dm: delay target

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 <mauelshagen@redhat.com>
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/device-mapper/delay.txt b/Documentation/device-mapper/delay.txt
new file mode 100644 (file)
index 0000000..15adc55
--- /dev/null
+++ b/Documentation/device-mapper/delay.txt
@@ -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
+]]

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 4540ade6b6b584385b11d65d337680c59ae96fc1..7df934d69134436cc2e1f5affb7f681dc0ab1671 100644 (file)
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -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

diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 34957a68d9215ac08061706c58b0fd66dc499d9d..38754084eac741462bc677f8c6911b662c719623 100644 (file)
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -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

diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
new file mode 100644 (file)
index 0000000..52c7cf9
--- /dev/null
+++ b/drivers/md/dm-delay.c
@@ -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 <mauelshagen@redhat.com>");
+MODULE_LICENSE("GPL");