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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/kmemleak.h> |
31 | #include <linux/notifier.h> |
32 | #include <linux/cpu.h> |
33 | #include <linux/string.h> |
34 | #include <linux/bitops.h> |
35 | #include <linux/rcupdate.h> |
36 | #include <linux/hardirq.h> /* in_interrupt() */ |
37 | |
38 | |
39 | /* |
40 | * The height_to_maxindex array needs to be one deeper than the maximum |
41 | * path as height 0 holds only 1 entry. |
42 | */ |
43 | static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly; |
44 | |
45 | /* |
46 | * Radix tree node cache. |
47 | */ |
48 | static struct kmem_cache *radix_tree_node_cachep; |
49 | |
50 | /* |
51 | * The radix tree is variable-height, so an insert operation not only has |
52 | * to build the branch to its corresponding item, it also has to build the |
53 | * branch to existing items if the size has to be increased (by |
54 | * radix_tree_extend). |
55 | * |
56 | * The worst case is a zero height tree with just a single item at index 0, |
57 | * and then inserting an item at index ULONG_MAX. This requires 2 new branches |
58 | * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared. |
59 | * Hence: |
60 | */ |
61 | #define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1) |
62 | |
63 | /* |
64 | * Per-cpu pool of preloaded nodes |
65 | */ |
66 | struct radix_tree_preload { |
67 | int nr; |
68 | struct radix_tree_node *nodes[RADIX_TREE_PRELOAD_SIZE]; |
69 | }; |
70 | static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, }; |
71 | |
72 | static inline void *ptr_to_indirect(void *ptr) |
73 | { |
74 | return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR); |
75 | } |
76 | |
77 | static inline void *indirect_to_ptr(void *ptr) |
78 | { |
79 | return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR); |
80 | } |
81 | |
82 | static inline gfp_t root_gfp_mask(struct radix_tree_root *root) |
83 | { |
84 | return root->gfp_mask & __GFP_BITS_MASK; |
85 | } |
86 | |
87 | static inline void tag_set(struct radix_tree_node *node, unsigned int tag, |
88 | int offset) |
89 | { |
90 | __set_bit(offset, node->tags[tag]); |
91 | } |
92 | |
93 | static inline void tag_clear(struct radix_tree_node *node, unsigned int tag, |
94 | int offset) |
95 | { |
96 | __clear_bit(offset, node->tags[tag]); |
97 | } |
98 | |
99 | static inline int tag_get(struct radix_tree_node *node, unsigned int tag, |
100 | int offset) |
101 | { |
102 | return test_bit(offset, node->tags[tag]); |
103 | } |
104 | |
105 | static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag) |
106 | { |
107 | root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT)); |
108 | } |
109 | |
110 | static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag) |
111 | { |
112 | root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT)); |
113 | } |
114 | |
115 | static inline void root_tag_clear_all(struct radix_tree_root *root) |
116 | { |
117 | root->gfp_mask &= __GFP_BITS_MASK; |
118 | } |
119 | |
120 | static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag) |
121 | { |
122 | return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT)); |
123 | } |
124 | |
125 | /* |
126 | * Returns 1 if any slot in the node has this tag set. |
127 | * Otherwise returns 0. |
128 | */ |
129 | static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag) |
130 | { |
131 | int idx; |
132 | for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) { |
133 | if (node->tags[tag][idx]) |
134 | return 1; |
135 | } |
136 | return 0; |
137 | } |
138 | |
139 | /** |
140 | * radix_tree_find_next_bit - find the next set bit in a memory region |
141 | * |
142 | * @addr: The address to base the search on |
143 | * @size: The bitmap size in bits |
144 | * @offset: The bitnumber to start searching at |
145 | * |
146 | * Unrollable variant of find_next_bit() for constant size arrays. |
147 | * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero. |
148 | * Returns next bit offset, or size if nothing found. |
149 | */ |
150 | static __always_inline unsigned long |
151 | radix_tree_find_next_bit(const unsigned long *addr, |
152 | unsigned long size, unsigned long offset) |
153 | { |
154 | if (!__builtin_constant_p(size)) |
155 | return find_next_bit(addr, size, offset); |
156 | |
157 | if (offset < size) { |
158 | unsigned long tmp; |
159 | |
160 | addr += offset / BITS_PER_LONG; |
161 | tmp = *addr >> (offset % BITS_PER_LONG); |
162 | if (tmp) |
163 | return __ffs(tmp) + offset; |
164 | offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1); |
165 | while (offset < size) { |
166 | tmp = *++addr; |
167 | if (tmp) |
168 | return __ffs(tmp) + offset; |
169 | offset += BITS_PER_LONG; |
170 | } |
171 | } |
172 | return size; |
173 | } |
174 | |
175 | /* |
176 | * This assumes that the caller has performed appropriate preallocation, and |
177 | * that the caller has pinned this thread of control to the current CPU. |
178 | */ |
179 | static struct radix_tree_node * |
180 | radix_tree_node_alloc(struct radix_tree_root *root) |
181 | { |
182 | struct radix_tree_node *ret = NULL; |
183 | gfp_t gfp_mask = root_gfp_mask(root); |
184 | |
185 | /* |
186 | * Preload code isn't irq safe and it doesn't make sence to use |
187 | * preloading in the interrupt anyway as all the allocations have to |
188 | * be atomic. So just do normal allocation when in interrupt. |
189 | */ |
190 | if (!(gfp_mask & __GFP_WAIT) && !in_interrupt()) { |
191 | struct radix_tree_preload *rtp; |
192 | |
193 | /* |
194 | * Provided the caller has preloaded here, we will always |
195 | * succeed in getting a node here (and never reach |
196 | * kmem_cache_alloc) |
197 | */ |
198 | rtp = this_cpu_ptr(&radix_tree_preloads); |
199 | if (rtp->nr) { |
200 | ret = rtp->nodes[rtp->nr - 1]; |
201 | rtp->nodes[rtp->nr - 1] = NULL; |
202 | rtp->nr--; |
203 | } |
204 | /* |
205 | * Update the allocation stack trace as this is more useful |
206 | * for debugging. |
207 | */ |
208 | kmemleak_update_trace(ret); |
209 | } |
210 | if (ret == NULL) |
211 | ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); |
212 | |
213 | BUG_ON(radix_tree_is_indirect_ptr(ret)); |
214 | return ret; |
215 | } |
216 | |
217 | static void radix_tree_node_rcu_free(struct rcu_head *head) |
218 | { |
219 | struct radix_tree_node *node = |
220 | container_of(head, struct radix_tree_node, rcu_head); |
221 | int i; |
222 | |
223 | /* |
224 | * must only free zeroed nodes into the slab. radix_tree_shrink |
225 | * can leave us with a non-NULL entry in the first slot, so clear |
226 | * that here to make sure. |
227 | */ |
228 | for (i = 0; i < RADIX_TREE_MAX_TAGS; i++) |
229 | tag_clear(node, i, 0); |
230 | |
231 | node->slots[0] = NULL; |
232 | node->count = 0; |
233 | |
234 | kmem_cache_free(radix_tree_node_cachep, node); |
235 | } |
236 | |
237 | static inline void |
238 | radix_tree_node_free(struct radix_tree_node *node) |
239 | { |
240 | call_rcu(&node->rcu_head, radix_tree_node_rcu_free); |
241 | } |
242 | |
243 | /* |
244 | * Load up this CPU's radix_tree_node buffer with sufficient objects to |
245 | * ensure that the addition of a single element in the tree cannot fail. On |
246 | * success, return zero, with preemption disabled. On error, return -ENOMEM |
247 | * with preemption not disabled. |
248 | * |
249 | * To make use of this facility, the radix tree must be initialised without |
250 | * __GFP_WAIT being passed to INIT_RADIX_TREE(). |
251 | */ |
252 | static int __radix_tree_preload(gfp_t gfp_mask) |
253 | { |
254 | struct radix_tree_preload *rtp; |
255 | struct radix_tree_node *node; |
256 | int ret = -ENOMEM; |
257 | |
258 | preempt_disable(); |
259 | rtp = this_cpu_ptr(&radix_tree_preloads); |
260 | while (rtp->nr < ARRAY_SIZE(rtp->nodes)) { |
261 | preempt_enable(); |
262 | node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); |
263 | if (node == NULL) |
264 | goto out; |
265 | preempt_disable(); |
266 | rtp = this_cpu_ptr(&radix_tree_preloads); |
267 | if (rtp->nr < ARRAY_SIZE(rtp->nodes)) |
268 | rtp->nodes[rtp->nr++] = node; |
269 | else |
270 | kmem_cache_free(radix_tree_node_cachep, node); |
271 | } |
272 | ret = 0; |
273 | out: |
274 | return ret; |
275 | } |
276 | |
277 | /* |
278 | * Load up this CPU's radix_tree_node buffer with sufficient objects to |
279 | * ensure that the addition of a single element in the tree cannot fail. On |
280 | * success, return zero, with preemption disabled. On error, return -ENOMEM |
281 | * with preemption not disabled. |
282 | * |
283 | * To make use of this facility, the radix tree must be initialised without |
284 | * __GFP_WAIT being passed to INIT_RADIX_TREE(). |
285 | */ |
286 | int radix_tree_preload(gfp_t gfp_mask) |
287 | { |
288 | /* Warn on non-sensical use... */ |
289 | WARN_ON_ONCE(!(gfp_mask & __GFP_WAIT)); |
290 | return __radix_tree_preload(gfp_mask); |
291 | } |
292 | EXPORT_SYMBOL(radix_tree_preload); |
293 | |
294 | /* |
295 | * The same as above function, except we don't guarantee preloading happens. |
296 | * We do it, if we decide it helps. On success, return zero with preemption |
297 | * disabled. On error, return -ENOMEM with preemption not disabled. |
298 | */ |
299 | int radix_tree_maybe_preload(gfp_t gfp_mask) |
300 | { |
301 | if (gfp_mask & __GFP_WAIT) |
302 | return __radix_tree_preload(gfp_mask); |
303 | /* Preloading doesn't help anything with this gfp mask, skip it */ |
304 | preempt_disable(); |
305 | return 0; |
306 | } |
307 | EXPORT_SYMBOL(radix_tree_maybe_preload); |
308 | |
309 | /* |
310 | * Return the maximum key which can be store into a |
311 | * radix tree with height HEIGHT. |
312 | */ |
313 | static inline unsigned long radix_tree_maxindex(unsigned int height) |
314 | { |
315 | return height_to_maxindex[height]; |
316 | } |
317 | |
318 | /* |
319 | * Extend a radix tree so it can store key @index. |
320 | */ |
321 | static int radix_tree_extend(struct radix_tree_root *root, unsigned long index) |
322 | { |
323 | struct radix_tree_node *node; |
324 | struct radix_tree_node *slot; |
325 | unsigned int height; |
326 | int tag; |
327 | |
328 | /* Figure out what the height should be. */ |
329 | height = root->height + 1; |
330 | while (index > radix_tree_maxindex(height)) |
331 | height++; |
332 | |
333 | if (root->rnode == NULL) { |
334 | root->height = height; |
335 | goto out; |
336 | } |
337 | |
338 | do { |
339 | unsigned int newheight; |
340 | if (!(node = radix_tree_node_alloc(root))) |
341 | return -ENOMEM; |
342 | |
343 | /* Propagate the aggregated tag info into the new root */ |
344 | for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { |
345 | if (root_tag_get(root, tag)) |
346 | tag_set(node, tag, 0); |
347 | } |
348 | |
349 | /* Increase the height. */ |
350 | newheight = root->height+1; |
351 | BUG_ON(newheight & ~RADIX_TREE_HEIGHT_MASK); |
352 | node->path = newheight; |
353 | node->count = 1; |
354 | node->parent = NULL; |
355 | slot = root->rnode; |
356 | if (newheight > 1) { |
357 | slot = indirect_to_ptr(slot); |
358 | slot->parent = node; |
359 | } |
360 | node->slots[0] = slot; |
361 | node = ptr_to_indirect(node); |
362 | rcu_assign_pointer(root->rnode, node); |
363 | root->height = newheight; |
364 | } while (height > root->height); |
365 | out: |
366 | return 0; |
367 | } |
368 | |
369 | /** |
370 | * __radix_tree_create - create a slot in a radix tree |
371 | * @root: radix tree root |
372 | * @index: index key |
373 | * @nodep: returns node |
374 | * @slotp: returns slot |
375 | * |
376 | * Create, if necessary, and return the node and slot for an item |
377 | * at position @index in the radix tree @root. |
378 | * |
379 | * Until there is more than one item in the tree, no nodes are |
380 | * allocated and @root->rnode is used as a direct slot instead of |
381 | * pointing to a node, in which case *@nodep will be NULL. |
382 | * |
383 | * Returns -ENOMEM, or 0 for success. |
384 | */ |
385 | int __radix_tree_create(struct radix_tree_root *root, unsigned long index, |
386 | struct radix_tree_node **nodep, void ***slotp) |
387 | { |
388 | struct radix_tree_node *node = NULL, *slot; |
389 | unsigned int height, shift, offset; |
390 | int error; |
391 | |
392 | /* Make sure the tree is high enough. */ |
393 | if (index > radix_tree_maxindex(root->height)) { |
394 | error = radix_tree_extend(root, index); |
395 | if (error) |
396 | return error; |
397 | } |
398 | |
399 | slot = indirect_to_ptr(root->rnode); |
400 | |
401 | height = root->height; |
402 | shift = (height-1) * RADIX_TREE_MAP_SHIFT; |
403 | |
404 | offset = 0; /* uninitialised var warning */ |
405 | while (height > 0) { |
406 | if (slot == NULL) { |
407 | /* Have to add a child node. */ |
408 | if (!(slot = radix_tree_node_alloc(root))) |
409 | return -ENOMEM; |
410 | slot->path = height; |
411 | slot->parent = node; |
412 | if (node) { |
413 | rcu_assign_pointer(node->slots[offset], slot); |
414 | node->count++; |
415 | slot->path |= offset << RADIX_TREE_HEIGHT_SHIFT; |
416 | } else |
417 | rcu_assign_pointer(root->rnode, ptr_to_indirect(slot)); |
418 | } |
419 | |
420 | /* Go a level down */ |
421 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; |
422 | node = slot; |
423 | slot = node->slots[offset]; |
424 | shift -= RADIX_TREE_MAP_SHIFT; |
425 | height--; |
426 | } |
427 | |
428 | if (nodep) |
429 | *nodep = node; |
430 | if (slotp) |
431 | *slotp = node ? node->slots + offset : (void **)&root->rnode; |
432 | return 0; |
433 | } |
434 | |
435 | /** |
436 | * radix_tree_insert - insert into a radix tree |
437 | * @root: radix tree root |
438 | * @index: index key |
439 | * @item: item to insert |
440 | * |
441 | * Insert an item into the radix tree at position @index. |
442 | */ |
443 | int radix_tree_insert(struct radix_tree_root *root, |
444 | unsigned long index, void *item) |
445 | { |
446 | struct radix_tree_node *node; |
447 | void **slot; |
448 | int error; |
449 | |
450 | BUG_ON(radix_tree_is_indirect_ptr(item)); |
451 | |
452 | error = __radix_tree_create(root, index, &node, &slot); |
453 | if (error) |
454 | return error; |
455 | if (*slot != NULL) |
456 | return -EEXIST; |
457 | rcu_assign_pointer(*slot, item); |
458 | |
459 | if (node) { |
460 | node->count++; |
461 | BUG_ON(tag_get(node, 0, index & RADIX_TREE_MAP_MASK)); |
462 | BUG_ON(tag_get(node, 1, index & RADIX_TREE_MAP_MASK)); |
463 | } else { |
464 | BUG_ON(root_tag_get(root, 0)); |
465 | BUG_ON(root_tag_get(root, 1)); |
466 | } |
467 | |
468 | return 0; |
469 | } |
470 | EXPORT_SYMBOL(radix_tree_insert); |
471 | |
472 | /** |
473 | * __radix_tree_lookup - lookup an item in a radix tree |
474 | * @root: radix tree root |
475 | * @index: index key |
476 | * @nodep: returns node |
477 | * @slotp: returns slot |
478 | * |
479 | * Lookup and return the item at position @index in the radix |
480 | * tree @root. |
481 | * |
482 | * Until there is more than one item in the tree, no nodes are |
483 | * allocated and @root->rnode is used as a direct slot instead of |
484 | * pointing to a node, in which case *@nodep will be NULL. |
485 | */ |
486 | void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index, |
487 | struct radix_tree_node **nodep, void ***slotp) |
488 | { |
489 | struct radix_tree_node *node, *parent; |
490 | unsigned int height, shift; |
491 | void **slot; |
492 | |
493 | node = rcu_dereference_raw(root->rnode); |
494 | if (node == NULL) |
495 | return NULL; |
496 | |
497 | if (!radix_tree_is_indirect_ptr(node)) { |
498 | if (index > 0) |
499 | return NULL; |
500 | |
501 | if (nodep) |
502 | *nodep = NULL; |
503 | if (slotp) |
504 | *slotp = (void **)&root->rnode; |
505 | return node; |
506 | } |
507 | node = indirect_to_ptr(node); |
508 | |
509 | height = node->path & RADIX_TREE_HEIGHT_MASK; |
510 | if (index > radix_tree_maxindex(height)) |
511 | return NULL; |
512 | |
513 | shift = (height-1) * RADIX_TREE_MAP_SHIFT; |
514 | |
515 | do { |
516 | parent = node; |
517 | slot = node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK); |
518 | node = rcu_dereference_raw(*slot); |
519 | if (node == NULL) |
520 | return NULL; |
521 | |
522 | shift -= RADIX_TREE_MAP_SHIFT; |
523 | height--; |
524 | } while (height > 0); |
525 | |
526 | if (nodep) |
527 | *nodep = parent; |
528 | if (slotp) |
529 | *slotp = slot; |
530 | return node; |
531 | } |
532 | |
533 | /** |
534 | * radix_tree_lookup_slot - lookup a slot in a radix tree |
535 | * @root: radix tree root |
536 | * @index: index key |
537 | * |
538 | * Returns: the slot corresponding to the position @index in the |
539 | * radix tree @root. This is useful for update-if-exists operations. |
540 | * |
541 | * This function can be called under rcu_read_lock iff the slot is not |
542 | * modified by radix_tree_replace_slot, otherwise it must be called |
543 | * exclusive from other writers. Any dereference of the slot must be done |
544 | * using radix_tree_deref_slot. |
545 | */ |
546 | void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index) |
547 | { |
548 | void **slot; |
549 | |
550 | if (!__radix_tree_lookup(root, index, NULL, &slot)) |
551 | return NULL; |
552 | return slot; |
553 | } |
554 | EXPORT_SYMBOL(radix_tree_lookup_slot); |
555 | |
556 | /** |
557 | * radix_tree_lookup - perform lookup operation on a radix tree |
558 | * @root: radix tree root |
559 | * @index: index key |
560 | * |
561 | * Lookup the item at the position @index in the radix tree @root. |
562 | * |
563 | * This function can be called under rcu_read_lock, however the caller |
564 | * must manage lifetimes of leaf nodes (eg. RCU may also be used to free |
565 | * them safely). No RCU barriers are required to access or modify the |
566 | * returned item, however. |
567 | */ |
568 | void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index) |
569 | { |
570 | return __radix_tree_lookup(root, index, NULL, NULL); |
571 | } |
572 | EXPORT_SYMBOL(radix_tree_lookup); |
573 | |
574 | /** |
575 | * radix_tree_tag_set - set a tag on a radix tree node |
576 | * @root: radix tree root |
577 | * @index: index key |
578 | * @tag: tag index |
579 | * |
580 | * Set the search tag (which must be < RADIX_TREE_MAX_TAGS) |
581 | * corresponding to @index in the radix tree. From |
582 | * the root all the way down to the leaf node. |
583 | * |
584 | * Returns the address of the tagged item. Setting a tag on a not-present |
585 | * item is a bug. |
586 | */ |
587 | void *radix_tree_tag_set(struct radix_tree_root *root, |
588 | unsigned long index, unsigned int tag) |
589 | { |
590 | unsigned int height, shift; |
591 | struct radix_tree_node *slot; |
592 | |
593 | height = root->height; |
594 | BUG_ON(index > radix_tree_maxindex(height)); |
595 | |
596 | slot = indirect_to_ptr(root->rnode); |
597 | shift = (height - 1) * RADIX_TREE_MAP_SHIFT; |
598 | |
599 | while (height > 0) { |
600 | int offset; |
601 | |
602 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; |
603 | if (!tag_get(slot, tag, offset)) |
604 | tag_set(slot, tag, offset); |
605 | slot = slot->slots[offset]; |
606 | BUG_ON(slot == NULL); |
607 | shift -= RADIX_TREE_MAP_SHIFT; |
608 | height--; |
609 | } |
610 | |
611 | /* set the root's tag bit */ |
612 | if (slot && !root_tag_get(root, tag)) |
613 | root_tag_set(root, tag); |
614 | |
615 | return slot; |
616 | } |
617 | EXPORT_SYMBOL(radix_tree_tag_set); |
618 | |
619 | /** |
620 | * radix_tree_tag_clear - clear a tag on a radix tree node |
621 | * @root: radix tree root |
622 | * @index: index key |
623 | * @tag: tag index |
624 | * |
625 | * Clear the search tag (which must be < RADIX_TREE_MAX_TAGS) |
626 | * corresponding to @index in the radix tree. If |
627 | * this causes the leaf node to have no tags set then clear the tag in the |
628 | * next-to-leaf node, etc. |
629 | * |
630 | * Returns the address of the tagged item on success, else NULL. ie: |
631 | * has the same return value and semantics as radix_tree_lookup(). |
632 | */ |
633 | void *radix_tree_tag_clear(struct radix_tree_root *root, |
634 | unsigned long index, unsigned int tag) |
635 | { |
636 | struct radix_tree_node *node = NULL; |
637 | struct radix_tree_node *slot = NULL; |
638 | unsigned int height, shift; |
639 | int uninitialized_var(offset); |
640 | |
641 | height = root->height; |
642 | if (index > radix_tree_maxindex(height)) |
643 | goto out; |
644 | |
645 | shift = height * RADIX_TREE_MAP_SHIFT; |
646 | slot = indirect_to_ptr(root->rnode); |
647 | |
648 | while (shift) { |
649 | if (slot == NULL) |
650 | goto out; |
651 | |
652 | shift -= RADIX_TREE_MAP_SHIFT; |
653 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; |
654 | node = slot; |
655 | slot = slot->slots[offset]; |
656 | } |
657 | |
658 | if (slot == NULL) |
659 | goto out; |
660 | |
661 | while (node) { |
662 | if (!tag_get(node, tag, offset)) |
663 | goto out; |
664 | tag_clear(node, tag, offset); |
665 | if (any_tag_set(node, tag)) |
666 | goto out; |
667 | |
668 | index >>= RADIX_TREE_MAP_SHIFT; |
669 | offset = index & RADIX_TREE_MAP_MASK; |
670 | node = node->parent; |
671 | } |
672 | |
673 | /* clear the root's tag bit */ |
674 | if (root_tag_get(root, tag)) |
675 | root_tag_clear(root, tag); |
676 | |
677 | out: |
678 | return slot; |
679 | } |
680 | EXPORT_SYMBOL(radix_tree_tag_clear); |
681 | |
682 | /** |
683 | * radix_tree_tag_get - get a tag on a radix tree node |
684 | * @root: radix tree root |
685 | * @index: index key |
686 | * @tag: tag index (< RADIX_TREE_MAX_TAGS) |
687 | * |
688 | * Return values: |
689 | * |
690 | * 0: tag not present or not set |
691 | * 1: tag set |
692 | * |
693 | * Note that the return value of this function may not be relied on, even if |
694 | * the RCU lock is held, unless tag modification and node deletion are excluded |
695 | * from concurrency. |
696 | */ |
697 | int radix_tree_tag_get(struct radix_tree_root *root, |
698 | unsigned long index, unsigned int tag) |
699 | { |
700 | unsigned int height, shift; |
701 | struct radix_tree_node *node; |
702 | |
703 | /* check the root's tag bit */ |
704 | if (!root_tag_get(root, tag)) |
705 | return 0; |
706 | |
707 | node = rcu_dereference_raw(root->rnode); |
708 | if (node == NULL) |
709 | return 0; |
710 | |
711 | if (!radix_tree_is_indirect_ptr(node)) |
712 | return (index == 0); |
713 | node = indirect_to_ptr(node); |
714 | |
715 | height = node->path & RADIX_TREE_HEIGHT_MASK; |
716 | if (index > radix_tree_maxindex(height)) |
717 | return 0; |
718 | |
719 | shift = (height - 1) * RADIX_TREE_MAP_SHIFT; |
720 | |
721 | for ( ; ; ) { |
722 | int offset; |
723 | |
724 | if (node == NULL) |
725 | return 0; |
726 | |
727 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; |
728 | if (!tag_get(node, tag, offset)) |
729 | return 0; |
730 | if (height == 1) |
731 | return 1; |
732 | node = rcu_dereference_raw(node->slots[offset]); |
733 | shift -= RADIX_TREE_MAP_SHIFT; |
734 | height--; |
735 | } |
736 | } |
737 | EXPORT_SYMBOL(radix_tree_tag_get); |
738 | |
739 | /** |
740 | * radix_tree_next_chunk - find next chunk of slots for iteration |
741 | * |
742 | * @root: radix tree root |
743 | * @iter: iterator state |
744 | * @flags: RADIX_TREE_ITER_* flags and tag index |
745 | * Returns: pointer to chunk first slot, or NULL if iteration is over |
746 | */ |
747 | void **radix_tree_next_chunk(struct radix_tree_root *root, |
748 | struct radix_tree_iter *iter, unsigned flags) |
749 | { |
750 | unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK; |
751 | struct radix_tree_node *rnode, *node; |
752 | unsigned long index, offset, height; |
753 | |
754 | if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag)) |
755 | return NULL; |
756 | |
757 | /* |
758 | * Catch next_index overflow after ~0UL. iter->index never overflows |
759 | * during iterating; it can be zero only at the beginning. |
760 | * And we cannot overflow iter->next_index in a single step, |
761 | * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG. |
762 | * |
763 | * This condition also used by radix_tree_next_slot() to stop |
764 | * contiguous iterating, and forbid swithing to the next chunk. |
765 | */ |
766 | index = iter->next_index; |
767 | if (!index && iter->index) |
768 | return NULL; |
769 | |
770 | rnode = rcu_dereference_raw(root->rnode); |
771 | if (radix_tree_is_indirect_ptr(rnode)) { |
772 | rnode = indirect_to_ptr(rnode); |
773 | } else if (rnode && !index) { |
774 | /* Single-slot tree */ |
775 | iter->index = 0; |
776 | iter->next_index = 1; |
777 | iter->tags = 1; |
778 | return (void **)&root->rnode; |
779 | } else |
780 | return NULL; |
781 | |
782 | restart: |
783 | height = rnode->path & RADIX_TREE_HEIGHT_MASK; |
784 | shift = (height - 1) * RADIX_TREE_MAP_SHIFT; |
785 | offset = index >> shift; |
786 | |
787 | /* Index outside of the tree */ |
788 | if (offset >= RADIX_TREE_MAP_SIZE) |
789 | return NULL; |
790 | |
791 | node = rnode; |
792 | while (1) { |
793 | if ((flags & RADIX_TREE_ITER_TAGGED) ? |
794 | !test_bit(offset, node->tags[tag]) : |
795 | !node->slots[offset]) { |
796 | /* Hole detected */ |
797 | if (flags & RADIX_TREE_ITER_CONTIG) |
798 | return NULL; |
799 | |
800 | if (flags & RADIX_TREE_ITER_TAGGED) |
801 | offset = radix_tree_find_next_bit( |
802 | node->tags[tag], |
803 | RADIX_TREE_MAP_SIZE, |
804 | offset + 1); |
805 | else |
806 | while (++offset < RADIX_TREE_MAP_SIZE) { |
807 | if (node->slots[offset]) |
808 | break; |
809 | } |
810 | index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1); |
811 | index += offset << shift; |
812 | /* Overflow after ~0UL */ |
813 | if (!index) |
814 | return NULL; |
815 | if (offset == RADIX_TREE_MAP_SIZE) |
816 | goto restart; |
817 | } |
818 | |
819 | /* This is leaf-node */ |
820 | if (!shift) |
821 | break; |
822 | |
823 | node = rcu_dereference_raw(node->slots[offset]); |
824 | if (node == NULL) |
825 | goto restart; |
826 | shift -= RADIX_TREE_MAP_SHIFT; |
827 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; |
828 | } |
829 | |
830 | /* Update the iterator state */ |
831 | iter->index = index; |
832 | iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1; |
833 | |
834 | /* Construct iter->tags bit-mask from node->tags[tag] array */ |
835 | if (flags & RADIX_TREE_ITER_TAGGED) { |
836 | unsigned tag_long, tag_bit; |
837 | |
838 | tag_long = offset / BITS_PER_LONG; |
839 | tag_bit = offset % BITS_PER_LONG; |
840 | iter->tags = node->tags[tag][tag_long] >> tag_bit; |
841 | /* This never happens if RADIX_TREE_TAG_LONGS == 1 */ |
842 | if (tag_long < RADIX_TREE_TAG_LONGS - 1) { |
843 | /* Pick tags from next element */ |
844 | if (tag_bit) |
845 | iter->tags |= node->tags[tag][tag_long + 1] << |
846 | (BITS_PER_LONG - tag_bit); |
847 | /* Clip chunk size, here only BITS_PER_LONG tags */ |
848 | iter->next_index = index + BITS_PER_LONG; |
849 | } |
850 | } |
851 | |
852 | return node->slots + offset; |
853 | } |
854 | EXPORT_SYMBOL(radix_tree_next_chunk); |
855 | |
856 | /** |
857 | * radix_tree_range_tag_if_tagged - for each item in given range set given |
858 | * tag if item has another tag set |
859 | * @root: radix tree root |
860 | * @first_indexp: pointer to a starting index of a range to scan |
861 | * @last_index: last index of a range to scan |
862 | * @nr_to_tag: maximum number items to tag |
863 | * @iftag: tag index to test |
864 | * @settag: tag index to set if tested tag is set |
865 | * |
866 | * This function scans range of radix tree from first_index to last_index |
867 | * (inclusive). For each item in the range if iftag is set, the function sets |
868 | * also settag. The function stops either after tagging nr_to_tag items or |
869 | * after reaching last_index. |
870 | * |
871 | * The tags must be set from the leaf level only and propagated back up the |
872 | * path to the root. We must do this so that we resolve the full path before |
873 | * setting any tags on intermediate nodes. If we set tags as we descend, then |
874 | * we can get to the leaf node and find that the index that has the iftag |
875 | * set is outside the range we are scanning. This reults in dangling tags and |
876 | * can lead to problems with later tag operations (e.g. livelocks on lookups). |
877 | * |
878 | * The function returns number of leaves where the tag was set and sets |
879 | * *first_indexp to the first unscanned index. |
880 | * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must |
881 | * be prepared to handle that. |
882 | */ |
883 | unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, |
884 | unsigned long *first_indexp, unsigned long last_index, |
885 | unsigned long nr_to_tag, |
886 | unsigned int iftag, unsigned int settag) |
887 | { |
888 | unsigned int height = root->height; |
889 | struct radix_tree_node *node = NULL; |
890 | struct radix_tree_node *slot; |
891 | unsigned int shift; |
892 | unsigned long tagged = 0; |
893 | unsigned long index = *first_indexp; |
894 | |
895 | last_index = min(last_index, radix_tree_maxindex(height)); |
896 | if (index > last_index) |
897 | return 0; |
898 | if (!nr_to_tag) |
899 | return 0; |
900 | if (!root_tag_get(root, iftag)) { |
901 | *first_indexp = last_index + 1; |
902 | return 0; |
903 | } |
904 | if (height == 0) { |
905 | *first_indexp = last_index + 1; |
906 | root_tag_set(root, settag); |
907 | return 1; |
908 | } |
909 | |
910 | shift = (height - 1) * RADIX_TREE_MAP_SHIFT; |
911 | slot = indirect_to_ptr(root->rnode); |
912 | |
913 | for (;;) { |
914 | unsigned long upindex; |
915 | int offset; |
916 | |
917 | offset = (index >> shift) & RADIX_TREE_MAP_MASK; |
918 | if (!slot->slots[offset]) |
919 | goto next; |
920 | if (!tag_get(slot, iftag, offset)) |
921 | goto next; |
922 | if (shift) { |
923 | /* Go down one level */ |
924 | shift -= RADIX_TREE_MAP_SHIFT; |
925 | node = slot; |
926 | slot = slot->slots[offset]; |
927 | continue; |
928 | } |
929 | |
930 | /* tag the leaf */ |
931 | tagged++; |
932 | tag_set(slot, settag, offset); |
933 | |
934 | /* walk back up the path tagging interior nodes */ |
935 | upindex = index; |
936 | while (node) { |
937 | upindex >>= RADIX_TREE_MAP_SHIFT; |
938 | offset = upindex & RADIX_TREE_MAP_MASK; |
939 | |
940 | /* stop if we find a node with the tag already set */ |
941 | if (tag_get(node, settag, offset)) |
942 | break; |
943 | tag_set(node, settag, offset); |
944 | node = node->parent; |
945 | } |
946 | |
947 | /* |
948 | * Small optimization: now clear that node pointer. |
949 | * Since all of this slot's ancestors now have the tag set |
950 | * from setting it above, we have no further need to walk |
951 | * back up the tree setting tags, until we update slot to |
952 | * point to another radix_tree_node. |
953 | */ |
954 | node = NULL; |
955 | |
956 | next: |
957 | /* Go to next item at level determined by 'shift' */ |
958 | index = ((index >> shift) + 1) << shift; |
959 | /* Overflow can happen when last_index is ~0UL... */ |
960 | if (index > last_index || !index) |
961 | break; |
962 | if (tagged >= nr_to_tag) |
963 | break; |
964 | while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) { |
965 | /* |
966 | * We've fully scanned this node. Go up. Because |
967 | * last_index is guaranteed to be in the tree, what |
968 | * we do below cannot wander astray. |
969 | */ |
970 | slot = slot->parent; |
971 | shift += RADIX_TREE_MAP_SHIFT; |
972 | } |
973 | } |
974 | /* |
975 | * We need not to tag the root tag if there is no tag which is set with |
976 | * settag within the range from *first_indexp to last_index. |
977 | */ |
978 | if (tagged > 0) |
979 | root_tag_set(root, settag); |
980 | *first_indexp = index; |
981 | |
982 | return tagged; |
983 | } |
984 | EXPORT_SYMBOL(radix_tree_range_tag_if_tagged); |
985 | |
986 | /** |
987 | * radix_tree_gang_lookup - perform multiple lookup on a radix tree |
988 | * @root: radix tree root |
989 | * @results: where the results of the lookup are placed |
990 | * @first_index: start the lookup from this key |
991 | * @max_items: place up to this many items at *results |
992 | * |
993 | * Performs an index-ascending scan of the tree for present items. Places |
994 | * them at *@results and returns the number of items which were placed at |
995 | * *@results. |
996 | * |
997 | * The implementation is naive. |
998 | * |
999 | * Like radix_tree_lookup, radix_tree_gang_lookup may be called under |
1000 | * rcu_read_lock. In this case, rather than the returned results being |
1001 | * an atomic snapshot of the tree at a single point in time, the semantics |
1002 | * of an RCU protected gang lookup are as though multiple radix_tree_lookups |
1003 | * have been issued in individual locks, and results stored in 'results'. |
1004 | */ |
1005 | unsigned int |
1006 | radix_tree_gang_lookup(struct radix_tree_root *root, void **results, |
1007 | unsigned long first_index, unsigned int max_items) |
1008 | { |
1009 | struct radix_tree_iter iter; |
1010 | void **slot; |
1011 | unsigned int ret = 0; |
1012 | |
1013 | if (unlikely(!max_items)) |
1014 | return 0; |
1015 | |
1016 | radix_tree_for_each_slot(slot, root, &iter, first_index) { |
1017 | results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot)); |
1018 | if (!results[ret]) |
1019 | continue; |
1020 | if (++ret == max_items) |
1021 | break; |
1022 | } |
1023 | |
1024 | return ret; |
1025 | } |
1026 | EXPORT_SYMBOL(radix_tree_gang_lookup); |
1027 | |
1028 | /** |
1029 | * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree |
1030 | * @root: radix tree root |
1031 | * @results: where the results of the lookup are placed |
1032 | * @indices: where their indices should be placed (but usually NULL) |
1033 | * @first_index: start the lookup from this key |
1034 | * @max_items: place up to this many items at *results |
1035 | * |
1036 | * Performs an index-ascending scan of the tree for present items. Places |
1037 | * their slots at *@results and returns the number of items which were |
1038 | * placed at *@results. |
1039 | * |
1040 | * The implementation is naive. |
1041 | * |
1042 | * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must |
1043 | * be dereferenced with radix_tree_deref_slot, and if using only RCU |
1044 | * protection, radix_tree_deref_slot may fail requiring a retry. |
1045 | */ |
1046 | unsigned int |
1047 | radix_tree_gang_lookup_slot(struct radix_tree_root *root, |
1048 | void ***results, unsigned long *indices, |
1049 | unsigned long first_index, unsigned int max_items) |
1050 | { |
1051 | struct radix_tree_iter iter; |
1052 | void **slot; |
1053 | unsigned int ret = 0; |
1054 | |
1055 | if (unlikely(!max_items)) |
1056 | return 0; |
1057 | |
1058 | radix_tree_for_each_slot(slot, root, &iter, first_index) { |
1059 | results[ret] = slot; |
1060 | if (indices) |
1061 | indices[ret] = iter.index; |
1062 | if (++ret == max_items) |
1063 | break; |
1064 | } |
1065 | |
1066 | return ret; |
1067 | } |
1068 | EXPORT_SYMBOL(radix_tree_gang_lookup_slot); |
1069 | |
1070 | /** |
1071 | * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree |
1072 | * based on a tag |
1073 | * @root: radix tree root |
1074 | * @results: where the results of the lookup are placed |
1075 | * @first_index: start the lookup from this key |
1076 | * @max_items: place up to this many items at *results |
1077 | * @tag: the tag index (< RADIX_TREE_MAX_TAGS) |
1078 | * |
1079 | * Performs an index-ascending scan of the tree for present items which |
1080 | * have the tag indexed by @tag set. Places the items at *@results and |
1081 | * returns the number of items which were placed at *@results. |
1082 | */ |
1083 | unsigned int |
1084 | radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results, |
1085 | unsigned long first_index, unsigned int max_items, |
1086 | unsigned int tag) |
1087 | { |
1088 | struct radix_tree_iter iter; |
1089 | void **slot; |
1090 | unsigned int ret = 0; |
1091 | |
1092 | if (unlikely(!max_items)) |
1093 | return 0; |
1094 | |
1095 | radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) { |
1096 | results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot)); |
1097 | if (!results[ret]) |
1098 | continue; |
1099 | if (++ret == max_items) |
1100 | break; |
1101 | } |
1102 | |
1103 | return ret; |
1104 | } |
1105 | EXPORT_SYMBOL(radix_tree_gang_lookup_tag); |
1106 | |
1107 | /** |
1108 | * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a |
1109 | * radix tree based on a tag |
1110 | * @root: radix tree root |
1111 | * @results: where the results of the lookup are placed |
1112 | * @first_index: start the lookup from this key |
1113 | * @max_items: place up to this many items at *results |
1114 | * @tag: the tag index (< RADIX_TREE_MAX_TAGS) |
1115 | * |
1116 | * Performs an index-ascending scan of the tree for present items which |
1117 | * have the tag indexed by @tag set. Places the slots at *@results and |
1118 | * returns the number of slots which were placed at *@results. |
1119 | */ |
1120 | unsigned int |
1121 | radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results, |
1122 | unsigned long first_index, unsigned int max_items, |
1123 | unsigned int tag) |
1124 | { |
1125 | struct radix_tree_iter iter; |
1126 | void **slot; |
1127 | unsigned int ret = 0; |
1128 | |
1129 | if (unlikely(!max_items)) |
1130 | return 0; |
1131 | |
1132 | radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) { |
1133 | results[ret] = slot; |
1134 | if (++ret == max_items) |
1135 | break; |
1136 | } |
1137 | |
1138 | return ret; |
1139 | } |
1140 | EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot); |
1141 | |
1142 | #if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP) |
1143 | #include <linux/sched.h> /* for cond_resched() */ |
1144 | |
1145 | /* |
1146 | * This linear search is at present only useful to shmem_unuse_inode(). |
1147 | */ |
1148 | static unsigned long __locate(struct radix_tree_node *slot, void *item, |
1149 | unsigned long index, unsigned long *found_index) |
1150 | { |
1151 | unsigned int shift, height; |
1152 | unsigned long i; |
1153 | |
1154 | height = slot->path & RADIX_TREE_HEIGHT_MASK; |
1155 | shift = (height-1) * RADIX_TREE_MAP_SHIFT; |
1156 | |
1157 | for ( ; height > 1; height--) { |
1158 | i = (index >> shift) & RADIX_TREE_MAP_MASK; |
1159 | for (;;) { |
1160 | if (slot->slots[i] != NULL) |
1161 | break; |
1162 | index &= ~((1UL << shift) - 1); |
1163 | index += 1UL << shift; |
1164 | if (index == 0) |
1165 | goto out; /* 32-bit wraparound */ |
1166 | i++; |
1167 | if (i == RADIX_TREE_MAP_SIZE) |
1168 | goto out; |
1169 | } |
1170 | |
1171 | shift -= RADIX_TREE_MAP_SHIFT; |
1172 | slot = rcu_dereference_raw(slot->slots[i]); |
1173 | if (slot == NULL) |
1174 | goto out; |
1175 | } |
1176 | |
1177 | /* Bottom level: check items */ |
1178 | for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) { |
1179 | if (slot->slots[i] == item) { |
1180 | *found_index = index + i; |
1181 | index = 0; |
1182 | goto out; |
1183 | } |
1184 | } |
1185 | index += RADIX_TREE_MAP_SIZE; |
1186 | out: |
1187 | return index; |
1188 | } |
1189 | |
1190 | /** |
1191 | * radix_tree_locate_item - search through radix tree for item |
1192 | * @root: radix tree root |
1193 | * @item: item to be found |
1194 | * |
1195 | * Returns index where item was found, or -1 if not found. |
1196 | * Caller must hold no lock (since this time-consuming function needs |
1197 | * to be preemptible), and must check afterwards if item is still there. |
1198 | */ |
1199 | unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item) |
1200 | { |
1201 | struct radix_tree_node *node; |
1202 | unsigned long max_index; |
1203 | unsigned long cur_index = 0; |
1204 | unsigned long found_index = -1; |
1205 | |
1206 | do { |
1207 | rcu_read_lock(); |
1208 | node = rcu_dereference_raw(root->rnode); |
1209 | if (!radix_tree_is_indirect_ptr(node)) { |
1210 | rcu_read_unlock(); |
1211 | if (node == item) |
1212 | found_index = 0; |
1213 | break; |
1214 | } |
1215 | |
1216 | node = indirect_to_ptr(node); |
1217 | max_index = radix_tree_maxindex(node->path & |
1218 | RADIX_TREE_HEIGHT_MASK); |
1219 | if (cur_index > max_index) { |
1220 | rcu_read_unlock(); |
1221 | break; |
1222 | } |
1223 | |
1224 | cur_index = __locate(node, item, cur_index, &found_index); |
1225 | rcu_read_unlock(); |
1226 | cond_resched(); |
1227 | } while (cur_index != 0 && cur_index <= max_index); |
1228 | |
1229 | return found_index; |
1230 | } |
1231 | #else |
1232 | unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item) |
1233 | { |
1234 | return -1; |
1235 | } |
1236 | #endif /* CONFIG_SHMEM && CONFIG_SWAP */ |
1237 | |
1238 | /** |
1239 | * radix_tree_shrink - shrink height of a radix tree to minimal |
1240 | * @root radix tree root |
1241 | */ |
1242 | static inline void radix_tree_shrink(struct radix_tree_root *root) |
1243 | { |
1244 | /* try to shrink tree height */ |
1245 | while (root->height > 0) { |
1246 | struct radix_tree_node *to_free = root->rnode; |
1247 | struct radix_tree_node *slot; |
1248 | |
1249 | BUG_ON(!radix_tree_is_indirect_ptr(to_free)); |
1250 | to_free = indirect_to_ptr(to_free); |
1251 | |
1252 | /* |
1253 | * The candidate node has more than one child, or its child |
1254 | * is not at the leftmost slot, we cannot shrink. |
1255 | */ |
1256 | if (to_free->count != 1) |
1257 | break; |
1258 | if (!to_free->slots[0]) |
1259 | break; |
1260 | |
1261 | /* |
1262 | * We don't need rcu_assign_pointer(), since we are simply |
1263 | * moving the node from one part of the tree to another: if it |
1264 | * was safe to dereference the old pointer to it |
1265 | * (to_free->slots[0]), it will be safe to dereference the new |
1266 | * one (root->rnode) as far as dependent read barriers go. |
1267 | */ |
1268 | slot = to_free->slots[0]; |
1269 | if (root->height > 1) { |
1270 | slot->parent = NULL; |
1271 | slot = ptr_to_indirect(slot); |
1272 | } |
1273 | root->rnode = slot; |
1274 | root->height--; |
1275 | |
1276 | /* |
1277 | * We have a dilemma here. The node's slot[0] must not be |
1278 | * NULLed in case there are concurrent lookups expecting to |
1279 | * find the item. However if this was a bottom-level node, |
1280 | * then it may be subject to the slot pointer being visible |
1281 | * to callers dereferencing it. If item corresponding to |
1282 | * slot[0] is subsequently deleted, these callers would expect |
1283 | * their slot to become empty sooner or later. |
1284 | * |
1285 | * For example, lockless pagecache will look up a slot, deref |
1286 | * the page pointer, and if the page is 0 refcount it means it |
1287 | * was concurrently deleted from pagecache so try the deref |
1288 | * again. Fortunately there is already a requirement for logic |
1289 | * to retry the entire slot lookup -- the indirect pointer |
1290 | * problem (replacing direct root node with an indirect pointer |
1291 | * also results in a stale slot). So tag the slot as indirect |
1292 | * to force callers to retry. |
1293 | */ |
1294 | if (root->height == 0) |
1295 | *((unsigned long *)&to_free->slots[0]) |= |
1296 | RADIX_TREE_INDIRECT_PTR; |
1297 | |
1298 | radix_tree_node_free(to_free); |
1299 | } |
1300 | } |
1301 | |
1302 | /** |
1303 | * __radix_tree_delete_node - try to free node after clearing a slot |
1304 | * @root: radix tree root |
1305 | * @node: node containing @index |
1306 | * |
1307 | * After clearing the slot at @index in @node from radix tree |
1308 | * rooted at @root, call this function to attempt freeing the |
1309 | * node and shrinking the tree. |
1310 | * |
1311 | * Returns %true if @node was freed, %false otherwise. |
1312 | */ |
1313 | bool __radix_tree_delete_node(struct radix_tree_root *root, |
1314 | struct radix_tree_node *node) |
1315 | { |
1316 | bool deleted = false; |
1317 | |
1318 | do { |
1319 | struct radix_tree_node *parent; |
1320 | |
1321 | if (node->count) { |
1322 | if (node == indirect_to_ptr(root->rnode)) { |
1323 | radix_tree_shrink(root); |
1324 | if (root->height == 0) |
1325 | deleted = true; |
1326 | } |
1327 | return deleted; |
1328 | } |
1329 | |
1330 | parent = node->parent; |
1331 | if (parent) { |
1332 | unsigned int offset; |
1333 | |
1334 | offset = node->path >> RADIX_TREE_HEIGHT_SHIFT; |
1335 | parent->slots[offset] = NULL; |
1336 | parent->count--; |
1337 | } else { |
1338 | root_tag_clear_all(root); |
1339 | root->height = 0; |
1340 | root->rnode = NULL; |
1341 | } |
1342 | |
1343 | radix_tree_node_free(node); |
1344 | deleted = true; |
1345 | |
1346 | node = parent; |
1347 | } while (node); |
1348 | |
1349 | return deleted; |
1350 | } |
1351 | |
1352 | /** |
1353 | * radix_tree_delete_item - delete an item from a radix tree |
1354 | * @root: radix tree root |
1355 | * @index: index key |
1356 | * @item: expected item |
1357 | * |
1358 | * Remove @item at @index from the radix tree rooted at @root. |
1359 | * |
1360 | * Returns the address of the deleted item, or NULL if it was not present |
1361 | * or the entry at the given @index was not @item. |
1362 | */ |
1363 | void *radix_tree_delete_item(struct radix_tree_root *root, |
1364 | unsigned long index, void *item) |
1365 | { |
1366 | struct radix_tree_node *node; |
1367 | unsigned int offset; |
1368 | void **slot; |
1369 | void *entry; |
1370 | int tag; |
1371 | |
1372 | entry = __radix_tree_lookup(root, index, &node, &slot); |
1373 | if (!entry) |
1374 | return NULL; |
1375 | |
1376 | if (item && entry != item) |
1377 | return NULL; |
1378 | |
1379 | if (!node) { |
1380 | root_tag_clear_all(root); |
1381 | root->rnode = NULL; |
1382 | return entry; |
1383 | } |
1384 | |
1385 | offset = index & RADIX_TREE_MAP_MASK; |
1386 | |
1387 | /* |
1388 | * Clear all tags associated with the item to be deleted. |
1389 | * This way of doing it would be inefficient, but seldom is any set. |
1390 | */ |
1391 | for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { |
1392 | if (tag_get(node, tag, offset)) |
1393 | radix_tree_tag_clear(root, index, tag); |
1394 | } |
1395 | |
1396 | node->slots[offset] = NULL; |
1397 | node->count--; |
1398 | |
1399 | __radix_tree_delete_node(root, node); |
1400 | |
1401 | return entry; |
1402 | } |
1403 | EXPORT_SYMBOL(radix_tree_delete_item); |
1404 | |
1405 | /** |
1406 | * radix_tree_delete - delete an item from a radix tree |
1407 | * @root: radix tree root |
1408 | * @index: index key |
1409 | * |
1410 | * Remove the item at @index from the radix tree rooted at @root. |
1411 | * |
1412 | * Returns the address of the deleted item, or NULL if it was not present. |
1413 | */ |
1414 | void *radix_tree_delete(struct radix_tree_root *root, unsigned long index) |
1415 | { |
1416 | return radix_tree_delete_item(root, index, NULL); |
1417 | } |
1418 | EXPORT_SYMBOL(radix_tree_delete); |
1419 | |
1420 | /** |
1421 | * radix_tree_tagged - test whether any items in the tree are tagged |
1422 | * @root: radix tree root |
1423 | * @tag: tag to test |
1424 | */ |
1425 | int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag) |
1426 | { |
1427 | return root_tag_get(root, tag); |
1428 | } |
1429 | EXPORT_SYMBOL(radix_tree_tagged); |
1430 | |
1431 | static void |
1432 | radix_tree_node_ctor(void *arg) |
1433 | { |
1434 | struct radix_tree_node *node = arg; |
1435 | |
1436 | memset(node, 0, sizeof(*node)); |
1437 | INIT_LIST_HEAD(&node->private_list); |
1438 | } |
1439 | |
1440 | static __init unsigned long __maxindex(unsigned int height) |
1441 | { |
1442 | unsigned int width = height * RADIX_TREE_MAP_SHIFT; |
1443 | int shift = RADIX_TREE_INDEX_BITS - width; |
1444 | |
1445 | if (shift < 0) |
1446 | return ~0UL; |
1447 | if (shift >= BITS_PER_LONG) |
1448 | return 0UL; |
1449 | return ~0UL >> shift; |
1450 | } |
1451 | |
1452 | static __init void radix_tree_init_maxindex(void) |
1453 | { |
1454 | unsigned int i; |
1455 | |
1456 | for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++) |
1457 | height_to_maxindex[i] = __maxindex(i); |
1458 | } |
1459 | |
1460 | static int radix_tree_callback(struct notifier_block *nfb, |
1461 | unsigned long action, |
1462 | void *hcpu) |
1463 | { |
1464 | int cpu = (long)hcpu; |
1465 | struct radix_tree_preload *rtp; |
1466 | |
1467 | /* Free per-cpu pool of perloaded nodes */ |
1468 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { |
1469 | rtp = &per_cpu(radix_tree_preloads, cpu); |
1470 | while (rtp->nr) { |
1471 | kmem_cache_free(radix_tree_node_cachep, |
1472 | rtp->nodes[rtp->nr-1]); |
1473 | rtp->nodes[rtp->nr-1] = NULL; |
1474 | rtp->nr--; |
1475 | } |
1476 | } |
1477 | return NOTIFY_OK; |
1478 | } |
1479 | |
1480 | void __init radix_tree_init(void) |
1481 | { |
1482 | radix_tree_node_cachep = kmem_cache_create("radix_tree_node", |
1483 | sizeof(struct radix_tree_node), 0, |
1484 | SLAB_PANIC | SLAB_RECLAIM_ACCOUNT, |
1485 | radix_tree_node_ctor); |
1486 | radix_tree_init_maxindex(); |
1487 | hotcpu_notifier(radix_tree_callback, 0); |
1488 | } |
1489 |
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