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Release 4.14 include/linux/sbitmap.h

Directory: include/linux
/*
 * Fast and scalable bitmaps.
 *
 * 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/>.
 */

#ifndef __LINUX_SCALE_BITMAP_H

#define __LINUX_SCALE_BITMAP_H

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

/**
 * struct sbitmap_word - Word in a &struct sbitmap.
 */

struct sbitmap_word {
	/**
         * @word: The bitmap word itself.
         */
	
unsigned long word;

	/**
         * @depth: Number of bits being used in @word.
         */
	
unsigned long depth;

} ____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;

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

/**
 * 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; }

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/** * 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). * * 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); /** * sbitmap_any_bit_clear() - Check for an unset bit in a &struct * sbitmap. * @sb: Bitmap to check. * * Return: true if any bit in the bitmap is clear, false otherwise. */ bool sbitmap_any_bit_clear(const struct sbitmap *sb); typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *); /** * 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. * * 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, sb_for_each_fn fn, void *data) { unsigned int i; for (i = 0; i < sb->map_nr; i++) { struct sbitmap_word *word = &sb->map[i]; unsigned int off, nr; if (!word->word) continue; nr = 0; off = i << sb->shift; while (1) { nr = find_next_bit(&word->word, word->depth, nr); if (nr >= word->depth) break; if (!fn(sb, off + nr, data)) return; nr++; } } }

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#define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift) #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
static inline unsigned long *__sbitmap_word(struct sbitmap *sb, unsigned int bitnr) { return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word; }

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/* 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)); }

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

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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)); }

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unsigned int sbitmap_weight(const struct sbitmap *sb); /** * 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); }

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/** * 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(). * * 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; }

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/** * 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(). * * 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; }

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/** * 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); }

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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); }

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/** * 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; }

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/** * 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_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); #endif /* __LINUX_SCALE_BITMAP_H */

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Directory: include/linux
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