Revision 4942de4a0e914f205d351a81873f4f63986bcc3c authored by Linus Torvalds on 25 September 2007, 00:33:10 UTC, committed by Linus Torvalds on 25 September 2007, 00:33:10 UTC
Getting there...
1 parent e0b9d13
dm-delay.c
/*
* Copyright (C) 2005-2007 Red Hat GmbH
*
* A target that delays reads and/or writes and can send
* them to different devices.
*
* This file is released under the GPL.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/slab.h>
#include "dm.h"
#include "dm-bio-list.h"
#define DM_MSG_PREFIX "delay"
struct delay_c {
struct timer_list delay_timer;
struct mutex timer_lock;
struct work_struct flush_expired_bios;
struct list_head delayed_bios;
atomic_t may_delay;
mempool_t *delayed_pool;
struct dm_dev *dev_read;
sector_t start_read;
unsigned read_delay;
unsigned reads;
struct dm_dev *dev_write;
sector_t start_write;
unsigned write_delay;
unsigned writes;
};
struct dm_delay_info {
struct delay_c *context;
struct list_head list;
struct bio *bio;
unsigned long expires;
};
static DEFINE_MUTEX(delayed_bios_lock);
static struct workqueue_struct *kdelayd_wq;
static struct kmem_cache *delayed_cache;
static void handle_delayed_timer(unsigned long data)
{
struct delay_c *dc = (struct delay_c *)data;
queue_work(kdelayd_wq, &dc->flush_expired_bios);
}
static void queue_timeout(struct delay_c *dc, unsigned long expires)
{
mutex_lock(&dc->timer_lock);
if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
mod_timer(&dc->delay_timer, expires);
mutex_unlock(&dc->timer_lock);
}
static void flush_bios(struct bio *bio)
{
struct bio *n;
while (bio) {
n = bio->bi_next;
bio->bi_next = NULL;
generic_make_request(bio);
bio = n;
}
}
static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all)
{
struct dm_delay_info *delayed, *next;
unsigned long next_expires = 0;
int start_timer = 0;
BIO_LIST(flush_bios);
mutex_lock(&delayed_bios_lock);
list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
if (flush_all || time_after_eq(jiffies, delayed->expires)) {
list_del(&delayed->list);
bio_list_add(&flush_bios, delayed->bio);
if ((bio_data_dir(delayed->bio) == WRITE))
delayed->context->writes--;
else
delayed->context->reads--;
mempool_free(delayed, dc->delayed_pool);
continue;
}
if (!start_timer) {
start_timer = 1;
next_expires = delayed->expires;
} else
next_expires = min(next_expires, delayed->expires);
}
mutex_unlock(&delayed_bios_lock);
if (start_timer)
queue_timeout(dc, next_expires);
return bio_list_get(&flush_bios);
}
static void flush_expired_bios(struct work_struct *work)
{
struct delay_c *dc;
dc = container_of(work, struct delay_c, flush_expired_bios);
flush_bios(flush_delayed_bios(dc, 0));
}
/*
* Mapping parameters:
* <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
*
* With separate write parameters, the first set is only used for reads.
* Delays are specified in milliseconds.
*/
static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct delay_c *dc;
unsigned long long tmpll;
if (argc != 3 && argc != 6) {
ti->error = "requires exactly 3 or 6 arguments";
return -EINVAL;
}
dc = kmalloc(sizeof(*dc), GFP_KERNEL);
if (!dc) {
ti->error = "Cannot allocate context";
return -ENOMEM;
}
dc->reads = dc->writes = 0;
if (sscanf(argv[1], "%llu", &tmpll) != 1) {
ti->error = "Invalid device sector";
goto bad;
}
dc->start_read = tmpll;
if (sscanf(argv[2], "%u", &dc->read_delay) != 1) {
ti->error = "Invalid delay";
goto bad;
}
if (dm_get_device(ti, argv[0], dc->start_read, ti->len,
dm_table_get_mode(ti->table), &dc->dev_read)) {
ti->error = "Device lookup failed";
goto bad;
}
if (argc == 3) {
dc->dev_write = NULL;
goto out;
}
if (sscanf(argv[4], "%llu", &tmpll) != 1) {
ti->error = "Invalid write device sector";
goto bad;
}
dc->start_write = tmpll;
if (sscanf(argv[5], "%u", &dc->write_delay) != 1) {
ti->error = "Invalid write delay";
goto bad;
}
if (dm_get_device(ti, argv[3], dc->start_write, ti->len,
dm_table_get_mode(ti->table), &dc->dev_write)) {
ti->error = "Write device lookup failed";
dm_put_device(ti, dc->dev_read);
goto bad;
}
out:
dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache);
if (!dc->delayed_pool) {
DMERR("Couldn't create delayed bio pool.");
goto bad;
}
setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);
INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
INIT_LIST_HEAD(&dc->delayed_bios);
mutex_init(&dc->timer_lock);
atomic_set(&dc->may_delay, 1);
ti->private = dc;
return 0;
bad:
kfree(dc);
return -EINVAL;
}
static void delay_dtr(struct dm_target *ti)
{
struct delay_c *dc = ti->private;
flush_workqueue(kdelayd_wq);
dm_put_device(ti, dc->dev_read);
if (dc->dev_write)
dm_put_device(ti, dc->dev_write);
mempool_destroy(dc->delayed_pool);
kfree(dc);
}
static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
{
struct dm_delay_info *delayed;
unsigned long expires = 0;
if (!delay || !atomic_read(&dc->may_delay))
return 1;
delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
delayed->context = dc;
delayed->bio = bio;
delayed->expires = expires = jiffies + (delay * HZ / 1000);
mutex_lock(&delayed_bios_lock);
if (bio_data_dir(bio) == WRITE)
dc->writes++;
else
dc->reads++;
list_add_tail(&delayed->list, &dc->delayed_bios);
mutex_unlock(&delayed_bios_lock);
queue_timeout(dc, expires);
return 0;
}
static void delay_presuspend(struct dm_target *ti)
{
struct delay_c *dc = ti->private;
atomic_set(&dc->may_delay, 0);
del_timer_sync(&dc->delay_timer);
flush_bios(flush_delayed_bios(dc, 1));
}
static void delay_resume(struct dm_target *ti)
{
struct delay_c *dc = ti->private;
atomic_set(&dc->may_delay, 1);
}
static int delay_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct delay_c *dc = ti->private;
if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
bio->bi_bdev = dc->dev_write->bdev;
bio->bi_sector = dc->start_write +
(bio->bi_sector - ti->begin);
return delay_bio(dc, dc->write_delay, bio);
}
bio->bi_bdev = dc->dev_read->bdev;
bio->bi_sector = dc->start_read +
(bio->bi_sector - ti->begin);
return delay_bio(dc, dc->read_delay, bio);
}
static int delay_status(struct dm_target *ti, status_type_t type,
char *result, unsigned maxlen)
{
struct delay_c *dc = ti->private;
int sz = 0;
switch (type) {
case STATUSTYPE_INFO:
DMEMIT("%u %u", dc->reads, dc->writes);
break;
case STATUSTYPE_TABLE:
DMEMIT("%s %llu %u", dc->dev_read->name,
(unsigned long long) dc->start_read,
dc->read_delay);
if (dc->dev_write)
DMEMIT("%s %llu %u", dc->dev_write->name,
(unsigned long long) dc->start_write,
dc->write_delay);
break;
}
return 0;
}
static struct target_type delay_target = {
.name = "delay",
.version = {1, 0, 2},
.module = THIS_MODULE,
.ctr = delay_ctr,
.dtr = delay_dtr,
.map = delay_map,
.presuspend = delay_presuspend,
.resume = delay_resume,
.status = delay_status,
};
static int __init dm_delay_init(void)
{
int r = -ENOMEM;
kdelayd_wq = create_workqueue("kdelayd");
if (!kdelayd_wq) {
DMERR("Couldn't start kdelayd");
goto bad_queue;
}
delayed_cache = KMEM_CACHE(dm_delay_info, 0);
if (!delayed_cache) {
DMERR("Couldn't create delayed bio cache.");
goto bad_memcache;
}
r = dm_register_target(&delay_target);
if (r < 0) {
DMERR("register failed %d", r);
goto bad_register;
}
return 0;
bad_register:
kmem_cache_destroy(delayed_cache);
bad_memcache:
destroy_workqueue(kdelayd_wq);
bad_queue:
return r;
}
static void __exit dm_delay_exit(void)
{
int r = dm_unregister_target(&delay_target);
if (r < 0)
DMERR("unregister failed %d", r);
kmem_cache_destroy(delayed_cache);
destroy_workqueue(kdelayd_wq);
}
/* Module hooks */
module_init(dm_delay_init);
module_exit(dm_delay_exit);
MODULE_DESCRIPTION(DM_NAME " delay target");
MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
MODULE_LICENSE("GPL");
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