lib/sbitmap.c - kernel/msm-5.4 - Gitiles

 /*
  * Copyright (C) 2016 Facebook
  * Copyright (C) 2013-2014 Jens Axboe
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public
  * License v2 as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */

 #include <linux/sched.h>
 #include <linux/random.h>
 #include <linux/sbitmap.h>
 #include <linux/seq_file.h>

 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
 		      gfp_t flags, int node)
 {
 	unsigned int bits_per_word;
 	unsigned int i;

 	if (shift < 0) {
 		shift = ilog2(BITS_PER_LONG);
 		/*
 		 * If the bitmap is small, shrink the number of bits per word so
 		 * we spread over a few cachelines, at least. If less than 4
 		 * bits, just forget about it, it's not going to work optimally
 		 * anyway.
 		 */
 		if (depth >= 4) {
 			while ((4U << shift) > depth)
 				shift--;
 		}
 	}
 	bits_per_word = 1U << shift;
 	if (bits_per_word > BITS_PER_LONG)
 		return -EINVAL;

 	sb->shift = shift;
 	sb->depth = depth;
 	sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);

 	if (depth == 0) {
 		sb->map = NULL;
 		return 0;
 	}

 	sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
 	if (!sb->map)
 		return -ENOMEM;

 	for (i = 0; i < sb->map_nr; i++) {
 		sb->map[i].depth = min(depth, bits_per_word);
 		depth -= sb->map[i].depth;
 	}
 	return 0;
 }
 EXPORT_SYMBOL_GPL(sbitmap_init_node);

 void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
 {
 	unsigned int bits_per_word = 1U << sb->shift;
 	unsigned int i;

 	sb->depth = depth;
 	sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);

 	for (i = 0; i < sb->map_nr; i++) {
 		sb->map[i].depth = min(depth, bits_per_word);
 		depth -= sb->map[i].depth;
 	}
 }
 EXPORT_SYMBOL_GPL(sbitmap_resize);

 static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
 			      unsigned int hint, bool wrap)
 {
 	unsigned int orig_hint = hint;
 	int nr;

 	while (1) {
 		nr = find_next_zero_bit(word, depth, hint);
 		if (unlikely(nr >= depth)) {
 			/*
 			 * We started with an offset, and we didn't reset the
 			 * offset to 0 in a failure case, so start from 0 to
 			 * exhaust the map.
 			 */
 			if (orig_hint && hint && wrap) {
 				hint = orig_hint = 0;
 				continue;
 			}
 			return -1;
 		}

 		if (!test_and_set_bit(nr, word))
 			break;

 		hint = nr + 1;
 		if (hint >= depth - 1)
 			hint = 0;
 	}

 	return nr;
 }

 int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
 {
 	unsigned int i, index;
 	int nr = -1;

 	index = SB_NR_TO_INDEX(sb, alloc_hint);

 	for (i = 0; i < sb->map_nr; i++) {
 		nr = __sbitmap_get_word(&sb->map[index].word,
 					sb->map[index].depth,
 					SB_NR_TO_BIT(sb, alloc_hint),
 					!round_robin);
 		if (nr != -1) {
 			nr += index << sb->shift;
 			break;
 		}

 		/* Jump to next index. */
 		index++;
 		alloc_hint = index << sb->shift;

 		if (index >= sb->map_nr) {
 			index = 0;
 			alloc_hint = 0;
 		}
 	}

 	return nr;
 }
 EXPORT_SYMBOL_GPL(sbitmap_get);

 int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
 			unsigned long shallow_depth)
 {
 	unsigned int i, index;
 	int nr = -1;

 	index = SB_NR_TO_INDEX(sb, alloc_hint);

 	for (i = 0; i < sb->map_nr; i++) {
 		nr = __sbitmap_get_word(&sb->map[index].word,
 					min(sb->map[index].depth, shallow_depth),
 					SB_NR_TO_BIT(sb, alloc_hint), true);
 		if (nr != -1) {
 			nr += index << sb->shift;
 			break;
 		}

 		/* Jump to next index. */
 		index++;
 		alloc_hint = index << sb->shift;

 		if (index >= sb->map_nr) {
 			index = 0;
 			alloc_hint = 0;
 		}
 	}

 	return nr;
 }
 EXPORT_SYMBOL_GPL(sbitmap_get_shallow);

 bool sbitmap_any_bit_set(const struct sbitmap *sb)
 {
 	unsigned int i;

 	for (i = 0; i < sb->map_nr; i++) {
 		if (sb->map[i].word)
 			return true;
 	}
 	return false;
 }
 EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);

 bool sbitmap_any_bit_clear(const struct sbitmap *sb)
 {
 	unsigned int i;

 	for (i = 0; i < sb->map_nr; i++) {
 		const struct sbitmap_word *word = &sb->map[i];
 		unsigned long ret;

 		ret = find_first_zero_bit(&word->word, word->depth);
 		if (ret < word->depth)
 			return true;
 	}
 	return false;
 }
 EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear);

 unsigned int sbitmap_weight(const struct sbitmap *sb)
 {
 	unsigned int i, weight = 0;

 	for (i = 0; i < sb->map_nr; i++) {
 		const struct sbitmap_word *word = &sb->map[i];

 		weight += bitmap_weight(&word->word, word->depth);
 	}
 	return weight;
 }
 EXPORT_SYMBOL_GPL(sbitmap_weight);

 void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
 {
 	seq_printf(m, "depth=%u\n", sb->depth);
 	seq_printf(m, "busy=%u\n", sbitmap_weight(sb));
 	seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
 	seq_printf(m, "map_nr=%u\n", sb->map_nr);
 }
 EXPORT_SYMBOL_GPL(sbitmap_show);

 static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
 {
 	if ((offset & 0xf) == 0) {
 		if (offset != 0)
 			seq_putc(m, '\n');
 		seq_printf(m, "%08x:", offset);
 	}
 	if ((offset & 0x1) == 0)
 		seq_putc(m, ' ');
 	seq_printf(m, "%02x", byte);
 }

 void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
 {
 	u8 byte = 0;
 	unsigned int byte_bits = 0;
 	unsigned int offset = 0;
 	int i;

 	for (i = 0; i < sb->map_nr; i++) {
 		unsigned long word = READ_ONCE(sb->map[i].word);
 		unsigned int word_bits = READ_ONCE(sb->map[i].depth);

 		while (word_bits > 0) {
 			unsigned int bits = min(8 - byte_bits, word_bits);

 			byte |= (word & (BIT(bits) - 1)) << byte_bits;
 			byte_bits += bits;
 			if (byte_bits == 8) {
 				emit_byte(m, offset, byte);
 				byte = 0;
 				byte_bits = 0;
 				offset++;
 			}
 			word >>= bits;
 			word_bits -= bits;
 		}
 	}
 	if (byte_bits) {
 		emit_byte(m, offset, byte);
 		offset++;
 	}
 	if (offset)
 		seq_putc(m, '\n');
 }
 EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);

 static unsigned int sbq_calc_wake_batch(unsigned int depth)
 {
 	unsigned int wake_batch;

 	/*
 	 * For each batch, we wake up one queue. We need to make sure that our
 	 * batch size is small enough that the full depth of the bitmap is
 	 * enough to wake up all of the queues.
 	 */
 	wake_batch = SBQ_WAKE_BATCH;
 	if (wake_batch > depth / SBQ_WAIT_QUEUES)
 		wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);

 	return wake_batch;
 }

 int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 			    int shift, bool round_robin, gfp_t flags, int node)
 {
 	int ret;
 	int i;

 	ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
 	if (ret)
 		return ret;

 	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
 	if (!sbq->alloc_hint) {
 		sbitmap_free(&sbq->sb);
 		return -ENOMEM;
 	}

 	if (depth && !round_robin) {
 		for_each_possible_cpu(i)
 			*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
 	}

 	sbq->wake_batch = sbq_calc_wake_batch(depth);
 	atomic_set(&sbq->wake_index, 0);

 	sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
 	if (!sbq->ws) {
 		free_percpu(sbq->alloc_hint);
 		sbitmap_free(&sbq->sb);
 		return -ENOMEM;
 	}

 	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 		init_waitqueue_head(&sbq->ws[i].wait);
 		atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
 	}

 	sbq->round_robin = round_robin;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);

 void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
 {
 	unsigned int wake_batch = sbq_calc_wake_batch(depth);
 	int i;

 	if (sbq->wake_batch != wake_batch) {
 		WRITE_ONCE(sbq->wake_batch, wake_batch);
 		/*
 		 * Pairs with the memory barrier in sbq_wake_up() to ensure that
 		 * the batch size is updated before the wait counts.
 		 */
 		smp_mb__before_atomic();
 		for (i = 0; i < SBQ_WAIT_QUEUES; i++)
 			atomic_set(&sbq->ws[i].wait_cnt, 1);
 	}
 	sbitmap_resize(&sbq->sb, depth);
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_resize);

 int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 {
 	unsigned int hint, depth;
 	int nr;

 	hint = this_cpu_read(*sbq->alloc_hint);
 	depth = READ_ONCE(sbq->sb.depth);
 	if (unlikely(hint >= depth)) {
 		hint = depth ? prandom_u32() % depth : 0;
 		this_cpu_write(*sbq->alloc_hint, hint);
 	}
 	nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);

 	if (nr == -1) {
 		/* If the map is full, a hint won't do us much good. */
 		this_cpu_write(*sbq->alloc_hint, 0);
 	} else if (nr == hint || unlikely(sbq->round_robin)) {
 		/* Only update the hint if we used it. */
 		hint = nr + 1;
 		if (hint >= depth - 1)
 			hint = 0;
 		this_cpu_write(*sbq->alloc_hint, hint);
 	}

 	return nr;
 }
 EXPORT_SYMBOL_GPL(__sbitmap_queue_get);

 int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 				unsigned int shallow_depth)
 {
 	unsigned int hint, depth;
 	int nr;

 	hint = this_cpu_read(*sbq->alloc_hint);
 	depth = READ_ONCE(sbq->sb.depth);
 	if (unlikely(hint >= depth)) {
 		hint = depth ? prandom_u32() % depth : 0;
 		this_cpu_write(*sbq->alloc_hint, hint);
 	}
 	nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);

 	if (nr == -1) {
 		/* If the map is full, a hint won't do us much good. */
 		this_cpu_write(*sbq->alloc_hint, 0);
 	} else if (nr == hint || unlikely(sbq->round_robin)) {
 		/* Only update the hint if we used it. */
 		hint = nr + 1;
 		if (hint >= depth - 1)
 			hint = 0;
 		this_cpu_write(*sbq->alloc_hint, hint);
 	}

 	return nr;
 }
 EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);

 static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
 {
 	int i, wake_index;

 	wake_index = atomic_read(&sbq->wake_index);
 	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 		struct sbq_wait_state *ws = &sbq->ws[wake_index];

 		if (waitqueue_active(&ws->wait)) {
 			int o = atomic_read(&sbq->wake_index);

 			if (wake_index != o)
 				atomic_cmpxchg(&sbq->wake_index, o, wake_index);
 			return ws;
 		}

 		wake_index = sbq_index_inc(wake_index);
 	}

 	return NULL;
 }

 static void sbq_wake_up(struct sbitmap_queue *sbq)
 {
 	struct sbq_wait_state *ws;
 	unsigned int wake_batch;
 	int wait_cnt;

 	/*
 	 * Pairs with the memory barrier in set_current_state() to ensure the
 	 * proper ordering of clear_bit()/waitqueue_active() in the waker and
 	 * test_and_set_bit()/prepare_to_wait()/finish_wait() in the waiter. See
 	 * the comment on waitqueue_active(). This is __after_atomic because we
 	 * just did clear_bit() in the caller.
 	 */
 	smp_mb__after_atomic();

 	ws = sbq_wake_ptr(sbq);
 	if (!ws)
 		return;

 	wait_cnt = atomic_dec_return(&ws->wait_cnt);
 	if (wait_cnt <= 0) {
 		wake_batch = READ_ONCE(sbq->wake_batch);
 		/*
 		 * Pairs with the memory barrier in sbitmap_queue_resize() to
 		 * ensure that we see the batch size update before the wait
 		 * count is reset.
 		 */
 		smp_mb__before_atomic();
 		/*
 		 * If there are concurrent callers to sbq_wake_up(), the last
 		 * one to decrement the wait count below zero will bump it back
 		 * up. If there is a concurrent resize, the count reset will
 		 * either cause the cmpxchg to fail or overwrite after the
 		 * cmpxchg.
 		 */
 		atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wait_cnt + wake_batch);
 		sbq_index_atomic_inc(&sbq->wake_index);
 		wake_up_nr(&ws->wait, wake_batch);
 	}
 }

 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 			 unsigned int cpu)
 {
 	sbitmap_clear_bit(&sbq->sb, nr);
 	sbq_wake_up(sbq);
 	if (likely(!sbq->round_robin && nr < sbq->sb.depth))
 		*per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_clear);

 void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
 {
 	int i, wake_index;

 	/*
 	 * Pairs with the memory barrier in set_current_state() like in
 	 * sbq_wake_up().
 	 */
 	smp_mb();
 	wake_index = atomic_read(&sbq->wake_index);
 	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 		struct sbq_wait_state *ws = &sbq->ws[wake_index];

 		if (waitqueue_active(&ws->wait))
 			wake_up(&ws->wait);

 		wake_index = sbq_index_inc(wake_index);
 	}
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);

 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
 {
 	bool first;
 	int i;

 	sbitmap_show(&sbq->sb, m);

 	seq_puts(m, "alloc_hint={");
 	first = true;
 	for_each_possible_cpu(i) {
 		if (!first)
 			seq_puts(m, ", ");
 		first = false;
 		seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i));
 	}
 	seq_puts(m, "}\n");

 	seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
 	seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));

 	seq_puts(m, "ws={\n");
 	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 		struct sbq_wait_state *ws = &sbq->ws[i];

 		seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n",
 			   atomic_read(&ws->wait_cnt),
 			   waitqueue_active(&ws->wait) ? "active" : "inactive");
 	}
 	seq_puts(m, "}\n");

 	seq_printf(m, "round_robin=%d\n", sbq->round_robin);
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_show);
	/*
	* Copyright (C) 2016 Facebook
	* Copyright (C) 2013-2014 Jens Axboe
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public
	* License v2 as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program. If not, see <https://www.gnu.org/licenses/>.
	*/

	#include <linux/sched.h>
	#include <linux/random.h>
	#include <linux/sbitmap.h>
	#include <linux/seq_file.h>

	int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
	gfp_t flags, int node)
	{
	unsigned int bits_per_word;
	unsigned int i;

	if (shift < 0) {
	shift = ilog2(BITS_PER_LONG);
	/*
	* If the bitmap is small, shrink the number of bits per word so
	* we spread over a few cachelines, at least. If less than 4
	* bits, just forget about it, it's not going to work optimally
	* anyway.
	*/
	if (depth >= 4) {
	while ((4U << shift) > depth)
	shift--;
	}
	}
	bits_per_word = 1U << shift;
	if (bits_per_word > BITS_PER_LONG)
	return -EINVAL;

	sb->shift = shift;
	sb->depth = depth;
	sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);

	if (depth == 0) {
	sb->map = NULL;
	return 0;
	}

	sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
	if (!sb->map)
	return -ENOMEM;

	for (i = 0; i < sb->map_nr; i++) {
	sb->map[i].depth = min(depth, bits_per_word);
	depth -= sb->map[i].depth;
	}
	return 0;
	}
	EXPORT_SYMBOL_GPL(sbitmap_init_node);

	void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
	{
	unsigned int bits_per_word = 1U << sb->shift;
	unsigned int i;

	sb->depth = depth;
	sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);

	for (i = 0; i < sb->map_nr; i++) {
	sb->map[i].depth = min(depth, bits_per_word);
	depth -= sb->map[i].depth;
	}
	}
	EXPORT_SYMBOL_GPL(sbitmap_resize);

	static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
	unsigned int hint, bool wrap)
	{
	unsigned int orig_hint = hint;
	int nr;

	while (1) {
	nr = find_next_zero_bit(word, depth, hint);
	if (unlikely(nr >= depth)) {
	/*
	* We started with an offset, and we didn't reset the
	* offset to 0 in a failure case, so start from 0 to
	* exhaust the map.
	*/
	if (orig_hint && hint && wrap) {
	hint = orig_hint = 0;
	continue;
	}
	return -1;
	}

	if (!test_and_set_bit(nr, word))
	break;

	hint = nr + 1;
	if (hint >= depth - 1)
	hint = 0;
	}

	return nr;
	}

	int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
	{
	unsigned int i, index;
	int nr = -1;

	index = SB_NR_TO_INDEX(sb, alloc_hint);

	for (i = 0; i < sb->map_nr; i++) {
	nr = __sbitmap_get_word(&sb->map[index].word,
	sb->map[index].depth,
	SB_NR_TO_BIT(sb, alloc_hint),
	!round_robin);
	if (nr != -1) {
	nr += index << sb->shift;
	break;
	}

	/* Jump to next index. */
	index++;
	alloc_hint = index << sb->shift;

	if (index >= sb->map_nr) {
	index = 0;
	alloc_hint = 0;
	}
	}

	return nr;
	}
	EXPORT_SYMBOL_GPL(sbitmap_get);

	int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
	unsigned long shallow_depth)
	{
	unsigned int i, index;
	int nr = -1;

	index = SB_NR_TO_INDEX(sb, alloc_hint);

	for (i = 0; i < sb->map_nr; i++) {
	nr = __sbitmap_get_word(&sb->map[index].word,
	min(sb->map[index].depth, shallow_depth),
	SB_NR_TO_BIT(sb, alloc_hint), true);
	if (nr != -1) {
	nr += index << sb->shift;
	break;
	}

	/* Jump to next index. */
	index++;
	alloc_hint = index << sb->shift;

	if (index >= sb->map_nr) {
	index = 0;
	alloc_hint = 0;
	}
	}

	return nr;
	}
	EXPORT_SYMBOL_GPL(sbitmap_get_shallow);

	bool sbitmap_any_bit_set(const struct sbitmap *sb)
	{
	unsigned int i;

	for (i = 0; i < sb->map_nr; i++) {
	if (sb->map[i].word)
	return true;
	}
	return false;
	}
	EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);

	bool sbitmap_any_bit_clear(const struct sbitmap *sb)
	{
	unsigned int i;

	for (i = 0; i < sb->map_nr; i++) {
	const struct sbitmap_word *word = &sb->map[i];
	unsigned long ret;

	ret = find_first_zero_bit(&word->word, word->depth);
	if (ret < word->depth)
	return true;
	}
	return false;
	}
	EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear);

	unsigned int sbitmap_weight(const struct sbitmap *sb)
	{
	unsigned int i, weight = 0;

	for (i = 0; i < sb->map_nr; i++) {
	const struct sbitmap_word *word = &sb->map[i];

	weight += bitmap_weight(&word->word, word->depth);
	}
	return weight;
	}
	EXPORT_SYMBOL_GPL(sbitmap_weight);

	void sbitmap_show(struct sbitmap sb, struct seq_file m)
	{
	seq_printf(m, "depth=%u\n", sb->depth);
	seq_printf(m, "busy=%u\n", sbitmap_weight(sb));
	seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
	seq_printf(m, "map_nr=%u\n", sb->map_nr);
	}
	EXPORT_SYMBOL_GPL(sbitmap_show);

	static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
	{
	if ((offset & 0xf) == 0) {
	if (offset != 0)
	seq_putc(m, '\n');
	seq_printf(m, "%08x:", offset);
	}
	if ((offset & 0x1) == 0)
	seq_putc(m, ' ');
	seq_printf(m, "%02x", byte);
	}

	void sbitmap_bitmap_show(struct sbitmap sb, struct seq_file m)
	{
	u8 byte = 0;
	unsigned int byte_bits = 0;
	unsigned int offset = 0;
	int i;

	for (i = 0; i < sb->map_nr; i++) {
	unsigned long word = READ_ONCE(sb->map[i].word);
	unsigned int word_bits = READ_ONCE(sb->map[i].depth);

	while (word_bits > 0) {
	unsigned int bits = min(8 - byte_bits, word_bits);

	byte \|= (word & (BIT(bits) - 1)) << byte_bits;
	byte_bits += bits;
	if (byte_bits == 8) {
	emit_byte(m, offset, byte);
	byte = 0;
	byte_bits = 0;
	offset++;
	}
	word >>= bits;
	word_bits -= bits;
	}
	}
	if (byte_bits) {
	emit_byte(m, offset, byte);
	offset++;
	}
	if (offset)
	seq_putc(m, '\n');
	}
	EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);

	static unsigned int sbq_calc_wake_batch(unsigned int depth)
	{
	unsigned int wake_batch;

	/*
	* For each batch, we wake up one queue. We need to make sure that our
	* batch size is small enough that the full depth of the bitmap is
	* enough to wake up all of the queues.
	*/
	wake_batch = SBQ_WAKE_BATCH;
	if (wake_batch > depth / SBQ_WAIT_QUEUES)
	wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);

	return wake_batch;
	}

	int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
	int shift, bool round_robin, gfp_t flags, int node)
	{
	int ret;
	int i;

	ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
	if (ret)
	return ret;

	sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
	if (!sbq->alloc_hint) {
	sbitmap_free(&sbq->sb);
	return -ENOMEM;
	}

	if (depth && !round_robin) {
	for_each_possible_cpu(i)
	*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
	}

	sbq->wake_batch = sbq_calc_wake_batch(depth);
	atomic_set(&sbq->wake_index, 0);

	sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
	if (!sbq->ws) {
	free_percpu(sbq->alloc_hint);
	sbitmap_free(&sbq->sb);
	return -ENOMEM;
	}

	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
	init_waitqueue_head(&sbq->ws[i].wait);
	atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
	}

	sbq->round_robin = round_robin;
	return 0;
	}
	EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);

	void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
	{
	unsigned int wake_batch = sbq_calc_wake_batch(depth);
	int i;

	if (sbq->wake_batch != wake_batch) {
	WRITE_ONCE(sbq->wake_batch, wake_batch);
	/*
	* Pairs with the memory barrier in sbq_wake_up() to ensure that
	* the batch size is updated before the wait counts.
	*/
	smp_mb__before_atomic();
	for (i = 0; i < SBQ_WAIT_QUEUES; i++)
	atomic_set(&sbq->ws[i].wait_cnt, 1);
	}
	sbitmap_resize(&sbq->sb, depth);
	}
	EXPORT_SYMBOL_GPL(sbitmap_queue_resize);

	int __sbitmap_queue_get(struct sbitmap_queue *sbq)
	{
	unsigned int hint, depth;
	int nr;

	hint = this_cpu_read(*sbq->alloc_hint);
	depth = READ_ONCE(sbq->sb.depth);
	if (unlikely(hint >= depth)) {
	hint = depth ? prandom_u32() % depth : 0;
	this_cpu_write(*sbq->alloc_hint, hint);
	}
	nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);

	if (nr == -1) {
	/* If the map is full, a hint won't do us much good. */
	this_cpu_write(*sbq->alloc_hint, 0);
	} else if (nr == hint \|\| unlikely(sbq->round_robin)) {
	/* Only update the hint if we used it. */
	hint = nr + 1;
	if (hint >= depth - 1)
	hint = 0;
	this_cpu_write(*sbq->alloc_hint, hint);
	}

	return nr;
	}
	EXPORT_SYMBOL_GPL(__sbitmap_queue_get);

	int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
	unsigned int shallow_depth)
	{
	unsigned int hint, depth;
	int nr;

	hint = this_cpu_read(*sbq->alloc_hint);
	depth = READ_ONCE(sbq->sb.depth);
	if (unlikely(hint >= depth)) {
	hint = depth ? prandom_u32() % depth : 0;
	this_cpu_write(*sbq->alloc_hint, hint);
	}
	nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);

	if (nr == -1) {
	/* If the map is full, a hint won't do us much good. */
	this_cpu_write(*sbq->alloc_hint, 0);
	} else if (nr == hint \|\| unlikely(sbq->round_robin)) {
	/* Only update the hint if we used it. */
	hint = nr + 1;
	if (hint >= depth - 1)
	hint = 0;
	this_cpu_write(*sbq->alloc_hint, hint);
	}

	return nr;
	}
	EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);

	static struct sbq_wait_state sbq_wake_ptr(struct sbitmap_queue sbq)
	{
	int i, wake_index;

	wake_index = atomic_read(&sbq->wake_index);
	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
	struct sbq_wait_state *ws = &sbq->ws[wake_index];

	if (waitqueue_active(&ws->wait)) {
	int o = atomic_read(&sbq->wake_index);

	if (wake_index != o)
	atomic_cmpxchg(&sbq->wake_index, o, wake_index);
	return ws;
	}

	wake_index = sbq_index_inc(wake_index);
	}

	return NULL;
	}

	static void sbq_wake_up(struct sbitmap_queue *sbq)
	{
	struct sbq_wait_state *ws;
	unsigned int wake_batch;
	int wait_cnt;

	/*
	* Pairs with the memory barrier in set_current_state() to ensure the
	* proper ordering of clear_bit()/waitqueue_active() in the waker and
	* test_and_set_bit()/prepare_to_wait()/finish_wait() in the waiter. See
	* the comment on waitqueue_active(). This is __after_atomic because we
	* just did clear_bit() in the caller.
	*/
	smp_mb__after_atomic();

	ws = sbq_wake_ptr(sbq);
	if (!ws)
	return;

	wait_cnt = atomic_dec_return(&ws->wait_cnt);
	if (wait_cnt <= 0) {
	wake_batch = READ_ONCE(sbq->wake_batch);
	/*
	* Pairs with the memory barrier in sbitmap_queue_resize() to
	* ensure that we see the batch size update before the wait
	* count is reset.
	*/
	smp_mb__before_atomic();
	/*
	* If there are concurrent callers to sbq_wake_up(), the last
	* one to decrement the wait count below zero will bump it back
	* up. If there is a concurrent resize, the count reset will
	* either cause the cmpxchg to fail or overwrite after the
	* cmpxchg.
	*/
	atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wait_cnt + wake_batch);
	sbq_index_atomic_inc(&sbq->wake_index);
	wake_up_nr(&ws->wait, wake_batch);
	}
	}

	void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
	unsigned int cpu)
	{
	sbitmap_clear_bit(&sbq->sb, nr);
	sbq_wake_up(sbq);
	if (likely(!sbq->round_robin && nr < sbq->sb.depth))
	*per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
	}
	EXPORT_SYMBOL_GPL(sbitmap_queue_clear);

	void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
	{
	int i, wake_index;

	/*
	* Pairs with the memory barrier in set_current_state() like in
	* sbq_wake_up().
	*/
	smp_mb();
	wake_index = atomic_read(&sbq->wake_index);
	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
	struct sbq_wait_state *ws = &sbq->ws[wake_index];

	if (waitqueue_active(&ws->wait))
	wake_up(&ws->wait);

	wake_index = sbq_index_inc(wake_index);
	}
	}
	EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);

	void sbitmap_queue_show(struct sbitmap_queue sbq, struct seq_file m)
	{
	bool first;
	int i;

	sbitmap_show(&sbq->sb, m);

	seq_puts(m, "alloc_hint={");
	first = true;
	for_each_possible_cpu(i) {
	if (!first)
	seq_puts(m, ", ");
	first = false;
	seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i));
	}
	seq_puts(m, "}\n");

	seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
	seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));

	seq_puts(m, "ws={\n");
	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
	struct sbq_wait_state *ws = &sbq->ws[i];

	seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n",
	atomic_read(&ws->wait_cnt),
	waitqueue_active(&ws->wait) ? "active" : "inactive");
	}
	seq_puts(m, "}\n");

	seq_printf(m, "round_robin=%d\n", sbq->round_robin);
	}
	EXPORT_SYMBOL_GPL(sbitmap_queue_show);