Linux Virtualization - Jun 2008 - [PATCH 0/2] dm-ioband: I/O bandwidth controller v1.1.0: Introduction

Hi everyone,

This is dm-ioband version 1.1.0 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-rc2-mm1.
- Changes from 1.0.0 (posted on May 19, 2008):
  - Measures against high memory pressure.
    I/O requests to reclaim pages won't be blocked in dm-ioband
    even when the group doesn't have the right to issue any more I/Os.
    But it can keep to control the bandwidth of the group since these
    I/Os will be counted as debt of the group.
  - Performance tuning
    Improve the performance when a lot of ioband groups are created.
    It is useful when you want to control bandwidth on a per user
    basis. For example, you can create an ioband group and give an
    weight to a user once the user is logged in. The combination of
    dm-ioband, the cgroup memory resource controller and the
    CPU resource controller will work more effectively.

I also announce that we have launched "Linux Block I/O Bandwidth
Control Project" website http://people.valinux.co.jp/~ryov/bwctl/ .
The goal of this project is to develop a block I/O bandwidth
controller on Linux. You can find information about the followings:

- dm-ioband
  This device mapper driver.
- iobandctl
  An administration tool for dm-ioband, which makes it easy to
  configure the dm-ioband device.
- Block I/O Tracking
  Block I/O tracking, which we call "bio cgroup", provides block I/O
  tracking mechanism. It makes dm-ioband be able to control the block
  I/O bandwidths even when it accepts delays write requests.

Thanks,
Ryo Tsuruta

Here is the patch of dm-ioband.

Based on 2.6.26-rc2-mm1
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-rc2-mm1.orig/drivers/md/Kconfig
linux-2.6.26-rc2-mm1/drivers/md/Kconfig
--- linux-2.6.26-rc2-mm1.orig/drivers/md/Kconfig	2008-05-16 16:20:23.000000000
+0900
+++ linux-2.6.26-rc2-mm1/drivers/md/Kconfig	2008-06-02 20:44:44.000000000 +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-rc2-mm1.orig/drivers/md/Makefile
linux-2.6.26-rc2-mm1/drivers/md/Makefile
--- linux-2.6.26-rc2-mm1.orig/drivers/md/Makefile	2008-05-16 16:20:23.000000000
+0900
+++ linux-2.6.26-rc2-mm1/drivers/md/Makefile	2008-06-02 20:44:44.000000000 +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-rc2-mm1.orig/drivers/md/dm-ioband-ctl.c
linux-2.6.26-rc2-mm1/drivers/md/dm-ioband-ctl.c
--- linux-2.6.26-rc2-mm1.orig/drivers/md/dm-ioband-ctl.c	1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.26-rc2-mm1/drivers/md/dm-ioband-ctl.c	2008-06-02
20:44:44.000000000 +0900
@@ -0,0 +1,1180 @@
+/*
+ * 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 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 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;
+	}
+
+	INIT_WORK(&new->g_conductor, ioband_conduct);
+	INIT_LIST_HEAD(&new->g_groups);
+	INIT_LIST_HEAD(&new->g_list);
+	spin_lock_init(&new->g_lock);
+	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 = 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 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 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;
+	}
+
+	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) {
+		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_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(gp, group);
+	ioband_group_release(NULL, 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;
+	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_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;
+	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);
+}
+
+/*
+ * 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;
+			}
+			gp->c_target = ti;
+			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 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 bio *bio)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (is_group_down(gp))
+		return 0;
+	if (!is_urgent_bio(bio) && is_group_blocked(gp))
+		return 1;
+	if (dp->g_should_block(gp)) {
+		set_group_blocked(gp);
+		return 1;
+	}
+	return 0;
+}
+
+static void do_nothing(void) {}
+
+static void prevent_burst_bios(struct ioband_group *gp, struct bio *bio)
+{
+	struct ioband_device *dp = gp->c_banddev;
+
+	if (!current->mm || current->flags & PF_BORROWED_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, bio),
+						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[bio_data_dir(bio)]++;
+}
+
+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);
+		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 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 void 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;
+
+	if (bio_list_empty(&gp->c_prio_bios))
+		return;
+	direct = prio_queue_direct(gp);
+	while (room_for_bio_rw(dp, direct)) {
+		bio = pop_prio_bio(gp);
+		if (!bio)
+			return;
+		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);
+	}
+}
+
+static void 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;
+
+	while (dp->g_can_submit(gp) && gp->c_blocked -
gp->c_prio_blocked) {
+		if (!room_for_bio(dp))
+			return;
+		bio = dp->g_pop_bio(gp);
+		if (!bio)
+			return;
+
+		direct = bio_data_dir(bio);
+		if (!room_for_bio_rw(dp, direct)) {
+			push_prio_bio(gp, bio, direct);
+			continue;
+		}
+		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);
+	}
+}
+
+static inline void release_bios(struct ioband_group *gp,
+		 struct bio_list *issue_list, struct bio_list *pushback_list)
+{
+
+	release_prio_bios(gp, issue_list, pushback_list);
+	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_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, 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;
+	bws = &gp->c_stat[bio_data_dir(bio)];
+	bws->sectors += bio_sectors(bio);
+retry:
+	if (!gp->c_blocked && room_for_bio_rw(dp, bio_data_dir(bio))) {
+		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[0] + dp->g_issued[1] == 0) {
+			if (!dp->g_blocked && dp->g_restart_bios(dp)) {
+				dprintk(KERN_ERR "ioband_map: token refilled "
+						"gp:%p bio:%p\n", gp, bio);
+				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 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);
+	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:
+	release_urgent_bios(dp, &issue_list, &pushback_list);
+	while (dp->g_blocked && (gp = choose_best_group(dp)))
+		release_bios(gp, &issue_list, &pushback_list);
+
+	if (dp->g_blocked
+	    && dp->g_issued[0] + dp->g_issued[1] <
dp->g_io_throttle) {
+		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);
+		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)))
+		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_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;
+	struct rb_node *node;
+	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);
+		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;
+	}
+
+	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 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(gp, 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;
+	struct rb_node *node;
+	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));
+		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")) {
+		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[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")) {
+		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[0] = val;
+		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")) {
+		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     = {1, 1, 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-rc2-mm1.orig/drivers/md/dm-ioband-policy.c
linux-2.6.26-rc2-mm1/drivers/md/dm-ioband-policy.c
--- linux-2.6.26-rc2-mm1.orig/drivers/md/dm-ioband-policy.c	1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.26-rc2-mm1/drivers/md/dm-ioband-policy.c	2008-06-02
20:44:44.000000000 +0900
@@ -0,0 +1,291 @@
+/*
+ * 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_TOKENBASE	8192
+#define IOBAND_IOPRIO_BASE 100
+
+static int make_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 "make_epoch %d --> %d\n",
+						dp->g_epoch-1, dp->g_epoch);
+	return 1;
+}
+
+static inline int make_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 (is_group_down(gp)) {
+		gp->c_token = gp->c_token_init_value;
+		return iopriority(gp);
+	}
+	if (make_epoch(gp)) {
+		gp->c_token += gp->c_token_init_value;
+		dprintk(KERN_ERR "refill token: gp:%p token:%d->%d\n",
+			gp, gp->c_token - gp->c_token_init_value, gp->c_token);
+		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;
+}
+
+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[0] + dp->g_io_limit[1]) *
+					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;
+	struct rb_node *node;
+	int sz = *szp; /* used in DMEMIT() */
+
+	DMEMIT(" %d :%d", dp->g_token_base, 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;
+}
+
+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 = 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_token_base = val;
+	dp->g_epoch = 0;
+	dp->g_weight_total = 0;
+	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 void w2_prepare_token(struct ioband_group *gp, struct bio *bio)
+{
+	gp->c_token -= bio_sectors(bio);
+}
+
+static int w2_policy_weight_init(struct ioband_device *dp,
+							int argc, char **argv)
+{
+	char *endp;
+	long val;
+	int r = 0;
+
+	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 << (PAGE_SHIFT - 9);
+
+	r = policy_weight_init(dp, argc, argv);
+	if (r < 0)
+		return r;
+
+	dp->g_prepare_bio = w2_prepare_token;
+	dp->g_token_base = val;
+	return 0;
+}
+/* weight balancing policy based on I/O size. --- 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},
+	{"weight-iosize", w2_policy_weight_init},
+	{NULL,     policy_default_init}
+};
diff -uprN linux-2.6.26-rc2-mm1.orig/drivers/md/dm-ioband-type.c
linux-2.6.26-rc2-mm1/drivers/md/dm-ioband-type.c
--- linux-2.6.26-rc2-mm1.orig/drivers/md/dm-ioband-type.c	1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.26-rc2-mm1/drivers/md/dm-ioband-type.c	2008-06-02
20:44:44.000000000 +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-rc2-mm1.orig/drivers/md/dm-ioband.h
linux-2.6.26-rc2-mm1/drivers/md/dm-ioband.h
--- linux-2.6.26-rc2-mm1.orig/drivers/md/dm-ioband.h	1970-01-01
09:00:00.000000000 +0900
+++ linux-2.6.26-rc2-mm1/drivers/md/dm-ioband.h	2008-06-02 20:44:44.000000000
+0900
@@ -0,0 +1,153 @@
+/*
+ * 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;
+	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;
+	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	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_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_PRIO_BIO_WRITE	1
+#define IOG_PRIO_QUEUE		2
+#define IOG_BIO_BLOCKED		4
+#define IOG_GOING_DOWN		8
+#define IOG_SUSPENDED		16
+
+#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_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)