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/*
* 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/random.h>
#include <linux/sbitmap.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(struct sbitmap_word *word, unsigned int hint,
bool wrap)
{
unsigned int orig_hint = hint;
int nr;
while (1) {
nr = find_next_zero_bit(&word->word, word->depth, hint);
if (unlikely(nr >= word->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->word))
break;
hint = nr + 1;
if (hint >= word->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],
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);
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);
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)
{
sbq->wake_batch = sbq_calc_wake_batch(depth);
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);
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;
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 (unlikely(wait_cnt < 0))
wait_cnt = atomic_inc_return(&ws->wait_cnt);
if (wait_cnt == 0) {
atomic_add(sbq->wake_batch, &ws->wait_cnt);
sbq_index_atomic_inc(&sbq->wake_index);
wake_up(&ws->wait);
}
}
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);
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