// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2016 Facebook
* Copyright (C) 2013-2014 Jens Axboe
*/
#include <linux/sched.h>
#include <linux/random.h>
#include <linux/sbitmap.h>
#include <linux/seq_file.h>
static int init_alloc_hint(struct sbitmap *sb, gfp_t flags)
{
unsigned depth = sb->depth;
sb->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
if (!sb->alloc_hint)
return -ENOMEM;
if (depth && !sb->round_robin) {
int i;
for_each_possible_cpu(i)
*per_cpu_ptr(sb->alloc_hint, i) = get_random_u32_below(depth);
}
return 0;
}
static inline unsigned update_alloc_hint_before_get(struct sbitmap *sb,
unsigned int depth)
{
unsigned hint;
hint = this_cpu_read(*sb->alloc_hint);
if (unlikely(hint >= depth)) {
hint = depth ? get_random_u32_below(depth) : 0;
this_cpu_write(*sb->alloc_hint, hint);
}
return hint;
}
static inline void update_alloc_hint_after_get(struct sbitmap *sb,
unsigned int depth,
unsigned int hint,
unsigned int nr)
{
if (nr == -1) {
/* If the map is full, a hint won't do us much good. */
this_cpu_write(*sb->alloc_hint, 0);
} else if (nr == hint || unlikely(sb->round_robin)) {
/* Only update the hint if we used it. */
hint = nr + 1;
if (hint >= depth - 1)
hint = 0;
this_cpu_write(*sb->alloc_hint, hint);
}
}
/*
* See if we have deferred clears that we can batch move
*/
static inline bool sbitmap_deferred_clear(struct sbitmap_word *map,
unsigned int depth, unsigned int alloc_hint, bool wrap)
{
unsigned long mask, word_mask;
guard(raw_spinlock_irqsave)(&map->swap_lock);
if (!map->cleared) {
if (depth == 0)
return false;
word_mask = (~0UL) >> (BITS_PER_LONG - depth);
/*
* The current behavior is to always retry after moving
* ->cleared to word, and we change it to retry in case
* of any free bits. To avoid an infinite loop, we need
* to take wrap & alloc_hint into account, otherwise a
* soft lockup may occur.
*/
if (!wrap && alloc_hint)
word_mask &= ~((1UL << alloc_hint) - 1);
return (READ_ONCE(map->word) & word_mask) != word_mask;
}
/*
* First get a stable cleared mask, setting the old mask to 0.
*/
mask = xchg(&map->cleared, 0);
/*
* Now clear the masked bits in our free word
*/
atomic_long_andnot(mask, (atomic_long_t *)&map->word);
BUILD_BUG_ON(sizeof(atomic_long_t) != sizeof(map->word));
return true;
}
int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
gfp_t flags, int node, bool round_robin,
bool alloc_hint)
{
unsigned int bits_per_word;
int i;
if (shift < 0)
shift = sbitmap_calculate_shift(depth);
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);
sb->round_robin = round_robin;
if (depth == 0) {
sb->map = NULL;
return 0;
}
if (alloc_hint) {
if (init_alloc_hint(sb, flags))
return -ENOMEM;
} else {
sb->alloc_hint = NULL;
}
sb->map = kvzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
if (!sb->map) {
free_percpu(sb->alloc_hint);
return -ENOMEM;
}
for (i = 0; i < sb->map_nr; i++)
raw_spin_lock_init(&sb->map[i].swap_lock);
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;
for (i = 0; i < sb->map_nr; i++)
sbitmap_deferred_clear(&sb->map[i], 0, 0, 0);
sb->depth = depth;
sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
}
EXPORT_SYMBOL_GPL(sbitmap_resize);
static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
unsigned int hint, bool wrap)
{
int nr;
/* don't wrap if starting from 0 */
wrap = wrap && hint;
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 (hint && wrap) {
hint = 0;
continue;
}
return -1;
}
if (!test_and_set_bit_lock(nr, word))
break;
hint = nr + 1;
if (hint >= depth - 1)
hint = 0;
}
return nr;
}
static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
unsigned int depth,
unsigned int alloc_hint,
bool wrap)
{
int nr;
do {
nr = __sbitmap_get_word(&map->word, depth,
alloc_hint, wrap);
if (nr != -1)
break;
if (!sbitmap_deferred_clear(map, depth, alloc_hint, wrap))
break;
} while (1);
return nr;
}
static int sbitmap_find_bit(struct sbitmap *sb,
unsigned int depth,
unsigned int index,
unsigned int alloc_hint,
bool wrap)
{
unsigned int i;
int nr = -1;
for (i = 0; i < sb->map_nr; i++) {
nr = sbitmap_find_bit_in_word(&sb->map[index],
min_t(unsigned int,
__map_depth(sb, index),
depth),
alloc_hint, wrap);
if (nr != -1) {
nr += index << sb->shift;
break;
}
/* Jump to next index. */
alloc_hint = 0;
if (++index >= sb->map_nr)
index = 0;
}
return nr;
}
static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
{
unsigned int index;
index = SB_NR_TO_INDEX(sb, alloc_hint);
/*
* Unless we're doing round robin tag allocation, just use the
* alloc_hint to find the right word index. No point in looping
* twice in find_next_zero_bit() for that case.
*/
if (sb->round_robin)
alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
else
alloc_hint = 0;
return sbitmap_find_bit(sb, UINT_MAX, index, alloc_hint,
!sb->round_robin);
}
int sbitmap_get(struct sbitmap *sb)
{
int nr;
unsigned int hint, depth;
if (WARN_ON_ONCE(unlikely(!sb->alloc_hint)))
return -1;
depth = READ_ONCE(sb->depth);
hint = update_alloc_hint_before_get(sb, depth);
nr = __sbitmap_get(sb, hint);
update_alloc_hint_after_get(sb, depth, hint, nr);
return nr;
}
EXPORT_SYMBOL_GPL(sbitmap_get);
static int __sbitmap_get_shallow(struct sbitmap *sb,
unsigned int alloc_hint,
unsigned long shallow_depth)
{
unsigned int index;
index = SB_NR_TO_INDEX(sb, alloc_hint);
alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
return sbitmap_find_bit(sb, shallow_depth, index, alloc_hint, true);
}
int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth)
{
int nr;
unsigned int hint, depth;
if (WARN_ON_ONCE(unlikely(!sb->alloc_hint)))
return -1;
depth = READ_ONCE(sb->depth);
hint = update_alloc_hint_before_get(sb, depth);
nr = __sbitmap_get_shallow(sb, hint, shallow_depth);
update_alloc_hint_after_get(sb, depth, hint, nr);
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 & ~sb->map[i].cleared)
return true;
}
return false;
}
EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
{
unsigned int i, weight = 0;
for (i = 0; i < sb->map_nr; i++) {
const struct sbitmap_word *word = &sb->map[i];
unsigned int word_depth = __map_depth(sb, i);
if (set)
weight += bitmap_weight(&word->word, word_depth);
else
weight += bitmap_weight(&word->cleared, word_depth);
}
return weight;
}
static unsigned int sbitmap_cleared(const struct sbitmap *sb)
{
return __sbitmap_weight(sb, false);
}
unsigned int sbitmap_weight(const struct sbitmap *sb)
{
return __sbitmap_weight(sb, true) - sbitmap_cleared(sb);
}
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, "cleared=%u\n", sbitmap_cleared(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 long cleared = READ_ONCE(sb->map[i].cleared);
unsigned int word_bits = __map_depth(sb, i);
word &= ~cleared;
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(struct sbitmap_queue *sbq,
unsigned int depth)
{
unsigned int wake_batch;
unsigned int shallow_depth;
/*
* Each full word of the bitmap has bits_per_word bits, and there might
* be a partial word. There are depth / bits_per_word full words and
* depth % bits_per_word bits left over. In bitwise arithmetic:
*
* bits_per_word = 1 << shift
* depth / bits_per_word = depth >> shift
* depth % bits_per_word = depth & ((1 << shift) - 1)
*
* Each word can be limited to sbq->min_shallow_depth bits.
*/
shallow_depth = min(1U << sbq->sb.shift, sbq->min_shallow_depth);
depth = ((depth >> sbq->sb.shift) * shallow_depth +
min(depth & ((1U << sbq->sb.shift) - 1), shallow_depth));
wake_batch = clamp_t(unsigned int, depth / SBQ_WAIT_QUEUES, 1,
SBQ_WAKE_BATCH);
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,
round_robin, true);
if (ret)
return ret;
sbq->min_shallow_depth = UINT_MAX;
sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
atomic_set(&sbq->wake_index, 0);
atomic_set(&sbq->ws_active, 0);
atomic_set(&sbq->completion_cnt, 0);
atomic_set(&sbq->wakeup_cnt, 0);
sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
if (!sbq->ws) {
sbitmap_free(&sbq->sb);
return -ENOMEM;
}
for (i = 0; i < SBQ_WAIT_QUEUES; i++)
init_waitqueue_head(&sbq->ws[i].wait);
return 0;
}
EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
unsigned int depth)
{
unsigned int wake_batch;
wake_batch = sbq_calc_wake_batch(sbq, depth);
if (sbq->wake_batch != wake_batch)
WRITE_ONCE(sbq->wake_batch, wake_batch);
}
void sbitmap_queue_recalculate_wake_batch(struct sbitmap_queue *sbq,
unsigned int users)
{
unsigned int wake_batch;
unsigned int depth = (sbq->sb.depth + users - 1) / users;
wake_batch = clamp_val(depth / SBQ_WAIT_QUEUES,
1, SBQ_WAKE_BATCH);
WRITE_ONCE(sbq->wake_batch, wake_batch);
}
EXPORT_SYMBOL_GPL(sbitmap_queue_recalculate_wake_batch);
void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
{
sbitmap_queue_update_wake_batch(sbq, depth);
sbitmap_resize(&sbq->sb, depth);
}
EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
int __sbitmap_queue_get(struct sbitmap_queue *sbq)
{
return sbitmap_get(&sbq->sb);
}
EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
unsigned int *offset)
{
struct sbitmap *sb = &sbq->sb;
unsigned int hint, depth;
unsigned long index, nr;
int i;
if (unlikely(sb->round_robin))
return 0;
depth = READ_ONCE(sb->depth);
hint = update_alloc_hint_before_get(sb, depth);
index = SB_NR_TO_INDEX(sb, hint);
for (i = 0; i < sb->map_nr; i++) {
struct sbitmap_word *map = &sb->map[index];
unsigned long get_mask;
unsigned int map_depth = __map_depth(sb, index);
unsigned long val;
sbitmap_deferred_clear(map, 0, 0, 0);
val = READ_ONCE(map->word);
if (val == (1UL << (map_depth - 1)) - 1)
goto next;
nr = find_first_zero_bit(&val, map_depth);
if (nr + nr_tags <= map_depth) {
atomic_long_t *ptr = (atomic_long_t *) &map->word;
get_mask = ((1UL << nr_tags) - 1) << nr;
while (!atomic_long_try_cmpxchg(ptr, &val,
get_mask | val))
;
get_mask = (get_mask & ~val) >> nr;
if (get_mask) {
*offset = nr + (index << sb->shift);
update_alloc_hint_after_get(sb, depth, hint,
*offset + nr_tags - 1);
return get_mask;
}
}
next:
/* Jump to next index. */
if (++index >= sb->map_nr)
index = 0;
}
return 0;
}
int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
unsigned int shallow_depth)
{
WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
return sbitmap_get_shallow(&sbq->sb, shallow_depth);
}
EXPORT_SYMBOL_GPL(sbitmap_queue_get_shallow);
void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
unsigned int min_shallow_depth)
{
sbq->min_shallow_depth = min_shallow_depth;
sbitmap_queue_update_wake_batch(sbq, sbq->sb.depth);
}
EXPORT_SYMBOL_GPL(sbitmap_queue_min_shallow_depth);
static void __sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr)
{
int i, wake_index, woken;
if (!atomic_read(&sbq->ws_active))
return;
wake_index = atomic_read(&sbq->wake_index);
for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
struct sbq_wait_state *ws = &sbq->ws[wake_index];
/*
* Advance the index before checking the current queue.
* It improves fairness, by ensuring the queue doesn't
* need to be fully emptied before trying to wake up
* from the next one.
*/
wake_index = sbq_index_inc(wake_index);
if (waitqueue_active(&ws->wait)) {
woken = wake_up_nr(&ws->wait, nr);
if (woken == nr)
break;
nr -= woken;
}
}
if (wake_index != atomic_read(&sbq->wake_index))
atomic_set(&sbq->wake_index, wake_index);
}
void sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr)
{
unsigned int wake_batch = READ_ONCE(sbq->wake_batch);
unsigned int wakeups;
if (!atomic_read(&sbq->ws_active))
return;
atomic_add(nr, &sbq->completion_cnt);
wakeups = atomic_read(&sbq->wakeup_cnt);
do {
if (atomic_read(&sbq->completion_cnt) - wakeups < wake_batch)
return;
} while (!atomic_try_cmpxchg(&sbq->wakeup_cnt,
&wakeups, wakeups + wake_batch));
__sbitmap_queue_wake_up(sbq, wake_batch);
}
EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
static inline void sbitmap_update_cpu_hint(struct sbitmap *sb, int cpu, int tag)
{
if (likely(!sb->round_robin && tag < sb->depth))
data_race(*per_cpu_ptr(sb->alloc_hint, cpu) = tag);
}
void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
int *tags, int nr_tags)
{
struct sbitmap *sb = &sbq->sb;
unsigned long *addr = NULL;
unsigned long mask = 0;
int i;
smp_mb__before_atomic();
for (i = 0; i < nr_tags; i++) {
const int tag = tags[i] - offset;
unsigned long *this_addr;
/* since we're clearing a batch, skip the deferred map */
this_addr = &sb->map[SB_NR_TO_INDEX(sb, tag)].word;
if (!addr) {
addr = this_addr;
} else if (addr != this_addr) {
atomic_long_andnot(mask, (atomic_long_t *) addr);
mask = 0;
addr = this_addr;
}
mask |= (1UL << SB_NR_TO_BIT(sb, tag));
}
if (mask)
atomic_long_andnot(mask, (atomic_long_t *) addr);
smp_mb__after_atomic();
sbitmap_queue_wake_up(sbq, nr_tags);
sbitmap_update_cpu_hint(&sbq->sb, raw_smp_processor_id(),
tags[nr_tags - 1] - offset);
}
void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
unsigned int cpu)
{
/*
* Once the clear bit is set, the bit may be allocated out.
*
* Orders READ/WRITE on the associated instance(such as request
* of blk_mq) by this bit for avoiding race with re-allocation,
* and its pair is the memory barrier implied in __sbitmap_get_word.
*
* One invariant is that the clear bit has to be zero when the bit
* is in use.
*/
smp_mb__before_atomic();
sbitmap_deferred_clear_bit(&sbq->sb, nr);
/*
* Pairs with the memory barrier in set_current_state() to ensure the
* proper ordering of clear_bit_unlock()/waitqueue_active() in the waker
* and test_and_set_bit_lock()/prepare_to_wait()/finish_wait() in the
* waiter. See the comment on waitqueue_active().
*/
smp_mb__after_atomic();
sbitmap_queue_wake_up(sbq, 1);
sbitmap_update_cpu_hint(&sbq->sb, 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
* sbitmap_queue_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->sb.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_printf(m, "ws_active=%d\n", atomic_read(&sbq->ws_active));
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=%s},\n",
waitqueue_active(&ws->wait) ? "active" : "inactive");
}
seq_puts(m, "}\n");
seq_printf(m, "round_robin=%d\n", sbq->sb.round_robin);
seq_printf(m, "min_shallow_depth=%u\n", sbq->min_shallow_depth);
}
EXPORT_SYMBOL_GPL(sbitmap_queue_show);
void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
struct sbq_wait_state *ws,
struct sbq_wait *sbq_wait)
{
if (!sbq_wait->sbq) {
sbq_wait->sbq = sbq;
atomic_inc(&sbq->ws_active);
add_wait_queue(&ws->wait, &sbq_wait->wait);
}
}
EXPORT_SYMBOL_GPL(sbitmap_add_wait_queue);
void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait)
{
list_del_init(&sbq_wait->wait.entry);
if (sbq_wait->sbq) {
atomic_dec(&sbq_wait->sbq->ws_active);
sbq_wait->sbq = NULL;
}
}
EXPORT_SYMBOL_GPL(sbitmap_del_wait_queue);
void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
struct sbq_wait_state *ws,
struct sbq_wait *sbq_wait, int state)
{
if (!sbq_wait->sbq) {
atomic_inc(&sbq->ws_active);
sbq_wait->sbq = sbq;
}
prepare_to_wait_exclusive(&ws->wait, &sbq_wait->wait, state);
}
EXPORT_SYMBOL_GPL(sbitmap_prepare_to_wait);
void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
struct sbq_wait *sbq_wait)
{
finish_wait(&ws->wait, &sbq_wait->wait);
if (sbq_wait->sbq) {
atomic_dec(&sbq->ws_active);
sbq_wait->sbq = NULL;
}
}
EXPORT_SYMBOL_GPL(sbitmap_finish_wait);
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