https://github.com/torvalds/linux
Tip revision: 7d194c2100ad2a6dded545887d02754948ca5241 authored by Linus Torvalds on 20 October 2019, 19:56:22 UTC
Linux 5.4-rc4
Linux 5.4-rc4
Tip revision: 7d194c2
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 <linux/device-mapper.h>
#define DM_MSG_PREFIX "delay"
struct delay_class {
struct dm_dev *dev;
sector_t start;
unsigned delay;
unsigned ops;
};
struct delay_c {
struct timer_list delay_timer;
struct mutex timer_lock;
struct workqueue_struct *kdelayd_wq;
struct work_struct flush_expired_bios;
struct list_head delayed_bios;
atomic_t may_delay;
struct delay_class read;
struct delay_class write;
struct delay_class flush;
int argc;
};
struct dm_delay_info {
struct delay_c *context;
struct delay_class *class;
struct list_head list;
unsigned long expires;
};
static DEFINE_MUTEX(delayed_bios_lock);
static void handle_delayed_timer(struct timer_list *t)
{
struct delay_c *dc = from_timer(dc, t, delay_timer);
queue_work(dc->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;
unsigned long start_timer = 0;
struct 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)) {
struct bio *bio = dm_bio_from_per_bio_data(delayed,
sizeof(struct dm_delay_info));
list_del(&delayed->list);
bio_list_add(&flush_bios, bio);
delayed->class->ops--;
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));
}
static void delay_dtr(struct dm_target *ti)
{
struct delay_c *dc = ti->private;
if (dc->kdelayd_wq)
destroy_workqueue(dc->kdelayd_wq);
if (dc->read.dev)
dm_put_device(ti, dc->read.dev);
if (dc->write.dev)
dm_put_device(ti, dc->write.dev);
if (dc->flush.dev)
dm_put_device(ti, dc->flush.dev);
mutex_destroy(&dc->timer_lock);
kfree(dc);
}
static int delay_class_ctr(struct dm_target *ti, struct delay_class *c, char **argv)
{
int ret;
unsigned long long tmpll;
char dummy;
if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1 || tmpll != (sector_t)tmpll) {
ti->error = "Invalid device sector";
return -EINVAL;
}
c->start = tmpll;
if (sscanf(argv[2], "%u%c", &c->delay, &dummy) != 1) {
ti->error = "Invalid delay";
return -EINVAL;
}
ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &c->dev);
if (ret) {
ti->error = "Device lookup failed";
return ret;
}
return 0;
}
/*
* Mapping parameters:
* <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
*
* With separate write parameters, the first set is only used for reads.
* Offsets are specified in sectors.
* Delays are specified in milliseconds.
*/
static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct delay_c *dc;
int ret;
if (argc != 3 && argc != 6 && argc != 9) {
ti->error = "Requires exactly 3, 6 or 9 arguments";
return -EINVAL;
}
dc = kzalloc(sizeof(*dc), GFP_KERNEL);
if (!dc) {
ti->error = "Cannot allocate context";
return -ENOMEM;
}
ti->private = dc;
timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
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);
dc->argc = argc;
ret = delay_class_ctr(ti, &dc->read, argv);
if (ret)
goto bad;
if (argc == 3) {
ret = delay_class_ctr(ti, &dc->write, argv);
if (ret)
goto bad;
ret = delay_class_ctr(ti, &dc->flush, argv);
if (ret)
goto bad;
goto out;
}
ret = delay_class_ctr(ti, &dc->write, argv + 3);
if (ret)
goto bad;
if (argc == 6) {
ret = delay_class_ctr(ti, &dc->flush, argv + 3);
if (ret)
goto bad;
goto out;
}
ret = delay_class_ctr(ti, &dc->flush, argv + 6);
if (ret)
goto bad;
out:
dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
if (!dc->kdelayd_wq) {
ret = -EINVAL;
DMERR("Couldn't start kdelayd");
goto bad;
}
ti->num_flush_bios = 1;
ti->num_discard_bios = 1;
ti->per_io_data_size = sizeof(struct dm_delay_info);
return 0;
bad:
delay_dtr(ti);
return ret;
}
static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio)
{
struct dm_delay_info *delayed;
unsigned long expires = 0;
if (!c->delay || !atomic_read(&dc->may_delay))
return DM_MAPIO_REMAPPED;
delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
delayed->context = dc;
delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay);
mutex_lock(&delayed_bios_lock);
c->ops++;
list_add_tail(&delayed->list, &dc->delayed_bios);
mutex_unlock(&delayed_bios_lock);
queue_timeout(dc, expires);
return DM_MAPIO_SUBMITTED;
}
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)
{
struct delay_c *dc = ti->private;
struct delay_class *c;
struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
if (bio_data_dir(bio) == WRITE) {
if (unlikely(bio->bi_opf & REQ_PREFLUSH))
c = &dc->flush;
else
c = &dc->write;
} else {
c = &dc->read;
}
delayed->class = c;
bio_set_dev(bio, c->dev->bdev);
if (bio_sectors(bio))
bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector);
return delay_bio(dc, c, bio);
}
#define DMEMIT_DELAY_CLASS(c) \
DMEMIT("%s %llu %u", (c)->dev->name, (unsigned long long)(c)->start, (c)->delay)
static void delay_status(struct dm_target *ti, status_type_t type,
unsigned status_flags, char *result, unsigned maxlen)
{
struct delay_c *dc = ti->private;
int sz = 0;
switch (type) {
case STATUSTYPE_INFO:
DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);
break;
case STATUSTYPE_TABLE:
DMEMIT_DELAY_CLASS(&dc->read);
if (dc->argc >= 6) {
DMEMIT(" ");
DMEMIT_DELAY_CLASS(&dc->write);
}
if (dc->argc >= 9) {
DMEMIT(" ");
DMEMIT_DELAY_CLASS(&dc->flush);
}
break;
}
}
static int delay_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
struct delay_c *dc = ti->private;
int ret = 0;
ret = fn(ti, dc->read.dev, dc->read.start, ti->len, data);
if (ret)
goto out;
ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);
if (ret)
goto out;
ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);
if (ret)
goto out;
out:
return ret;
}
static struct target_type delay_target = {
.name = "delay",
.version = {1, 2, 1},
.features = DM_TARGET_PASSES_INTEGRITY,
.module = THIS_MODULE,
.ctr = delay_ctr,
.dtr = delay_dtr,
.map = delay_map,
.presuspend = delay_presuspend,
.resume = delay_resume,
.status = delay_status,
.iterate_devices = delay_iterate_devices,
};
static int __init dm_delay_init(void)
{
int r;
r = dm_register_target(&delay_target);
if (r < 0) {
DMERR("register failed %d", r);
goto bad_register;
}
return 0;
bad_register:
return r;
}
static void __exit dm_delay_exit(void)
{
dm_unregister_target(&delay_target);
}
/* 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");