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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 : : static inline void sbitmap_free(struct sbitmap *sb)
163 : : {
164 : 0 : kfree(sb->map);
165 : 0 : sb->map = NULL;
166 : : }
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 : : /**
220 : : * sbitmap_any_bit_clear() - Check for an unset bit in a &struct
221 : : * sbitmap.
222 : : * @sb: Bitmap to check.
223 : : *
224 : : * Return: true if any bit in the bitmap is clear, false otherwise.
225 : : */
226 : : bool sbitmap_any_bit_clear(const struct sbitmap *sb);
227 : :
228 : : #define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
229 : : #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
230 : :
231 : : typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);
232 : :
233 : : /**
234 : : * __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
235 : : * @start: Where to start the iteration.
236 : : * @sb: Bitmap to iterate over.
237 : : * @fn: Callback. Should return true to continue or false to break early.
238 : : * @data: Pointer to pass to callback.
239 : : *
240 : : * This is inline even though it's non-trivial so that the function calls to the
241 : : * callback will hopefully get optimized away.
242 : : */
243 : 3 : static inline void __sbitmap_for_each_set(struct sbitmap *sb,
244 : : unsigned int start,
245 : : sb_for_each_fn fn, void *data)
246 : : {
247 : : unsigned int index;
248 : : unsigned int nr;
249 : : unsigned int scanned = 0;
250 : :
251 : 3 : if (start >= sb->depth)
252 : : start = 0;
253 : 3 : index = SB_NR_TO_INDEX(sb, start);
254 : 3 : nr = SB_NR_TO_BIT(sb, start);
255 : :
256 : 3 : while (scanned < sb->depth) {
257 : : unsigned long word;
258 : 3 : unsigned int depth = min_t(unsigned int,
259 : : sb->map[index].depth - nr,
260 : : sb->depth - scanned);
261 : :
262 : 3 : scanned += depth;
263 : 3 : word = sb->map[index].word & ~sb->map[index].cleared;
264 : 3 : if (!word)
265 : : goto next;
266 : :
267 : : /*
268 : : * On the first iteration of the outer loop, we need to add the
269 : : * bit offset back to the size of the word for find_next_bit().
270 : : * On all other iterations, nr is zero, so this is a noop.
271 : : */
272 : 3 : depth += nr;
273 : : while (1) {
274 : 3 : nr = find_next_bit(&word, depth, nr);
275 : 3 : if (nr >= depth)
276 : : break;
277 : 3 : if (!fn(sb, (index << sb->shift) + nr, data))
278 : 3 : return;
279 : :
280 : 3 : nr++;
281 : 3 : }
282 : : next:
283 : : nr = 0;
284 : 3 : if (++index >= sb->map_nr)
285 : : index = 0;
286 : : }
287 : : }
288 : :
289 : : /**
290 : : * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
291 : : * @sb: Bitmap to iterate over.
292 : : * @fn: Callback. Should return true to continue or false to break early.
293 : : * @data: Pointer to pass to callback.
294 : : */
295 : : static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
296 : : void *data)
297 : : {
298 : 3 : __sbitmap_for_each_set(sb, 0, fn, data);
299 : : }
300 : :
301 : : static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
302 : : unsigned int bitnr)
303 : : {
304 : 0 : return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
305 : : }
306 : :
307 : : /* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */
308 : :
309 : 0 : static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
310 : : {
311 : 0 : set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
312 : 0 : }
313 : :
314 : 0 : static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
315 : : {
316 : 0 : clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
317 : 0 : }
318 : :
319 : : /*
320 : : * This one is special, since it doesn't actually clear the bit, rather it
321 : : * sets the corresponding bit in the ->cleared mask instead. Paired with
322 : : * the caller doing sbitmap_deferred_clear() if a given index is full, which
323 : : * will clear the previously freed entries in the corresponding ->word.
324 : : */
325 : 3 : static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int bitnr)
326 : : {
327 : 3 : unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared;
328 : :
329 : 3 : set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
330 : 3 : }
331 : :
332 : : static inline void sbitmap_clear_bit_unlock(struct sbitmap *sb,
333 : : unsigned int bitnr)
334 : : {
335 : : clear_bit_unlock(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
336 : : }
337 : :
338 : : static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
339 : : {
340 : 0 : return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
341 : : }
342 : :
343 : : /**
344 : : * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
345 : : * @sb: Bitmap to show.
346 : : * @m: struct seq_file to write to.
347 : : *
348 : : * This is intended for debugging. The format may change at any time.
349 : : */
350 : : void sbitmap_show(struct sbitmap *sb, struct seq_file *m);
351 : :
352 : : /**
353 : : * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
354 : : * seq_file.
355 : : * @sb: Bitmap to show.
356 : : * @m: struct seq_file to write to.
357 : : *
358 : : * This is intended for debugging. The output isn't guaranteed to be internally
359 : : * consistent.
360 : : */
361 : : void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m);
362 : :
363 : : /**
364 : : * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
365 : : * memory node.
366 : : * @sbq: Bitmap queue to initialize.
367 : : * @depth: See sbitmap_init_node().
368 : : * @shift: See sbitmap_init_node().
369 : : * @round_robin: See sbitmap_get().
370 : : * @flags: Allocation flags.
371 : : * @node: Memory node to allocate on.
372 : : *
373 : : * Return: Zero on success or negative errno on failure.
374 : : */
375 : : int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
376 : : int shift, bool round_robin, gfp_t flags, int node);
377 : :
378 : : /**
379 : : * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
380 : : *
381 : : * @sbq: Bitmap queue to free.
382 : : */
383 : 0 : static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
384 : : {
385 : 0 : kfree(sbq->ws);
386 : 0 : free_percpu(sbq->alloc_hint);
387 : : sbitmap_free(&sbq->sb);
388 : 0 : }
389 : :
390 : : /**
391 : : * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
392 : : * @sbq: Bitmap queue to resize.
393 : : * @depth: New number of bits to resize to.
394 : : *
395 : : * Like sbitmap_resize(), this doesn't reallocate anything. It has to do
396 : : * some extra work on the &struct sbitmap_queue, so it's not safe to just
397 : : * resize the underlying &struct sbitmap.
398 : : */
399 : : void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);
400 : :
401 : : /**
402 : : * __sbitmap_queue_get() - Try to allocate a free bit from a &struct
403 : : * sbitmap_queue with preemption already disabled.
404 : : * @sbq: Bitmap queue to allocate from.
405 : : *
406 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
407 : : */
408 : : int __sbitmap_queue_get(struct sbitmap_queue *sbq);
409 : :
410 : : /**
411 : : * __sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
412 : : * sbitmap_queue, limiting the depth used from each word, with preemption
413 : : * already disabled.
414 : : * @sbq: Bitmap queue to allocate from.
415 : : * @shallow_depth: The maximum number of bits to allocate from a single word.
416 : : * See sbitmap_get_shallow().
417 : : *
418 : : * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
419 : : * initializing @sbq.
420 : : *
421 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
422 : : */
423 : : int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
424 : : unsigned int shallow_depth);
425 : :
426 : : /**
427 : : * sbitmap_queue_get() - Try to allocate a free bit from a &struct
428 : : * sbitmap_queue.
429 : : * @sbq: Bitmap queue to allocate from.
430 : : * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
431 : : * sbitmap_queue_clear()).
432 : : *
433 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
434 : : */
435 : : static inline int sbitmap_queue_get(struct sbitmap_queue *sbq,
436 : : unsigned int *cpu)
437 : : {
438 : : int nr;
439 : :
440 : : *cpu = get_cpu();
441 : : nr = __sbitmap_queue_get(sbq);
442 : : put_cpu();
443 : : return nr;
444 : : }
445 : :
446 : : /**
447 : : * sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
448 : : * sbitmap_queue, limiting the depth used from each word.
449 : : * @sbq: Bitmap queue to allocate from.
450 : : * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
451 : : * sbitmap_queue_clear()).
452 : : * @shallow_depth: The maximum number of bits to allocate from a single word.
453 : : * See sbitmap_get_shallow().
454 : : *
455 : : * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
456 : : * initializing @sbq.
457 : : *
458 : : * Return: Non-negative allocated bit number if successful, -1 otherwise.
459 : : */
460 : : static inline int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
461 : : unsigned int *cpu,
462 : : unsigned int shallow_depth)
463 : : {
464 : : int nr;
465 : :
466 : : *cpu = get_cpu();
467 : : nr = __sbitmap_queue_get_shallow(sbq, shallow_depth);
468 : : put_cpu();
469 : : return nr;
470 : : }
471 : :
472 : : /**
473 : : * sbitmap_queue_min_shallow_depth() - Inform a &struct sbitmap_queue of the
474 : : * minimum shallow depth that will be used.
475 : : * @sbq: Bitmap queue in question.
476 : : * @min_shallow_depth: The minimum shallow depth that will be passed to
477 : : * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
478 : : *
479 : : * sbitmap_queue_clear() batches wakeups as an optimization. The batch size
480 : : * depends on the depth of the bitmap. Since the shallow allocation functions
481 : : * effectively operate with a different depth, the shallow depth must be taken
482 : : * into account when calculating the batch size. This function must be called
483 : : * with the minimum shallow depth that will be used. Failure to do so can result
484 : : * in missed wakeups.
485 : : */
486 : : void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
487 : : unsigned int min_shallow_depth);
488 : :
489 : : /**
490 : : * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
491 : : * &struct sbitmap_queue.
492 : : * @sbq: Bitmap to free from.
493 : : * @nr: Bit number to free.
494 : : * @cpu: CPU the bit was allocated on.
495 : : */
496 : : void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
497 : : unsigned int cpu);
498 : :
499 : : static inline int sbq_index_inc(int index)
500 : : {
501 : 0 : return (index + 1) & (SBQ_WAIT_QUEUES - 1);
502 : : }
503 : :
504 : : static inline void sbq_index_atomic_inc(atomic_t *index)
505 : : {
506 : 0 : int old = atomic_read(index);
507 : : int new = sbq_index_inc(old);
508 : 0 : atomic_cmpxchg(index, old, new);
509 : : }
510 : :
511 : : /**
512 : : * sbq_wait_ptr() - Get the next wait queue to use for a &struct
513 : : * sbitmap_queue.
514 : : * @sbq: Bitmap queue to wait on.
515 : : * @wait_index: A counter per "user" of @sbq.
516 : : */
517 : 0 : static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
518 : : atomic_t *wait_index)
519 : : {
520 : : struct sbq_wait_state *ws;
521 : :
522 : 0 : ws = &sbq->ws[atomic_read(wait_index)];
523 : : sbq_index_atomic_inc(wait_index);
524 : 0 : return ws;
525 : : }
526 : :
527 : : /**
528 : : * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
529 : : * sbitmap_queue.
530 : : * @sbq: Bitmap queue to wake up.
531 : : */
532 : : void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);
533 : :
534 : : /**
535 : : * sbitmap_queue_wake_up() - Wake up some of waiters in one waitqueue
536 : : * on a &struct sbitmap_queue.
537 : : * @sbq: Bitmap queue to wake up.
538 : : */
539 : : void sbitmap_queue_wake_up(struct sbitmap_queue *sbq);
540 : :
541 : : /**
542 : : * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct
543 : : * seq_file.
544 : : * @sbq: Bitmap queue to show.
545 : : * @m: struct seq_file to write to.
546 : : *
547 : : * This is intended for debugging. The format may change at any time.
548 : : */
549 : : void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m);
550 : :
551 : : struct sbq_wait {
552 : : struct sbitmap_queue *sbq; /* if set, sbq_wait is accounted */
553 : : struct wait_queue_entry wait;
554 : : };
555 : :
556 : : #define DEFINE_SBQ_WAIT(name) \
557 : : struct sbq_wait name = { \
558 : : .sbq = NULL, \
559 : : .wait = { \
560 : : .private = current, \
561 : : .func = autoremove_wake_function, \
562 : : .entry = LIST_HEAD_INIT((name).wait.entry), \
563 : : } \
564 : : }
565 : :
566 : : /*
567 : : * Wrapper around prepare_to_wait_exclusive(), which maintains some extra
568 : : * internal state.
569 : : */
570 : : void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
571 : : struct sbq_wait_state *ws,
572 : : struct sbq_wait *sbq_wait, int state);
573 : :
574 : : /*
575 : : * Must be paired with sbitmap_prepare_to_wait().
576 : : */
577 : : void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
578 : : struct sbq_wait *sbq_wait);
579 : :
580 : : /*
581 : : * Wrapper around add_wait_queue(), which maintains some extra internal state
582 : : */
583 : : void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
584 : : struct sbq_wait_state *ws,
585 : : struct sbq_wait *sbq_wait);
586 : :
587 : : /*
588 : : * Must be paired with sbitmap_add_wait_queue()
589 : : */
590 : : void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait);
591 : :
592 : : #endif /* __LINUX_SCALE_BITMAP_H */
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