | if (index == 0) | |
1150 | goto out; /* 32-bit wraparound */ | |
1151 | i++; | |
1152 | if (i == RADIX_TREE_MAP_SIZE) | |
1153 | goto out; | |
1154 | } | |
1155 | ||
1156 | shift -= RADIX_TREE_MAP_SHIFT; | |
1157 | slot = rcu_dereference_raw(slot->slots[i]); | |
1158 | if (slot == NULL) | |
1159 | goto out; | |
1160 | } | |
1161 | ||
1162 | /* Bottom level: check items */ | |
1163 | for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) { | |
1164 | if (slot->slots[i] == item) { | |
1165 | *found_index = index + i; | |
1166 | index = 0; | |
1167 | goto out; | |
1168 | } | |
1169 | } | |
1170 | index += RADIX_TREE_MAP_SIZE; | |
1171 | out: | |
1172 | return index; | |
1173 | } | |
1174 | ||
1175 | /** | |
1176 | * radix_tree_locate_item - search through radix tree for item | |
1177 | * @root: radix tree root | |
1178 | * @item: item to be found | |
1179 | * | |
1180 | * Returns index where item was found, or -1 if not found. | |
1181 | * Caller must hold no lock (since this time-consuming function needs | |
1182 | * to be preemptible), and must check afterwards if item is still there. | |
1183 | */ | |
1184 | unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item) | |
1185 | { | |
1186 | struct radix_tree_node *node; | |
1187 | unsigned long max_index; | |
1188 | unsigned long cur_index = 0; | |
1189 | unsigned long found_index = -1; | |
1190 | ||
1191 | do { | |
1192 | rcu_read_lock(); | |
1193 | node = rcu_dereference_raw(root->rnode); | |
1194 | if (!radix_tree_is_indirect_ptr(node)) { | |
1195 | rcu_read_unlock(); | |
1196 | if (node == item) | |
1197 | found_index = 0; | |
1198 | break; | |
1199 | } | |
1200 | ||
1201 | node = indirect_to_ptr(node); | |
1202 | max_index = radix_tree_maxindex(node->height); | |
1203 | if (cur_index > max_index) | |
1204 | break; | |
1205 | ||
1206 | cur_index = __locate(node, item, cur_index, &found_index); | |
1207 | rcu_read_unlock(); | |
1208 | cond_resched(); | |
1209 | } while (cur_index != 0 && cur_index <= max_index); | |
1210 | ||
1211 | return found_index; | |
1212 | } | |
1213 | #else | |
1214 | unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item) | |
1215 | { | |
1216 | return -1; | |
1217 | } | |
1218 | #endif /* CONFIG_SHMEM && CONFIG_SWAP */ | |
1219 | ||
1220 | /** | |
1221 | * radix_tree_shrink - shrink height of a radix tree to minimal | |
1222 | * @root radix tree root | |
1223 | */ | |
1224 | static inline void radix_tree_shrink(struct radix_tree_root *root) | |
1225 | { | |
1226 | /* try to shrink tree height */ | |
1227 | while (root->height > 0) { | |
1228 | struct radix_tree_node *to_free = root->rnode; | |
1229 | struct radix_tree_node *slot; | |
1230 | ||
1231 | BUG_ON(!radix_tree_is_indirect_ptr(to_free)); | |
1232 | to_free = indirect_to_ptr(to_free); | |
1233 | ||
1234 | /* | |
1235 | * The candidate node has more than one child, or its child | |
1236 | * is not at the leftmost slot, we cannot shrink. | |
1237 | */ | |
1238 | if (to_free->count != 1) | |
1239 | break; | |
1240 | if (!to_free->slots[0]) | |
1241 | break; | |
1242 | ||
1243 | /* | |
1244 | * We don't need rcu_assign_pointer(), since we are simply | |
1245 | * moving the node from one part of the tree to another: if it | |
1246 | * was safe to dereference the old pointer to it | |
1247 | * (to_free->slots[0]), it will be safe to dereference the new | |
1248 | * one (root->rnode) as far as dependent read barriers go. | |
1249 | */ | |
1250 | slot = to_free->slots[0]; | |
1251 | if (root->height > 1) { | |
1252 | slot->parent = NULL; | |
1253 | slot = ptr_to_indirect(slot); | |
1254 | } | |
1255 | root->rnode = slot; | |
1256 | root->height--; | |
1257 | ||
1258 | /* | |
1259 | * We have a dilemma here. The node's slot[0] must not be | |
1260 | * NULLed in case there are concurrent lookups expecting to | |
1261 | * find the item. However if this was a bottom-level node, | |
1262 | * then it may be subject to the slot pointer being visible | |
1263 | * to callers dereferencing it. If item corresponding to | |
1264 | * slot[0] is subsequently deleted, these callers would expect | |
1265 | * their slot to become empty sooner or later. | |
1266 | * | |
1267 | * For example, lockless pagecache will look up a slot, deref | |
1268 | * the page pointer, and if the page is 0 refcount it means it | |
1269 | * was concurrently deleted from pagecache so try the deref | |
1270 | * again. Fortunately there is already a requirement for logic | |
1271 | * to retry the entire slot lookup -- the indirect pointer | |
1272 | * problem (replacing direct root node with an indirect pointer | |
1273 | * also results in a stale slot). So tag the slot as indirect | |
1274 | * to force callers to retry. | |
1275 | */ | |
1276 | if (root->height == 0) | |
1277 | *((unsigned long *)&to_free->slots[0]) |= | |
1278 | RADIX_TREE_INDIRECT_PTR; | |
1279 | ||
1280 | radix_tree_node_free(to_free); | |
1281 | } | |
1282 | } | |
1283 | ||
1284 | /** | |
1285 | * radix_tree_delete - delete an item from a radix tree | |
1286 | * @root: radix tree root | |
1287 | * @index: index key | |
1288 | * | |
1289 | * Remove the item at @index from the radix tree rooted at @root. | |
1290 | * | |
1291 | * Returns the address of the deleted item, or NULL if it was not present. | |
1292 | */ | |
1293 | void *radix_tree_delete(struct radix_tree_root *root, unsigned long index) | |
1294 | { | |
1295 | struct radix_tree_node *node = NULL; | |
1296 | struct radix_tree_node *slot = NULL; | |
1297 | struct radix_tree_node *to_free; | |
1298 | unsigned int height, shift; | |
1299 | int tag; | |
1300 | int uninitialized_var(offset); | |
1301 | ||
1302 | height = root->height; | |
1303 | if (index > radix_tree_maxindex(height)) | |
1304 | goto out; | |
1305 | ||
1306 | slot = root->rnode; | |
1307 | if (height == 0) { | |
1308 | root_tag_clear_all(root); | |
1309 | root->rnode = NULL; | |
1310 | goto out; | |
1311 | } | |
1312 | slot = indirect_to_ptr(slot); | |
1313 | shift = height * RADIX_TREE_MAP_SHIFT; | |
1314 | ||
1315 | do { | |
1316 | if (slot == NULL) | |
1317 | goto out; | |
1318 | ||
1319 | shift -= RADIX_TREE_MAP_SHIFT; | |
1320 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; | |
1321 | node = slot; | |
1322 | slot = slot->slots[offset]; | |
1323 | } while (shift); | |
1324 | ||
1325 | if (slot == NULL) | |
1326 | goto out; | |
1327 | ||
1328 | /* | |
1329 | * Clear all tags associated with the item to be deleted. | |
1330 | * This way of doing it would be inefficient, but seldom is any set. | |
1331 | */ | |
1332 | for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { | |
1333 | if (tag_get(node, tag, offset)) | |
1334 | radix_tree_tag_clear(root, index, tag); | |
1335 | } | |
1336 | ||
1337 | to_free = NULL; | |
1338 | /* Now free the nodes we do not need anymore */ | |
1339 | while (node) { | |
1340 | node->slots[offset] = NULL; | |
1341 | node->count--; | |
1342 | /* | |
1343 | * Queue the node for deferred freeing after the | |
1344 | * last reference to it disappears (set NULL, above). | |
1345 | */ | |
1346 | if (to_free) | |
1347 | radix_tree_node_free(to_free); | |
1348 | ||
1349 | if (node->count) { | |
1350 | if (node == indirect_to_ptr(root->rnode)) | |
1351 | radix_tree_shrink(root); | |
1352 | goto out; | |
1353 | } | |
1354 | ||
1355 | /* Node with zero slots in use so free it */ | |
1356 | to_free = node; | |
1357 | ||
1358 | index >>= RADIX_TREE_MAP_SHIFT; | |
1359 | offset = index & RADIX_TREE_MAP_MASK; | |
1360 | node = node->parent; | |
1361 | } | |
1362 | ||
1363 | root_tag_clear_all(root); | |
1364 | root->height = 0; | |
1365 | root->rnode = NULL; | |
1366 | if (to_free) | |
1367 | radix_tree_node_free(to_free); | |
1368 | ||
1369 | out: | |
1370 | return slot; | |
1371 | } | |
1372 | EXPORT_SYMBOL(radix_tree_delete); | |
1373 | ||
1374 | /** | |
1375 | * radix_tree_tagged - test whether any items in the tree are tagged | |
1376 | * @root: radix tree root | |
1377 | * @tag: tag to test | |
1378 | */ | |
1379 | int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag) | |
1380 | { | |
1381 | return root_tag_get(root, tag); | |
1382 | } | |
1383 | EXPORT_SYMBOL(radix_tree_tagged); | |
1384 | ||
1385 | static void | |
1386 | radix_tree_node_ctor(void *node) | |
1387 | { | |
1388 | memset(node, 0, sizeof(struct radix_tree_node)); | |
1389 | } | |
1390 | ||
1391 | static __init unsigned long __maxindex(unsigned int height) | |
1392 | { | |
1393 | unsigned int width = height * RADIX_TREE_MAP_SHIFT; | |
1394 | int shift = RADIX_TREE_INDEX_BITS - width; | |
1395 | ||
1396 | if (shift < 0) | |
1397 | return ~0UL; | |
1398 | if (shift >= BITS_PER_LONG) | |
1399 | return 0UL; | |
1400 | return ~0UL >> shift; | |
1401 | } | |
1402 | ||
1403 | static __init void radix_tree_init_maxindex(void) | |
1404 | { | |
1405 | unsigned int i; | |
1406 | ||
1407 | for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++) | |
1408 | height_to_maxindex[i] = __maxindex(i); | |
1409 | } | |
1410 | ||
1411 | static int radix_tree_callback(struct notifier_block *nfb, | |
1412 | unsigned long action, | |
1413 | void *hcpu) | |
1414 | { | |
1415 | int cpu = (long)hcpu; | |
1416 | struct radix_tree_preload *rtp; | |
1417 | ||
1418 | /* Free per-cpu pool of perloaded nodes */ | |
1419 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { | |
1420 | rtp = &per_cpu(radix_tree_preloads, cpu); | |
1421 | while (rtp->nr) { | |
1422 | kmem_cache_free(radix_tree_node_cachep, | |
1423 | rtp->nodes[rtp->nr-1]); | |
1424 | rtp->nodes[rtp->nr-1] = NULL; | |
1425 | rtp->nr--; | |
1426 | } | |
1427 | } | |
1428 | return NOTIFY_OK; | |
1429 | } | |
1430 | ||
1431 | void __init radix_tree_init(void) | |
1432 | { | |
1433 | radix_tree_node_cachep = kmem_cache_create("radix_tree_node", | |
1434 | sizeof(struct radix_tree_node), 0, | |
1435 | SLAB_PANIC | SLAB_RECLAIM_ACCOUNT, | |
1436 | radix_tree_node_ctor); | |
1437 | radix_tree_init_maxindex(); | |
1438 | hotcpu_notifier(radix_tree_callback, 0); | |
1439 | } |