xref: /linux/include/linux/sbitmap.h (revision 11a299a7933e03c83818b431e6a1c53ad387423d)
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/atomic.h>
13 #include <linux/bitops.h>
14 #include <linux/cache.h>
15 #include <linux/list.h>
16 #include <linux/log2.h>
17 #include <linux/minmax.h>
18 #include <linux/percpu.h>
19 #include <linux/slab.h>
20 #include <linux/smp.h>
21 #include <linux/types.h>
22 #include <linux/wait.h>
23 
24 struct seq_file;
25 
26 /**
27  * struct sbitmap_word - Word in a &struct sbitmap.
28  */
29 struct sbitmap_word {
30 	/**
31 	 * @word: word holding free bits
32 	 */
33 	unsigned long word;
34 
35 	/**
36 	 * @cleared: word holding cleared bits
37 	 */
38 	unsigned long cleared ____cacheline_aligned_in_smp;
39 
40 	/**
41 	 * @swap_lock: serializes simultaneous updates of ->word and ->cleared
42 	 */
43 	raw_spinlock_t swap_lock;
44 } ____cacheline_aligned_in_smp;
45 
46 /**
47  * struct sbitmap - Scalable bitmap.
48  *
49  * A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This
50  * trades off higher memory usage for better scalability.
51  */
52 struct sbitmap {
53 	/**
54 	 * @depth: Number of bits used in the whole bitmap.
55 	 */
56 	unsigned int depth;
57 
58 	/**
59 	 * @shift: log2(number of bits used per word)
60 	 */
61 	unsigned int shift;
62 
63 	/**
64 	 * @map_nr: Number of words (cachelines) being used for the bitmap.
65 	 */
66 	unsigned int map_nr;
67 
68 	/**
69 	 * @round_robin: Allocate bits in strict round-robin order.
70 	 */
71 	bool round_robin;
72 
73 	/**
74 	 * @map: Allocated bitmap.
75 	 */
76 	struct sbitmap_word *map;
77 
78 	/*
79 	 * @alloc_hint: Cache of last successfully allocated or freed bit.
80 	 *
81 	 * This is per-cpu, which allows multiple users to stick to different
82 	 * cachelines until the map is exhausted.
83 	 */
84 	unsigned int __percpu *alloc_hint;
85 };
86 
87 #define SBQ_WAIT_QUEUES 8
88 #define SBQ_WAKE_BATCH 8
89 
90 /**
91  * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue.
92  */
93 struct sbq_wait_state {
94 	/**
95 	 * @wait: Wait queue.
96 	 */
97 	wait_queue_head_t wait;
98 } ____cacheline_aligned_in_smp;
99 
100 /**
101  * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free
102  * bits.
103  *
104  * A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to
105  * avoid contention on the wait queue spinlock. This ensures that we don't hit a
106  * scalability wall when we run out of free bits and have to start putting tasks
107  * to sleep.
108  */
109 struct sbitmap_queue {
110 	/**
111 	 * @sb: Scalable bitmap.
112 	 */
113 	struct sbitmap sb;
114 
115 	/**
116 	 * @wake_batch: Number of bits which must be freed before we wake up any
117 	 * waiters.
118 	 */
119 	unsigned int wake_batch;
120 
121 	/**
122 	 * @wake_index: Next wait queue in @ws to wake up.
123 	 */
124 	atomic_t wake_index;
125 
126 	/**
127 	 * @ws: Wait queues.
128 	 */
129 	struct sbq_wait_state *ws;
130 
131 	/*
132 	 * @ws_active: count of currently active ws waitqueues
133 	 */
134 	atomic_t ws_active;
135 
136 	/**
137 	 * @min_shallow_depth: The minimum shallow depth which may be passed to
138 	 * sbitmap_queue_get_shallow()
139 	 */
140 	unsigned int min_shallow_depth;
141 
142 	/**
143 	 * @completion_cnt: Number of bits cleared passed to the
144 	 * wakeup function.
145 	 */
146 	atomic_t completion_cnt;
147 
148 	/**
149 	 * @wakeup_cnt: Number of thread wake ups issued.
150 	 */
151 	atomic_t wakeup_cnt;
152 };
153 
154 /**
155  * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node.
156  * @sb: Bitmap to initialize.
157  * @depth: Number of bits to allocate.
158  * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
159  *         given, a good default is chosen.
160  * @flags: Allocation flags.
161  * @node: Memory node to allocate on.
162  * @round_robin: If true, be stricter about allocation order; always allocate
163  *               starting from the last allocated bit. This is less efficient
164  *               than the default behavior (false).
165  * @alloc_hint: If true, apply percpu hint for where to start searching for
166  *              a free bit.
167  *
168  * Return: Zero on success or negative errno on failure.
169  */
170 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
171 		      gfp_t flags, int node, bool round_robin, bool alloc_hint);
172 
173 /* sbitmap internal helper */
__map_depth(const struct sbitmap * sb,int index)174 static inline unsigned int __map_depth(const struct sbitmap *sb, int index)
175 {
176 	if (index == sb->map_nr - 1)
177 		return sb->depth - (index << sb->shift);
178 	return 1U << sb->shift;
179 }
180 
181 /**
182  * sbitmap_free() - Free memory used by a &struct sbitmap.
183  * @sb: Bitmap to free.
184  */
sbitmap_free(struct sbitmap * sb)185 static inline void sbitmap_free(struct sbitmap *sb)
186 {
187 	free_percpu(sb->alloc_hint);
188 	kvfree(sb->map);
189 	sb->map = NULL;
190 }
191 
192 /**
193  * sbitmap_resize() - Resize a &struct sbitmap.
194  * @sb: Bitmap to resize.
195  * @depth: New number of bits to resize to.
196  *
197  * Doesn't reallocate anything. It's up to the caller to ensure that the new
198  * depth doesn't exceed the depth that the sb was initialized with.
199  */
200 void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
201 
202 /**
203  * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
204  * @sb: Bitmap to allocate from.
205  *
206  * This operation provides acquire barrier semantics if it succeeds.
207  *
208  * Return: Non-negative allocated bit number if successful, -1 otherwise.
209  */
210 int sbitmap_get(struct sbitmap *sb);
211 
212 /**
213  * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
214  * limiting the depth used from each word.
215  * @sb: Bitmap to allocate from.
216  * @shallow_depth: The maximum number of bits to allocate from a single word.
217  *
218  * This rather specific operation allows for having multiple users with
219  * different allocation limits. E.g., there can be a high-priority class that
220  * uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow()
221  * with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority
222  * class can only allocate half of the total bits in the bitmap, preventing it
223  * from starving out the high-priority class.
224  *
225  * Return: Non-negative allocated bit number if successful, -1 otherwise.
226  */
227 int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth);
228 
229 /**
230  * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
231  * @sb: Bitmap to check.
232  *
233  * Return: true if any bit in the bitmap is set, false otherwise.
234  */
235 bool sbitmap_any_bit_set(const struct sbitmap *sb);
236 
237 #define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
238 #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
239 
240 typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);
241 
242 /**
243  * __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
244  * @start: Where to start the iteration.
245  * @sb: Bitmap to iterate over.
246  * @fn: Callback. Should return true to continue or false to break early.
247  * @data: Pointer to pass to callback.
248  *
249  * This is inline even though it's non-trivial so that the function calls to the
250  * callback will hopefully get optimized away.
251  */
__sbitmap_for_each_set(struct sbitmap * sb,unsigned int start,sb_for_each_fn fn,void * data)252 static inline void __sbitmap_for_each_set(struct sbitmap *sb,
253 					  unsigned int start,
254 					  sb_for_each_fn fn, void *data)
255 {
256 	unsigned int index;
257 	unsigned int nr;
258 	unsigned int scanned = 0;
259 
260 	if (start >= sb->depth)
261 		start = 0;
262 	index = SB_NR_TO_INDEX(sb, start);
263 	nr = SB_NR_TO_BIT(sb, start);
264 
265 	while (scanned < sb->depth) {
266 		unsigned long word;
267 		unsigned int depth = min_t(unsigned int,
268 					   __map_depth(sb, index) - nr,
269 					   sb->depth - scanned);
270 
271 		scanned += depth;
272 		word = sb->map[index].word & ~sb->map[index].cleared;
273 		if (!word)
274 			goto next;
275 
276 		/*
277 		 * On the first iteration of the outer loop, we need to add the
278 		 * bit offset back to the size of the word for find_next_bit().
279 		 * On all other iterations, nr is zero, so this is a noop.
280 		 */
281 		depth += nr;
282 		while (1) {
283 			nr = find_next_bit(&word, depth, nr);
284 			if (nr >= depth)
285 				break;
286 			if (!fn(sb, (index << sb->shift) + nr, data))
287 				return;
288 
289 			nr++;
290 		}
291 next:
292 		nr = 0;
293 		if (++index >= sb->map_nr)
294 			index = 0;
295 	}
296 }
297 
298 /**
299  * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
300  * @sb: Bitmap to iterate over.
301  * @fn: Callback. Should return true to continue or false to break early.
302  * @data: Pointer to pass to callback.
303  */
sbitmap_for_each_set(struct sbitmap * sb,sb_for_each_fn fn,void * data)304 static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
305 					void *data)
306 {
307 	__sbitmap_for_each_set(sb, 0, fn, data);
308 }
309 
__sbitmap_word(struct sbitmap * sb,unsigned int bitnr)310 static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
311 					    unsigned int bitnr)
312 {
313 	return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
314 }
315 
316 /* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */
317 
sbitmap_set_bit(struct sbitmap * sb,unsigned int bitnr)318 static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
319 {
320 	set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
321 }
322 
sbitmap_clear_bit(struct sbitmap * sb,unsigned int bitnr)323 static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
324 {
325 	clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
326 }
327 
328 /*
329  * This one is special, since it doesn't actually clear the bit, rather it
330  * sets the corresponding bit in the ->cleared mask instead. Paired with
331  * the caller doing sbitmap_deferred_clear() if a given index is full, which
332  * will clear the previously freed entries in the corresponding ->word.
333  */
sbitmap_deferred_clear_bit(struct sbitmap * sb,unsigned int bitnr)334 static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int bitnr)
335 {
336 	unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared;
337 
338 	set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
339 }
340 
341 /*
342  * Pair of sbitmap_get, and this one applies both cleared bit and
343  * allocation hint.
344  */
sbitmap_put(struct sbitmap * sb,unsigned int bitnr)345 static inline void sbitmap_put(struct sbitmap *sb, unsigned int bitnr)
346 {
347 	sbitmap_deferred_clear_bit(sb, bitnr);
348 
349 	if (likely(sb->alloc_hint && !sb->round_robin && bitnr < sb->depth))
350 		*raw_cpu_ptr(sb->alloc_hint) = bitnr;
351 }
352 
sbitmap_test_bit(struct sbitmap * sb,unsigned int bitnr)353 static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
354 {
355 	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
356 }
357 
sbitmap_calculate_shift(unsigned int depth)358 static inline int sbitmap_calculate_shift(unsigned int depth)
359 {
360 	int	shift = ilog2(BITS_PER_LONG);
361 
362 	/*
363 	 * If the bitmap is small, shrink the number of bits per word so
364 	 * we spread over a few cachelines, at least. If less than 4
365 	 * bits, just forget about it, it's not going to work optimally
366 	 * anyway.
367 	 */
368 	if (depth >= 4) {
369 		while ((4U << shift) > depth)
370 			shift--;
371 	}
372 
373 	return shift;
374 }
375 
376 /**
377  * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
378  * @sb: Bitmap to show.
379  * @m: struct seq_file to write to.
380  *
381  * This is intended for debugging. The format may change at any time.
382  */
383 void sbitmap_show(struct sbitmap *sb, struct seq_file *m);
384 
385 
386 /**
387  * sbitmap_weight() - Return how many set and not cleared bits in a &struct
388  * sbitmap.
389  * @sb: Bitmap to check.
390  *
391  * Return: How many set and not cleared bits set
392  */
393 unsigned int sbitmap_weight(const struct sbitmap *sb);
394 
395 /**
396  * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
397  * seq_file.
398  * @sb: Bitmap to show.
399  * @m: struct seq_file to write to.
400  *
401  * This is intended for debugging. The output isn't guaranteed to be internally
402  * consistent.
403  */
404 void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m);
405 
406 /**
407  * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
408  * memory node.
409  * @sbq: Bitmap queue to initialize.
410  * @depth: See sbitmap_init_node().
411  * @shift: See sbitmap_init_node().
412  * @round_robin: See sbitmap_get().
413  * @flags: Allocation flags.
414  * @node: Memory node to allocate on.
415  *
416  * Return: Zero on success or negative errno on failure.
417  */
418 int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
419 			    int shift, bool round_robin, gfp_t flags, int node);
420 
421 /**
422  * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
423  *
424  * @sbq: Bitmap queue to free.
425  */
sbitmap_queue_free(struct sbitmap_queue * sbq)426 static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
427 {
428 	kfree(sbq->ws);
429 	sbitmap_free(&sbq->sb);
430 }
431 
432 /**
433  * sbitmap_queue_recalculate_wake_batch() - Recalculate wake batch
434  * @sbq: Bitmap queue to recalculate wake batch.
435  * @users: Number of shares.
436  *
437  * Like sbitmap_queue_update_wake_batch(), this will calculate wake batch
438  * by depth. This interface is for HCTX shared tags or queue shared tags.
439  */
440 void sbitmap_queue_recalculate_wake_batch(struct sbitmap_queue *sbq,
441 					    unsigned int users);
442 
443 /**
444  * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
445  * @sbq: Bitmap queue to resize.
446  * @depth: New number of bits to resize to.
447  *
448  * Like sbitmap_resize(), this doesn't reallocate anything. It has to do
449  * some extra work on the &struct sbitmap_queue, so it's not safe to just
450  * resize the underlying &struct sbitmap.
451  */
452 void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);
453 
454 /**
455  * __sbitmap_queue_get() - Try to allocate a free bit from a &struct
456  * sbitmap_queue with preemption already disabled.
457  * @sbq: Bitmap queue to allocate from.
458  *
459  * Return: Non-negative allocated bit number if successful, -1 otherwise.
460  */
461 int __sbitmap_queue_get(struct sbitmap_queue *sbq);
462 
463 /**
464  * __sbitmap_queue_get_batch() - Try to allocate a batch of free bits
465  * @sbq: Bitmap queue to allocate from.
466  * @nr_tags: number of tags requested
467  * @offset: offset to add to returned bits
468  *
469  * Return: Mask of allocated tags, 0 if none are found. Each tag allocated is
470  * a bit in the mask returned, and the caller must add @offset to the value to
471  * get the absolute tag value.
472  */
473 unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
474 					unsigned int *offset);
475 
476 /**
477  * sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
478  * sbitmap_queue, limiting the depth used from each word, with preemption
479  * already disabled.
480  * @sbq: Bitmap queue to allocate from.
481  * @shallow_depth: The maximum number of bits to allocate from a single word.
482  * See sbitmap_get_shallow().
483  *
484  * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
485  * initializing @sbq.
486  *
487  * Return: Non-negative allocated bit number if successful, -1 otherwise.
488  */
489 int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
490 			      unsigned int shallow_depth);
491 
492 /**
493  * sbitmap_queue_get() - Try to allocate a free bit from a &struct
494  * sbitmap_queue.
495  * @sbq: Bitmap queue to allocate from.
496  * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
497  *       sbitmap_queue_clear()).
498  *
499  * Return: Non-negative allocated bit number if successful, -1 otherwise.
500  */
sbitmap_queue_get(struct sbitmap_queue * sbq,unsigned int * cpu)501 static inline int sbitmap_queue_get(struct sbitmap_queue *sbq,
502 				    unsigned int *cpu)
503 {
504 	int nr;
505 
506 	*cpu = get_cpu();
507 	nr = __sbitmap_queue_get(sbq);
508 	put_cpu();
509 	return nr;
510 }
511 
512 /**
513  * sbitmap_queue_min_shallow_depth() - Inform a &struct sbitmap_queue of the
514  * minimum shallow depth that will be used.
515  * @sbq: Bitmap queue in question.
516  * @min_shallow_depth: The minimum shallow depth that will be passed to
517  * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
518  *
519  * sbitmap_queue_clear() batches wakeups as an optimization. The batch size
520  * depends on the depth of the bitmap. Since the shallow allocation functions
521  * effectively operate with a different depth, the shallow depth must be taken
522  * into account when calculating the batch size. This function must be called
523  * with the minimum shallow depth that will be used. Failure to do so can result
524  * in missed wakeups.
525  */
526 void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
527 				     unsigned int min_shallow_depth);
528 
529 /**
530  * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
531  * &struct sbitmap_queue.
532  * @sbq: Bitmap to free from.
533  * @nr: Bit number to free.
534  * @cpu: CPU the bit was allocated on.
535  */
536 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
537 			 unsigned int cpu);
538 
539 /**
540  * sbitmap_queue_clear_batch() - Free a batch of allocated bits
541  * &struct sbitmap_queue.
542  * @sbq: Bitmap to free from.
543  * @offset: offset for each tag in array
544  * @tags: array of tags
545  * @nr_tags: number of tags in array
546  */
547 void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
548 				int *tags, int nr_tags);
549 
sbq_index_inc(int index)550 static inline int sbq_index_inc(int index)
551 {
552 	return (index + 1) & (SBQ_WAIT_QUEUES - 1);
553 }
554 
sbq_index_atomic_inc(atomic_t * index)555 static inline void sbq_index_atomic_inc(atomic_t *index)
556 {
557 	int old = atomic_read(index);
558 	int new = sbq_index_inc(old);
559 	atomic_cmpxchg(index, old, new);
560 }
561 
562 /**
563  * sbq_wait_ptr() - Get the next wait queue to use for a &struct
564  * sbitmap_queue.
565  * @sbq: Bitmap queue to wait on.
566  * @wait_index: A counter per "user" of @sbq.
567  */
sbq_wait_ptr(struct sbitmap_queue * sbq,atomic_t * wait_index)568 static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
569 						  atomic_t *wait_index)
570 {
571 	struct sbq_wait_state *ws;
572 
573 	ws = &sbq->ws[atomic_read(wait_index)];
574 	sbq_index_atomic_inc(wait_index);
575 	return ws;
576 }
577 
578 /**
579  * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
580  * sbitmap_queue.
581  * @sbq: Bitmap queue to wake up.
582  */
583 void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);
584 
585 /**
586  * sbitmap_queue_wake_up() - Wake up some of waiters in one waitqueue
587  * on a &struct sbitmap_queue.
588  * @sbq: Bitmap queue to wake up.
589  * @nr: Number of bits cleared.
590  */
591 void sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr);
592 
593 /**
594  * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct
595  * seq_file.
596  * @sbq: Bitmap queue to show.
597  * @m: struct seq_file to write to.
598  *
599  * This is intended for debugging. The format may change at any time.
600  */
601 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m);
602 
603 struct sbq_wait {
604 	struct sbitmap_queue *sbq;	/* if set, sbq_wait is accounted */
605 	struct wait_queue_entry wait;
606 };
607 
608 #define DEFINE_SBQ_WAIT(name)							\
609 	struct sbq_wait name = {						\
610 		.sbq = NULL,							\
611 		.wait = {							\
612 			.private	= current,				\
613 			.func		= autoremove_wake_function,		\
614 			.entry		= LIST_HEAD_INIT((name).wait.entry),	\
615 		}								\
616 	}
617 
618 /*
619  * Wrapper around prepare_to_wait_exclusive(), which maintains some extra
620  * internal state.
621  */
622 void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
623 				struct sbq_wait_state *ws,
624 				struct sbq_wait *sbq_wait, int state);
625 
626 /*
627  * Must be paired with sbitmap_prepare_to_wait().
628  */
629 void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
630 				struct sbq_wait *sbq_wait);
631 
632 /*
633  * Wrapper around add_wait_queue(), which maintains some extra internal state
634  */
635 void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
636 			    struct sbq_wait_state *ws,
637 			    struct sbq_wait *sbq_wait);
638 
639 /*
640  * Must be paired with sbitmap_add_wait_queue()
641  */
642 void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait);
643 
644 #endif /* __LINUX_SCALE_BITMAP_H */
645