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1 : : /* SPDX-License-Identifier: GPL-2.0-only */
2 : : /*
3 : : * Fast and scalable bitmaps.
4 : : *
5 : : * Copyright (C) 2016 Facebook
6 : : * Copyright (C) 2013-2014 Jens Axboe
7 : : */
8 : :
9 : : #ifndef __LINUX_SCALE_BITMAP_H
10 : : #define __LINUX_SCALE_BITMAP_H
11 : :
12 : : #include <linux/kernel.h>
13 : : #include <linux/slab.h>
14 : :
15 : : struct seq_file;
16 : :
17 : : /**
18 : : * struct sbitmap_word - Word in a &struct sbitmap.
19 : : */
20 : : struct sbitmap_word {
21 : : /**
22 : : * @depth: Number of bits being used in @word/@cleared
23 : : */
24 : : unsigned long depth;
25 : :
26 : : /**
27 : : * @word: word holding free bits
28 : : */
29 : : unsigned long word ____cacheline_aligned_in_smp;
30 : :
31 : : /**
32 : : * @cleared: word holding cleared bits
33 : : */
34 : : unsigned long cleared ____cacheline_aligned_in_smp;
35 : :
36 : : /**
37 : : * @swap_lock: Held while swapping word <-> cleared
38 : : */
39 : : spinlock_t swap_lock;
40 : : } ____cacheline_aligned_in_smp;
41 : :
42 : : /**
43 : : * struct sbitmap - Scalable bitmap.
44 : : *
45 : : * A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This
46 : : * trades off higher memory usage for better scalability.
47 : : */
48 : : struct sbitmap {
49 : : /**
50 : : * @depth: Number of bits used in the whole bitmap.
51 : : */
52 : : unsigned int depth;
53 : :
54 : : /**
55 : : * @shift: log2(number of bits used per word)
56 : : */
57 : : unsigned int shift;
58 : :
59 : : /**
60 : : * @map_nr: Number of words (cachelines) being used for the bitmap.
61 : : */
62 : : unsigned int map_nr;
63 : :
64 : : /**
65 : : * @map: Allocated bitmap.
66 : : */
67 : : struct sbitmap_word *map;
68 : : };
69 : :
70 : : #define SBQ_WAIT_QUEUES 8
71 : : #define SBQ_WAKE_BATCH 8
72 : :
73 : : /**
74 : : * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue.
75 : : */
76 : : struct sbq_wait_state {
77 : : /**
78 : : * @wait_cnt: Number of frees remaining before we wake up.
79 : : */
80 : : atomic_t wait_cnt;
81 : :
82 : : /**
83 : : * @wait: Wait queue.
84 : : */
85 : : wait_queue_head_t wait;
86 : : } ____cacheline_aligned_in_smp;
87 : :
88 : : /**
89 : : * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free
90 : : * bits.
91 : : *
92 : : * A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to
93 : : * avoid contention on the wait queue spinlock. This ensures that we don't hit a
94 : : * scalability wall when we run out of free bits and have to start putting tasks
95 : : * to sleep.
96 : : */
97 : : struct sbitmap_queue {
98 : : /**
99 : : * @sb: Scalable bitmap.
100 : : */
101 : : struct sbitmap sb;
102 : :
103 : : /*
104 : : * @alloc_hint: Cache of last successfully allocated or freed bit.
105 : : *
106 : : * This is per-cpu, which allows multiple users to stick to different
107 : : * cachelines until the map is exhausted.
108 : : */
109 : : unsigned int __percpu *alloc_hint;
110 : :
111 : : /**
112 : : * @wake_batch: Number of bits which must be freed before we wake up any
113 : : * waiters.
114 : : */
115 : : unsigned int wake_batch;
116 : :
117 : : /**
118 : : * @wake_index: Next wait queue in @ws to wake up.
119 : : */
120 : : atomic_t wake_index;
121 : :
122 : : /**
123 : : * @ws: Wait queues.
124 : : */
125 : : struct sbq_wait_state *ws;
126 : :
127 : : /*
128 : : * @ws_active: count of currently active ws waitqueues
129 : : */
130 : : atomic_t ws_active;
131 : :
132 : : /**
133 : : * @round_robin: Allocate bits in strict round-robin order.
134 : : */
135 : : bool round_robin;
136 : :
137 : : /**
138 : : * @min_shallow_depth: The minimum shallow depth which may be passed to
139 : : * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
140 : : */
141 : : unsigned int min_shallow_depth;
142 : : };
143 : :
144 : : /**
145 : : * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node.
146 : : * @sb: Bitmap to initialize.
147 : : * @depth: Number of bits to allocate.
148 : : * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
149 : : * given, a good default is chosen.
150 : : * @flags: Allocation flags.
151 : : * @node: Memory node to allocate on.
152 : : *
153 : : * Return: Zero on success or negative errno on failure.
154 : : */
155 : : int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
156 : : gfp_t flags, int node);
157 : :
158 : : /**
159 : : * sbitmap_free() - Free memory used by a &struct sbitmap.
160 : : * @sb: Bitmap to free.
161 : : */
162 : 0 : static inline void sbitmap_free(struct sbitmap *sb)
163 : : {
164 : 0 : kfree(sb->map);
165 : 0 : sb->map = NULL;
166 : 0 : }
167 : :
168 : : /**
169 : : * sbitmap_resize() - Resize a &struct sbitmap.
170 : : * @sb: Bitmap to resize.
171 : : * @depth: New number of bits to resize to.
172 : : *
173 : : * Doesn't reallocate anything. It's up to the caller to ensure that the new
174 : : * depth doesn't exceed the depth that the sb was initialized with.
175 : : */
176 : : void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
177 : :
178 : : /**
179 : : * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
180 : : * @sb: Bitmap to allocate from.
181 : : * @alloc_hint: Hint for where to start searching for a free bit.
182 : : * @round_robin: If true, be stricter about allocation order; always allocate
183 : : * starting from the last allocated bit. This is less efficient
184 : : * than the default behavior (false).
185 : : *
186 : : * This operation provides acquire barrier semantics if it succeeds.
187 : : *
188 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
189 : : */
190 : : int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin);
191 : :
192 : : /**
193 : : * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
194 : : * limiting the depth used from each word.
195 : : * @sb: Bitmap to allocate from.
196 : : * @alloc_hint: Hint for where to start searching for a free bit.
197 : : * @shallow_depth: The maximum number of bits to allocate from a single word.
198 : : *
199 : : * This rather specific operation allows for having multiple users with
200 : : * different allocation limits. E.g., there can be a high-priority class that
201 : : * uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow()
202 : : * with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority
203 : : * class can only allocate half of the total bits in the bitmap, preventing it
204 : : * from starving out the high-priority class.
205 : : *
206 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
207 : : */
208 : : int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
209 : : unsigned long shallow_depth);
210 : :
211 : : /**
212 : : * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
213 : : * @sb: Bitmap to check.
214 : : *
215 : : * Return: true if any bit in the bitmap is set, false otherwise.
216 : : */
217 : : bool sbitmap_any_bit_set(const struct sbitmap *sb);
218 : :
219 : : #define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
220 : : #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
221 : :
222 : : typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);
223 : :
224 : : /**
225 : : * __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
226 : : * @start: Where to start the iteration.
227 : : * @sb: Bitmap to iterate over.
228 : : * @fn: Callback. Should return true to continue or false to break early.
229 : : * @data: Pointer to pass to callback.
230 : : *
231 : : * This is inline even though it's non-trivial so that the function calls to the
232 : : * callback will hopefully get optimized away.
233 : : */
234 : 128 : static inline void __sbitmap_for_each_set(struct sbitmap *sb,
235 : : unsigned int start,
236 : : sb_for_each_fn fn, void *data)
237 : : {
238 : 128 : unsigned int index;
239 : 128 : unsigned int nr;
240 : 128 : unsigned int scanned = 0;
241 : :
242 [ - + ]: 128 : if (start >= sb->depth)
243 : 0 : start = 0;
244 : 128 : index = SB_NR_TO_INDEX(sb, start);
245 : 128 : nr = SB_NR_TO_BIT(sb, start);
246 : :
247 [ + + ]: 256 : while (scanned < sb->depth) {
248 : 128 : unsigned long word;
249 : 128 : unsigned int depth = min_t(unsigned int,
250 : : sb->map[index].depth - nr,
251 : : sb->depth - scanned);
252 : :
253 : 128 : scanned += depth;
254 : 128 : word = sb->map[index].word & ~sb->map[index].cleared;
255 [ + + ]: 128 : if (!word)
256 : 12 : goto next;
257 : :
258 : : /*
259 : : * On the first iteration of the outer loop, we need to add the
260 : : * bit offset back to the size of the word for find_next_bit().
261 : : * On all other iterations, nr is zero, so this is a noop.
262 : : */
263 : 116 : depth += nr;
264 : 348 : while (1) {
265 : 232 : nr = find_next_bit(&word, depth, nr);
266 [ + + ]: 232 : if (nr >= depth)
267 : : break;
268 [ - + ]: 116 : if (!fn(sb, (index << sb->shift) + nr, data))
269 : 0 : return;
270 : :
271 : 116 : nr++;
272 : : }
273 : 116 : next:
274 : 128 : nr = 0;
275 [ + - ]: 128 : if (++index >= sb->map_nr)
276 : 128 : index = 0;
277 : : }
278 : : }
279 : :
280 : : /**
281 : : * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
282 : : * @sb: Bitmap to iterate over.
283 : : * @fn: Callback. Should return true to continue or false to break early.
284 : : * @data: Pointer to pass to callback.
285 : : */
286 : 128 : static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
287 : : void *data)
288 : : {
289 : 128 : __sbitmap_for_each_set(sb, 0, fn, data);
290 : 99 : }
291 : :
292 : 0 : static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
293 : : unsigned int bitnr)
294 : : {
295 : 0 : return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
296 : : }
297 : :
298 : : /* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */
299 : :
300 : 0 : static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
301 : : {
302 : 0 : set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
303 : 0 : }
304 : :
305 : 0 : static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
306 : : {
307 : 0 : clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
308 : 0 : }
309 : :
310 : : /*
311 : : * This one is special, since it doesn't actually clear the bit, rather it
312 : : * sets the corresponding bit in the ->cleared mask instead. Paired with
313 : : * the caller doing sbitmap_deferred_clear() if a given index is full, which
314 : : * will clear the previously freed entries in the corresponding ->word.
315 : : */
316 : 6620 : static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int bitnr)
317 : : {
318 : 6620 : unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared;
319 : :
320 : 6620 : set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
321 : 6620 : }
322 : :
323 : : static inline void sbitmap_clear_bit_unlock(struct sbitmap *sb,
324 : : unsigned int bitnr)
325 : : {
326 : : clear_bit_unlock(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
327 : : }
328 : :
329 : 0 : static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
330 : : {
331 : 0 : return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
332 : : }
333 : :
334 : : /**
335 : : * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
336 : : * @sb: Bitmap to show.
337 : : * @m: struct seq_file to write to.
338 : : *
339 : : * This is intended for debugging. The format may change at any time.
340 : : */
341 : : void sbitmap_show(struct sbitmap *sb, struct seq_file *m);
342 : :
343 : : /**
344 : : * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
345 : : * seq_file.
346 : : * @sb: Bitmap to show.
347 : : * @m: struct seq_file to write to.
348 : : *
349 : : * This is intended for debugging. The output isn't guaranteed to be internally
350 : : * consistent.
351 : : */
352 : : void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m);
353 : :
354 : : /**
355 : : * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
356 : : * memory node.
357 : : * @sbq: Bitmap queue to initialize.
358 : : * @depth: See sbitmap_init_node().
359 : : * @shift: See sbitmap_init_node().
360 : : * @round_robin: See sbitmap_get().
361 : : * @flags: Allocation flags.
362 : : * @node: Memory node to allocate on.
363 : : *
364 : : * Return: Zero on success or negative errno on failure.
365 : : */
366 : : int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
367 : : int shift, bool round_robin, gfp_t flags, int node);
368 : :
369 : : /**
370 : : * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
371 : : *
372 : : * @sbq: Bitmap queue to free.
373 : : */
374 : 0 : static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
375 : : {
376 : 0 : kfree(sbq->ws);
377 : 0 : free_percpu(sbq->alloc_hint);
378 : 0 : sbitmap_free(&sbq->sb);
379 : 0 : }
380 : :
381 : : /**
382 : : * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
383 : : * @sbq: Bitmap queue to resize.
384 : : * @depth: New number of bits to resize to.
385 : : *
386 : : * Like sbitmap_resize(), this doesn't reallocate anything. It has to do
387 : : * some extra work on the &struct sbitmap_queue, so it's not safe to just
388 : : * resize the underlying &struct sbitmap.
389 : : */
390 : : void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);
391 : :
392 : : /**
393 : : * __sbitmap_queue_get() - Try to allocate a free bit from a &struct
394 : : * sbitmap_queue with preemption already disabled.
395 : : * @sbq: Bitmap queue to allocate from.
396 : : *
397 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
398 : : */
399 : : int __sbitmap_queue_get(struct sbitmap_queue *sbq);
400 : :
401 : : /**
402 : : * __sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
403 : : * sbitmap_queue, limiting the depth used from each word, with preemption
404 : : * already disabled.
405 : : * @sbq: Bitmap queue to allocate from.
406 : : * @shallow_depth: The maximum number of bits to allocate from a single word.
407 : : * See sbitmap_get_shallow().
408 : : *
409 : : * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
410 : : * initializing @sbq.
411 : : *
412 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
413 : : */
414 : : int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
415 : : unsigned int shallow_depth);
416 : :
417 : : /**
418 : : * sbitmap_queue_get() - Try to allocate a free bit from a &struct
419 : : * sbitmap_queue.
420 : : * @sbq: Bitmap queue to allocate from.
421 : : * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
422 : : * sbitmap_queue_clear()).
423 : : *
424 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
425 : : */
426 : : static inline int sbitmap_queue_get(struct sbitmap_queue *sbq,
427 : : unsigned int *cpu)
428 : : {
429 : : int nr;
430 : :
431 : : *cpu = get_cpu();
432 : : nr = __sbitmap_queue_get(sbq);
433 : : put_cpu();
434 : : return nr;
435 : : }
436 : :
437 : : /**
438 : : * sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
439 : : * sbitmap_queue, limiting the depth used from each word.
440 : : * @sbq: Bitmap queue to allocate from.
441 : : * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
442 : : * sbitmap_queue_clear()).
443 : : * @shallow_depth: The maximum number of bits to allocate from a single word.
444 : : * See sbitmap_get_shallow().
445 : : *
446 : : * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
447 : : * initializing @sbq.
448 : : *
449 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
450 : : */
451 : : static inline int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
452 : : unsigned int *cpu,
453 : : unsigned int shallow_depth)
454 : : {
455 : : int nr;
456 : :
457 : : *cpu = get_cpu();
458 : : nr = __sbitmap_queue_get_shallow(sbq, shallow_depth);
459 : : put_cpu();
460 : : return nr;
461 : : }
462 : :
463 : : /**
464 : : * sbitmap_queue_min_shallow_depth() - Inform a &struct sbitmap_queue of the
465 : : * minimum shallow depth that will be used.
466 : : * @sbq: Bitmap queue in question.
467 : : * @min_shallow_depth: The minimum shallow depth that will be passed to
468 : : * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
469 : : *
470 : : * sbitmap_queue_clear() batches wakeups as an optimization. The batch size
471 : : * depends on the depth of the bitmap. Since the shallow allocation functions
472 : : * effectively operate with a different depth, the shallow depth must be taken
473 : : * into account when calculating the batch size. This function must be called
474 : : * with the minimum shallow depth that will be used. Failure to do so can result
475 : : * in missed wakeups.
476 : : */
477 : : void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
478 : : unsigned int min_shallow_depth);
479 : :
480 : : /**
481 : : * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
482 : : * &struct sbitmap_queue.
483 : : * @sbq: Bitmap to free from.
484 : : * @nr: Bit number to free.
485 : : * @cpu: CPU the bit was allocated on.
486 : : */
487 : : void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
488 : : unsigned int cpu);
489 : :
490 : 940 : static inline int sbq_index_inc(int index)
491 : : {
492 : 800 : return (index + 1) & (SBQ_WAIT_QUEUES - 1);
493 : : }
494 : :
495 : 332 : static inline void sbq_index_atomic_inc(atomic_t *index)
496 : : {
497 : 332 : int old = atomic_read(index);
498 : 332 : int new = sbq_index_inc(old);
499 : 332 : atomic_cmpxchg(index, old, new);
500 : 332 : }
501 : :
502 : : /**
503 : : * sbq_wait_ptr() - Get the next wait queue to use for a &struct
504 : : * sbitmap_queue.
505 : : * @sbq: Bitmap queue to wait on.
506 : : * @wait_index: A counter per "user" of @sbq.
507 : : */
508 : 192 : static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
509 : : atomic_t *wait_index)
510 : : {
511 : 192 : struct sbq_wait_state *ws;
512 : :
513 : 192 : ws = &sbq->ws[atomic_read(wait_index)];
514 : 192 : sbq_index_atomic_inc(wait_index);
515 : 192 : return ws;
516 : : }
517 : :
518 : : /**
519 : : * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
520 : : * sbitmap_queue.
521 : : * @sbq: Bitmap queue to wake up.
522 : : */
523 : : void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);
524 : :
525 : : /**
526 : : * sbitmap_queue_wake_up() - Wake up some of waiters in one waitqueue
527 : : * on a &struct sbitmap_queue.
528 : : * @sbq: Bitmap queue to wake up.
529 : : */
530 : : void sbitmap_queue_wake_up(struct sbitmap_queue *sbq);
531 : :
532 : : /**
533 : : * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct
534 : : * seq_file.
535 : : * @sbq: Bitmap queue to show.
536 : : * @m: struct seq_file to write to.
537 : : *
538 : : * This is intended for debugging. The format may change at any time.
539 : : */
540 : : void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m);
541 : :
542 : : struct sbq_wait {
543 : : struct sbitmap_queue *sbq; /* if set, sbq_wait is accounted */
544 : : struct wait_queue_entry wait;
545 : : };
546 : :
547 : : #define DEFINE_SBQ_WAIT(name) \
548 : : struct sbq_wait name = { \
549 : : .sbq = NULL, \
550 : : .wait = { \
551 : : .private = current, \
552 : : .func = autoremove_wake_function, \
553 : : .entry = LIST_HEAD_INIT((name).wait.entry), \
554 : : } \
555 : : }
556 : :
557 : : /*
558 : : * Wrapper around prepare_to_wait_exclusive(), which maintains some extra
559 : : * internal state.
560 : : */
561 : : void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
562 : : struct sbq_wait_state *ws,
563 : : struct sbq_wait *sbq_wait, int state);
564 : :
565 : : /*
566 : : * Must be paired with sbitmap_prepare_to_wait().
567 : : */
568 : : void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
569 : : struct sbq_wait *sbq_wait);
570 : :
571 : : /*
572 : : * Wrapper around add_wait_queue(), which maintains some extra internal state
573 : : */
574 : : void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
575 : : struct sbq_wait_state *ws,
576 : : struct sbq_wait *sbq_wait);
577 : :
578 : : /*
579 : : * Must be paired with sbitmap_add_wait_queue()
580 : : */
581 : : void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait);
582 : :
583 : : #endif /* __LINUX_SCALE_BITMAP_H */
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