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products/sources/formale Sprachen/C/Linux/include/linux/ (Open Source Betriebssystem Version 6.17.9^©) Datei vom 24.10.2025 mit Größe 17 kB

Quelle sbitmap.h Sprache: C

/* 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/atomic.h>
#include <linux/bitops.h>
#include <linux/cache.h>
#include <linux/list.h>
#include <linux/log2.h>
#include <linux/minmax.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/types.h>
#include <linux/wait.h>

struct seq_file;

/**
* struct sbitmap_word - Word in a &struct sbitmap.
*/
struct sbitmap_word {
/**
* @word: word holding free bits
*/
unsigned long word;

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

/**
* @swap_lock: serializes simultaneous updates of ->word and ->cleared
*/
raw_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;

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

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

/*
* @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;
};

#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: 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;

/**
* @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;

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

/**
* @completion_cnt: Number of bits cleared passed to the
* wakeup function.
*/
atomic_t completion_cnt;

/**
* @wakeup_cnt: Number of thread wake ups issued.
*/
atomic_t wakeup_cnt;
};

/**
* 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.
* @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).
* @alloc_hint: If true, apply percpu hint for where to start searching for
*              a free bit.
*
* 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, bool round_robin, bool alloc_hint);

/* sbitmap internal helper */
static inline unsigned int __map_depth(const struct sbitmap *sb, int index)
{
if (index == sb->map_nr - 1)
  return sb->depth - (index << sb->shift);
return 1U << sb->shift;
}

/**
* sbitmap_free() - Free memory used by a &struct sbitmap.
* @sb: Bitmap to free.
*/
static inline void sbitmap_free(struct sbitmap *sb)
{
free_percpu(sb->alloc_hint);
kvfree(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.
*
* 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);

/**
* 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,
        __map_depth(sb, index) - 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);
}

/*
* Pair of sbitmap_get, and this one applies both cleared bit and
* allocation hint.
*/
static inline void sbitmap_put(struct sbitmap *sb, unsigned int bitnr)
{
sbitmap_deferred_clear_bit(sb, bitnr);

if (likely(sb->alloc_hint && !sb->round_robin && bitnr < sb->depth))
  *raw_cpu_ptr(sb->alloc_hint) = 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));
}

static inline int sbitmap_calculate_shift(unsigned int depth)
{
int 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--;
}

return shift;
}

/**
* 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_weight() - Return how many set and not cleared bits in a &struct
* sbitmap.
* @sb: Bitmap to check.
*
* Return: How many set and not cleared bits set
*/
unsigned int sbitmap_weight(const struct sbitmap *sb);

/**
* 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);
sbitmap_free(&sbq->sb);
}

/**
* sbitmap_queue_recalculate_wake_batch() - Recalculate wake batch
* @sbq: Bitmap queue to recalculate wake batch.
* @users: Number of shares.
*
* Like sbitmap_queue_update_wake_batch(), this will calculate wake batch
* by depth. This interface is for HCTX shared tags or queue shared tags.
*/
void sbitmap_queue_recalculate_wake_batch(struct sbitmap_queue *sbq,
         unsigned int users);

/**
* 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_batch() - Try to allocate a batch of free bits
* @sbq: Bitmap queue to allocate from.
* @nr_tags: number of tags requested
* @offset: offset to add to returned bits
*
* Return: Mask of allocated tags, 0 if none are found. Each tag allocated is
* a bit in the mask returned, and the caller must add @offset to the value to
* get the absolute tag value.
*/
unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
     unsigned int *offset);

/**
* 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 the queue.
* 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_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);

/**
* sbitmap_queue_clear_batch() - Free a batch of allocated bits
* &struct sbitmap_queue.
* @sbq: Bitmap to free from.
* @offset: offset for each tag in array
* @tags: array of tags
* @nr_tags: number of tags in array
*/
void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
    int *tags, int nr_tags);

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.
* @nr: Number of bits cleared.
*/
void sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr);

/**
* 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 */

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