Xen devel - Jul 2008 - Subject: [PATCH 0/2] dm-ioband: I/O bandwidth controller v1.3.0: Introduction

Hi everyone,

This is the dm-ioband version 1.3.0 release.

Dm-ioband is an I/O bandwidth controller implemented as a device-mapper
driver, which gives specified bandwidth to each job running on the same
physical device.

- Can be applied to the kernel 2.6.26-rc5-mm3.
- Changes from 1.2.0 (posted on Jul 4, 2008):
  - I/O smoothing take #2
    This feature makes I/O requests of each group issued smoothly.
    Once a certain group has used up its tokens, all I/O requests to
    the group will be blocked until all the other groups used up
    theirs. This feature is to minimize this blocking time and to
    issue I/O requests at a constant rate according to the weight,
    without decreasing throughput.
    We have tested various ideas to achieve this feature and we have
    chosen the most effective ways as follows:
      - Shorten the epoch period of dm-ioband, each of which every
        ioband group will get new tokens. On the other hand, the
        leftover tokens for the past few epochs can be taken over to
        the next epoch so that it can keep the fairness between the
        groups even when the I/O loads of some groups are changing.
      - Make a new epoch immediately when a group with large weight
        used up its tokens even though there remain a lot of in-flight
        I/Os.
        To gain the throughput, dm-ioband will recharge tokens to all
        the groups without waiting their I/O completion if possible.
      - Make the I/O requests which user process have just made
        be handled ahead of the blocked I/O requests, since it
        would make sense that you assume the groups which issued
        these blocked I/O requests will have small weights.
      - Make the number of I/O requests which can be queued in dm-ioband
        smaller, so it will prevents all the I/O request of each
	group from being issued at the same time when a new epoch
	gets made.
- TODO
  - Implementing cgroup support for dm-ioband is in progress. This
    feature makes it be able to handle asynchronous I/O requests properly.

I added a new benchmark result on the dm-ioband webpage. This result
shows that dm-ioband can control a bandwidth even when an unbalanced
I/O load is applied.
http://people.valinux.co.jp/~ryov/dm-ioband/benchmark/partition3.html

Thanks,
Ryo Tsuruta
Linux Block I/O Bandwidth Control Project
http://people.valinux.co.jp/~ryov/bwctl/

Here is the patch of dm-ioband.

Based on 2.6.26-rc5-mm3
Signed-off-by: Ryo Tsuruta <ryov at valinux.co.jp>
Signed-off-by: Hirokazu Takahashi <taka at valinux.co.jp>

diff -uprN linux-2.6.26-rc5-mm3.orig/drivers/md/Kconfig
linux-2.6.26-rc5-mm3/drivers/md/Kconfig
--- linux-2.6.26-rc5-mm3.orig/drivers/md/Kconfig	2008-06-25 15:58:50.000000000
+0900
+++ linux-2.6.26-rc5-mm3/drivers/md/Kconfig	2008-07-11 19:24:05.000000000 +0900
@@ -271,4 +271,17 @@ config DM_UEVENT
 	---help---
 	Generate udev events for DM events.
 
+config DM_IOBAND
+	tristate "I/O bandwidth control (EXPERIMENTAL)"
+	depends on BLK_DEV_DM && EXPERIMENTAL
+	---help---
+	This device-mapper target allows to define how the
+	available bandwidth of a storage device should be
+	shared between processes, cgroups, the partitions or the LUNs.
+
+	Information on how to use dm-ioband is available in:
+	   <file:Documentation/device-mapper/ioband.txt>.
+
+	If unsure, say N.
+
 endif # MD
diff -uprN linux-2.6.26-rc5-mm3.orig/drivers/md/Makefile
linux-2.6.26-rc5-mm3/drivers/md/Makefile
--- linux-2.6.26-rc5-mm3.orig/drivers/md/Makefile	2008-06-25 15:58:50.000000000
+0900
+++ linux-2.6.26-rc5-mm3/drivers/md/Makefile	2008-07-11 19:24:05.000000000 +0900
@@ -7,6 +7,7 @@ dm-mod-objs	:= dm.o dm-table.o dm-target
 dm-multipath-objs := dm-path-selector.o dm-mpath.o
 dm-snapshot-objs := dm-snap.o dm-exception-store.o
 dm-mirror-objs	:= dm-raid1.o
+dm-ioband-objs	:= dm-ioband-ctl.o dm-ioband-policy.o dm-ioband-type.o
 md-mod-objs     := md.o bitmap.o
 raid456-objs	:= raid5.o raid6algos.o raid6recov.o raid6tables.o \
 		   raid6int1.o raid6int2.o raid6int4.o \
@@ -36,6 +37,7 @@ obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipa
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o dm-log.o
 obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
+obj-$(CONFIG_DM_IOBAND)		+= dm-ioband.o
 
 quiet_cmd_unroll = UNROLL  $@
       cmd_unroll = $(PERL) $(srctree)/$(src)/unroll.pl $(UNROLL) \
diff -uprN linux-2.6.26-rc5-mm3.orig/drivers/md/dm-ioband-ctl.c
linux-2.6.26-rc5-mm3/drivers/md/dm-ioband-ctl.c
--- linux-2.6.26-rc5-mm3.orig/drivers/md/dm-ioband-ctl.c	1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.26-rc5-mm3/drivers/md/dm-ioband-ctl.c	2008-07-11
19:24:05.000000000 +0900
@@ -0,0 +1,1319 @@
+/*
+ * Copyright (C) 2008 VA Linux Systems Japan K.K.
+ * Authors: Hirokazu Takahashi <taka at valinux.co.jp>
+ *          Ryo Tsuruta <ryov at valinux.co.jp>
+ *
+ *  I/O bandwidth control
+ *
+ * This file is released under the GPL.
+ */
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/raid/md.h>
+#include <linux/rbtree.h>
+#include "dm.h"
+#include "dm-bio-list.h"
+#include "dm-ioband.h"
+
+#define DM_MSG_PREFIX "ioband"
+#define POLICY_PARAM_START 6
+#define POLICY_PARAM_DELIM "=:,"
+
+static LIST_HEAD(ioband_device_list);
+/* to protect ioband_device_list */
+static DEFINE_SPINLOCK(ioband_devicelist_lock);
+
+static void suspend_ioband_device(struct ioband_device *, unsigned long, int);
+static void resume_ioband_device(struct ioband_device *);
+static void ioband_conduct(struct work_struct *);
+static void ioband_hold_bio(struct ioband_group *, struct bio *);
+static struct bio *ioband_pop_bio(struct ioband_group *);
+static int ioband_set_param(struct ioband_group *, char *, char *);
+static int ioband_group_attach(struct ioband_group *, int, char *);
+static int ioband_group_type_select(struct ioband_group *, char *);
+
+long ioband_debug;	/* just for debugging */
+
+static void do_nothing(void) {}
+
+static int policy_init(struct ioband_device *dp, char *name,
+						int argc, char **argv)
+{
+	struct policy_type *p;
+	struct ioband_group *gp;
+	unsigned long flags;
+	int r;
+
+	for (p = dm_ioband_policy_type; p->p_name; p++) {
+		if (!strcmp(name, p->p_name))
+			break;
+	}
+	if (!p->p_name)
+		return -EINVAL;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	if (dp->g_policy == p) {
+		/* do nothing if the same policy is already set */
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		return 0;
+	}
+
+	suspend_ioband_device(dp, flags, 1);
+	list_for_each_entry(gp, &dp->g_groups, c_list)
+		dp->g_group_dtr(gp);
+
+	/* switch to the new policy */
+	dp->g_policy = p;
+	r = p->p_policy_init(dp, argc, argv);
+	if (!dp->g_hold_bio)
+		dp->g_hold_bio = ioband_hold_bio;
+	if (!dp->g_pop_bio)
+		dp->g_pop_bio = ioband_pop_bio;
+
+	list_for_each_entry(gp, &dp->g_groups, c_list)
+		dp->g_group_ctr(gp, NULL);
+	resume_ioband_device(dp);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	return r;
+}
+
+static struct ioband_device *alloc_ioband_device(char *name,
+					int io_throttle, int io_limit)
+
+{
+	struct ioband_device *dp, *new;
+	unsigned long flags;
+
+	new = kzalloc(sizeof(struct ioband_device), GFP_KERNEL);
+	if (!new)
+		return NULL;
+
+	spin_lock_irqsave(&ioband_devicelist_lock, flags);
+	list_for_each_entry(dp, &ioband_device_list, g_list) {
+		if (!strcmp(dp->g_name, name)) {
+			dp->g_ref++;
+			spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
+			kfree(new);
+			return dp;
+		}
+	}
+
+	/*
+	 * Prepare its own workqueue as generic_make_request() may
+	 * potentially block the workqueue when submitting BIOs.
+	 */
+	new->g_ioband_wq = create_workqueue("kioband");
+	if (!new->g_ioband_wq) {
+		spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
+		kfree(new);
+		return NULL;
+	}
+
+	INIT_DELAYED_WORK(&new->g_conductor, ioband_conduct);
+	INIT_LIST_HEAD(&new->g_groups);
+	INIT_LIST_HEAD(&new->g_list);
+	spin_lock_init(&new->g_lock);
+	mutex_init(&new->g_lock_device);
+	bio_list_init(&new->g_urgent_bios);
+	new->g_io_throttle = io_throttle;
+	new->g_io_limit[0] = io_limit;
+	new->g_io_limit[1] = io_limit;
+	new->g_issued[0] = 0;
+	new->g_issued[1] = 0;
+	new->g_blocked = 0;
+	new->g_ref = 1;
+	new->g_flags = 0;
+	strlcpy(new->g_name, name, sizeof(new->g_name));
+	new->g_policy = NULL;
+	new->g_hold_bio = NULL;
+	new->g_pop_bio = NULL;
+	init_waitqueue_head(&new->g_waitq);
+	init_waitqueue_head(&new->g_waitq_suspend);
+	init_waitqueue_head(&new->g_waitq_flush);
+	list_add_tail(&new->g_list, &ioband_device_list);
+
+	spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
+	return new;
+}
+
+static void release_ioband_device(struct ioband_device *dp)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ioband_devicelist_lock, flags);
+	dp->g_ref--;
+	if (dp->g_ref > 0) {
+		spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
+		return;
+	}
+	list_del(&dp->g_list);
+	spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
+	destroy_workqueue(dp->g_ioband_wq);
+	kfree(dp);
+}
+
+static int is_ioband_device_flushed(struct ioband_device *dp,
+						int wait_completion)
+{
+	struct ioband_group *gp;
+
+	if (wait_completion && dp->g_issued[0] + dp->g_issued[1] > 0)
+		return 0;
+	if (dp->g_blocked || waitqueue_active(&dp->g_waitq))
+		return 0;
+	list_for_each_entry(gp, &dp->g_groups, c_list)
+		if (waitqueue_active(&gp->c_waitq))
+			return 0;
+	return 1;
+}
+
+static void suspend_ioband_device(struct ioband_device *dp,
+				unsigned long flags, int wait_completion)
+{
+	struct ioband_group *gp;
+
+	/* block incoming bios */
+	set_device_suspended(dp);
+
+	/* wake up all blocked processes and go down all ioband groups */
+	wake_up_all(&dp->g_waitq);
+	list_for_each_entry(gp, &dp->g_groups, c_list) {
+		if (!is_group_down(gp)) {
+			set_group_down(gp);
+			set_group_need_up(gp);
+		}
+		wake_up_all(&gp->c_waitq);
+	}
+
+	/* flush the already mapped bios */
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	queue_delayed_work(dp->g_ioband_wq, &dp->g_conductor, 0);
+	flush_workqueue(dp->g_ioband_wq);
+
+	/* wait for all processes to wake up and bios to release */
+	spin_lock_irqsave(&dp->g_lock, flags);
+	wait_event_lock_irq(dp->g_waitq_flush,
+			is_ioband_device_flushed(dp, wait_completion),
+			dp->g_lock, do_nothing());
+}
+
+static void resume_ioband_device(struct ioband_device *dp)
+{
+	struct ioband_group *gp;
+
+	/* go up ioband groups */
+	list_for_each_entry(gp, &dp->g_groups, c_list) {
+		if (group_need_up(gp)) {
+			clear_group_need_up(gp);
+			clear_group_down(gp);
+		}
+	}
+
+	/* accept incoming bios */
+	wake_up_all(&dp->g_waitq_suspend);
+	clear_device_suspended(dp);
+}
+
+static struct ioband_group *ioband_group_find(
+					struct ioband_group *head, int id)
+{
+	struct rb_node *node = head->c_group_root.rb_node;
+
+	while (node) {
+		struct ioband_group *p +			container_of(node, struct ioband_group,
c_group_node);
+
+		if (p->c_id == id || id == IOBAND_ID_ANY)
+			return p;
+		node = (id < p->c_id) ? node->rb_left : node->rb_right;
+	}
+	return NULL;
+}
+
+static void ioband_group_add_node(struct rb_root *root,
+						struct ioband_group *gp)
+{
+	struct rb_node **new = &root->rb_node, *parent = NULL;
+	struct ioband_group *p;
+
+	while (*new) {
+		p = container_of(*new, struct ioband_group, c_group_node);
+		parent = *new;
+		new = (gp->c_id < p->c_id) ?
+					&(*new)->rb_left : &(*new)->rb_right;
+	}
+
+	rb_link_node(&gp->c_group_node, parent, new);
+	rb_insert_color(&gp->c_group_node, root);
+}
+
+static int ioband_group_init(struct ioband_group *gp,
+    struct ioband_group *head, struct ioband_device *dp, int id, char *param)
+{
+	unsigned long flags;
+	int r;
+
+	INIT_LIST_HEAD(&gp->c_list);
+	bio_list_init(&gp->c_blocked_bios);
+	bio_list_init(&gp->c_prio_bios);
+	gp->c_id = id;	/* should be verified */
+	gp->c_blocked = 0;
+	gp->c_prio_blocked = 0;
+	memset(gp->c_stat, 0, sizeof(gp->c_stat));
+	init_waitqueue_head(&gp->c_waitq);
+	gp->c_flags = 0;
+	gp->c_group_root = RB_ROOT;
+	gp->c_banddev = dp;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	if (head && ioband_group_find(head, id)) {
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		DMWARN("ioband_group: id=%d already exists.", id);
+		return -EEXIST;
+	}
+
+	list_add_tail(&gp->c_list, &dp->g_groups);
+
+	r = dp->g_group_ctr(gp, param);
+	if (r) {
+		list_del(&gp->c_list);
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		return r;
+	}
+
+	if (head) {
+		ioband_group_add_node(&head->c_group_root, gp);
+		gp->c_dev = head->c_dev;
+		gp->c_target = head->c_target;
+	}
+
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+
+	return 0;
+}
+
+static void ioband_group_release(struct ioband_group *head,
+						struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	list_del(&gp->c_list);
+	if (head)
+		rb_erase(&gp->c_group_node, &head->c_group_root);
+	dp->g_group_dtr(gp);
+	kfree(gp);
+}
+
+static void ioband_group_destroy_all(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *group;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	while ((group = ioband_group_find(gp, IOBAND_ID_ANY)))
+		ioband_group_release(gp, group);
+	ioband_group_release(NULL, gp);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+}
+
+static void ioband_group_stop_all(struct ioband_group *head, int suspend)
+{
+	struct ioband_device *dp = head->c_banddev;
+	struct ioband_group *p;
+	struct rb_node *node;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	for (node = rb_first(&head->c_group_root); node; node = rb_next(node))
{
+		p = rb_entry(node, struct ioband_group, c_group_node);
+		set_group_down(p);
+		if (suspend) {
+			set_group_suspended(p);
+			dprintk(KERN_ERR "ioband suspend: gp(%p)\n", p);
+		}
+	}
+	set_group_down(head);
+	if (suspend) {
+		set_group_suspended(head);
+		dprintk(KERN_ERR "ioband suspend: gp(%p)\n", head);
+	}
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	queue_delayed_work(dp->g_ioband_wq, &dp->g_conductor, 0);
+	flush_workqueue(dp->g_ioband_wq);
+}
+
+static void ioband_group_resume_all(struct ioband_group *head)
+{
+	struct ioband_device *dp = head->c_banddev;
+	struct ioband_group *p;
+	struct rb_node *node;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	for (node = rb_first(&head->c_group_root); node;
+							node = rb_next(node)) {
+		p = rb_entry(node, struct ioband_group, c_group_node);
+		clear_group_down(p);
+		clear_group_suspended(p);
+		dprintk(KERN_ERR "ioband resume: gp(%p)\n", p);
+	}
+	clear_group_down(head);
+	clear_group_suspended(head);
+	dprintk(KERN_ERR "ioband resume: gp(%p)\n", head);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+}
+
+static int split_string(char *s, long *id, char **v)
+{
+	char *p, *q;
+	int r = 0;
+
+	*id = IOBAND_ID_ANY;
+	p = strsep(&s, POLICY_PARAM_DELIM);
+	q = strsep(&s, POLICY_PARAM_DELIM);
+	if (!q) {
+		*v = p;
+	} else {
+		r = strict_strtol(p, 0, id);
+		*v = q;
+	}
+	return r;
+}
+
+/*
+ * Create a new band device:
+ *   parameters:  <device> <device-group-id> <io_throttle>
<io_limit>
+ *     <type> <policy> <policy-param...>
<group-id:group-param...>
+ */
+static int ioband_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+	struct ioband_group *gp;
+	struct ioband_device *dp;
+	struct dm_dev *dev;
+	int io_throttle;
+	int io_limit;
+	int i, r, start;
+	long val, id;
+	char *param;
+
+	if (argc < POLICY_PARAM_START) {
+		ti->error = "Requires " __stringify(POLICY_PARAM_START)
+							" or more arguments";
+		return -EINVAL;
+	}
+
+	if (strlen(argv[1]) > IOBAND_NAME_MAX) {
+		ti->error = "Ioband device name is too long";
+		return -EINVAL;
+	}
+	dprintk(KERN_ERR "ioband_ctr ioband device name:%s\n", argv[1]);
+
+	r = strict_strtol(argv[2], 0, &val);
+	if (r || val < 0) {
+		ti->error = "Invalid io_throttle";
+		return -EINVAL;
+	}
+	io_throttle = (val == 0) ? DEFAULT_IO_THROTTLE : val;
+
+	r = strict_strtol(argv[3], 0, &val);
+	if (r || val < 0) {
+		ti->error = "Invalid io_limit";
+		return -EINVAL;
+	}
+	io_limit = val;
+
+	r = dm_get_device(ti, argv[0], 0, ti->len,
+				dm_table_get_mode(ti->table), &dev);
+	if (r) {
+		ti->error = "Device lookup failed";
+		return r;
+	}
+
+	if (io_limit == 0) {
+		struct request_queue *q;
+
+		q = bdev_get_queue(dev->bdev);
+		if (!q) {
+			ti->error = "Can't get queue size";
+			r = -ENXIO;
+			goto release_dm_device;
+		}
+		dprintk(KERN_ERR "ioband_ctr nr_requests:%lu\n",
+							q->nr_requests);
+		io_limit = q->nr_requests;
+	}
+
+	if (io_limit < io_throttle)
+		io_limit = io_throttle;
+	dprintk(KERN_ERR "ioband_ctr io_throttle:%d io_limit:%d\n",
+						io_throttle, io_limit);
+
+	dp = alloc_ioband_device(argv[1], io_throttle, io_limit);
+	if (!dp) {
+		ti->error = "Cannot create ioband device";
+		r = -EINVAL;
+		goto release_dm_device;
+	}
+
+	mutex_lock(&dp->g_lock_device);
+	r = policy_init(dp, argv[POLICY_PARAM_START - 1],
+			argc - POLICY_PARAM_START, &argv[POLICY_PARAM_START]);
+	if (r) {
+		ti->error = "Invalid policy parameter";
+		goto release_ioband_device;
+	}
+
+	gp = kzalloc(sizeof(struct ioband_group), GFP_KERNEL);
+	if (!gp) {
+		ti->error = "Cannot allocate memory for ioband group";
+		r = -ENOMEM;
+		goto release_ioband_device;
+	}
+
+	ti->private = gp;
+	gp->c_target = ti;
+	gp->c_dev = dev;
+
+	/* Find a default group parameter */
+	for (start = POLICY_PARAM_START; start < argc; start++)
+		if (argv[start][0] == ':')
+			break;
+	param = (start < argc) ? &argv[start][1] : NULL;
+
+	/* Create a default ioband group */
+	r = ioband_group_init(gp, NULL, dp, IOBAND_ID_ANY, param);
+	if (r) {
+		kfree(gp);
+		ti->error = "Cannot create default ioband group";
+		goto release_ioband_device;
+	}
+
+	r = ioband_group_type_select(gp, argv[4]);
+	if (r) {
+		ti->error = "Cannot set ioband group type";
+		goto release_ioband_group;
+	}
+
+	/* Create sub ioband groups */
+	for (i = start + 1; i < argc; i++) {
+		r = split_string(argv[i], &id, &param);
+		if (r) {
+			ti->error = "Invalid ioband group parameter";
+			goto release_ioband_group;
+		}
+		r = ioband_group_attach(gp, id, param);
+		if (r) {
+			ti->error = "Cannot create ioband group";
+			goto release_ioband_group;
+		}
+	}
+	mutex_unlock(&dp->g_lock_device);
+	return 0;
+
+release_ioband_group:
+	ioband_group_destroy_all(gp);
+release_ioband_device:
+	mutex_unlock(&dp->g_lock_device);
+	release_ioband_device(dp);
+release_dm_device:
+	dm_put_device(ti, dev);
+	return r;
+}
+
+static void ioband_dtr(struct dm_target *ti)
+{
+	struct ioband_group *gp = ti->private;
+	struct ioband_device *dp = gp->c_banddev;
+
+	mutex_lock(&dp->g_lock_device);
+	ioband_group_stop_all(gp, 0);
+	cancel_delayed_work_sync(&dp->g_conductor);
+	dm_put_device(ti, gp->c_dev);
+	ioband_group_destroy_all(gp);
+	mutex_unlock(&dp->g_lock_device);
+	release_ioband_device(dp);
+}
+
+static void ioband_hold_bio(struct ioband_group *gp, struct bio *bio)
+{
+	/* Todo: The list should be split into a read list and a write list */
+	bio_list_add(&gp->c_blocked_bios, bio);
+}
+
+static struct bio *ioband_pop_bio(struct ioband_group *gp)
+{
+	return bio_list_pop(&gp->c_blocked_bios);
+}
+
+static int is_urgent_bio(struct bio *bio)
+{
+	struct page *page = bio_iovec_idx(bio, 0)->bv_page;
+	/*
+	 * ToDo: A new flag should be added to struct bio, which indicates
+	 * 	it contains urgent I/O requests.
+	 */
+	if (!PageReclaim(page))
+		return 0;
+	if (PageSwapCache(page))
+		return 2;
+	return 1;
+}
+
+static inline void resume_to_accept_bios(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (is_device_blocked(dp)
+	    && dp->g_blocked <
dp->g_io_limit[0]+dp->g_io_limit[1]) {
+		clear_device_blocked(dp);
+		wake_up_all(&dp->g_waitq);
+	}
+	if (is_group_blocked(gp)) {
+		clear_group_blocked(gp);
+		wake_up_all(&gp->c_waitq);
+	}
+}
+
+static inline int device_should_block(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (is_group_down(gp))
+		return 0;
+	if (is_device_blocked(dp))
+		return 1;
+	if (dp->g_blocked >= dp->g_io_limit[0] + dp->g_io_limit[1]) {
+		set_device_blocked(dp);
+		return 1;
+	}
+	return 0;
+}
+
+static inline int group_should_block(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (is_group_down(gp))
+		return 0;
+	if (is_group_blocked(gp))
+		return 1;
+	if (dp->g_should_block(gp)) {
+		set_group_blocked(gp);
+		return 1;
+	}
+	return 0;
+}
+
+static void prevent_burst_bios(struct ioband_group *gp, struct bio *bio)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (current->flags & PF_KTHREAD || is_urgent_bio(bio)) {
+		/*
+		 * Kernel threads shouldn't be blocked easily since each of
+		 * them may handle BIOs for several groups on several
+		 * partitions.
+		 */
+		wait_event_lock_irq(dp->g_waitq, !device_should_block(gp),
+						dp->g_lock, do_nothing());
+	} else {
+		wait_event_lock_irq(gp->c_waitq, !group_should_block(gp),
+						dp->g_lock, do_nothing());
+	}
+}
+
+static inline int should_pushback_bio(struct ioband_group *gp)
+{
+	return is_group_suspended(gp) &&
dm_noflush_suspending(gp->c_target);
+}
+
+static inline int prepare_to_issue(struct ioband_group *gp, struct bio *bio)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	dp->g_issued[bio_data_dir(bio)]++;
+	return dp->g_prepare_bio(gp, bio, 0);
+}
+
+static inline int room_for_bio(struct ioband_device *dp)
+{
+	return dp->g_issued[0] < dp->g_io_limit[0]
+		|| dp->g_issued[1] < dp->g_io_limit[1];
+}
+
+static void hold_bio(struct ioband_group *gp, struct bio *bio)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	dp->g_blocked++;
+	if (is_urgent_bio(bio)) {
+		/*
+		 * ToDo:
+		 * When barrier mode is supported, write bios sharing the same
+		 * file system with the currnt one would be all moved
+		 * to g_urgent_bios list.
+		 * You don't have to care about barrier handling if the bio
+		 * is for swapping.
+		 */
+		dp->g_prepare_bio(gp, bio, IOBAND_URGENT);
+		bio_list_add(&dp->g_urgent_bios, bio);
+	} else {
+		gp->c_blocked++;
+		dp->g_hold_bio(gp, bio);
+	}
+}
+
+static inline int room_for_bio_rw(struct ioband_device *dp, int direct)
+{
+	return dp->g_issued[direct] < dp->g_io_limit[direct];
+}
+
+static void push_prio_bio(struct ioband_group *gp, struct bio *bio, int direct)
+{
+	if (bio_list_empty(&gp->c_prio_bios))
+		set_prio_queue(gp, direct);
+	bio_list_add(&gp->c_prio_bios, bio);
+	gp->c_prio_blocked++;
+}
+
+static struct bio *pop_prio_bio(struct ioband_group *gp)
+{
+	struct bio *bio = bio_list_pop(&gp->c_prio_bios);
+
+	if (bio_list_empty(&gp->c_prio_bios))
+		clear_prio_queue(gp);
+
+	if (bio)
+		gp->c_prio_blocked--;
+	return bio;
+}
+
+static int make_issue_list(struct ioband_group *gp, struct bio *bio,
+		 struct bio_list *issue_list, struct bio_list *pushback_list)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	dp->g_blocked--;
+	gp->c_blocked--;
+	if (!gp->c_blocked)
+		resume_to_accept_bios(gp);
+	if (should_pushback_bio(gp))
+		bio_list_add(pushback_list, bio);
+	else {
+		int rw = bio_data_dir(bio);
+
+		gp->c_stat[rw].deferred++;
+		gp->c_stat[rw].sectors += bio_sectors(bio);
+		bio_list_add(issue_list, bio);
+	}
+	return prepare_to_issue(gp, bio);
+}
+
+static void release_urgent_bios(struct ioband_device *dp,
+		struct bio_list *issue_list, struct bio_list *pushback_list)
+{
+	struct bio *bio;
+
+	if (bio_list_empty(&dp->g_urgent_bios))
+		return;
+	while (room_for_bio_rw(dp, 1)) {
+		bio = bio_list_pop(&dp->g_urgent_bios);
+		if (!bio)
+			return;
+		dp->g_blocked--;
+		dp->g_issued[1]++;
+		bio_list_add(issue_list, bio);
+	}
+}
+
+static int release_prio_bios(struct ioband_group *gp,
+		struct bio_list *issue_list, struct bio_list *pushback_list)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct bio *bio;
+	int direct;
+	int ret;
+
+	if (bio_list_empty(&gp->c_prio_bios))
+		return R_OK;
+	direct = prio_queue_direct(gp);
+	while (gp->c_prio_blocked) {
+		if (!dp->g_can_submit(gp))
+			return R_BLOCK;
+		if (!room_for_bio_rw(dp, direct))
+			return R_OK;
+		bio = pop_prio_bio(gp);
+		if (!bio)
+			return R_OK;
+		ret = make_issue_list(gp, bio, issue_list, pushback_list);
+		if (ret)
+			return ret;
+	}
+	return R_OK;
+}
+
+static int release_norm_bios(struct ioband_group *gp,
+		struct bio_list *issue_list, struct bio_list *pushback_list)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct bio *bio;
+	int direct;
+	int ret;
+
+	while (gp->c_blocked - gp->c_prio_blocked) {
+		if (!dp->g_can_submit(gp))
+			return R_BLOCK;
+		if (!room_for_bio(dp))
+			return R_OK;
+		bio = dp->g_pop_bio(gp);
+		if (!bio)
+			return R_OK;
+
+		direct = bio_data_dir(bio);
+		if (!room_for_bio_rw(dp, direct)) {
+			push_prio_bio(gp, bio, direct);
+			continue;
+		}
+		ret = make_issue_list(gp, bio, issue_list, pushback_list);
+		if (ret)
+			return ret;
+	}
+	return R_OK;
+}
+
+static inline int release_bios(struct ioband_group *gp,
+		struct bio_list *issue_list, struct bio_list *pushback_list)
+{
+	int ret = release_prio_bios(gp, issue_list, pushback_list);
+	if (ret)
+		return ret;
+	return release_norm_bios(gp, issue_list, pushback_list);
+}
+
+static struct ioband_group *ioband_group_get(struct ioband_group *head,
+							struct bio *bio)
+{
+	struct ioband_group *gp;
+
+	if (!head->c_type->t_getid)
+		return head;
+
+	gp = ioband_group_find(head, head->c_type->t_getid(bio));
+
+	if (!gp)
+		gp = head;
+	return gp;
+}
+
+/*
+ * Start to control the bandwidth once the number of uncompleted BIOs
+ * exceeds the value of "io_throttle".
+ */
+static int ioband_map(struct dm_target *ti, struct bio *bio,
+						union map_info *map_context)
+{
+	struct ioband_group *gp = ti->private;
+	struct ioband_device *dp = gp->c_banddev;
+	unsigned long flags;
+	int rw;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+
+	/*
+	 * The device is suspended while some of the ioband device
+	 * configurations are being changed.
+	 */
+	if (is_device_suspended(dp))
+		wait_event_lock_irq(dp->g_waitq_suspend,
+			!is_device_suspended(dp), dp->g_lock, do_nothing());
+
+	gp = ioband_group_get(gp, bio);
+	prevent_burst_bios(gp, bio);
+	if (should_pushback_bio(gp)) {
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		return DM_MAPIO_REQUEUE;
+	}
+
+	bio->bi_bdev = gp->c_dev->bdev;
+	bio->bi_sector -= ti->begin;
+	rw = bio_data_dir(bio);
+
+	if (!gp->c_blocked && room_for_bio_rw(dp, rw)) {
+		if (dp->g_can_submit(gp)) {
+			prepare_to_issue(gp, bio);
+			gp->c_stat[rw].immediate++;
+			gp->c_stat[rw].sectors += bio_sectors(bio);
+			spin_unlock_irqrestore(&dp->g_lock, flags);
+			return DM_MAPIO_REMAPPED;
+		} else if (!dp->g_blocked
+				&& dp->g_issued[0] + dp->g_issued[1] == 0) {
+			dprintk(KERN_ERR "ioband_map: token expired "
+					"gp:%p bio:%p\n", gp, bio);
+			queue_delayed_work(dp->g_ioband_wq,
+							&dp->g_conductor, 1);
+		}
+	}
+	hold_bio(gp, bio);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+
+	return DM_MAPIO_SUBMITTED;
+}
+
+/*
+ * Select the best group to resubmit its BIOs.
+ */
+static struct ioband_group *choose_best_group(struct ioband_device *dp)
+{
+	struct ioband_group *gp;
+	struct ioband_group *best = NULL;
+	int	highest = 0;
+	int	pri;
+
+	/* Todo: The algorithm should be optimized.
+	 *       It would be better to use rbtree.
+	 */
+	list_for_each_entry(gp, &dp->g_groups, c_list) {
+		if (!gp->c_blocked || !room_for_bio(dp))
+			continue;
+		if (gp->c_blocked == gp->c_prio_blocked
+			&& !room_for_bio_rw(dp, prio_queue_direct(gp))) {
+			continue;
+		}
+		pri = dp->g_can_submit(gp);
+		if (pri > highest) {
+			highest = pri;
+			best = gp;
+		}
+	}
+
+	return best;
+}
+
+/*
+ * This function is called right after it becomes able to resubmit BIOs.
+ * It selects the best BIOs and passes them to the underlying layer.
+ */
+static void ioband_conduct(struct work_struct *work)
+{
+	struct ioband_device *dp +		container_of(work, struct ioband_device,
g_conductor.work);
+	struct ioband_group *gp = NULL;
+	struct bio *bio;
+	unsigned long flags;
+	struct bio_list issue_list, pushback_list;
+
+	bio_list_init(&issue_list);
+	bio_list_init(&pushback_list);
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	release_urgent_bios(dp, &issue_list, &pushback_list);
+	if (dp->g_blocked) {
+		gp = choose_best_group(dp);
+		if (gp && release_bios(gp, &issue_list, &pushback_list)
+								== R_YIELD)
+			queue_delayed_work(dp->g_ioband_wq,
+							&dp->g_conductor, 0);
+	}
+
+	if (dp->g_blocked && room_for_bio_rw(dp, 0) &&
room_for_bio_rw(dp, 1) &&
+		bio_list_empty(&issue_list) && bio_list_empty(&pushback_list)
&&
+		dp->g_restart_bios(dp)) {
+		dprintk(KERN_ERR "ioband_conduct: token expired dp:%p "
+			"issued(%d,%d) g_blocked(%d)\n", dp,
+			 dp->g_issued[0], dp->g_issued[1], dp->g_blocked);
+		queue_delayed_work(dp->g_ioband_wq, &dp->g_conductor, 0);
+	}
+
+
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+
+	while ((bio = bio_list_pop(&issue_list)))
+		generic_make_request(bio);
+	while ((bio = bio_list_pop(&pushback_list)))
+		bio_endio(bio, -EIO);
+}
+
+static int ioband_end_io(struct dm_target *ti, struct bio *bio,
+				int error, union map_info *map_context)
+{
+	struct ioband_group *gp = ti->private;
+	struct ioband_device *dp = gp->c_banddev;
+	unsigned long flags;
+	int r = error;
+
+	/*
+	 *  XXX: A new error code for device mapper devices should be used
+	 *       rather than EIO.
+	 */
+	if (error == -EIO && should_pushback_bio(gp)) {
+		/* This ioband device is suspending */
+		r = DM_ENDIO_REQUEUE;
+	}
+	/*
+	 * Todo: The algorithm should be optimized to eliminate the spinlock.
+	 */
+	spin_lock_irqsave(&dp->g_lock, flags);
+	dp->g_issued[bio_data_dir(bio)]--;
+
+	/*
+	 * Todo: It would be better to introduce high/low water marks here
+	 * 	 not to kick the workqueues so often.
+	 */
+	if (dp->g_blocked)
+		queue_delayed_work(dp->g_ioband_wq, &dp->g_conductor, 0);
+	else if (is_device_suspended(dp)
+				&& dp->g_issued[0] + dp->g_issued[1] == 0)
+		wake_up_all(&dp->g_waitq_flush);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	return r;
+}
+
+static void ioband_presuspend(struct dm_target *ti)
+{
+	struct ioband_group *gp = ti->private;
+	struct ioband_device *dp = gp->c_banddev;
+
+	mutex_lock(&dp->g_lock_device);
+	ioband_group_stop_all(gp, 1);
+	mutex_unlock(&dp->g_lock_device);
+}
+
+static void ioband_resume(struct dm_target *ti)
+{
+	struct ioband_group *gp = ti->private;
+	struct ioband_device *dp = gp->c_banddev;
+
+	mutex_lock(&dp->g_lock_device);
+	ioband_group_resume_all(gp);
+	mutex_unlock(&dp->g_lock_device);
+}
+
+
+static void ioband_group_status(struct ioband_group *gp, int *szp,
+					char *result, unsigned int maxlen)
+{
+	struct ioband_group_stat *stat;
+	int i, sz = *szp; /* used in DMEMIT() */
+
+	DMEMIT(" %d", gp->c_id);
+	for (i = 0; i < 2; i++) {
+		stat = &gp->c_stat[i];
+		DMEMIT(" %lu %lu %lu",
+			stat->immediate + stat->deferred, stat->deferred,
+			stat->sectors);
+	}
+	*szp = sz;
+}
+
+static int ioband_status(struct dm_target *ti, status_type_t type,
+					char *result, unsigned int maxlen)
+{
+	struct ioband_group *gp = ti->private, *p;
+	struct ioband_device *dp = gp->c_banddev;
+	struct rb_node *node;
+	int sz = 0;	/* used in DMEMIT() */
+	unsigned long flags;
+
+	mutex_lock(&dp->g_lock_device);
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		spin_lock_irqsave(&dp->g_lock, flags);
+		DMEMIT("%s", dp->g_name);
+		ioband_group_status(gp, &sz, result, maxlen);
+		for (node = rb_first(&gp->c_group_root); node;
+						node = rb_next(node)) {
+			p = rb_entry(node, struct ioband_group, c_group_node);
+			ioband_group_status(p, &sz, result, maxlen);
+		}
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		break;
+
+	case STATUSTYPE_TABLE:
+		spin_lock_irqsave(&dp->g_lock, flags);
+		DMEMIT("%s %s %d %d %s %s",
+				gp->c_dev->name, dp->g_name,
+				dp->g_io_throttle, dp->g_io_limit[0],
+				gp->c_type->t_name, dp->g_policy->p_name);
+		dp->g_show(gp, &sz, result, maxlen);
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		break;
+	}
+
+	mutex_unlock(&dp->g_lock_device);
+	return 0;
+}
+
+static int ioband_group_type_select(struct ioband_group *gp, char *name)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct group_type *t;
+	unsigned long flags;
+
+	for (t = dm_ioband_group_type; (t->t_name); t++) {
+		if (!strcmp(name, t->t_name))
+			break;
+	}
+	if (!t->t_name) {
+		DMWARN("ioband type select: %s isn't supported.", name);
+		return -EINVAL;
+	}
+	spin_lock_irqsave(&dp->g_lock, flags);
+	if (!RB_EMPTY_ROOT(&gp->c_group_root)) {
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		return -EBUSY;
+	}
+	gp->c_type = t;
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+
+	return 0;
+}
+
+static int ioband_set_param(struct ioband_group *gp, char *cmd, char *value)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	char *val_str;
+	long id;
+	unsigned long flags;
+	int r;
+
+	r = split_string(value, &id, &val_str);
+	if (r)
+		return r;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	if (id != IOBAND_ID_ANY) {
+		gp = ioband_group_find(gp, id);
+		if (!gp) {
+			spin_unlock_irqrestore(&dp->g_lock, flags);
+			DMWARN("ioband_set_param: id=%ld not found.", id);
+			return -EINVAL;
+		}
+	}
+	r = dp->g_set_param(gp, cmd, val_str);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	return r;
+}
+
+static int ioband_group_attach(struct ioband_group *gp, int id, char *param)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *sub_gp;
+	int r;
+
+	if (id < 0) {
+		DMWARN("ioband_group_attach: invalid id:%d", id);
+		return -EINVAL;
+	}
+	if (!gp->c_type->t_getid) {
+		DMWARN("ioband_group_attach: "
+		       "no ioband group type is specified");
+		return -EINVAL;
+	}
+
+	sub_gp = kzalloc(sizeof(struct ioband_group), GFP_KERNEL);
+	if (!sub_gp)
+		return -ENOMEM;
+
+	r = ioband_group_init(sub_gp, gp, dp, id, param);
+	if (r < 0) {
+		kfree(sub_gp);
+		return r;
+	}
+	return 0;
+}
+
+static int ioband_group_detach(struct ioband_group *gp, int id)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *sub_gp;
+	unsigned long flags;
+
+	if (id < 0) {
+		DMWARN("ioband_group_detach: invalid id:%d", id);
+		return -EINVAL;
+	}
+	spin_lock_irqsave(&dp->g_lock, flags);
+	sub_gp = ioband_group_find(gp, id);
+	if (!sub_gp) {
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		DMWARN("ioband_group_detach: invalid id:%d", id);
+		return -EINVAL;
+	}
+
+	/*
+	 * Todo: Calling suspend_ioband_device() before releasing the
+	 *       ioband group has a large overhead. Need improvement.
+	 */
+	suspend_ioband_device(dp, flags, 0);
+	ioband_group_release(gp, sub_gp);
+	resume_ioband_device(dp);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	return 0;
+}
+
+/*
+ * Message parameters:
+ *	"policy"      <name>
+ *       ex)
+ *		"policy" "weight"
+ *	"type"       
"none"|"pid"|"pgrp"|"node"|"cpuset"|"cgroup"|"user"|"gid"
+ * 	"io_throttle" <value>
+ * 	"io_limit"    <value>
+ *	"attach"      <group id>
+ *	"detach"      <group id>
+ *	"any-command" <group id>:<value>
+ *       ex)
+ *		"weight" 0:<value>
+ *		"token"  24:<value>
+ */
+static int __ioband_message(struct dm_target *ti,
+					unsigned int argc, char **argv)
+{
+	struct ioband_group *gp = ti->private, *p;
+	struct ioband_device *dp = gp->c_banddev;
+	struct rb_node *node;
+	long val;
+	int r = 0;
+	unsigned long flags;
+
+	if (argc == 1 && !strcmp(argv[0], "reset")) {
+		spin_lock_irqsave(&dp->g_lock, flags);
+		memset(gp->c_stat, 0, sizeof(gp->c_stat));
+		for (node = rb_first(&gp->c_group_root); node;
+						 node = rb_next(node)) {
+			p = rb_entry(node, struct ioband_group, c_group_node);
+			memset(p->c_stat, 0, sizeof(p->c_stat));
+		}
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		return 0;
+	}
+
+	if (argc != 2) {
+		DMWARN("Unrecognised band message received.");
+		return -EINVAL;
+	}
+	if (!strcmp(argv[0], "debug")) {
+		r = strict_strtol(argv[1], 0, &val);
+		if (r || val < 0)
+			return -EINVAL;
+		ioband_debug = val;
+		return 0;
+	} else if (!strcmp(argv[0], "io_throttle")) {
+		r = strict_strtol(argv[1], 0, &val);
+		spin_lock_irqsave(&dp->g_lock, flags);
+		if (r || val < 0 ||
+			val > dp->g_io_limit[0] || val > dp->g_io_limit[1]) {
+			spin_unlock_irqrestore(&dp->g_lock, flags);
+			return -EINVAL;
+		}
+		dp->g_io_throttle = (val == 0) ? DEFAULT_IO_THROTTLE : val;
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		ioband_set_param(gp, argv[0], argv[1]);
+		return 0;
+	} else if (!strcmp(argv[0], "io_limit")) {
+		r = strict_strtol(argv[1], 0, &val);
+		if (r || val < 0)
+			return -EINVAL;
+		spin_lock_irqsave(&dp->g_lock, flags);
+		if (val == 0) {
+			struct request_queue *q;
+
+			q = bdev_get_queue(gp->c_dev->bdev);
+			if (!q) {
+				spin_unlock_irqrestore(&dp->g_lock, flags);
+				return -ENXIO;
+			}
+			val = q->nr_requests;
+		}
+		if (val < dp->g_io_throttle) {
+			spin_unlock_irqrestore(&dp->g_lock, flags);
+			return -EINVAL;
+		}
+		dp->g_io_limit[0] = dp->g_io_limit[1] = val;
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		ioband_set_param(gp, argv[0], argv[1]);
+		return 0;
+	} else if (!strcmp(argv[0], "type")) {
+		return ioband_group_type_select(gp, argv[1]);
+	} else if (!strcmp(argv[0], "attach")) {
+		r = strict_strtol(argv[1], 0, &val);
+		if (r)
+			return r;
+		return ioband_group_attach(gp, val, NULL);
+	} else if (!strcmp(argv[0], "detach")) {
+		r = strict_strtol(argv[1], 0, &val);
+		if (r)
+			return r;
+		return ioband_group_detach(gp, val);
+	} else if (!strcmp(argv[0], "policy")) {
+		r = policy_init(dp, argv[1], 0, &argv[2]);
+		return r;
+	} else {
+		/* message anycommand <group-id>:<value> */
+		r = ioband_set_param(gp, argv[0], argv[1]);
+		if (r < 0)
+			DMWARN("Unrecognised band message received.");
+		return r;
+	}
+	return 0;
+}
+
+static int ioband_message(struct dm_target *ti, unsigned int argc, char **argv)
+{
+	struct ioband_group *gp = ti->private;
+	struct ioband_device *dp = gp->c_banddev;
+	int r;
+
+	mutex_lock(&dp->g_lock_device);
+	r = __ioband_message(ti, argc, argv);
+	mutex_unlock(&dp->g_lock_device);
+	return r;
+}
+
+static struct target_type ioband_target = {
+	.name	     = "ioband",
+	.module      = THIS_MODULE,
+	.version     = {1, 3, 0},
+	.ctr	     = ioband_ctr,
+	.dtr	     = ioband_dtr,
+	.map	     = ioband_map,
+	.end_io	     = ioband_end_io,
+	.presuspend  = ioband_presuspend,
+	.resume	     = ioband_resume,
+	.status	     = ioband_status,
+	.message     = ioband_message,
+};
+
+static int __init dm_ioband_init(void)
+{
+	int r;
+
+	r = dm_register_target(&ioband_target);
+	if (r < 0) {
+		DMERR("register failed %d", r);
+		return r;
+	}
+	return r;
+}
+
+static void __exit dm_ioband_exit(void)
+{
+	int r;
+
+	r = dm_unregister_target(&ioband_target);
+	if (r < 0)
+		DMERR("unregister failed %d", r);
+}
+
+module_init(dm_ioband_init);
+module_exit(dm_ioband_exit);
+
+MODULE_DESCRIPTION(DM_NAME " I/O bandwidth control");
+MODULE_AUTHOR("Hirokazu Takahashi <taka at valinux.co.jp>, "
+	      "Ryo Tsuruta <ryov at valinux.co.jp");
+MODULE_LICENSE("GPL");
diff -uprN linux-2.6.26-rc5-mm3.orig/drivers/md/dm-ioband-policy.c
linux-2.6.26-rc5-mm3/drivers/md/dm-ioband-policy.c
--- linux-2.6.26-rc5-mm3.orig/drivers/md/dm-ioband-policy.c	1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.26-rc5-mm3/drivers/md/dm-ioband-policy.c	2008-07-11
19:24:05.000000000 +0900
@@ -0,0 +1,446 @@
+/*
+ * Copyright (C) 2008 VA Linux Systems Japan K.K.
+ *
+ *  I/O bandwidth control
+ *
+ * This file is released under the GPL.
+ */
+#include <linux/bio.h>
+#include <linux/workqueue.h>
+#include <linux/rbtree.h>
+#include "dm.h"
+#include "dm-bio-list.h"
+#include "dm-ioband.h"
+
+/*
+ * The following functions determine when and which BIOs should
+ * be submitted to control the I/O flow.
+ * It is possible to add a new BIO scheduling policy with it.
+ */
+
+
+/*
+ * Functions for weight balancing policy based on the number of I/Os.
+ */
+#define DEFAULT_WEIGHT		100
+#define DEFAULT_TOKENPOOL	2048
+#define DEFAULT_BUCKET		2
+#define IOBAND_IOPRIO_BASE	100
+#define TOKEN_BATCH_UNIT	20
+#define PROCEED_THRESHOLD	8
+#define	LOCAL_ACTIVE_RATIO	8
+#define	GLOBAL_ACTIVE_RATIO	16
+#define OVERCOMMIT_RATE		4
+
+/*
+ * Calculate the effective number of tokens this group has.
+ */
+static int get_token(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int token = gp->c_token;
+	int allowance = dp->g_epoch - gp->c_my_epoch;
+
+	if (allowance) {
+		if (allowance > dp->g_carryover)
+			allowance = dp->g_carryover;
+		token += gp->c_token_initial * allowance;
+	}
+	if (is_group_down(gp))
+		token += gp->c_token_initial * dp->g_carryover * 2;
+
+	return token;
+}
+
+/*
+ * Calculate the priority of a given group.
+ */
+static int iopriority(struct ioband_group *gp)
+{
+	return get_token(gp) * IOBAND_IOPRIO_BASE / gp->c_token_initial + 1;
+}
+
+/*
+ * This function is called when all the active group on the same ioband
+ * device has used up their tokens. It makes a new global epoch so that
+ * all groups on this device will get freshly assigned tokens.
+ */
+static int make_global_epoch(struct ioband_device *dp)
+{
+	struct ioband_group *gp = dp->g_dominant;
+
+	/*
+	 * Don't make a new epoch if the dominant group still has a lot of
+	 * tokens, except when the I/O load is low.
+	 */
+	if (gp) {
+		int iopri = iopriority(gp);
+		if (iopri * PROCEED_THRESHOLD > IOBAND_IOPRIO_BASE &&
+			dp->g_issued[0] + dp->g_issued[1] >= dp->g_io_throttle)
+		return 0;
+	}
+
+	dp->g_epoch++;
+	dprintk(KERN_ERR "make_epoch %d --> %d\n",
+						dp->g_epoch-1, dp->g_epoch);
+
+	/* The leftover tokens will be used in the next epoch. */
+	dp->g_token_extra = dp->g_token_left;
+	if (dp->g_token_extra < 0)
+		dp->g_token_extra = 0;
+	dp->g_token_left = dp->g_token_bucket;
+
+	dp->g_expired = NULL;
+	dp->g_dominant = NULL;
+
+	return 1;
+}
+
+/*
+ * This function is called when this group has used up its own tokens.
+ * It will check whether it's possible to make a new epoch of this group.
+ */
+static inline int make_epoch(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int allowance = dp->g_epoch - gp->c_my_epoch;
+
+	if (!allowance)
+		return 0;
+	if (allowance > dp->g_carryover)
+		allowance = dp->g_carryover;
+	gp->c_my_epoch = dp->g_epoch;
+	return allowance;
+}
+
+/*
+ * Check whether this group has tokens to issue an I/O. Return 0 if it
+ * doesn't have any, otherwise return the priority of this group.
+ */
+static int is_token_left(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int allowance;
+	int delta;
+	int extra;
+
+	if (gp->c_token > 0)
+		return iopriority(gp);
+
+	if (is_group_down(gp)) {
+		gp->c_token = gp->c_token_initial;
+		return iopriority(gp);
+	}
+	allowance = make_epoch(gp);
+	if (!allowance)
+		return 0;
+	/*
+	 * If this group has the right to get tokens for several epochs,
+	 * give all of them to the group here.
+	 */
+	delta = gp->c_token_initial * allowance;
+	dp->g_token_left -= delta;
+	/*
+	 * Give some extra tokens to this group when there have left unused
+	 * tokens on this ioband device from the previous epoch.
+	 */
+	extra = dp->g_token_extra * gp->c_token_initial /
+				 (dp->g_token_bucket - dp->g_token_extra/2);
+	delta += extra;
+	gp->c_token += delta;
+	gp->c_consumed = 0;
+
+	if (gp == dp->g_current)
+		dp->g_yield_mark += delta;
+	dprintk(KERN_ERR "refill token: "
+		"gp:%p token:%d->%d extra(%d) allowance(%d)\n",
+		gp, gp->c_token - delta, gp->c_token, extra, allowance);
+	if (gp->c_token > 0)
+		return iopriority(gp);
+	dprintk(KERN_ERR "refill token: yet empty gp:%p token:%d\n",
+						gp, gp->c_token);
+	return 0;
+}
+
+/*
+ * Use tokens to issue an I/O. After the operation, the number of tokens left
+ * on this group may become negative value, which will be treated as debt.
+ */
+static int consume_token(struct ioband_group *gp, int count, int flag)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (gp->c_consumed * LOCAL_ACTIVE_RATIO < gp->c_token_initial
&&
+		gp->c_consumed * GLOBAL_ACTIVE_RATIO < dp->g_token_bucket) {
+		; /* Do nothing unless this group is really active. */
+	} else if (!dp->g_dominant ||
+			get_token(gp) > get_token(dp->g_dominant)) {
+		/*
+		 * Regard this group as the dominant group on this
+		 * ioband device when it has larger number of tokens
+		 * than those of the previous one.
+		 */
+		dp->g_dominant = gp;
+	}
+	if (dp->g_epoch == gp->c_my_epoch &&
+			gp->c_token > 0 && gp->c_token - count <= 0) {
+		/* Remember the last group which used up its own tokens. */
+		dp->g_expired = gp;
+		if (dp->g_dominant == gp)
+			dp->g_dominant = NULL;
+	}
+
+	if (gp != dp->g_current) {
+		/* This group is the current already. */
+		dp->g_current = gp;
+		dp->g_yield_mark +			gp->c_token - (TOKEN_BATCH_UNIT <<
dp->g_token_unit);
+	}
+	gp->c_token -= count;
+	gp->c_consumed += count;
+	if (gp->c_token <= dp->g_yield_mark && !(flag &
IOBAND_URGENT)) {
+		/*
+		 * Return-value 1 means that this policy requests dm-ioband
+		 * to give a chance to another group to be selected since
+		 * this group has already issued enough amount of I/Os.
+		 */
+		dp->g_current = NULL;
+		return R_YIELD;
+	}
+	/*
+	 * Return-value 0 means that this policy allows dm-ioband to select
+	 * this group to issue I/Os without a break.
+	 */
+	return R_OK;
+}
+
+/*
+ * Consume one token on each I/O.
+ */
+static int prepare_token(struct ioband_group *gp, struct bio *bio, int flag)
+{
+	return consume_token(gp, 1, flag);
+}
+
+/*
+ * Check if this group is able to receive a new bio.
+ */
+static int is_queue_full(struct ioband_group *gp)
+{
+	return gp->c_blocked >= gp->c_limit;
+}
+
+static void set_weight(struct ioband_group *gp, int new)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	struct ioband_group *p;
+
+	dp->g_weight_total += (new - gp->c_weight);
+	gp->c_weight = new;
+
+	if (dp->g_weight_total == 0) {
+		list_for_each_entry(p, &dp->g_groups, c_list)
+			p->c_token = p->c_token_initial = p->c_limit = 1;
+	} else {
+		list_for_each_entry(p, &dp->g_groups, c_list) {
+			p->c_token = p->c_token_initial +				dp->g_token_bucket *
p->c_weight /
+				dp->g_weight_total + 1;
+			p->c_limit = (dp->g_io_limit[0] + dp->g_io_limit[1]) *
+				p->c_weight / dp->g_weight_total /
+				OVERCOMMIT_RATE + 1;
+		}
+	}
+}
+
+static void init_token_bucket(struct ioband_device *dp, int val)
+{
+	dp->g_token_bucket = ((dp->g_io_limit[0] + dp->g_io_limit[1]) *
+				 DEFAULT_BUCKET) << dp->g_token_unit;
+	if (!val)
+		val = DEFAULT_TOKENPOOL << dp->g_token_unit;
+	else if (val < dp->g_token_bucket)
+		val = dp->g_token_bucket;
+	dp->g_carryover = val/dp->g_token_bucket;
+}
+
+static int policy_weight_param(struct ioband_group *gp, char *cmd, char *value)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	long val;
+	int r = 0, err;
+
+	err = strict_strtol(value, 0, &val);
+	if (!strcmp(cmd, "weight")) {
+		if (!err && 0 < val && val <= SHORT_MAX)
+			set_weight(gp, val);
+		else
+			r = -EINVAL;
+	} else if (!strcmp(cmd, "token")) {
+		if (!err && val > 0) {
+			init_token_bucket(dp, val);
+			set_weight(gp, gp->c_weight);
+			dp->g_token_extra = 0;
+		} else
+			r = -EINVAL;
+	} else if (!strcmp(cmd, "io_limit")) {
+		init_token_bucket(dp, dp->g_token_bucket * dp->g_carryover);
+		set_weight(gp, gp->c_weight);
+	} else {
+		r = -EINVAL;
+	}
+	return r;
+}
+
+static int policy_weight_ctr(struct ioband_group *gp, char *arg)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (!arg)
+		arg = __stringify(DEFAULT_WEIGHT);
+	gp->c_my_epoch = dp->g_epoch;
+	gp->c_weight = 0;
+	gp->c_consumed = 0;
+	return policy_weight_param(gp, "weight", arg);
+}
+
+static void policy_weight_dtr(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	set_weight(gp, 0);
+	dp->g_dominant = NULL;
+	dp->g_expired = NULL;
+}
+
+static void policy_weight_show(struct ioband_group *gp, int *szp,
+					char *result, unsigned int maxlen)
+{
+	struct ioband_group *p;
+	struct ioband_device *dp = gp->c_banddev;
+	struct rb_node *node;
+	int sz = *szp; /* used in DMEMIT() */
+
+	DMEMIT(" %d :%d", dp->g_token_bucket * dp->g_carryover,
gp->c_weight);
+
+	for (node = rb_first(&gp->c_group_root); node; node = rb_next(node)) {
+		p = rb_entry(node, struct ioband_group, c_group_node);
+		DMEMIT(" %d:%d", p->c_id, p->c_weight);
+	}
+	*szp = sz;
+}
+
+/*
+ *  <Method>      <description>
+ * g_can_submit   : To determine whether a given group has the right to
+ *                  submit BIOs. The larger the return value the higher the
+ *                  priority to submit. Zero means it has no right.
+ * g_prepare_bio  : Called right before submitting each BIO.
+ * g_restart_bios : Called if this ioband device has some BIOs blocked but none
+ *                  of them can be submitted now. This method has to
+ *                  reinitialize the data to restart to submit BIOs and return
+ *                  0 or 1.
+ *                  The return value 0 means that it has become able to submit
+ *                  them now so that this ioband device will continue its work.
+ *                  The return value 1 means that it is still unable to submit
+ *                  them so that this device will stop its work. And this
+ *                  policy module has to reactivate the device when it gets
+ *                  to be able to submit BIOs.
+ * g_hold_bio     : To hold a given BIO until it is submitted.
+ *                  The default function is used when this method is undefined.
+ * g_pop_bio      : To select and get the best BIO to submit.
+ * g_group_ctr    : To initalize the policy own members of struct ioband_group.
+ * g_group_dtr    : Called when struct ioband_group is removed.
+ * g_set_param    : To update the policy own date.
+ *                  The parameters can be passed through "dmsetup
message"
+ *                  command.
+ * g_should_block : Called every time this ioband device receive a BIO.
+ *                  Return 1 if a given group can't receive any more BIOs,
+ *                  otherwise return 0.
+ * g_show         : Show the configuration.
+ */
+static int policy_weight_init(struct ioband_device *dp, int argc, char **argv)
+{
+	long val;
+	int r = 0;
+
+	if (argc < 1)
+		val = 0;
+	else {
+		r = strict_strtol(argv[0], 0, &val);
+		if (r || val < 0)
+			return -EINVAL;
+	}
+
+	dp->g_can_submit = is_token_left;
+	dp->g_prepare_bio = prepare_token;
+	dp->g_restart_bios = make_global_epoch;
+	dp->g_group_ctr = policy_weight_ctr;
+	dp->g_group_dtr = policy_weight_dtr;
+	dp->g_set_param = policy_weight_param;
+	dp->g_should_block = is_queue_full;
+	dp->g_show  = policy_weight_show;
+
+	dp->g_epoch = 0;
+	dp->g_weight_total = 0;
+	dp->g_current = NULL;
+	dp->g_dominant = NULL;
+	dp->g_expired = NULL;
+	dp->g_token_extra = 0;
+	dp->g_token_unit = 0;
+	init_token_bucket(dp, val);
+	dp->g_token_left = dp->g_token_bucket;
+
+	return 0;
+}
+/* weight balancing policy based on the number of I/Os. --- End --- */
+
+
+/*
+ * Functions for weight balancing policy based on I/O size.
+ * It just borrows a lot of functions from the regular weight balancing policy.
+ */
+static int w2_prepare_token(struct ioband_group *gp, struct bio *bio, int flag)
+{
+	/* Consume tokens depending on the size of a given bio. */
+	return consume_token(gp, bio_sectors(bio), flag);
+}
+
+static int w2_policy_weight_init(struct ioband_device *dp,
+							int argc, char **argv)
+{
+	long val;
+	int r = 0;
+
+	if (argc < 1)
+		val = 0;
+	else {
+		r = strict_strtol(argv[0], 0, &val);
+		if (r || val < 0)
+			return -EINVAL;
+	}
+
+	r = policy_weight_init(dp, argc, argv);
+	if (r < 0)
+		return r;
+
+	dp->g_prepare_bio = w2_prepare_token;
+	dp->g_token_unit = PAGE_SHIFT - 9;
+	init_token_bucket(dp, val);
+	dp->g_token_left = dp->g_token_bucket;
+	return 0;
+}
+/* weight balancing policy based on I/O size. --- End --- */
+
+
+static int policy_default_init(struct ioband_device *dp,
+					int argc, char **argv)
+{
+	return policy_weight_init(dp, argc, argv);
+}
+
+struct policy_type dm_ioband_policy_type[] = {
+	{"default", policy_default_init},
+	{"weight", policy_weight_init},
+	{"weight-iosize", w2_policy_weight_init},
+	{NULL,     policy_default_init}
+};
diff -uprN linux-2.6.26-rc5-mm3.orig/drivers/md/dm-ioband-type.c
linux-2.6.26-rc5-mm3/drivers/md/dm-ioband-type.c
--- linux-2.6.26-rc5-mm3.orig/drivers/md/dm-ioband-type.c	1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.26-rc5-mm3/drivers/md/dm-ioband-type.c	2008-07-11
19:24:05.000000000 +0900
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2008 VA Linux Systems Japan K.K.
+ *
+ *  I/O bandwidth control
+ *
+ * This file is released under the GPL.
+ */
+#include <linux/bio.h>
+#include "dm.h"
+#include "dm-bio-list.h"
+#include "dm-ioband.h"
+
+/*
+ * Any I/O bandwidth can be divided into several bandwidth groups, each of
which
+ * has its own unique ID. The following functions are called to determine
+ * which group a given BIO belongs to and return the ID of the group.
+ */
+
+/* ToDo: unsigned long value would be better for group ID */
+
+static int ioband_process_id(struct bio *bio)
+{
+	/*
+	 * This function will work for KVM and Xen.
+	 */
+	return (int)current->tgid;
+}
+
+static int ioband_process_group(struct bio *bio)
+{
+	return (int)task_pgrp_nr(current);
+}
+
+static int ioband_uid(struct bio *bio)
+{
+	return (int)current->uid;
+}
+
+static int ioband_gid(struct bio *bio)
+{
+	return (int)current->gid;
+}
+
+static int ioband_cpuset(struct bio *bio)
+{
+	return 0;	/* not implemented yet */
+}
+
+static int ioband_node(struct bio *bio)
+{
+	return 0;	/* not implemented yet */
+}
+
+static int ioband_cgroup(struct bio *bio)
+{
+  /*
+   * This function should return the ID of the cgroup which issued
"bio".
+   * The ID of the cgroup which the current process belongs to won't be
+   * suitable ID for this purpose, since some BIOs will be handled by kernel
+   * threads like aio or pdflush on behalf of the process requesting the BIOs.
+   */
+	return 0;	/* not implemented yet */
+}
+
+struct group_type dm_ioband_group_type[] = {
+	{"none",   NULL},
+	{"pgrp",   ioband_process_group},
+	{"pid",    ioband_process_id},
+	{"node",   ioband_node},
+	{"cpuset", ioband_cpuset},
+	{"cgroup", ioband_cgroup},
+	{"user",   ioband_uid},
+	{"uid",    ioband_uid},
+	{"gid",    ioband_gid},
+	{NULL,     NULL}
+};
diff -uprN linux-2.6.26-rc5-mm3.orig/drivers/md/dm-ioband.h
linux-2.6.26-rc5-mm3/drivers/md/dm-ioband.h
--- linux-2.6.26-rc5-mm3.orig/drivers/md/dm-ioband.h	1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.26-rc5-mm3/drivers/md/dm-ioband.h	2008-07-11 19:24:05.000000000
+0900
@@ -0,0 +1,190 @@
+/*
+ * Copyright (C) 2008 VA Linux Systems Japan K.K.
+ *
+ *  I/O bandwidth control
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/version.h>
+#include <linux/wait.h>
+
+#define DEFAULT_IO_THROTTLE	4
+#define DEFAULT_IO_LIMIT	128
+#define IOBAND_NAME_MAX 31
+#define IOBAND_ID_ANY (-1)
+
+struct ioband_group;
+
+struct ioband_device {
+	struct list_head	g_groups;
+	struct delayed_work     g_conductor;
+	struct workqueue_struct	*g_ioband_wq;
+	struct	bio_list	g_urgent_bios;
+	int	g_io_throttle;
+	int	g_io_limit[2];
+	int	g_issued[2];
+	int	g_blocked;
+	spinlock_t	g_lock;
+	struct mutex	g_lock_device;
+	wait_queue_head_t g_waitq;
+	wait_queue_head_t g_waitq_suspend;
+	wait_queue_head_t g_waitq_flush;
+
+	int	g_ref;
+	struct	list_head g_list;
+	int	g_flags;
+	char	g_name[IOBAND_NAME_MAX + 1];
+	struct	policy_type *g_policy;
+
+	/* policy dependent */
+	int	(*g_can_submit)(struct ioband_group *);
+	int	(*g_prepare_bio)(struct ioband_group *, struct bio *, int);
+	int	(*g_restart_bios)(struct ioband_device *);
+	void	(*g_hold_bio)(struct ioband_group *, struct bio *);
+	struct bio * (*g_pop_bio)(struct ioband_group *);
+	int	(*g_group_ctr)(struct ioband_group *, char *);
+	void	(*g_group_dtr)(struct ioband_group *);
+	int	(*g_set_param)(struct ioband_group *, char *cmd, char *value);
+	int	(*g_should_block)(struct ioband_group *);
+	void	(*g_show)(struct ioband_group *, int *, char *, unsigned int);
+
+	/* members for weight balancing policy */
+	int	g_epoch;
+	int	g_weight_total;
+		/* the number of tokens which can be used in every epoch */
+	int	g_token_bucket;
+		/* how many epochs tokens can be carried over */
+	int	g_carryover;
+		/* how many tokens should be used for one page-sized I/O */
+	int	g_token_unit;
+		/* the last group which used a token */
+	struct ioband_group *g_current;
+		/* give another group a chance to be scheduled when the rest
+		   of tokens of the current group reaches this mark */
+	int	g_yield_mark;
+		/* the latest group which used up its tokens */
+	struct ioband_group *g_expired;
+		/* the group which has the largest number of tokens in the
+		   active groups */
+	struct ioband_group *g_dominant;
+		/* the number of unused tokens in this epoch */
+	int	g_token_left;
+		/* left-over tokens from the previous epoch */
+	int	g_token_extra;
+};
+
+struct ioband_group_stat {
+	unsigned long	sectors;
+	unsigned long	immediate;
+	unsigned long	deferred;
+};
+
+struct ioband_group {
+	struct	list_head c_list;
+	struct ioband_device *c_banddev;
+	struct dm_dev *c_dev;
+	struct dm_target *c_target;
+	struct	bio_list c_blocked_bios;
+	struct	bio_list c_prio_bios;
+	struct	rb_root c_group_root;
+	struct  rb_node c_group_node;
+	int	c_id;	/* should be unsigned long or unsigned long long */
+	char	c_name[IOBAND_NAME_MAX + 1];	/* rfu */
+	int	c_blocked;
+	int	c_prio_blocked;
+	wait_queue_head_t c_waitq;
+	int	c_flags;
+	struct	ioband_group_stat c_stat[2];	/* hold rd/wr status */
+	struct	group_type *c_type;
+
+	/* members for weight balancing policy */
+	int	c_weight;
+	int	c_my_epoch;
+	int	c_token;
+	int	c_token_initial;
+	int	c_limit;
+	int     c_consumed;
+
+	/* rfu */
+	/* struct bio_list	c_ordered_tag_bios; */
+};
+
+#define IOBAND_URGENT 1
+
+#define DEV_BIO_BLOCKED		1
+#define DEV_SUSPENDED		2
+
+#define set_device_blocked(dp)		((dp)->g_flags |= DEV_BIO_BLOCKED)
+#define clear_device_blocked(dp)	((dp)->g_flags &= ~DEV_BIO_BLOCKED)
+#define is_device_blocked(dp)		((dp)->g_flags & DEV_BIO_BLOCKED)
+
+#define set_device_suspended(dp)	((dp)->g_flags |= DEV_SUSPENDED)
+#define clear_device_suspended(dp)	((dp)->g_flags &= ~DEV_SUSPENDED)
+#define is_device_suspended(dp)		((dp)->g_flags & DEV_SUSPENDED)
+
+#define IOG_PRIO_BIO_WRITE	1
+#define IOG_PRIO_QUEUE		2
+#define IOG_BIO_BLOCKED		4
+#define IOG_GOING_DOWN		8
+#define IOG_SUSPENDED		16
+#define IOG_NEED_UP		32
+
+#define R_OK		0
+#define R_BLOCK		1
+#define R_YIELD		2
+
+#define set_group_blocked(gp)		((gp)->c_flags |= IOG_BIO_BLOCKED)
+#define clear_group_blocked(gp)		((gp)->c_flags &= ~IOG_BIO_BLOCKED)
+#define is_group_blocked(gp)		((gp)->c_flags & IOG_BIO_BLOCKED)
+
+#define set_group_down(gp)		((gp)->c_flags |= IOG_GOING_DOWN)
+#define clear_group_down(gp)		((gp)->c_flags &= ~IOG_GOING_DOWN)
+#define is_group_down(gp)		((gp)->c_flags & IOG_GOING_DOWN)
+
+#define set_group_suspended(gp)		((gp)->c_flags |= IOG_SUSPENDED)
+#define clear_group_suspended(gp)	((gp)->c_flags &= ~IOG_SUSPENDED)
+#define is_group_suspended(gp)		((gp)->c_flags & IOG_SUSPENDED)
+
+#define set_group_need_up(gp)		((gp)->c_flags |= IOG_NEED_UP)
+#define clear_group_need_up(gp)		((gp)->c_flags &= ~IOG_NEED_UP)
+#define group_need_up(gp)		((gp)->c_flags & IOG_NEED_UP)
+
+#define set_prio_read(gp)		((gp)->c_flags |= IOG_PRIO_QUEUE)
+#define clear_prio_read(gp)		((gp)->c_flags &= ~IOG_PRIO_QUEUE)
+#define is_prio_read(gp) \
+	((gp)->c_flags & (IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE) == IOG_PRIO_QUEUE)
+
+#define set_prio_write(gp) \
+	((gp)->c_flags |= (IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE))
+#define clear_prio_write(gp) \
+	((gp)->c_flags &= ~(IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE))
+#define is_prio_write(gp) \
+	((gp)->c_flags & (IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE) == \
+		(IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE))
+
+#define set_prio_queue(gp, direct) \
+	((gp)->c_flags |= (IOG_PRIO_QUEUE|direct))
+#define clear_prio_queue(gp)		clear_prio_write(gp)
+#define is_prio_queue(gp)		((gp)->c_flags & IOG_PRIO_QUEUE)
+#define prio_queue_direct(gp)		((gp)->c_flags & IOG_PRIO_BIO_WRITE)
+
+
+struct policy_type {
+	const char *p_name;
+	int	  (*p_policy_init)(struct ioband_device *, int, char **);
+};
+
+extern struct policy_type dm_ioband_policy_type[];
+
+struct group_type {
+	const char *t_name;
+	int	  (*t_getid)(struct bio *);
+};
+
+extern struct group_type dm_ioband_group_type[];
+
+/* Just for debugging */
+extern long ioband_debug;
+#define dprintk(format, a...) \
+	if (ioband_debug > 0) ioband_debug--, printk(format, ##a)