This is the core io-throttle kernel infrastructure. It creates the basic
interfaces to cgroups and implements the I/O measurement and throttling
functions.

Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
---
 block/Makefile                  |    2 +
 block/blk-io-throttle.c         |  529 +++++++++++++++++++++++++++++++++++++++
 include/linux/blk-io-throttle.h |   14 +
 include/linux/cgroup_subsys.h   |    6 +
 init/Kconfig                    |   10 +
 5 files changed, 561 insertions(+), 0 deletions(-)
 create mode 100644 block/blk-io-throttle.c
 create mode 100644 include/linux/blk-io-throttle.h

diff --git a/block/Makefile b/block/Makefile
index 5a43c7d..8dec69b 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -14,3 +14,5 @@ obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o
 
 obj-$(CONFIG_BLK_DEV_IO_TRACE)	+= blktrace.o
 obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o
+
+obj-$(CONFIG_CGROUP_IO_THROTTLE)	+= blk-io-throttle.o
diff --git a/block/blk-io-throttle.c b/block/blk-io-throttle.c
new file mode 100644
index 0000000..caf740a
--- /dev/null
+++ b/block/blk-io-throttle.c
@@ -0,0 +1,529 @@
+/*
+ * blk-io-throttle.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ *
+ * Copyright (C) 2008 Andrea Righi <righi.andrea@gmail.com>
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/cgroup.h>
+#include <linux/slab.h>
+#include <linux/gfp.h>
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/genhd.h>
+#include <linux/fs.h>
+#include <linux/jiffies.h>
+#include <linux/hardirq.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include <linux/blk-io-throttle.h>
+
+/**
+ * struct iothrottle_node - throttling rule of a single block device
+ * @node: list of per block device throttling rules
+ * @dev: block device number, used as key in the list
+ * @iorate: max i/o bandwidth (in bytes/s)
+ * @strategy: throttling strategy (0 = leaky bucket, 1 = token bucket)
+ * @timestamp: timestamp of the last I/O request (in jiffies)
+ * @stat: i/o activity counter (leaky bucket only)
+ * @bucket_size: bucket size in bytes (token bucket only)
+ * @token: token counter (token bucket only)
+ *
+ * Define a i/o throttling rule for a single block device.
+ *
+ * NOTE: limiting rules always refer to dev_t; if a block device is unplugged
+ * the limiting rules defined for that device persist and they are still valid
+ * if a new device is plugged and it uses the same dev_t number.
+ */
+struct iothrottle_node {
+	struct list_head node;
+	dev_t dev;
+	u64 iorate;
+	long strategy;
+	unsigned long timestamp;
+	atomic_long_t stat;
+	s64 bucket_size;
+	atomic_long_t token;
+};
+
+/**
+ * struct iothrottle - throttling rules for a cgroup
+ * @css: pointer to the cgroup state
+ * @lock: spinlock used to protect write operations in the list
+ * @list: list of iothrottle_node elements
+ *
+ * Define multiple per-block device i/o throttling rules.
+ * Note: the list of the throttling rules is protected by RCU locking.
+ */
+struct iothrottle {
+	struct cgroup_subsys_state css;
+	spinlock_t lock;
+	struct list_head list;
+};
+
+static inline struct iothrottle *cgroup_to_iothrottle(struct cgroup *cont)
+{
+	return container_of(cgroup_subsys_state(cont, iothrottle_subsys_id),
+			    struct iothrottle, css);
+}
+
+static inline struct iothrottle *task_to_iothrottle(struct task_struct *task)
+{
+	return container_of(task_subsys_state(task, iothrottle_subsys_id),
+			    struct iothrottle, css);
+}
+
+/*
+ * Note: called with rcu_read_lock() held.
+ */
+static struct iothrottle_node *
+iothrottle_search_node(const struct iothrottle *iot, dev_t dev)
+{
+	struct iothrottle_node *n;
+
+	list_for_each_entry_rcu(n, &iot->list, node)
+		if (n->dev == dev)
+			return n;
+	return NULL;
+}
+
+/*
+ * Note: called with iot->lock held.
+ */
+static inline void iothrottle_insert_node(struct iothrottle *iot,
+						struct iothrottle_node *n)
+{
+	list_add_rcu(&n->node, &iot->list);
+}
+
+/*
+ * Note: called with iot->lock held.
+ */
+static inline struct iothrottle_node *
+iothrottle_replace_node(struct iothrottle *iot, struct iothrottle_node *old,
+			struct iothrottle_node *new)
+{
+	list_replace_rcu(&old->node, &new->node);
+	return old;
+}
+
+/*
+ * Note: called with iot->lock held.
+ */
+static struct iothrottle_node *
+iothrottle_delete_node(struct iothrottle *iot, dev_t dev)
+{
+	struct iothrottle_node *n;
+
+	list_for_each_entry_rcu(n, &iot->list, node)
+		if (n->dev == dev) {
+			list_del_rcu(&n->node);
+			return n;
+		}
+	return NULL;
+}
+
+/*
+ * Note: called from kernel/cgroup.c with cgroup_lock() held.
+ */
+static struct cgroup_subsys_state *
+iothrottle_create(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+	struct iothrottle *iot;
+
+	iot = kmalloc(sizeof(*iot), GFP_KERNEL);
+	if (unlikely(!iot))
+		return ERR_PTR(-ENOMEM);
+
+	INIT_LIST_HEAD(&iot->list);
+	spin_lock_init(&iot->lock);
+
+	return &iot->css;
+}
+
+/*
+ * Note: called from kernel/cgroup.c with cgroup_lock() held.
+ */
+static void iothrottle_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+	struct iothrottle_node *n, *p;
+	struct iothrottle *iot = cgroup_to_iothrottle(cont);
+
+	/*
+	 * don't worry about locking here, at this point there must be not any
+	 * reference to the list.
+	 */
+	list_for_each_entry_safe(n, p, &iot->list, node)
+		kfree(n);
+	kfree(iot);
+}
+
+static ssize_t iothrottle_read(struct cgroup *cont, struct cftype *cft,
+				struct file *file, char __user *userbuf,
+				size_t nbytes, loff_t *ppos)
+{
+	struct iothrottle *iot;
+	char *buffer;
+	int s = 0;
+	struct iothrottle_node *n;
+	ssize_t ret;
+
+	buffer = kmalloc(nbytes + 1, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	cgroup_lock();
+	if (cgroup_is_removed(cont)) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	iot = cgroup_to_iothrottle(cont);
+	rcu_read_lock();
+	list_for_each_entry_rcu(n, &iot->list, node) {
+		unsigned long delta;
+
+		BUG_ON(!n->dev);
+		delta = jiffies_to_msecs((long)jiffies - (long)n->timestamp);
+		s += scnprintf(buffer + s, nbytes - s,
+				"%u %u %llu %li %li %lli %li %lu\n",
+				MAJOR(n->dev), MINOR(n->dev), n->iorate,
+				n->strategy, atomic_long_read(&n->stat),
+				n->bucket_size, atomic_long_read(&n->token),
+				delta);
+	}
+	rcu_read_unlock();
+	ret = simple_read_from_buffer(userbuf, nbytes, ppos, buffer, s);
+out:
+	cgroup_unlock();
+	kfree(buffer);
+	return ret;
+}
+
+static dev_t devname2dev_t(const char *buf)
+{
+	struct block_device *bdev;
+	dev_t dev = 0;
+	struct gendisk *disk;
+	int part;
+
+	/* use a lookup to validate the block device */
+	bdev = lookup_bdev(buf);
+	if (IS_ERR(bdev))
+		return 0;
+
+	/* only entire devices are allowed, not single partitions */
+	disk = get_gendisk(bdev->bd_dev, &part);
+	if (disk && !part) {
+		BUG_ON(!bdev->bd_inode);
+		dev = bdev->bd_inode->i_rdev;
+	}
+	bdput(bdev);
+
+	return dev;
+}
+
+/*
+ * The userspace input string must use the following syntax:
+ *
+ * device:bw-limit:strategy:bucket-size
+ */
+static int iothrottle_parse_args(char *buf, size_t nbytes,
+					dev_t *dev, u64 *iorate,
+					long *strategy, s64 *bucket_size)
+{
+	char *ioratep, *strategyp, *bucket_sizep;
+	int ret;
+
+	ioratep = memchr(buf, ':', nbytes);
+	if (!ioratep)
+		return -EINVAL;
+	*ioratep++ = '\0';
+
+	strategyp = memchr(ioratep, ':', buf + nbytes - ioratep);
+	if (!strategyp)
+		return -EINVAL;
+	*strategyp++ = '\0';
+
+	bucket_sizep = memchr(strategyp, ':', buf + nbytes - strategyp);
+	if (!bucket_sizep)
+		return -EINVAL;
+	*bucket_sizep++ = '\0';
+
+	/* i/o bandwidth limit (0 to delete a limiting rule) */
+	ret = strict_strtoull(ioratep, 10, iorate);
+	if (ret < 0)
+		return ret;
+	*iorate = ALIGN(*iorate, 1024);
+
+	/* throttling strategy */
+	ret = strict_strtol(strategyp, 10, strategy);
+	if (ret < 0)
+		return ret;
+
+	/* bucket size */
+	ret = strict_strtoll(bucket_sizep, 10, bucket_size);
+	if (ret < 0)
+		return ret;
+	if (*bucket_size < 0)
+		return -EINVAL;
+	*bucket_size = ALIGN(*bucket_size, 1024);
+
+	/* block device number */
+	*dev = devname2dev_t(buf);
+	if (!*dev)
+		return -EINVAL;
+
+	return 0;
+}
+
+static ssize_t iothrottle_write(struct cgroup *cont, struct cftype *cft,
+				struct file *file, const char __user *userbuf,
+				size_t nbytes, loff_t *ppos)
+{
+	struct iothrottle *iot;
+	struct iothrottle_node *n, *newn = NULL;
+	char *buffer, *s;
+	dev_t dev;
+	u64 iorate;
+	long strategy;
+	s64 bucket_size;
+	int ret;
+
+	if (!nbytes)
+		return -EINVAL;
+
+	/* Upper limit on largest io-throttle rule string user might write. */
+	if (nbytes > 1024)
+		return -E2BIG;
+
+	buffer = kmalloc(nbytes + 1, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	ret = strncpy_from_user(buffer, userbuf, nbytes);
+	if (ret < 0)
+		goto out1;
+	buffer[nbytes] = '\0';
+	s = strstrip(buffer);
+
+	ret = iothrottle_parse_args(s, nbytes, &dev, &iorate,
+					&strategy, &bucket_size);
+	if (ret)
+		goto out1;
+
+	if (iorate) {
+		newn = kmalloc(sizeof(*newn), GFP_KERNEL);
+		if (!newn) {
+