From: Heinz Mauelshagen <[email protected]>
New device-mapper target that can delay I/O (for testing).
Reads can be separated from writes, redirected to different underlying
devices and delayed by differing amounts of time.
Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Milan Broz <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
---
Documentation/device-mapper/delay.txt | 26 ++
drivers/md/Kconfig | 9
drivers/md/Makefile | 1
drivers/md/dm-delay.c | 383 ++++++++++++++++++++++++++++++++++
4 files changed, 419 insertions(+)
Index: linux-2.6.21/Documentation/device-mapper/delay.txt
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.21/Documentation/device-mapper/delay.txt 2007-05-01 17:40:55.000000000 +0100
@@ -0,0 +1,26 @@
+dm-delay
+========
+
+Device-Mapper's "delay" target delays reads and/or writes
+and maps them to different devices.
+
+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.
+
+Example scripts
+===============
+[[
+#!/bin/sh
+# Create device delaying rw operation for 500ms
+echo "0 `blockdev --getsize $1` delay $1 0 500" | dmsetup create delayed
+]]
+
+[[
+#!/bin/sh
+# Create device delaying only write operation for 500ms and
+# splitting reads and writes to different devices $1 $2
+echo "0 `blockdev --getsize $1` delay $1 0 0 $2 0 500" | dmsetup create delayed
+]]
Index: linux-2.6.21/drivers/md/Kconfig
===================================================================
--- linux-2.6.21.orig/drivers/md/Kconfig 2007-05-01 17:38:31.000000000 +0100
+++ linux-2.6.21/drivers/md/Kconfig 2007-05-01 17:40:55.000000000 +0100
@@ -262,6 +262,15 @@ config DM_MULTIPATH_EMC
---help---
Multipath support for EMC CX/AX series hardware.
+config DM_DELAY
+ tristate "I/O delaying target (EXPERIMENTAL)"
+ depends on BLK_DEV_DM && EXPERIMENTAL
+ ---help---
+ A target that delays reads and/or writes and can send
+ them to different devices. Useful for testing.
+
+ If unsure, say N.
+
endmenu
endif
Index: linux-2.6.21/drivers/md/Makefile
===================================================================
--- linux-2.6.21.orig/drivers/md/Makefile 2007-05-01 17:38:31.000000000 +0100
+++ linux-2.6.21/drivers/md/Makefile 2007-05-01 17:40:55.000000000 +0100
@@ -31,6 +31,7 @@ obj-$(CONFIG_MD_FAULTY) += faulty.o
obj-$(CONFIG_BLK_DEV_MD) += md-mod.o
obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o
obj-$(CONFIG_DM_CRYPT) += dm-crypt.o
+obj-$(CONFIG_DM_DELAY) += dm-delay.o
obj-$(CONFIG_DM_MULTIPATH) += dm-multipath.o dm-round-robin.o
obj-$(CONFIG_DM_MULTIPATH_EMC) += dm-emc.o
obj-$(CONFIG_DM_SNAPSHOT) += dm-snapshot.o
Index: linux-2.6.21/drivers/md/dm-delay.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.21/drivers/md/dm-delay.c 2007-05-01 17:40:55.000000000 +0100
@@ -0,0 +1,383 @@
+/*
+ * 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 semaphore 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 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)
+{
+ down(&dc->timer_lock);
+
+ if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
+ mod_timer(&dc->delay_timer, expires);
+
+ up(&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 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;
+ }
+
+ init_timer(&dc->delay_timer);
+ dc->delay_timer.function = handle_delayed_timer;
+ dc->delay_timer.data = (unsigned long)dc;
+
+ INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
+ INIT_LIST_HEAD(&dc->delayed_bios);
+ init_MUTEX(&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 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_create("dm-delay",
+ sizeof(struct delay_info),
+ __alignof__(struct delay_info),
+ 0, NULL, NULL);
+ 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 <[email protected]>");
+MODULE_LICENSE("GPL");
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