kernel-ark/lib/sbitmap.c
Colin Ian King 60658e0dc1 sbitmap: initialize weight to zero
Variable weight is not being initialized to zero before it is
used to compute the weight sum. Ensure it is initialized to zero.

Found with static analysis with cppcheck:
[lib/sbitmap.c:177]: (error) Uninitialized variable: weight

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-19 08:19:40 -06:00

348 lines
7.9 KiB
C

/*
* 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;
/* Ensure that the wait list checks occur after clear_bit(). */
smp_mb();
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;
/*
* Make sure all changes prior to this are visible from other CPUs.
*/
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);