linux/block/blk-stat.c
Jens Axboe a83b576c9c block: fix stacked driver stats init and free
If a driver allocates a queue for stacked usage, then it does
not currently get stats allocated. This causes the later init
of, eg, writeback throttling to blow up. Move the init to the
queue allocation instead.

Additionally, allow a NULL callback unregistration. This avoids
having the caller check for that, fixing another oops on
removal of a block device that doesn't have poll stats allocated.

Fixes: 34dbad5d26 ("blk-stat: convert to callback-based statistics reporting")
Signed-off-by: Jens Axboe <axboe@fb.com>
2017-03-21 17:20:01 -06:00

241 lines
5.2 KiB
C

/*
* Block stat tracking code
*
* Copyright (C) 2016 Jens Axboe
*/
#include <linux/kernel.h>
#include <linux/rculist.h>
#include <linux/blk-mq.h>
#include "blk-stat.h"
#include "blk-mq.h"
#define BLK_RQ_STAT_BATCH 64
struct blk_queue_stats {
struct list_head callbacks;
spinlock_t lock;
};
unsigned int blk_stat_rq_ddir(const struct request *rq)
{
return rq_data_dir(rq);
}
EXPORT_SYMBOL_GPL(blk_stat_rq_ddir);
static void blk_stat_init(struct blk_rq_stat *stat)
{
stat->min = -1ULL;
stat->max = stat->nr_samples = stat->mean = 0;
stat->batch = stat->nr_batch = 0;
}
static void blk_stat_flush_batch(struct blk_rq_stat *stat)
{
const s32 nr_batch = READ_ONCE(stat->nr_batch);
const s32 nr_samples = READ_ONCE(stat->nr_samples);
if (!nr_batch)
return;
if (!nr_samples)
stat->mean = div64_s64(stat->batch, nr_batch);
else {
stat->mean = div64_s64((stat->mean * nr_samples) +
stat->batch,
nr_batch + nr_samples);
}
stat->nr_samples += nr_batch;
stat->nr_batch = stat->batch = 0;
}
static void blk_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
{
blk_stat_flush_batch(src);
if (!src->nr_samples)
return;
dst->min = min(dst->min, src->min);
dst->max = max(dst->max, src->max);
if (!dst->nr_samples)
dst->mean = src->mean;
else {
dst->mean = div64_s64((src->mean * src->nr_samples) +
(dst->mean * dst->nr_samples),
dst->nr_samples + src->nr_samples);
}
dst->nr_samples += src->nr_samples;
}
static void __blk_stat_add(struct blk_rq_stat *stat, u64 value)
{
stat->min = min(stat->min, value);
stat->max = max(stat->max, value);
if (stat->batch + value < stat->batch ||
stat->nr_batch + 1 == BLK_RQ_STAT_BATCH)
blk_stat_flush_batch(stat);
stat->batch += value;
stat->nr_batch++;
}
void blk_stat_add(struct request *rq)
{
struct request_queue *q = rq->q;
struct blk_stat_callback *cb;
struct blk_rq_stat *stat;
int bucket;
s64 now, value;
now = __blk_stat_time(ktime_to_ns(ktime_get()));
if (now < blk_stat_time(&rq->issue_stat))
return;
value = now - blk_stat_time(&rq->issue_stat);
rcu_read_lock();
list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
if (blk_stat_is_active(cb)) {
bucket = cb->bucket_fn(rq);
stat = &this_cpu_ptr(cb->cpu_stat)[bucket];
__blk_stat_add(stat, value);
}
}
rcu_read_unlock();
}
static void blk_stat_timer_fn(unsigned long data)
{
struct blk_stat_callback *cb = (void *)data;
unsigned int bucket;
int cpu;
for (bucket = 0; bucket < cb->buckets; bucket++)
blk_stat_init(&cb->stat[bucket]);
for_each_online_cpu(cpu) {
struct blk_rq_stat *cpu_stat;
cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
for (bucket = 0; bucket < cb->buckets; bucket++) {
blk_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
blk_stat_init(&cpu_stat[bucket]);
}
}
cb->timer_fn(cb);
}
struct blk_stat_callback *
blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
unsigned int (*bucket_fn)(const struct request *),
unsigned int buckets, void *data)
{
struct blk_stat_callback *cb;
cb = kmalloc(sizeof(*cb), GFP_KERNEL);
if (!cb)
return NULL;
cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
GFP_KERNEL);
if (!cb->stat) {
kfree(cb);
return NULL;
}
cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
__alignof__(struct blk_rq_stat));
if (!cb->cpu_stat) {
kfree(cb->stat);
kfree(cb);
return NULL;
}
cb->timer_fn = timer_fn;
cb->bucket_fn = bucket_fn;
cb->data = data;
cb->buckets = buckets;
setup_timer(&cb->timer, blk_stat_timer_fn, (unsigned long)cb);
return cb;
}
EXPORT_SYMBOL_GPL(blk_stat_alloc_callback);
void blk_stat_add_callback(struct request_queue *q,
struct blk_stat_callback *cb)
{
unsigned int bucket;
int cpu;
for_each_possible_cpu(cpu) {
struct blk_rq_stat *cpu_stat;
cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
for (bucket = 0; bucket < cb->buckets; bucket++)
blk_stat_init(&cpu_stat[bucket]);
}
spin_lock(&q->stats->lock);
list_add_tail_rcu(&cb->list, &q->stats->callbacks);
set_bit(QUEUE_FLAG_STATS, &q->queue_flags);
spin_unlock(&q->stats->lock);
}
EXPORT_SYMBOL_GPL(blk_stat_add_callback);
void blk_stat_remove_callback(struct request_queue *q,
struct blk_stat_callback *cb)
{
spin_lock(&q->stats->lock);
list_del_rcu(&cb->list);
if (list_empty(&q->stats->callbacks))
clear_bit(QUEUE_FLAG_STATS, &q->queue_flags);
spin_unlock(&q->stats->lock);
del_timer_sync(&cb->timer);
}
EXPORT_SYMBOL_GPL(blk_stat_remove_callback);
static void blk_stat_free_callback_rcu(struct rcu_head *head)
{
struct blk_stat_callback *cb;
cb = container_of(head, struct blk_stat_callback, rcu);
free_percpu(cb->cpu_stat);
kfree(cb->stat);
kfree(cb);
}
void blk_stat_free_callback(struct blk_stat_callback *cb)
{
if (cb)
call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
}
EXPORT_SYMBOL_GPL(blk_stat_free_callback);
struct blk_queue_stats *blk_alloc_queue_stats(void)
{
struct blk_queue_stats *stats;
stats = kmalloc(sizeof(*stats), GFP_KERNEL);
if (!stats)
return NULL;
INIT_LIST_HEAD(&stats->callbacks);
spin_lock_init(&stats->lock);
return stats;
}
void blk_free_queue_stats(struct blk_queue_stats *stats)
{
if (!stats)
return;
WARN_ON(!list_empty(&stats->callbacks));
kfree(stats);
}