Hi everyone,

This is dm-ioband version 0.0.4 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.

Changes since 0.0.3 (5th February):
   - Improve the performance when many processes are issuing I/Os
     simultaneously. 
   - Change the table format to fully support dmsetup table/load commands.
     The table format consists all configuration parameters.
   - Port to linux-2.6.25.

An administration tool is available. It makes it easy to configure
bandwidths of disk partitions.
You can download it and find the manual at
http://people.valinux.co.jp/~kaizuka/dm-ioband/iobandctl/

For more details, please refer to:
http://people.valinux.co.jp/~ryov/dm-ioband/

Thanks,
Ryo Tsuruta
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Here is the patch of dm-ioband.

Based on 2.6.25
Signed-off-by: Ryo Tsuruta <ryov@valinux.co.jp>
Signed-off-by: Hirokazu Takahashi <taka@valinux.co.jp>

diff -uprN linux-2.6.25.orig/drivers/md/dm-ioband-ctl.c linux-2.6.25/drivers/md/dm-ioband-ctl.c
--- linux-2.6.25.orig/drivers/md/dm-ioband-ctl.c	1970-01-01 09:00:00.000000000 +0900
+++ linux-2.6.25/drivers/md/dm-ioband-ctl.c	2008-04-24 19:44:08.000000000 +0900
@@ -0,0 +1,1036 @@
+/*
+ * Copyright (C) 2008 VA Linux Systems Japan K.K.
+ * Authors: Hirokazu Takahashi <taka@valinux.co.jp>
+ *          Ryo Tsuruta <ryov@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 "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);
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)
+static void ioband_conduct(void *);
+#else
+static void ioband_conduct(struct work_struct *);
+#endif
+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 int policy_init(struct ioband_device *dp, char *name,
+							int argc, char **argv)
+{
+	struct policy_type *p;
+	int r;
+
+	for (p = dm_ioband_policy_type; (p->p_name); p++) {
+		if (!strcmp(name, p->p_name))
+			break;
+	}
+
+	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;
+	return r;
+}
+
+static struct ioband_device *alloc_ioband_device(char *name, char *policy,
+			int io_throttle, int io_limit, int argc, char **argv)
+
+{
+	struct ioband_device *dp = NULL;
+	struct ioband_device *p;
+	struct ioband_device *new;
+	unsigned long flags;
+
+	new = kzalloc(sizeof(struct ioband_device), GFP_KERNEL);
+	if (!new)
+		goto try_to_find;
+
+	/*
+	 * 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) {
+		kfree(new);
+		new = NULL;
+		goto try_to_find;
+	}
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)
+	INIT_WORK(&new->g_conductor, ioband_conduct, new);
+#else
+	INIT_WORK(&new->g_conductor, ioband_conduct);
+#endif
+	INIT_LIST_HEAD(&new->g_groups);
+	INIT_LIST_HEAD(&new->g_list);
+	spin_lock_init(&new->g_lock);
+	new->g_io_throttle = io_throttle;
+	new->g_io_limit = io_limit;
+	new->g_issued = 0;
+	new->g_blocked = 0;
+	new->g_ref = 0;
+	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);
+
+try_to_find:
+	spin_lock_irqsave(&ioband_devicelist_lock, flags);
+	list_for_each_entry(p, &ioband_device_list, g_list) {
+		if (!strcmp(p->g_name, name)) {
+			dp = p;
+			break;
+		}
+	}
+	if (!dp && (new)) {
+		if (policy_init(new, policy, argc, argv) == 0) {
+			dp = new;
+			new = NULL;
+			list_add_tail(&dp->g_list, &ioband_device_list);
+		}
+	}
+	spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
+
+	if (new) {
+		destroy_workqueue(new->g_ioband_wq);
+		kfree(new);
+	}
+
+	return dp;
+}
+
+static inline void release_ioband_device(struct ioband_device *dp)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ioband_devicelist_lock, flags);
+	if (!list_empty(&dp->g_groups)) {
+		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 struct ioband_group *ioband_group_find(struct ioband_group *head,int id)
+{
+	struct ioband_group *p;
+	struct ioband_group *gp = NULL;
+
+	list_for_each_entry(p, &head->c_group_list, c_group_list) {
+		if (p->c_id == id || id == IOBAND_ID_ANY)
+			gp = p;
+	}
+	return gp;
+}
+
+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);
+	gp->c_id = id;	/* should be verified */
+	gp->c_blocked = 0;
+	memset(gp->c_stat, 0, sizeof(gp->c_stat));
+	init_waitqueue_head(&gp->c_waitq);
+	gp->c_flags = 0;
+
+	INIT_LIST_HEAD(&gp->c_group_list);
+
+	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;
+	}
+
+	dp->g_ref++;
+	list_add_tail(&gp->c_list, &dp->g_groups);
+
+	r = dp->g_group_ctr(gp, param);
+	if (r) {
+		list_del(&gp->c_list);
+		dp->g_ref--;
+		return r;
+	}
+
+	if (head) {
+		list_add_tail(&gp->c_group_list, &head->c_group_list);
+		gp->c_dev = head->c_dev;
+		gp->c_target = head->c_target;
+	}
+
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+
+	return 0;
+}
+
+static inline void ioband_group_release(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	list_del(&gp->c_list);
+	list_del(&gp->c_group_list);
+	dp->g_ref--;
+	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(group);
+	ioband_group_release(gp);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+}
+
+static void ioband_group_stop(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	set_group_down(gp);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	queue_work(dp->g_ioband_wq, &dp->g_conductor);
+	flush_workqueue(dp->g_ioband_wq);
+}
+
+static void ioband_group_stop_all(struct ioband_group *head, int suspend)
+{
+	struct ioband_device *dp = head->c_banddev;
+	struct ioband_group *p;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	list_for_each_entry(p, &head->c_group_list, c_group_list) {
+		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_work(dp->g_ioband_wq, &dp->g_conductor);
+	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;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	list_for_each_entry(p, &head->c_group_list, c_group_list) {
+		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);
+}
+
+/*
+ * 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, *defgrp;
+	struct ioband_device *dp;
+	int io_throttle = DEFAULT_IO_THROTTLE;
+	int io_limit = DEFAULT_IO_LIMIT;
+	int i, r = 0;
+	long val, id;
+	char *param, *endp;
+
+	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]);
+
+	gp = kzalloc(sizeof(struct ioband_group), GFP_KERNEL);
+	if (!gp) {
+		ti->error = "Cannot allocate memory for ioband group";
+		return -ENOMEM;
+	}
+
+	r = dm_get_device(ti, argv[0], 0, ti->len,
+			  dm_table_get_mode(ti->table), &gp->c_dev);
+	if (r) {
+		kfree(gp);
+		ti->error = "Device lookup failed";
+		return r;
+	}
+	ti->private = gp;
+
+	val = simple_strtol(argv[2], NULL, 0);
+	if (val > 0)
+		io_throttle = val;
+
+	val = simple_strtol(argv[3], NULL, 0);
+	if (val > 0)
+		io_limit = val;
+	else {
+		struct request_queue *q;
+
+		q = bdev_get_queue(gp->c_dev->bdev);
+		if (!q) {
+			dm_put_device(ti, gp->c_dev);
+			kfree(gp);
+			ti->error = "Can't get queue size";
+			return -ENXIO;
+		}
+		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], argv[5], io_throttle, io_limit,
+			argc - POLICY_PARAM_START, &argv[POLICY_PARAM_START]);
+	if (!dp) {
+		dm_put_device(ti, gp->c_dev);
+		kfree(gp);
+		ti->error = "Cannot create ioband device";
+		return -EINVAL;
+	}
+
+	for (i = POLICY_PARAM_START, defgrp = NULL; i < argc; i++) {
+		param = strpbrk(argv[i], POLICY_PARAM_DELIM);
+		if (!param)
+			continue;
+		if (param == argv[i]) { /* default ioband group */
+			if (defgrp) {
+				ti->error =
+					"Default ioband group specified twice";
+				r = -EINVAL;
+				goto error;
+			}
+			param++;
+			r = ioband_group_init(gp, NULL, dp,
+							IOBAND_ID_ANY, param);
+			if (r) {
+				ti->error =
+					"Cannot create default ioband group";
+				goto error;
+			}
+			defgrp = gp;
+			r = ioband_group_type_select(defgrp, argv[4]);
+			if (r) {
+				ti->error = "Cannot set ioband group type";
+				goto error;
+			}
+		} else { /* sub ioband group */
+			if (!defgrp)
+				break;
+			id = simple_strtol(argv[i], &endp, 0);
+			if (!strchr(POLICY_PARAM_DELIM, *endp)) {
+				ti->error = "Invalid ioband group ID";
+				r = -EINVAL;
+				goto error;
+			}
+			param++;
+			r = ioband_group_attach(defgrp, id, param);
+			if (r) {
+				ti->error = "Cannot create ioband group";
+				goto error;
+			}
+		}
+	}
+
+	if (!defgrp) {
+		ti->error = "No default ioband group specified";
+		r = -EINVAL;
+		goto error;
+	}
+	return 0;
+
+error:
+	dm_put_device(ti, gp->c_dev);
+	if (!defgrp)
+		kfree(gp);
+	else
+		ioband_group_destroy_all(gp);
+	release_ioband_device(dp);
+	return r;
+}
+
+static void ioband_dtr(struct dm_target *ti)
+{
+	struct ioband_group *gp = ti->private;
+	struct ioband_device *dp = gp->c_banddev;
+
+	ioband_group_stop_all(gp, 0);
+	dm_put_device(ti, gp->c_dev);
+	ioband_group_destroy_all(gp);
+	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 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) {
+		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) {
+		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 inline void do_nothing(void) {}
+
+static inline void prevent_burst_bios(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (!current->mm) {
+		/*
+		 * 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 void prepare_to_issue(struct ioband_group *gp, struct bio *bio)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	dp->g_prepare_bio(gp, bio);
+	dp->g_issued++;
+}
+
+static inline int room_for_bio(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	return dp->g_issued < dp->g_io_limit || is_group_down(gp);
+}
+
+static inline void hold_bio(struct ioband_group *gp, struct bio *bio)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	dp->g_blocked++;
+	gp->c_blocked++;
+	dp->g_hold_bio(gp, bio);
+}
+
+static inline int release_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;
+
+	while (dp->g_can_submit(gp) && gp->c_blocked) {
+		if (!room_for_bio(gp))
+			return 1;
+		bio = dp->g_pop_bio(gp);
+		if (!bio)
+			return 0;
+		dp->g_blocked--;
+		gp->c_blocked--;
+		if (!gp->c_blocked)
+			resume_to_accept_bios(gp);
+		prepare_to_issue(gp, bio);
+		if (is_group_suspended(gp))
+			bio_list_add(pushback_list, bio);
+		else
+			bio_list_add(issue_list, bio);
+	}
+
+	return 0;
+}
+
+static inline 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_group_stat *bws;
+	struct ioband_device *dp = gp->c_banddev;
+	unsigned long flags;
+
+#if 0	/* not supported yet */
+	if (bio_barrier(bio))
+		return -EOPNOTSUPP;
+#endif
+
+	spin_lock_irqsave(&dp->g_lock, flags);
+	gp = ioband_group_get(gp, bio);
+	prevent_burst_bios(gp);
+	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;
+	bws = &gp->c_stat[bio_data_dir(bio)];
+	bws->sectors += bio_sectors(bio);
+retry:
+	if (!gp->c_blocked && room_for_bio(gp)) {
+		if (dp->g_can_submit(gp)) {
+			prepare_to_issue(gp, bio);
+			bws->immediate++;
+			spin_unlock_irqrestore(&dp->g_lock, flags);
+			return DM_MAPIO_REMAPPED;
+		} else if (dp->g_issued < dp->g_io_throttle) {
+			dprintk(KERN_ERR "ioband_map: token expired "
+						"gp:%p bio:%p\n", gp, bio);
+			if (dp->g_restart_bios(dp))
+				goto retry;
+		}
+	}
+	hold_bio(gp, bio);
+	bws->deferred++;
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+
+	return DM_MAPIO_SUBMITTED;
+}
+
+/*
+ * Select the best group to resubmit its BIOs.
+ */
+static inline 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(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.
+ */
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)
+static void ioband_conduct(void *p)
+{
+	struct ioband_device *dp = (struct ioband_device *)p;
+#else
+static void ioband_conduct(struct work_struct *work)
+{
+	struct ioband_device *dp =
+		container_of(work, struct ioband_device, g_conductor);
+#endif
+	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);
+retry:
+	while (dp->g_blocked && (gp = choose_best_group(dp)))
+		release_bios(gp, &issue_list, &pushback_list);
+
+	if (dp->g_blocked && dp->g_issued < dp->g_io_throttle) {
+		dprintk(KERN_ERR "ioband_conduct: token expired gp:%p\n", gp);
+		if (dp->g_restart_bios(dp))
+			goto retry;
+	}
+
+	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)))
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
+		bio_endio(bio, bio->bi_size, -EIO);
+#else
+		bio_endio(bio, -EIO);
+#endif
+}
+
+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--;
+
+	/*
+	 * Todo: It would be better to introduce high/low water marks here
+	 * 	 not to kick the workqueues so often.
+	 */
+	if (dp->g_blocked)
+		queue_work(dp->g_ioband_wq, &dp->g_conductor);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	return r;
+}
+
+static void ioband_presuspend(struct dm_target *ti)
+{
+	struct ioband_group *gp = ti->private;
+	ioband_group_stop_all(gp, 1);
+}
+
+static void ioband_resume(struct dm_target *ti)
+{
+	struct ioband_group *gp = ti->private;
+	ioband_group_resume_all(gp);
+}
+
+
+static void ioband_group_status(struct ioband_group *gp, int *szp,
+					char *result, unsigned int maxlen)
+{
+	struct ioband_group_stat *bws;
+	unsigned long reqs;
+	int i, sz = *szp; /* used in DMEMIT() */
+
+	DMEMIT(" %d", gp->c_id);
+	for (i = 0; i < 2; i++) {
+		bws = &gp->c_stat[i];
+		reqs = bws->immediate + bws->deferred;
+		DMEMIT(" %lu %lu %lu",
+			bws->immediate + bws->deferred, bws->deferred,
+			bws->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;
+	int sz = 0;	/* used in DMEMIT() */
+	unsigned long flags;
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		spin_lock_irqsave(&dp->g_lock, flags);
+		DMEMIT("%s", dp->g_name);
+		ioband_group_status(gp, &sz, result, maxlen);
+		list_for_each_entry(p, &gp->c_group_list, c_group_list)
+			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,
+				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;
+	}
+
+	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 (!list_empty(&gp->c_group_list)) {
+		spin_unlock_irqrestore(&dp->g_lock, flags);
+		return -EBUSY;
+	}
+	gp->c_type = t;
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+
+	return 0;
+}
+
+static inline int split_string(char *s, char **v)
+{
+	long id = IOBAND_ID_ANY;
+	char *p, *q;
+
+	p = strsep(&s, POLICY_PARAM_DELIM);
+	q = strsep(&s, POLICY_PARAM_DELIM);
+	if (!q) {
+		*v = p;
+	} else {
+		id = simple_strtol(p, NULL, 0);
+		*v = q;
+	}
+	return id;
+}
+
+static int ioband_set_param(struct ioband_group *gp, char *cmd, char *value)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	char *val_str;
+	int id;
+	unsigned long flags;
+	int r;
+
+	id = split_string(value, &val_str);
+
+	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=%d 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);
+	spin_unlock_irqrestore(&dp->g_lock, flags);
+	if (!sub_gp) {
+		DMWARN("ioband_group_detach: invalid id:%d", id);
+		return -EINVAL;
+	}
+	ioband_group_stop(sub_gp);
+	spin_lock_irqsave(&dp->g_lock, flags);
+	ioband_group_release(sub_gp);
+	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;
+	long val = 0;
+	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));
+		list_for_each_entry(p, &gp->c_group_list, c_group_list)
+			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")) {
+		ioband_debug = simple_strtol(argv[1], NULL, 0);
+		if (ioband_debug < 0) ioband_debug = 0;
+		return 0;
+	} else if (!strcmp(argv[0], "io_throttle")) {
+		val = simple_strtol(argv[1], NULL, 0);
+		spin_lock_irqsave(&dp->g_lock, flags);
+		if (val < 0 || val > dp->g_io_limit) {
+			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")) {
+		val = simple_strtol(argv[1], NULL, 0);
+		if (val == 0) {
+			struct request_queue *q;
+
+			q = bdev_get_queue(gp->c_dev->bdev);
+			if (!q)
+				return -ENXIO;
+			val = q->nr_requests;
+		}
+		spin_lock_irqsave(&dp->g_lock, flags);
+		if (val < dp->g_io_throttle) {
+			spin_unlock_irqrestore(&dp->g_lock, flags);
+			return -EINVAL;
+		}
+		dp->g_io_limit = 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")) {
+		long id = simple_strtol(argv[1], NULL, 0);
+		return ioband_group_attach(gp, id, NULL);
+	} else if (!strcmp(argv[0], "detach")) {
+		long id = simple_strtol(argv[1], NULL, 0);
+		return ioband_group_detach(gp, id);
+	} 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 struct target_type ioband_target = {
+	.name	     = "ioband",
+	.module      = THIS_MODULE,
+	.version     = {0, 0, 4},
+	.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@valinux.co.jp>, "
+	      "Ryo Tsuruta <ryov@valinux.co.jp");
+MODULE_LICENSE("GPL");
diff -uprN linux-2.6.25.orig/drivers/md/dm-ioband.h linux-2.6.25/drivers/md/dm-ioband.h
--- linux-2.6.25.orig/drivers/md/dm-ioband.h	1970-01-01 09:00:00.000000000 +0900
+++ linux-2.6.25/drivers/md/dm-ioband.h	2008-04-24 12:14:51.000000000 +0900
@@ -0,0 +1,127 @@
+/*
+ * 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 work_struct	g_conductor;
+	struct workqueue_struct	*g_ioband_wq;
+	int	g_io_throttle;
+	int	g_io_limit;
+	int	g_issued;
+	int	g_blocked;
+	spinlock_t	g_lock;
+	wait_queue_head_t g_waitq;
+
+	int	g_ref;		/* just for debugging */
+	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 *);
+	void	(*g_prepare_bio)(struct ioband_group *, struct bio *);
+	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;
+	int	g_token_base;
+
+};
+
+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	list_head c_group_list;
+	int	c_id;	/* should be unsigned long or unsigned long long */
+	char	c_name[IOBAND_NAME_MAX + 1];	/* rfu */
+	int	c_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_init_value;
+	int	c_limit;
+
+	/* rfu */
+	/* struct bio_list	c_ordered_tag_bios; */
+};
+
+#define DEV_BIO_BLOCKED	1
+
+#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 IOG_BIO_BLOCKED	1
+#define IOG_GOING_DOWN	2
+#define IOG_SUSPENDED	4
+
+#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)
+
+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)
diff -uprN linux-2.6.25.orig/drivers/md/dm-ioband-policy.c linux-2.6.25/drivers/md/dm-ioband-policy.c
--- linux-2.6.25.orig/drivers/md/dm-ioband-policy.c	1970-01-01 09:00:00.000000000 +0900
+++ linux-2.6.25/drivers/md/dm-ioband-policy.c	2008-04-24 19:49:22.000000000 +0900
@@ -0,0 +1,241 @@
+/*
+ * 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 "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.
+ */
+#define DEFAULT_WEIGHT	100
+#define DEFAULT_TOKENBASE	2048
+#define IOBAND_IOPRIO_BASE 100
+
+static int proceed_global_epoch(struct ioband_device *dp)
+{
+	dp->g_epoch++;
+#if 0	/* this will also work correctly */
+	if (dp->g_blocked)
+		queue_work(dp->g_ioband_wq, &dp->g_conductor);
+	return 0;
+#endif
+	dprintk(KERN_ERR "proceed_epoch %d --> %d\n",
+						dp->g_epoch-1, dp->g_epoch);
+	return 1;
+}
+
+static inline int proceed_epoch(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (gp->c_my_epoch != dp->g_epoch) {
+		gp->c_my_epoch = dp->g_epoch;
+		return 1;
+	}
+	return 0;
+}
+
+static inline int iopriority(struct ioband_group *gp)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	int iopri;
+
+	iopri = gp->c_token*IOBAND_IOPRIO_BASE/gp->c_token_init_value + 1;
+	if (gp->c_my_epoch != dp->g_epoch)
+		iopri += IOBAND_IOPRIO_BASE;
+	if (is_group_down(gp))
+		iopri += IOBAND_IOPRIO_BASE*2;
+
+	return iopri;
+}
+
+static int is_token_left(struct ioband_group *gp)
+{
+	if (gp->c_token > 0)
+		return iopriority(gp);
+
+	if (proceed_epoch(gp) || is_group_down(gp)) {
+		gp->c_token = gp->c_token_init_value;
+		dprintk(KERN_ERR "refill token: gp:%p token:%d\n",
+							gp, gp->c_token);
+		return iopriority(gp);
+	}
+	return 0;
+}
+
+static void prepare_token(struct ioband_group *gp, struct bio *bio)
+{
+	gp->c_token--;
+}
+
+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;
+
+	list_for_each_entry(p, &dp->g_groups, c_list) {
+		/* Fixme: it might overflow */
+		p->c_token = p->c_token_init_value =
+		   dp->g_token_base*p->c_weight/dp->g_weight_total + 1;
+		p->c_limit =
+		   dp->g_io_limit*p->c_weight/dp->g_weight_total + 1;
+	}
+}
+
+static int policy_weight_ctr(struct ioband_group *gp, char *arg)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	char *endp;
+	long weight;
+
+	if (!arg)
+		weight = DEFAULT_WEIGHT;
+	else {
+		weight = simple_strtol(arg, &endp, 0);
+		if (*endp != '\0' || weight <= 0)
+			return -EINVAL;
+	}
+
+	gp->c_my_epoch = dp->g_epoch;
+	gp->c_weight = 0;
+	set_weight(gp, weight);
+	return 0;
+}
+
+static void policy_weight_dtr(struct ioband_group *gp)
+{
+	set_weight(gp, 0);
+}
+
+static int policy_weight_param(struct ioband_group *gp, char *cmd, char *value)
+{
+	struct ioband_device *dp = gp->c_banddev;
+	long val = simple_strtol(value, NULL, 0);
+	int r = 0;
+
+	if (!strcmp(cmd, "weight")) {
+		if (val > 0)
+			set_weight(gp, val);
+		else
+			r = -EINVAL;
+	} else if (!strcmp(cmd, "token")) {
+		if (val > 0) {
+			dp->g_token_base = val;
+			set_weight(gp, gp->c_weight);
+		} else
+			r = -EINVAL;
+	} else if (!strcmp(cmd, "io_limit")) {
+		set_weight(gp, gp->c_weight);
+	} else {
+		r = -EINVAL;
+	}
+	return r;
+}
+
+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;
+	int sz = *szp; /* used in DMEMIT() */
+
+	DMEMIT(" %d :%d", dp->g_token_base, gp->c_weight);
+	list_for_each_entry(p, &gp->c_group_list, c_group_list)
+		DMEMIT(" %d:%d", p->c_id, p->c_weight);
+	*szp = sz;
+}
+
+static int is_queue_full(struct ioband_group *gp)
+{
+	return gp->c_blocked >= gp->c_limit;
+}
+
+
+/*
+ *  <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)
+{
+	char *endp;
+	long val;
+
+	if (argc < 1)
+		return -EINVAL;
+
+	val = simple_strtol(argv[0], &endp, 0);
+	if (*endp != '\0' || val < 0)
+		return -EINVAL;
+	if (val == 0)
+		val = DEFAULT_TOKENBASE;
+
+	dp->g_can_submit = is_token_left;
+	dp->g_prepare_bio = prepare_token;
+	dp->g_restart_bios = proceed_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_token_base = val;
+	dp->g_epoch = 0;
+	dp->g_weight_total = 0;
+	return 0;
+}
+/* weight balancing policy. --- End --- */
+
+
+static int policy_default_init(struct ioband_device *dp,
+					int argc, char **argv) /*XXX*/
+{
+	return policy_weight_init(dp, argc, argv);	/* temp */
+}
+
+struct policy_type dm_ioband_policy_type[] = {
+	{"default", policy_default_init},
+	{"weight", policy_weight_init},
+	{NULL,     policy_default_init}
+};
diff -uprN linux-2.6.25.orig/drivers/md/dm-ioband-type.c linux-2.6.25/drivers/md/dm-ioband-type.c
--- linux-2.6.25.orig/drivers/md/dm-ioband-type.c	1970-01-01 09:00:00.000000000 +0900
+++ linux-2.6.25/drivers/md/dm-ioband-type.c	2008-04-24 19:40:54.000000000 +0900
@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2008 VA Linux Systems Japan K.K.
+ *
+ *  I/O bandwidth control
+ *
+ * This file is released under the GPL.
+ */
+#include <linux/bio.h>
+#ifdef CONFIG_CGROUP_BIO
+#include <linux/biocontrol.h>
+#endif
+#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)
+{
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
+	return (int)process_group(current);
+#else
+	return (int)task_pgrp_nr(current);
+#endif
+}
+
+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)
+{
+#ifdef CONFIG_CGROUP_BIO
+	return get_bio_cgroup_id(bio->bi_io_vec[0].bv_page);
+#else
+  /*
+   * 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 */
+#endif
+}
+
+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-2.6.25.orig/drivers/md/Kconfig linux-2.6.25/drivers/md/Kconfig
--- linux-2.6.25.orig/drivers/md/Kconfig	2008-04-17 11:49:44.000000000 +0900
+++ linux-2.6.25/drivers/md/Kconfig	2008-04-24 17:40:43.000000000 +0900
@@ -288,4 +288,17 @@ 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 bandwith 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-2.6.25.orig/drivers/md/Makefile linux-2.6.25/drivers/md/Makefile
--- linux-2.6.25.orig/drivers/md/Makefile	2008-04-17 11:49:44.000000000 +0900
+++ linux-2.6.25/drivers/md/Makefile	2008-04-24 17:40:18.000000000 +0900
@@ -3,12 +3,13 @@
 #
 
 dm-mod-objs	:= dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
-		   dm-ioctl.o dm-io.o kcopyd.o
+		   dm-ioctl.o dm-io.o dm-kcopyd.o
 dm-multipath-objs := dm-hw-handler.o dm-path-selector.o dm-mpath.o
 dm-snapshot-objs := dm-snap.o dm-exception-store.o
-dm-mirror-objs	:= dm-log.o dm-raid1.o
+dm-mirror-objs	:= dm-raid1.o
 dm-rdac-objs	:= dm-mpath-rdac.o
 dm-hp-sw-objs	:= dm-mpath-hp-sw.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 \
@@ -39,8 +40,9 @@ obj-$(CONFIG_DM_MULTIPATH_EMC)	+= dm-emc
 obj-$(CONFIG_DM_MULTIPATH_HP)	+= dm-hp-sw.o
 obj-$(CONFIG_DM_MULTIPATH_RDAC)	+= dm-rdac.o
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
-obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
+obj-$(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) \
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Here is the document of dm-ioband.

Based on 2.6.25
Signed-off-by: Ryo Tsuruta <ryov@valinux.co.jp>
Signed-off-by: Hirokazu Takahashi <taka@valinux.co.jp>

diff -uprN linux-2.6.25.orig/Documentation/device-mapper/ioband.txt linux-2.6.25/Documentation/device-mapper/ioband.txt
--- linux-2.6.25.orig/Documentation/device-mapper/ioband.txt	1970-01-01 09:00:00.000000000 +0900
+++ linux-2.6.25/Documentation/device-mapper/ioband.txt	2008-04-24 16:51:58.000000000 +0900
@@ -0,0 +1,883 @@
+                     Block I/O bandwidth control: dm-ioband
+
+            -------------------------------------------------------
+
+   Table of Contents
+
+   [1]What's dm-ioband all about?
+
+   [2]Differences from the CFQ I/O scheduler
+
+   [3]How dm-ioband works.
+
+   [4]Setup and Installation
+
+   [5]Getting started
+
+   [6]Command Reference
+
+   [7]Examples
+
+What's dm-ioband all about?
+
+     dm-ioband is an I/O bandwidth controller implemented as a device-mapper
+   driver. Several jobs using the same physical device have to share the
+   bandwidth of the device. dm-ioband gives bandwidth to each job according
+   to its weight, which each job can set its own value to.
+
+     At this time, a job is a group of processes with the same pid or pgrp or
+   uid. There is also a plan to make it support cgroup. A job can also be a
+   virtual machine such as KVM or Xen.
+
+     +------+ +------+ +------+   +------+ +------+ +------+
+     |cgroup| |cgroup| | the  |   | pid  | | pid  | | the  |  jobs
+     |  A   | |  B   | |others|   |  X   | |  Y   | |others|
+     +--|---+ +--|---+ +--|---+   +--|---+ +--|---+ +--|---+
+     +--V----+---V---+----V---+   +--V----+---V---+----V---+
+     | group | group | default|   | group | group | default|  ioband groups
+     |       |       |  group |   |       |       |  group |
+     +-------+-------+--------+   +-------+-------+--------+
+     |        ioband1         |   |       ioband2          |  ioband devices
+     +-----------|------------+   +-----------|------------+
+     +-----------V--------------+-------------V------------+
+     |                          |                          |
+     |          sdb1            |           sdb2           |  physical devices
+     +--------------------------+--------------------------+
+
+
+   --------------------------------------------------------------------------
+
+Differences from the CFQ I/O scheduler
+
+     Dm-ioband is flexible to configure the bandwidth settings.
+
+     Dm-ioband can work with any type of I/O scheduler such as the NOOP
+   scheduler, which is often chosen for high-end storages, since it is
+   implemented outside the I/O scheduling layer. It allows both of partition
+   based bandwidth control and job --- a group of processes --- based
+   control. In addition, it can set different configuration on each physical
+   device to control its bandwidth.
+
+     Meanwhile the current implementation of the CFQ scheduler has 8 IO
+   priority levels and all jobs whose processes have the same IO priority
+   share the bandwidth assigned to this level between them. And IO priority
+   is an attribute of a process so that it equally effects to all block
+   devices.
+
+   --------------------------------------------------------------------------
+
+How dm-ioband works.
+
+     Every ioband device has one ioband group, which by default is called the
+   default group.
+
+     Ioband devices can also have extra ioband groups in them. Each ioband
+   group has a job to support and a weight. Proportional to the weight,
+   dm-ioband gives tokens to the group.
+
+     A group passes on I/O requests that its job issues to the underlying
+   layer so long as it has tokens left, while requests are blocked if there
+   aren't any tokens left in the group. One token is consumed each time the
+   group passes on a request. dm-ioband will refill groups with tokens once
+   all of groups that have requests on a given physical device use up their
+   tokens.
+
+     With this approach, a job running on an ioband group with large weight
+   is guaranteed to be able to issue a large number of I/O requests.
+
+   --------------------------------------------------------------------------
+
+Setup and Installation
+
+     Build a kernel with these options enabled:
+
+     CONFIG_MD
+     CONFIG_BLK_DEV_DM
+     CONFIG_DM_IOBAND
+
+
+     If compiled as module, use modprobe to load dm-ioband.
+
+     # make modules
+     # make modules_install
+     # depmod -a
+     # modprobe dm-ioband
+
+
+     "dmsetup targets" command shows all available device-mapper targets.
+   "ioband" is displayed if dm-ioband has been loaded.
+
+     # dmsetup targets
+     ioband           v0.0.4
+
+
+   --------------------------------------------------------------------------
+
+Getting started
+
+     The following is a brief description how to control the I/O bandwidth of
+   disks. In this description, we'll take one disk with two partitions as an
+   example target.
+
+   --------------------------------------------------------------------------
+
+  Create and map ioband devices
+
+     Create two ioband devices "ioband1" and "ioband2". "ioband1" is mapped
+   to "/dev/sda1" and has a weight of 40. "ioband2" is mapped to "/dev/sda2"
+   and has a weight of 10. "ioband1" can use 80% --- 40/(40+10)*100 --- of
+   the bandwidth of the physical disk "/dev/sda" while "ioband2" can use 20%.
+
+    # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1 0 0 none" \
+        "weight 0 :40" | dmsetup create ioband1
+    # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1 0 0 none" \
+        "weight 0 :10" | dmsetup create ioband2
+
+
+     If the commands are successful then the device files
+   "/dev/mapper/ioband1" and "/dev/mapper/ioband2" will have been created.
+
+   --------------------------------------------------------------------------
+
+  Additional bandwidth control
+
+     In this example two extra ioband groups are created on "ioband1". The
+   first group consists of all the processes with user-id 1000 and the second
+   group consists of all the processes with user-id 2000. Their weights are
+   30 and 20 respectively.
+
+    # dmsetup message ioband1 0 type user
+    # dmsetup message ioband1 0 attach 1000
+    # dmsetup message ioband1 0 attach 2000
+    # dmsetup message ioband1 0 weight 1000:30
+    # dmsetup message ioband1 0 weight 2000:20
+
+
+     Now the processes in the user-id 1000 group can use 30% ---
+   30/(30+20+40+10)*100 --- of the bandwidth of the physical disk.
+
+   Table 1. Weight assignments
+
+   +----------------------------------------------------------------+
+   | ioband device |          ioband group          | ioband weight |
+   |---------------+--------------------------------+---------------|
+   | ioband1       | user id 1000                   | 30            |
+   |---------------+--------------------------------+---------------|
+   | ioband1       | user id 2000                   | 20            |
+   |---------------+--------------------------------+---------------|
+   | ioband1       | default group(the other users) | 40            |
+   |---------------+--------------------------------+---------------|
+   | ioband2       | default group                  | 10            |
+   +----------------------------------------------------------------+
+
+   --------------------------------------------------------------------------
+
+  Remove the ioband devices
+
+     Remove the ioband devices when no longer used.
+
+     # dmsetup remove ioband1
+     # dmsetup remove ioband2
+
+
+   --------------------------------------------------------------------------
+
+Command Reference
+
+  Create an ioband device
+
+   SYNOPSIS
+
+           dmsetup create IOBAND_DEVICE
+
+   DESCRIPTION
+
+             Create an ioband device with the given name IOBAND_DEVICE.
+           Generally, dmsetup reads a table from standard input. Each line of
+           the table specifies a single target and is of the form:
+
+             start_sector num_sectors "ioband" device_file ioband_device_id \
+                 io_throttle io_limit ioband_group_type policy token_base \
+                 :weight [ioband_group_id:weight...]
+
+
+                start_sector, num_sectors
+
+                          The sector range of the underlying device where
+                        dm-ioband maps.
+
+                ioband
+
+                          Specify the string "ioband" as a target type.
+
+                device_file
+
+                          Underlying device name.
+
+                ioband_device_id
+
+                          The ID number for an ioband device. The same ID
+                        must be set among the ioband devices that share the
+                        same bandwidth, which means they work on the same
+                        physical disk.
+
+                io_throttle
+
+                          Dm-ioband starts to control the bandwidth when the
+                        number of BIOs in progress exceeds this value. If 0
+                        is specified, dm-ioband uses the default value.
+
+                io_limit
+
+                          Dm-ioband blocks all I/O requests for the
+                        IOBAND_DEVICE when the number of BIOs in progress
+                        exceeds this value. If 0 is specified, dm-ioband uses
+                        the default value.
+
+                ioband_group_type
+
+                          Specify how to evaluate the ioband group ID. The
+                        type must be one of "none", "user", "gid", "pid" or
+                        "pgrp." Specify "none"

On Thu, 24 Apr 2008 20:22:19 +0900 (JST) Ryo Tsuruta <ryov@valinux.co.jp> wrote:

> +What's dm-ioband all about?
> +
> +     dm-ioband is an I/O bandwidth controller implemented as a device-mapper
> +   driver. Several jobs using the same physical device have to share the
> +   bandwidth of the device. dm-ioband gives bandwidth to each job according
> +   to its weight, which each job can set its own value to.
> +
> +     At this time, a job is a group of processes with the same pid or pgrp or
> +   uid. There is also a plan to make it support cgroup. A job can also be a
> +   virtual machine such as KVM or Xen.

Most writes are performed by pdflush, kswapd, etc.  This will lead to large
inaccuracy.

It isn't trivial to fix.  We'd need deep, long tracking of ownership
probably all the way up to the pagecache page.  The same infrastructure
would be needed to make Sergey's "BSD acct: disk I/O accounting" vaguely
accurate.  Other proposals need it, but I forget what they are.

Much more minor points: when merge-time comes, the patches should have the
LINUX_VERSION_CODE stuff removed.  And probably all of the many `inline's
should be removed.


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Hi,

> > +What's dm-ioband all about?
> > +
> > +     dm-ioband is an I/O bandwidth controller implemented as a device-mapper
> > +   driver. Several jobs using the same physical device have to share the
> > +   bandwidth of the device. dm-ioband gives bandwidth to each job according
> > +   to its weight, which each job can set its own value to.
> > +
> > +     At this time, a job is a group of processes with the same pid or pgrp or
> > +   uid. There is also a plan to make it support cgroup. A job can also be a
> > +   virtual machine such as KVM or Xen.
> 
> Most writes are performed by pdflush, kswapd, etc.  This will lead to large
> inaccuracy.
> 
> It isn't trivial to fix.  We'd need deep, long tracking of ownership
> probably all the way up to the pagecache page.  The same infrastructure
> would be needed to make Sergey's "BSD acct: disk I/O accounting" vaguely
> accurate.  Other proposals need it, but I forget what they are.

I'm working on this topic and I've posted patches once.
http://lwn.net/Articles/273802/

The current linux kernel already has the memory subsystem of cgroup.
You can determine which page is owned by which cgroup with it.
I realized we could easily implement "tracking mechanism of block I/O"
on the feature of this memory subsystem. 

When you have an I/O request, it requires data transfer between a certain
page and certain sectors in a disk. This means every I/O requests has
a target page, so you can find out the owner of the page using this
feature. I think it will be okay to assume that the owner of the page
is the owner of the I/O request to the page.

I have a plan on porting the patch to the latest version of linux.
I'm going to make it general, so not only dm-ioband but also OpenVz
team and the NEC team, which are is working on having the CFQ scheduler
control the bandwidth, will be able to make use of this feature.

But it will take some time to port it since the code of the memory
subsystem has been being modified a lot recently.

Thank you,
Hirokazu Takahashi.
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Hi,

> Most writes are performed by pdflush, kswapd, etc.  This will lead to large
> inaccuracy.
>
> It isn't trivial to fix.  We'd need deep, long tracking of ownership
> probably all the way up to the pagecache page.  The same infrastructure
> would be needed to make Sergey's "BSD acct: disk I/O accounting" vaguely
> accurate.  Other proposals need it, but I forget what they are.

I also realize that some kernel threads such as pdflush perform actual
writes instead of tasks which originally issued write requests.
So, taka is developing a blocking I/O tacking down mechanism which is
based on cgroup memory controller and posted it to LKML:
http://lwn.net/Articles/273802/

However, the current implementation works well with Xen virtual
machines, because virtual machine's I/Os are issued from its own kernel
thread and can be tracked down. Please see a benchmark result of Xen
virtual machine:
http://people.valinux.co.jp/~ryov/dm-ioband/benchmark/xen-blktap.html

As for KVM, dm-ioband was also able to track down block I/Os as I
expected. When dm-ioband is used in virtual machine environment,
I think even the current implementation will work fairly.

But unfortunately I found KVM still had a performance problem that
it couldn't handle I/Os efficiently yet, which should be improved.
I already posted this problem to kvm-devel list:
http://sourceforge.net/mailarchive/forum.php?thread_name=20080229.210531.226799765.ryov%40valinux.co.jp&forum_name=kvm-devel
 
> Much more minor points: when merge-time comes, the patches should have the
> LINUX_VERSION_CODE stuff removed.  And probably all of the many `inline's
> should be removed.

Thank you for your advice. I'll have these fixes included in the next
release.

Ryo Tsuruta
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