include/linux/sbitmap.h - third_party/kernel - Git at Google

 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * Fast and scalable bitmaps.
  *
  * Copyright (C) 2016 Facebook
  * Copyright (C) 2013-2014 Jens Axboe
  */

 #ifndef __LINUX_SCALE_BITMAP_H
 #define __LINUX_SCALE_BITMAP_H

 #include <linux/kernel.h>
 #include <linux/slab.h>

 struct seq_file;

 /**
  * struct sbitmap_word - Word in a &struct sbitmap.
  */
 struct sbitmap_word {
 	/**
 	 * @depth: Number of bits being used in @word/@cleared
 	 */
 	unsigned long depth;

 	/**
 	 * @word: word holding free bits
 	 */
 	unsigned long word ____cacheline_aligned_in_smp;

 	/**
 	 * @cleared: word holding cleared bits
 	 */
 	unsigned long cleared ____cacheline_aligned_in_smp;

 	/**
 	 * @swap_lock: Held while swapping word <-> cleared
 	 */
 	spinlock_t swap_lock;
 } ____cacheline_aligned_in_smp;

 /**
  * struct sbitmap - Scalable bitmap.
  *
  * A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This
  * trades off higher memory usage for better scalability.
  */
 struct sbitmap {
 	/**
 	 * @depth: Number of bits used in the whole bitmap.
 	 */
 	unsigned int depth;

 	/**
 	 * @shift: log2(number of bits used per word)
 	 */
 	unsigned int shift;

 	/**
 	 * @map_nr: Number of words (cachelines) being used for the bitmap.
 	 */
 	unsigned int map_nr;

 	/**
 	 * @map: Allocated bitmap.
 	 */
 	struct sbitmap_word *map;
 };

 #define SBQ_WAIT_QUEUES 8
 #define SBQ_WAKE_BATCH 8

 /**
  * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue.
  */
 struct sbq_wait_state {
 	/**
 	 * @wait_cnt: Number of frees remaining before we wake up.
 	 */
 	atomic_t wait_cnt;

 	/**
 	 * @wait: Wait queue.
 	 */
 	wait_queue_head_t wait;
 } ____cacheline_aligned_in_smp;

 /**
  * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free
  * bits.
  *
  * A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to
  * avoid contention on the wait queue spinlock. This ensures that we don't hit a
  * scalability wall when we run out of free bits and have to start putting tasks
  * to sleep.
  */
 struct sbitmap_queue {
 	/**
 	 * @sb: Scalable bitmap.
 	 */
 	struct sbitmap sb;

 	/*
 	 * @alloc_hint: Cache of last successfully allocated or freed bit.
 	 *
 	 * This is per-cpu, which allows multiple users to stick to different
 	 * cachelines until the map is exhausted.
 	 */
 	unsigned int __percpu *alloc_hint;

 	/**
 	 * @wake_batch: Number of bits which must be freed before we wake up any
 	 * waiters.
 	 */
 	unsigned int wake_batch;

 	/**
 	 * @wake_index: Next wait queue in @ws to wake up.
 	 */
 	atomic_t wake_index;

 	/**
 	 * @ws: Wait queues.
 	 */
 	struct sbq_wait_state *ws;

 	/*
 	 * @ws_active: count of currently active ws waitqueues
 	 */
 	atomic_t ws_active;

 	/**
 	 * @round_robin: Allocate bits in strict round-robin order.
 	 */
 	bool round_robin;

 	/**
 	 * @min_shallow_depth: The minimum shallow depth which may be passed to
 	 * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
 	 */
 	unsigned int min_shallow_depth;
 };

 /**
  * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node.
  * @sb: Bitmap to initialize.
  * @depth: Number of bits to allocate.
  * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
  *         given, a good default is chosen.
  * @flags: Allocation flags.
  * @node: Memory node to allocate on.
  *
  * Return: Zero on success or negative errno on failure.
  */
 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
 		      gfp_t flags, int node);

 /**
  * sbitmap_free() - Free memory used by a &struct sbitmap.
  * @sb: Bitmap to free.
  */
 static inline void sbitmap_free(struct sbitmap *sb)
 {
 	kfree(sb->map);
 	sb->map = NULL;
 }

 /**
  * sbitmap_resize() - Resize a &struct sbitmap.
  * @sb: Bitmap to resize.
  * @depth: New number of bits to resize to.
  *
  * Doesn't reallocate anything. It's up to the caller to ensure that the new
  * depth doesn't exceed the depth that the sb was initialized with.
  */
 void sbitmap_resize(struct sbitmap *sb, unsigned int depth);

 /**
  * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
  * @sb: Bitmap to allocate from.
  * @alloc_hint: Hint for where to start searching for a free bit.
  * @round_robin: If true, be stricter about allocation order; always allocate
  *               starting from the last allocated bit. This is less efficient
  *               than the default behavior (false).
  *
  * This operation provides acquire barrier semantics if it succeeds.
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
 int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin);

 /**
  * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
  * limiting the depth used from each word.
  * @sb: Bitmap to allocate from.
  * @alloc_hint: Hint for where to start searching for a free bit.
  * @shallow_depth: The maximum number of bits to allocate from a single word.
  *
  * This rather specific operation allows for having multiple users with
  * different allocation limits. E.g., there can be a high-priority class that
  * uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow()
  * with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority
  * class can only allocate half of the total bits in the bitmap, preventing it
  * from starving out the high-priority class.
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
 int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
 			unsigned long shallow_depth);

 /**
  * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
  * @sb: Bitmap to check.
  *
  * Return: true if any bit in the bitmap is set, false otherwise.
  */
 bool sbitmap_any_bit_set(const struct sbitmap *sb);

 #define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
 #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))

 typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);

 /**
  * __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
  * @start: Where to start the iteration.
  * @sb: Bitmap to iterate over.
  * @fn: Callback. Should return true to continue or false to break early.
  * @data: Pointer to pass to callback.
  *
  * This is inline even though it's non-trivial so that the function calls to the
  * callback will hopefully get optimized away.
  */
 static inline void __sbitmap_for_each_set(struct sbitmap *sb,
 					  unsigned int start,
 					  sb_for_each_fn fn, void *data)
 {
 	unsigned int index;
 	unsigned int nr;
 	unsigned int scanned = 0;

 	if (start >= sb->depth)
 		start = 0;
 	index = SB_NR_TO_INDEX(sb, start);
 	nr = SB_NR_TO_BIT(sb, start);

 	while (scanned < sb->depth) {
 		unsigned long word;
 		unsigned int depth = min_t(unsigned int,
 					   sb->map[index].depth - nr,
 					   sb->depth - scanned);

 		scanned += depth;
 		word = sb->map[index].word & ~sb->map[index].cleared;
 		if (!word)
 			goto next;

 		/*
 		 * On the first iteration of the outer loop, we need to add the
 		 * bit offset back to the size of the word for find_next_bit().
 		 * On all other iterations, nr is zero, so this is a noop.
 		 */
 		depth += nr;
 		while (1) {
 			nr = find_next_bit(&word, depth, nr);
 			if (nr >= depth)
 				break;
 			if (!fn(sb, (index << sb->shift) + nr, data))
 				return;

 			nr++;
 		}
 next:
 		nr = 0;
 		if (++index >= sb->map_nr)
 			index = 0;
 	}
 }

 /**
  * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
  * @sb: Bitmap to iterate over.
  * @fn: Callback. Should return true to continue or false to break early.
  * @data: Pointer to pass to callback.
  */
 static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
 					void *data)
 {
 	__sbitmap_for_each_set(sb, 0, fn, data);
 }

 static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
 					    unsigned int bitnr)
 {
 	return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
 }

 /* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */

 static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
 {
 	set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
 }

 static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
 {
 	clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
 }

 /*
  * This one is special, since it doesn't actually clear the bit, rather it
  * sets the corresponding bit in the ->cleared mask instead. Paired with
  * the caller doing sbitmap_deferred_clear() if a given index is full, which
  * will clear the previously freed entries in the corresponding ->word.
  */
 static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int bitnr)
 {
 	unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared;

 	set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
 }

 static inline void sbitmap_clear_bit_unlock(struct sbitmap *sb,
 					    unsigned int bitnr)
 {
 	clear_bit_unlock(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
 }

 static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
 {
 	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
 }

 /**
  * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
  * @sb: Bitmap to show.
  * @m: struct seq_file to write to.
  *
  * This is intended for debugging. The format may change at any time.
  */
 void sbitmap_show(struct sbitmap *sb, struct seq_file *m);

 /**
  * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
  * seq_file.
  * @sb: Bitmap to show.
  * @m: struct seq_file to write to.
  *
  * This is intended for debugging. The output isn't guaranteed to be internally
  * consistent.
  */
 void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m);

 /**
  * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
  * memory node.
  * @sbq: Bitmap queue to initialize.
  * @depth: See sbitmap_init_node().
  * @shift: See sbitmap_init_node().
  * @round_robin: See sbitmap_get().
  * @flags: Allocation flags.
  * @node: Memory node to allocate on.
  *
  * Return: Zero on success or negative errno on failure.
  */
 int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 			    int shift, bool round_robin, gfp_t flags, int node);

 /**
  * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
  *
  * @sbq: Bitmap queue to free.
  */
 static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
 {
 	kfree(sbq->ws);
 	free_percpu(sbq->alloc_hint);
 	sbitmap_free(&sbq->sb);
 }

 /**
  * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
  * @sbq: Bitmap queue to resize.
  * @depth: New number of bits to resize to.
  *
  * Like sbitmap_resize(), this doesn't reallocate anything. It has to do
  * some extra work on the &struct sbitmap_queue, so it's not safe to just
  * resize the underlying &struct sbitmap.
  */
 void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);

 /**
  * __sbitmap_queue_get() - Try to allocate a free bit from a &struct
  * sbitmap_queue with preemption already disabled.
  * @sbq: Bitmap queue to allocate from.
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
 int __sbitmap_queue_get(struct sbitmap_queue *sbq);

 /**
  * __sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
  * sbitmap_queue, limiting the depth used from each word, with preemption
  * already disabled.
  * @sbq: Bitmap queue to allocate from.
  * @shallow_depth: The maximum number of bits to allocate from a single word.
  * See sbitmap_get_shallow().
  *
  * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
  * initializing @sbq.
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
 int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 				unsigned int shallow_depth);

 /**
  * sbitmap_queue_get() - Try to allocate a free bit from a &struct
  * sbitmap_queue.
  * @sbq: Bitmap queue to allocate from.
  * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
  *       sbitmap_queue_clear()).
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
 static inline int sbitmap_queue_get(struct sbitmap_queue *sbq,
 				    unsigned int *cpu)
 {
 	int nr;

 	*cpu = get_cpu();
 	nr = __sbitmap_queue_get(sbq);
 	put_cpu();
 	return nr;
 }

 /**
  * sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
  * sbitmap_queue, limiting the depth used from each word.
  * @sbq: Bitmap queue to allocate from.
  * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
  *       sbitmap_queue_clear()).
  * @shallow_depth: The maximum number of bits to allocate from a single word.
  * See sbitmap_get_shallow().
  *
  * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
  * initializing @sbq.
  *
  * Return: Non-negative allocated bit number if successful, -1 otherwise.
  */
 static inline int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 					    unsigned int *cpu,
 					    unsigned int shallow_depth)
 {
 	int nr;

 	*cpu = get_cpu();
 	nr = __sbitmap_queue_get_shallow(sbq, shallow_depth);
 	put_cpu();
 	return nr;
 }

 /**
  * sbitmap_queue_min_shallow_depth() - Inform a &struct sbitmap_queue of the
  * minimum shallow depth that will be used.
  * @sbq: Bitmap queue in question.
  * @min_shallow_depth: The minimum shallow depth that will be passed to
  * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
  *
  * sbitmap_queue_clear() batches wakeups as an optimization. The batch size
  * depends on the depth of the bitmap. Since the shallow allocation functions
  * effectively operate with a different depth, the shallow depth must be taken
  * into account when calculating the batch size. This function must be called
  * with the minimum shallow depth that will be used. Failure to do so can result
  * in missed wakeups.
  */
 void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
 				     unsigned int min_shallow_depth);

 /**
  * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
  * &struct sbitmap_queue.
  * @sbq: Bitmap to free from.
  * @nr: Bit number to free.
  * @cpu: CPU the bit was allocated on.
  */
 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 			 unsigned int cpu);

 static inline int sbq_index_inc(int index)
 {
 	return (index + 1) & (SBQ_WAIT_QUEUES - 1);
 }

 static inline void sbq_index_atomic_inc(atomic_t *index)
 {
 	int old = atomic_read(index);
 	int new = sbq_index_inc(old);
 	atomic_cmpxchg(index, old, new);
 }

 /**
  * sbq_wait_ptr() - Get the next wait queue to use for a &struct
  * sbitmap_queue.
  * @sbq: Bitmap queue to wait on.
  * @wait_index: A counter per "user" of @sbq.
  */
 static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
 						  atomic_t *wait_index)
 {
 	struct sbq_wait_state *ws;

 	ws = &sbq->ws[atomic_read(wait_index)];
 	sbq_index_atomic_inc(wait_index);
 	return ws;
 }

 /**
  * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
  * sbitmap_queue.
  * @sbq: Bitmap queue to wake up.
  */
 void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);

 /**
  * sbitmap_queue_wake_up() - Wake up some of waiters in one waitqueue
  * on a &struct sbitmap_queue.
  * @sbq: Bitmap queue to wake up.
  */
 void sbitmap_queue_wake_up(struct sbitmap_queue *sbq);

 /**
  * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct
  * seq_file.
  * @sbq: Bitmap queue to show.
  * @m: struct seq_file to write to.
  *
  * This is intended for debugging. The format may change at any time.
  */
 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m);

 struct sbq_wait {
 	struct sbitmap_queue *sbq;	/* if set, sbq_wait is accounted */
 	struct wait_queue_entry wait;
 };

 #define DEFINE_SBQ_WAIT(name)							\
 	struct sbq_wait name = {						\
 		.sbq = NULL,							\
 		.wait = {							\
 			.private	= current,				\
 			.func		= autoremove_wake_function,		\
 			.entry		= LIST_HEAD_INIT((name).wait.entry),	\
 		}								\
 	}

 /*
  * Wrapper around prepare_to_wait_exclusive(), which maintains some extra
  * internal state.
  */
 void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
 				struct sbq_wait_state *ws,
 				struct sbq_wait *sbq_wait, int state);

 /*
  * Must be paired with sbitmap_prepare_to_wait().
  */
 void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
 				struct sbq_wait *sbq_wait);

 /*
  * Wrapper around add_wait_queue(), which maintains some extra internal state
  */
 void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
 			    struct sbq_wait_state *ws,
 			    struct sbq_wait *sbq_wait);

 /*
  * Must be paired with sbitmap_add_wait_queue()
  */
 void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait);

 #endif /* __LINUX_SCALE_BITMAP_H */
	/* SPDX-License-Identifier: GPL-2.0-only */
	/*
	* Fast and scalable bitmaps.
	*
	* Copyright (C) 2016 Facebook
	* Copyright (C) 2013-2014 Jens Axboe
	*/

	#ifndef __LINUX_SCALE_BITMAP_H
	#define __LINUX_SCALE_BITMAP_H

	#include <linux/kernel.h>
	#include <linux/slab.h>

	struct seq_file;

	/**
	* struct sbitmap_word - Word in a &struct sbitmap.
	*/
	struct sbitmap_word {
	/**
	* @depth: Number of bits being used in @word/@cleared
	*/
	unsigned long depth;

	/**
	* @word: word holding free bits
	*/
	unsigned long word ____cacheline_aligned_in_smp;

	/**
	* @cleared: word holding cleared bits
	*/
	unsigned long cleared ____cacheline_aligned_in_smp;

	/**
	* @swap_lock: Held while swapping word <-> cleared
	*/
	spinlock_t swap_lock;
	} ____cacheline_aligned_in_smp;

	/**
	* struct sbitmap - Scalable bitmap.
	*
	* A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This
	* trades off higher memory usage for better scalability.
	*/
	struct sbitmap {
	/**
	* @depth: Number of bits used in the whole bitmap.
	*/
	unsigned int depth;

	/**
	* @shift: log2(number of bits used per word)
	*/
	unsigned int shift;

	/**
	* @map_nr: Number of words (cachelines) being used for the bitmap.
	*/
	unsigned int map_nr;

	/**
	* @map: Allocated bitmap.
	*/
	struct sbitmap_word *map;
	};

	#define SBQ_WAIT_QUEUES 8
	#define SBQ_WAKE_BATCH 8

	/**
	* struct sbq_wait_state - Wait queue in a &struct sbitmap_queue.
	*/
	struct sbq_wait_state {
	/**
	* @wait_cnt: Number of frees remaining before we wake up.
	*/
	atomic_t wait_cnt;

	/**
	* @wait: Wait queue.
	*/
	wait_queue_head_t wait;
	} ____cacheline_aligned_in_smp;

	/**
	* struct sbitmap_queue - Scalable bitmap with the added ability to wait on free
	* bits.
	*
	* A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to
	* avoid contention on the wait queue spinlock. This ensures that we don't hit a
	* scalability wall when we run out of free bits and have to start putting tasks
	* to sleep.
	*/
	struct sbitmap_queue {
	/**
	* @sb: Scalable bitmap.
	*/
	struct sbitmap sb;

	/*
	* @alloc_hint: Cache of last successfully allocated or freed bit.
	*
	* This is per-cpu, which allows multiple users to stick to different
	* cachelines until the map is exhausted.
	*/
	unsigned int __percpu *alloc_hint;

	/**
	* @wake_batch: Number of bits which must be freed before we wake up any
	* waiters.
	*/
	unsigned int wake_batch;

	/**
	* @wake_index: Next wait queue in @ws to wake up.
	*/
	atomic_t wake_index;

	/**
	* @ws: Wait queues.
	*/
	struct sbq_wait_state *ws;

	/*
	* @ws_active: count of currently active ws waitqueues
	*/
	atomic_t ws_active;

	/**
	* @round_robin: Allocate bits in strict round-robin order.
	*/
	bool round_robin;

	/**
	* @min_shallow_depth: The minimum shallow depth which may be passed to
	* sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
	*/
	unsigned int min_shallow_depth;
	};

	/**
	* sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node.
	* @sb: Bitmap to initialize.
	* @depth: Number of bits to allocate.
	* @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
	* given, a good default is chosen.
	* @flags: Allocation flags.
	* @node: Memory node to allocate on.
	*
	* Return: Zero on success or negative errno on failure.
	*/
	int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
	gfp_t flags, int node);

	/**
	* sbitmap_free() - Free memory used by a &struct sbitmap.
	* @sb: Bitmap to free.
	*/
	static inline void sbitmap_free(struct sbitmap *sb)
	{
	kfree(sb->map);
	sb->map = NULL;
	}

	/**
	* sbitmap_resize() - Resize a &struct sbitmap.
	* @sb: Bitmap to resize.
	* @depth: New number of bits to resize to.
	*
	* Doesn't reallocate anything. It's up to the caller to ensure that the new
	* depth doesn't exceed the depth that the sb was initialized with.
	*/
	void sbitmap_resize(struct sbitmap *sb, unsigned int depth);

	/**
	* sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
	* @sb: Bitmap to allocate from.
	* @alloc_hint: Hint for where to start searching for a free bit.
	* @round_robin: If true, be stricter about allocation order; always allocate
	* starting from the last allocated bit. This is less efficient
	* than the default behavior (false).
	*
	* This operation provides acquire barrier semantics if it succeeds.
	*
	* Return: Non-negative allocated bit number if successful, -1 otherwise.
	*/
	int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin);

	/**
	* sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap,
	* limiting the depth used from each word.
	* @sb: Bitmap to allocate from.
	* @alloc_hint: Hint for where to start searching for a free bit.
	* @shallow_depth: The maximum number of bits to allocate from a single word.
	*
	* This rather specific operation allows for having multiple users with
	* different allocation limits. E.g., there can be a high-priority class that
	* uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow()
	* with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority
	* class can only allocate half of the total bits in the bitmap, preventing it
	* from starving out the high-priority class.
	*
	* Return: Non-negative allocated bit number if successful, -1 otherwise.
	*/
	int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
	unsigned long shallow_depth);

	/**
	* sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
	* @sb: Bitmap to check.
	*
	* Return: true if any bit in the bitmap is set, false otherwise.
	*/
	bool sbitmap_any_bit_set(const struct sbitmap *sb);

	#define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
	#define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))

	typedef bool (sb_for_each_fn)(struct sbitmap , unsigned int, void *);

	/**
	* __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
	* @start: Where to start the iteration.
	* @sb: Bitmap to iterate over.
	* @fn: Callback. Should return true to continue or false to break early.
	* @data: Pointer to pass to callback.
	*
	* This is inline even though it's non-trivial so that the function calls to the
	* callback will hopefully get optimized away.
	*/
	static inline void __sbitmap_for_each_set(struct sbitmap *sb,
	unsigned int start,
	sb_for_each_fn fn, void *data)
	{
	unsigned int index;
	unsigned int nr;
	unsigned int scanned = 0;

	if (start >= sb->depth)
	start = 0;
	index = SB_NR_TO_INDEX(sb, start);
	nr = SB_NR_TO_BIT(sb, start);

	while (scanned < sb->depth) {
	unsigned long word;
	unsigned int depth = min_t(unsigned int,
	sb->map[index].depth - nr,
	sb->depth - scanned);

	scanned += depth;
	word = sb->map[index].word & ~sb->map[index].cleared;
	if (!word)
	goto next;

	/*
	* On the first iteration of the outer loop, we need to add the
	* bit offset back to the size of the word for find_next_bit().
	* On all other iterations, nr is zero, so this is a noop.
	*/
	depth += nr;
	while (1) {
	nr = find_next_bit(&word, depth, nr);
	if (nr >= depth)
	break;
	if (!fn(sb, (index << sb->shift) + nr, data))
	return;

	nr++;
	}
	next:
	nr = 0;
	if (++index >= sb->map_nr)
	index = 0;
	}
	}

	/**
	* sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
	* @sb: Bitmap to iterate over.
	* @fn: Callback. Should return true to continue or false to break early.
	* @data: Pointer to pass to callback.
	*/
	static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
	void *data)
	{
	__sbitmap_for_each_set(sb, 0, fn, data);
	}

	static inline unsigned long __sbitmap_word(struct sbitmap sb,
	unsigned int bitnr)
	{
	return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
	}

	/* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */

	static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
	{
	set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
	}

	static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
	{
	clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
	}

	/*
	* This one is special, since it doesn't actually clear the bit, rather it
	* sets the corresponding bit in the ->cleared mask instead. Paired with
	* the caller doing sbitmap_deferred_clear() if a given index is full, which
	* will clear the previously freed entries in the corresponding ->word.
	*/
	static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int bitnr)
	{
	unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared;

	set_bit(SB_NR_TO_BIT(sb, bitnr), addr);
	}

	static inline void sbitmap_clear_bit_unlock(struct sbitmap *sb,
	unsigned int bitnr)
	{
	clear_bit_unlock(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
	}

	static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
	{
	return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
	}

	/**
	* sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
	* @sb: Bitmap to show.
	* @m: struct seq_file to write to.
	*
	* This is intended for debugging. The format may change at any time.
	*/
	void sbitmap_show(struct sbitmap sb, struct seq_file m);

	/**
	* sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct
	* seq_file.
	* @sb: Bitmap to show.
	* @m: struct seq_file to write to.
	*
	* This is intended for debugging. The output isn't guaranteed to be internally
	* consistent.
	*/
	void sbitmap_bitmap_show(struct sbitmap sb, struct seq_file m);

	/**
	* sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
	* memory node.
	* @sbq: Bitmap queue to initialize.
	* @depth: See sbitmap_init_node().
	* @shift: See sbitmap_init_node().
	* @round_robin: See sbitmap_get().
	* @flags: Allocation flags.
	* @node: Memory node to allocate on.
	*
	* Return: Zero on success or negative errno on failure.
	*/
	int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
	int shift, bool round_robin, gfp_t flags, int node);

	/**
	* sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
	*
	* @sbq: Bitmap queue to free.
	*/
	static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
	{
	kfree(sbq->ws);
	free_percpu(sbq->alloc_hint);
	sbitmap_free(&sbq->sb);
	}

	/**
	* sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
	* @sbq: Bitmap queue to resize.
	* @depth: New number of bits to resize to.
	*
	* Like sbitmap_resize(), this doesn't reallocate anything. It has to do
	* some extra work on the &struct sbitmap_queue, so it's not safe to just
	* resize the underlying &struct sbitmap.
	*/
	void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);

	/**
	* __sbitmap_queue_get() - Try to allocate a free bit from a &struct
	* sbitmap_queue with preemption already disabled.
	* @sbq: Bitmap queue to allocate from.
	*
	* Return: Non-negative allocated bit number if successful, -1 otherwise.
	*/
	int __sbitmap_queue_get(struct sbitmap_queue *sbq);

	/**
	* __sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
	* sbitmap_queue, limiting the depth used from each word, with preemption
	* already disabled.
	* @sbq: Bitmap queue to allocate from.
	* @shallow_depth: The maximum number of bits to allocate from a single word.
	* See sbitmap_get_shallow().
	*
	* If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
	* initializing @sbq.
	*
	* Return: Non-negative allocated bit number if successful, -1 otherwise.
	*/
	int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
	unsigned int shallow_depth);

	/**
	* sbitmap_queue_get() - Try to allocate a free bit from a &struct
	* sbitmap_queue.
	* @sbq: Bitmap queue to allocate from.
	* @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
	* sbitmap_queue_clear()).
	*
	* Return: Non-negative allocated bit number if successful, -1 otherwise.
	*/
	static inline int sbitmap_queue_get(struct sbitmap_queue *sbq,
	unsigned int *cpu)
	{
	int nr;

	*cpu = get_cpu();
	nr = __sbitmap_queue_get(sbq);
	put_cpu();
	return nr;
	}

	/**
	* sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
	* sbitmap_queue, limiting the depth used from each word.
	* @sbq: Bitmap queue to allocate from.
	* @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to
	* sbitmap_queue_clear()).
	* @shallow_depth: The maximum number of bits to allocate from a single word.
	* See sbitmap_get_shallow().
	*
	* If you call this, make sure to call sbitmap_queue_min_shallow_depth() after
	* initializing @sbq.
	*
	* Return: Non-negative allocated bit number if successful, -1 otherwise.
	*/
	static inline int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
	unsigned int *cpu,
	unsigned int shallow_depth)
	{
	int nr;

	*cpu = get_cpu();
	nr = __sbitmap_queue_get_shallow(sbq, shallow_depth);
	put_cpu();
	return nr;
	}

	/**
	* sbitmap_queue_min_shallow_depth() - Inform a &struct sbitmap_queue of the
	* minimum shallow depth that will be used.
	* @sbq: Bitmap queue in question.
	* @min_shallow_depth: The minimum shallow depth that will be passed to
	* sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow().
	*
	* sbitmap_queue_clear() batches wakeups as an optimization. The batch size
	* depends on the depth of the bitmap. Since the shallow allocation functions
	* effectively operate with a different depth, the shallow depth must be taken
	* into account when calculating the batch size. This function must be called
	* with the minimum shallow depth that will be used. Failure to do so can result
	* in missed wakeups.
	*/
	void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
	unsigned int min_shallow_depth);

	/**
	* sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
	* &struct sbitmap_queue.
	* @sbq: Bitmap to free from.
	* @nr: Bit number to free.
	* @cpu: CPU the bit was allocated on.
	*/
	void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
	unsigned int cpu);

	static inline int sbq_index_inc(int index)
	{
	return (index + 1) & (SBQ_WAIT_QUEUES - 1);
	}

	static inline void sbq_index_atomic_inc(atomic_t *index)
	{
	int old = atomic_read(index);
	int new = sbq_index_inc(old);
	atomic_cmpxchg(index, old, new);
	}

	/**
	* sbq_wait_ptr() - Get the next wait queue to use for a &struct
	* sbitmap_queue.
	* @sbq: Bitmap queue to wait on.
	* @wait_index: A counter per "user" of @sbq.
	*/
	static inline struct sbq_wait_state sbq_wait_ptr(struct sbitmap_queue sbq,
	atomic_t *wait_index)
	{
	struct sbq_wait_state *ws;

	ws = &sbq->ws[atomic_read(wait_index)];
	sbq_index_atomic_inc(wait_index);
	return ws;
	}

	/**
	* sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
	* sbitmap_queue.
	* @sbq: Bitmap queue to wake up.
	*/
	void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);

	/**
	* sbitmap_queue_wake_up() - Wake up some of waiters in one waitqueue
	* on a &struct sbitmap_queue.
	* @sbq: Bitmap queue to wake up.
	*/
	void sbitmap_queue_wake_up(struct sbitmap_queue *sbq);

	/**
	* sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct
	* seq_file.
	* @sbq: Bitmap queue to show.
	* @m: struct seq_file to write to.
	*
	* This is intended for debugging. The format may change at any time.
	*/
	void sbitmap_queue_show(struct sbitmap_queue sbq, struct seq_file m);

	struct sbq_wait {
	struct sbitmap_queue sbq; / if set, sbq_wait is accounted */
	struct wait_queue_entry wait;
	};

	#define DEFINE_SBQ_WAIT(name) \
	struct sbq_wait name = { \
	.sbq = NULL, \
	.wait = { \
	.private = current, \
	.func = autoremove_wake_function, \
	.entry = LIST_HEAD_INIT((name).wait.entry), \
	} \
	}

	/*
	* Wrapper around prepare_to_wait_exclusive(), which maintains some extra
	* internal state.
	*/
	void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
	struct sbq_wait_state *ws,
	struct sbq_wait *sbq_wait, int state);

	/*
	* Must be paired with sbitmap_prepare_to_wait().
	*/
	void sbitmap_finish_wait(struct sbitmap_queue sbq, struct sbq_wait_state ws,
	struct sbq_wait *sbq_wait);

	/*
	* Wrapper around add_wait_queue(), which maintains some extra internal state
	*/
	void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
	struct sbq_wait_state *ws,
	struct sbq_wait *sbq_wait);

	/*
	* Must be paired with sbitmap_add_wait_queue()
	*/
	void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait);

	#endif /* __LINUX_SCALE_BITMAP_H */