drivers/md/dm-delay.c - pub/scm/linux/kernel/git/trace/linux-trace - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 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/kthread.h>
 #include <linux/delay.h>

 #include <linux/device-mapper.h>

 #define DM_MSG_PREFIX "delay"

 #define SLEEP_SHIFT 3

 struct delay_class {
 	struct dm_dev *dev;
 	sector_t start;
 	unsigned int delay;
 	unsigned int ops;
 };

 struct delay_c {
 	struct timer_list delay_timer;
 	struct mutex process_bios_lock; /* hold while removing bios to be processed from list */
 	spinlock_t delayed_bios_lock; /* hold on all accesses to delayed_bios list */
 	struct workqueue_struct *kdelayd_wq;
 	struct work_struct flush_expired_bios;
 	struct list_head delayed_bios;
 	struct task_struct *worker;
 	unsigned int worker_sleep_us;
 	bool 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 void handle_delayed_timer(struct timer_list *t)
 {
 	struct delay_c *dc = timer_container_of(dc, t, delay_timer);

 	queue_work(dc->kdelayd_wq, &dc->flush_expired_bios);
 }

 static void queue_timeout(struct delay_c *dc, unsigned long expires)
 {
 	timer_reduce(&dc->delay_timer, expires);
 }

 static inline bool delay_is_fast(struct delay_c *dc)
 {
 	return !!dc->worker;
 }

 static void flush_bios(struct bio *bio)
 {
 	struct bio *n;

 	while (bio) {
 		n = bio->bi_next;
 		bio->bi_next = NULL;
 		dm_submit_bio_remap(bio, NULL);
 		bio = n;
 	}
 }

 static void flush_delayed_bios(struct delay_c *dc, bool flush_all)
 {
 	struct dm_delay_info *delayed, *next;
 	struct bio_list flush_bio_list;
 	LIST_HEAD(local_list);
 	unsigned long next_expires = 0;
 	bool start_timer = false;
 	bio_list_init(&flush_bio_list);

 	mutex_lock(&dc->process_bios_lock);
 	spin_lock(&dc->delayed_bios_lock);
 	list_replace_init(&dc->delayed_bios, &local_list);
 	spin_unlock(&dc->delayed_bios_lock);
 	list_for_each_entry_safe(delayed, next, &local_list, list) {
 		cond_resched();
 		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_bio_list, bio);
 			delayed->class->ops--;
 			continue;
 		}

 		if (!delay_is_fast(dc)) {
 			if (!start_timer) {
 				start_timer = true;
 				next_expires = delayed->expires;
 			} else {
 				next_expires = min(next_expires, delayed->expires);
 			}
 		}
 	}
 	spin_lock(&dc->delayed_bios_lock);
 	list_splice(&local_list, &dc->delayed_bios);
 	spin_unlock(&dc->delayed_bios_lock);
 	mutex_unlock(&dc->process_bios_lock);

 	if (start_timer)
 		queue_timeout(dc, next_expires);

 	flush_bios(bio_list_get(&flush_bio_list));
 }

 static int flush_worker_fn(void *data)
 {
 	struct delay_c *dc = data;

 	while (!kthread_should_stop()) {
 		flush_delayed_bios(dc, false);
 		spin_lock(&dc->delayed_bios_lock);
 		if (unlikely(list_empty(&dc->delayed_bios))) {
 			set_current_state(TASK_INTERRUPTIBLE);
 			spin_unlock(&dc->delayed_bios_lock);
 			schedule();
 		} else {
 			spin_unlock(&dc->delayed_bios_lock);
 			fsleep(dc->worker_sleep_us);
 			cond_resched();
 		}
 	}

 	return 0;
 }

 static void flush_expired_bios(struct work_struct *work)
 {
 	struct delay_c *dc;

 	dc = container_of(work, struct delay_c, flush_expired_bios);
 	flush_delayed_bios(dc, false);
 }

 static void delay_dtr(struct dm_target *ti)
 {
 	struct delay_c *dc = ti->private;

 	if (dc->kdelayd_wq) {
 		timer_shutdown_sync(&dc->delay_timer);
 		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);
 	if (dc->worker)
 		kthread_stop(dc->worker);

 	mutex_destroy(&dc->process_bios_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;
 	unsigned int max_delay, min_delay;

 	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;
 	INIT_LIST_HEAD(&dc->delayed_bios);
 	mutex_init(&dc->process_bios_lock);
 	spin_lock_init(&dc->delayed_bios_lock);
 	dc->may_delay = true;
 	dc->argc = argc;

 	ret = delay_class_ctr(ti, &dc->read, argv);
 	if (ret)
 		goto bad;
 	min_delay = max_delay = dc->read.delay;

 	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;
 	max_delay = max(max_delay, dc->write.delay);
 	min_delay = min_not_zero(min_delay, dc->write.delay);

 	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;
 	max_delay = max(max_delay, dc->flush.delay);
 	min_delay = min_not_zero(min_delay, dc->flush.delay);

 out:
 	if (max_delay < 50) {
 		if (min_delay >> SLEEP_SHIFT)
 			dc->worker_sleep_us = 1000;
 		else
 			dc->worker_sleep_us = (min_delay * 1000) >> SLEEP_SHIFT;
 		/*
 		 * In case of small requested delays, use kthread instead of
 		 * timers and workqueue to achieve better latency.
 		 */
 		dc->worker = kthread_run(&flush_worker_fn, dc, "dm-delay-flush-worker");
 		if (IS_ERR(dc->worker)) {
 			ret = PTR_ERR(dc->worker);
 			dc->worker = NULL;
 			goto bad;
 		}
 	} else {
 		timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
 		INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 		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->accounts_remapped_io = true;
 	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)
 		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);

 	spin_lock(&dc->delayed_bios_lock);
 	if (unlikely(!dc->may_delay)) {
 		spin_unlock(&dc->delayed_bios_lock);
 		return DM_MAPIO_REMAPPED;
 	}
 	c->ops++;
 	list_add_tail(&delayed->list, &dc->delayed_bios);
 	spin_unlock(&dc->delayed_bios_lock);

 	if (delay_is_fast(dc))
 		wake_up_process(dc->worker);
 	else
 		queue_timeout(dc, expires);

 	return DM_MAPIO_SUBMITTED;
 }

 static void delay_presuspend(struct dm_target *ti)
 {
 	struct delay_c *dc = ti->private;

 	spin_lock(&dc->delayed_bios_lock);
 	dc->may_delay = false;
 	spin_unlock(&dc->delayed_bios_lock);

 	if (!delay_is_fast(dc))
 		timer_delete(&dc->delay_timer);
 	flush_delayed_bios(dc, true);
 }

 static void delay_resume(struct dm_target *ti)
 {
 	struct delay_c *dc = ti->private;

 	dc->may_delay = true;
 }

 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);
 	bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector);

 	return delay_bio(dc, c, bio);
 }

 #ifdef CONFIG_BLK_DEV_ZONED
 static int delay_report_zones(struct dm_target *ti,
 		struct dm_report_zones_args *args, unsigned int nr_zones)
 {
 	struct delay_c *dc = ti->private;
 	struct delay_class *c = &dc->read;

 	return dm_report_zones(c->dev->bdev, c->start,
 			c->start + dm_target_offset(ti, args->next_sector),
 			args, nr_zones);
 }
 #else
 #define delay_report_zones	NULL
 #endif

 #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 int status_flags, char *result, unsigned int 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;

 	case STATUSTYPE_IMA:
 		*result = '\0';
 		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, 5, 0},
 	.features    = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_ZONED_HM,
 	.module      = THIS_MODULE,
 	.ctr	     = delay_ctr,
 	.dtr	     = delay_dtr,
 	.map	     = delay_map,
 	.report_zones = delay_report_zones,
 	.presuspend  = delay_presuspend,
 	.resume	     = delay_resume,
 	.status	     = delay_status,
 	.iterate_devices = delay_iterate_devices,
 };
 module_dm(delay);

 MODULE_DESCRIPTION(DM_NAME " delay target");
 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* 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/kthread.h>
	#include <linux/delay.h>

	#include <linux/device-mapper.h>

	#define DM_MSG_PREFIX "delay"

	#define SLEEP_SHIFT 3

	struct delay_class {
	struct dm_dev *dev;
	sector_t start;
	unsigned int delay;
	unsigned int ops;
	};

	struct delay_c {
	struct timer_list delay_timer;
	struct mutex process_bios_lock; /* hold while removing bios to be processed from list */
	spinlock_t delayed_bios_lock; /* hold on all accesses to delayed_bios list */
	struct workqueue_struct *kdelayd_wq;
	struct work_struct flush_expired_bios;
	struct list_head delayed_bios;
	struct task_struct *worker;
	unsigned int worker_sleep_us;
	bool 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 void handle_delayed_timer(struct timer_list *t)
	{
	struct delay_c *dc = timer_container_of(dc, t, delay_timer);

	queue_work(dc->kdelayd_wq, &dc->flush_expired_bios);
	}

	static void queue_timeout(struct delay_c *dc, unsigned long expires)
	{
	timer_reduce(&dc->delay_timer, expires);
	}

	static inline bool delay_is_fast(struct delay_c *dc)
	{
	return !!dc->worker;
	}

	static void flush_bios(struct bio *bio)
	{
	struct bio *n;

	while (bio) {
	n = bio->bi_next;
	bio->bi_next = NULL;
	dm_submit_bio_remap(bio, NULL);
	bio = n;
	}
	}

	static void flush_delayed_bios(struct delay_c *dc, bool flush_all)
	{
	struct dm_delay_info delayed, next;
	struct bio_list flush_bio_list;
	LIST_HEAD(local_list);
	unsigned long next_expires = 0;
	bool start_timer = false;
	bio_list_init(&flush_bio_list);

	mutex_lock(&dc->process_bios_lock);
	spin_lock(&dc->delayed_bios_lock);
	list_replace_init(&dc->delayed_bios, &local_list);
	spin_unlock(&dc->delayed_bios_lock);
	list_for_each_entry_safe(delayed, next, &local_list, list) {
	cond_resched();
	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_bio_list, bio);
	delayed->class->ops--;
	continue;
	}

	if (!delay_is_fast(dc)) {
	if (!start_timer) {
	start_timer = true;
	next_expires = delayed->expires;
	} else {
	next_expires = min(next_expires, delayed->expires);
	}
	}
	}
	spin_lock(&dc->delayed_bios_lock);
	list_splice(&local_list, &dc->delayed_bios);
	spin_unlock(&dc->delayed_bios_lock);
	mutex_unlock(&dc->process_bios_lock);

	if (start_timer)
	queue_timeout(dc, next_expires);

	flush_bios(bio_list_get(&flush_bio_list));
	}

	static int flush_worker_fn(void *data)
	{
	struct delay_c *dc = data;

	while (!kthread_should_stop()) {
	flush_delayed_bios(dc, false);
	spin_lock(&dc->delayed_bios_lock);
	if (unlikely(list_empty(&dc->delayed_bios))) {
	set_current_state(TASK_INTERRUPTIBLE);
	spin_unlock(&dc->delayed_bios_lock);
	schedule();
	} else {
	spin_unlock(&dc->delayed_bios_lock);
	fsleep(dc->worker_sleep_us);
	cond_resched();
	}
	}

	return 0;
	}

	static void flush_expired_bios(struct work_struct *work)
	{
	struct delay_c *dc;

	dc = container_of(work, struct delay_c, flush_expired_bios);
	flush_delayed_bios(dc, false);
	}

	static void delay_dtr(struct dm_target *ti)
	{
	struct delay_c *dc = ti->private;

	if (dc->kdelayd_wq) {
	timer_shutdown_sync(&dc->delay_timer);
	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);
	if (dc->worker)
	kthread_stop(dc->worker);

	mutex_destroy(&dc->process_bios_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;
	unsigned int max_delay, min_delay;

	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;
	INIT_LIST_HEAD(&dc->delayed_bios);
	mutex_init(&dc->process_bios_lock);
	spin_lock_init(&dc->delayed_bios_lock);
	dc->may_delay = true;
	dc->argc = argc;

	ret = delay_class_ctr(ti, &dc->read, argv);
	if (ret)
	goto bad;
	min_delay = max_delay = dc->read.delay;

	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;
	max_delay = max(max_delay, dc->write.delay);
	min_delay = min_not_zero(min_delay, dc->write.delay);

	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;
	max_delay = max(max_delay, dc->flush.delay);
	min_delay = min_not_zero(min_delay, dc->flush.delay);

	out:
	if (max_delay < 50) {
	if (min_delay >> SLEEP_SHIFT)
	dc->worker_sleep_us = 1000;
	else
	dc->worker_sleep_us = (min_delay * 1000) >> SLEEP_SHIFT;
	/*
	* In case of small requested delays, use kthread instead of
	* timers and workqueue to achieve better latency.
	*/
	dc->worker = kthread_run(&flush_worker_fn, dc, "dm-delay-flush-worker");
	if (IS_ERR(dc->worker)) {
	ret = PTR_ERR(dc->worker);
	dc->worker = NULL;
	goto bad;
	}
	} else {
	timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
	INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
	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->accounts_remapped_io = true;
	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)
	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);

	spin_lock(&dc->delayed_bios_lock);
	if (unlikely(!dc->may_delay)) {
	spin_unlock(&dc->delayed_bios_lock);
	return DM_MAPIO_REMAPPED;
	}
	c->ops++;
	list_add_tail(&delayed->list, &dc->delayed_bios);
	spin_unlock(&dc->delayed_bios_lock);

	if (delay_is_fast(dc))
	wake_up_process(dc->worker);
	else
	queue_timeout(dc, expires);

	return DM_MAPIO_SUBMITTED;
	}

	static void delay_presuspend(struct dm_target *ti)
	{
	struct delay_c *dc = ti->private;

	spin_lock(&dc->delayed_bios_lock);
	dc->may_delay = false;
	spin_unlock(&dc->delayed_bios_lock);

	if (!delay_is_fast(dc))
	timer_delete(&dc->delay_timer);
	flush_delayed_bios(dc, true);
	}

	static void delay_resume(struct dm_target *ti)
	{
	struct delay_c *dc = ti->private;

	dc->may_delay = true;
	}

	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);
	bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector);

	return delay_bio(dc, c, bio);
	}

	#ifdef CONFIG_BLK_DEV_ZONED
	static int delay_report_zones(struct dm_target *ti,
	struct dm_report_zones_args *args, unsigned int nr_zones)
	{
	struct delay_c *dc = ti->private;
	struct delay_class *c = &dc->read;

	return dm_report_zones(c->dev->bdev, c->start,
	c->start + dm_target_offset(ti, args->next_sector),
	args, nr_zones);
	}
	#else
	#define delay_report_zones NULL
	#endif

	#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 int status_flags, char *result, unsigned int 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;

	case STATUSTYPE_IMA:
	*result = '\0';
	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, 5, 0},
	.features = DM_TARGET_PASSES_INTEGRITY \| DM_TARGET_ZONED_HM,
	.module = THIS_MODULE,
	.ctr = delay_ctr,
	.dtr = delay_dtr,
	.map = delay_map,
	.report_zones = delay_report_zones,
	.presuspend = delay_presuspend,
	.resume = delay_resume,
	.status = delay_status,
	.iterate_devices = delay_iterate_devices,
	};
	module_dm(delay);

	MODULE_DESCRIPTION(DM_NAME " delay target");
	MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
	MODULE_LICENSE("GPL");