[RFC PATCH] Block device bio throttling support [V2]

[RFC PATCH] Block device bio throttling support [V2]

[Vivek Goyal]

Hi,

This is V2 of the bio throttling patches. Following are changes since V1.

- Move throttling hook point from __make_request() to __generic_make_request().
  This will make sure that now throttling will work any block device which
  instanciated a request queue and I don't have to modify each block driver.
  So now it should work with device mapper devices also. Thanks to Mike Snitzer
  for the suggestion.

- Renamed blkio.read_bps_device to blkio.throttle.read_bps_device. Similar
  changes were done for blkio.write_bps_device.

- Exported two new files blkio.throttle.io_serviced and
  blkio.throttle_io_service_bytes to export number of bio and number of bytes
  served on request queue as seen by throttling policy.

- Introduce a config option CONFIG_BLK_DEV_THROTTLING, so that all the
  throttling logic can be compiled out. 

Previous version of patches are available here.

[V1] http://lkml.org/lkml/2010/9/1/251

Overview
========
Currently CFQ provides the weight based proportional division of bandwidth.
People also have been looking at extending block IO controller to provide
throttling/max bandwidth control.

I have started to write the support for throttling in block layer on
request queue so that it can be used both for higher level logical
devices as well as leaf nodes. This patch is still work in progress but
I wanted to post it for early feedback.

Basically currently I have hooked into __generic_make_request() function to
check which cgroup bio belongs to and if it is exceeding the specified
BW rate. If no, thread can continue to dispatch bio as it is otherwise
bio is queued internally and dispatched later with the help of a worker
thread.

HOWTO
=====
- Make sure CONFIG_BLK_CGROUP=y and CONFIG_BLK_DEV_THROTTLING=y.

- Mount blkio controller
        mount -t cgroup -o blkio none /cgroup/blkio

- Specify a bandwidth rate on particular device for root group. The format
  for policy is "<major>:<minor>  <byes_per_second>".

        echo "8:16  1048576" > /cgroup/blkio/blkio.throttle.read_bps_device

  Above will put a limit of 1MB/second on reads happening for root group
  on device having major/minor number 8:16.

- Run dd to read a file and see if rate is throttled to 1MB/s or not.

       	# dd if=/mnt/common/zerofile of=/dev/null bs=4K count=1024 iflag=direct
        1024+0 records in
        1024+0 records out
        4194304 bytes (4.2 MB) copied, 4.0001 s, 1.0 MB/s

 Limits for writes can be put using blkio.throttle.write_bps_device file.

Open Issues
===========
- Do we need to provide additional queue congestion semantics as we are
  throttling and queuing bios at request queue and probably we don't want
  a user space application to consume all the memory allocating bios
  and bombarding request queue with those bios.

TODO
====
- Lots of testing, bug fixes.
- Provide support for enforcing limits in IOPS.

Any feedback is welcome.

Overall changes look as follows.

 Documentation/cgroups/blkio-controller.txt |   89 +++-
 block/Kconfig                              |   12 +
 block/Makefile                             |    1 +
 block/blk-cgroup.c                         |  699 ++++++++++++++++-----
 block/blk-cgroup.h                         |   75 +++-
 block/blk-core.c                           |   24 +
 block/blk-throttle.c                       |  946 ++++++++++++++++++++++++++++
 block/blk.h                                |    4 +-
 block/cfq-iosched.c                        |    4 +
 block/cfq.h                                |    2 +-
 include/linux/blk_types.h                  |    3 +
 include/linux/blkdev.h                     |   24 +
 init/Kconfig                               |    9 +-

Thanks
Vivek

[PATCH 1/4] Kill the header printed at the start of blkio.weight_device file

[Vivek Goyal]

o Kill extra "dev weight" header which is printed when somebody reads
  blkio.weight_device file. This really seems to be out of convention. No other
  blkio files are printing any header at the start of file. I think it is ok
  to just print values and how to interpret values should be part of
  documentation.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 block/blk-cgroup.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index a680964..c1a39d9 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -811,8 +811,6 @@ static int blkiocg_weight_device_read(struct cgroup *cgrp, struct cftype *cft,
 	struct blkio_cgroup *blkcg;
 	struct blkio_policy_node *pn;
 
-	seq_printf(m, "dev\tweight\n");
-
 	blkcg = cgroup_to_blkio_cgroup(cgrp);
 	if (!list_empty(&blkcg->policy_list)) {
 		spin_lock_irq(&blkcg->lock);
-- 
1.7.2.2

[PATCH 2/4] blkio: blkio cgroup interface related changes to support new throttling policy

[Vivek Goyal]

o Changes to blkio controller cgroup interface to accomodate more than one
  policy. New policy being introduced is throttling.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 block/blk-cgroup.c |  697 ++++++++++++++++++++++++++++++++++++++++------------
 block/blk-cgroup.h |   75 ++++++-
 block/cfq.h        |    2 +-
 3 files changed, 618 insertions(+), 156 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index c1a39d9..004aeb3 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -37,6 +37,12 @@ static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
 static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
 static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
 
+/* for encoding cft->private value on file */
+#define BLKIOFILE_PRIVATE(x, val)	(((x) << 16) | (val))
+/* What policy owns the file, proportional or throttle */
+#define BLKIOFILE_POLICY(val)		(((val) >> 16) & 0xffff)
+#define BLKIOFILE_ATTR(val)		((val) & 0xffff)
+
 struct cgroup_subsys blkio_subsys = {
 	.name = "blkio",
 	.create = blkiocg_create,
@@ -65,14 +71,55 @@ static inline void blkio_policy_delete_node(struct blkio_policy_node *pn)
 	list_del(&pn->node);
 }
 
+static inline bool cftype_blkg_same_policy(struct cftype *cft,
+			struct blkio_group *blkg)
+{
+	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
+
+	if (blkg->plid == plid)
+		return 1;
+
+	return 0;
+}
+
+/* Determines if policy node matches cgroup file being accessed */
+static inline bool pn_matches_cftype(struct cftype *cft,
+			struct blkio_policy_node *pn)
+{
+	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
+	int name = BLKIOFILE_ATTR(cft->private);
+
+	if (plid != pn->plid)
+		return 0;
+
+	if (plid == BLKIO_POLICY_PROP) {
+		switch(name) {
+		case BLKIO_PROP_weight_device:
+			return (pn->rulet == BLKIO_RULE_WEIGHT);
+		}
+	}
+
+	if (plid == BLKIO_POLICY_THROTL) {
+		switch(name) {
+		case BLKIO_THROTL_read_bps_device:
+			return (pn->rulet == BLKIO_RULE_READ);
+		case BLKIO_THROTL_write_bps_device:
+			return (pn->rulet == BLKIO_RULE_WRITE);
+		}
+	}
+
+	return 0;
+}
+
 /* Must be called with blkcg->lock held */
 static struct blkio_policy_node *
-blkio_policy_search_node(const struct blkio_cgroup *blkcg, dev_t dev)
+blkio_policy_search_node(const struct blkio_cgroup *blkcg, dev_t dev,
+		enum blkio_policy_id plid, enum blkio_rule_type rulet)
 {
 	struct blkio_policy_node *pn;
 
 	list_for_each_entry(pn, &blkcg->policy_list, node) {
-		if (pn->dev == dev)
+		if (pn->dev == dev && pn->plid == plid && pn->rulet == rulet)
 			return pn;
 	}
 
@@ -86,6 +133,33 @@ struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
 }
 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
 
+static inline void
+blkio_update_group_weight(struct blkio_group *blkg, unsigned int weight)
+{
+	struct blkio_policy_type *blkiop;
+
+	list_for_each_entry(blkiop, &blkio_list, list) {
+		if (blkiop->ops.blkio_update_group_weight_fn)
+			blkiop->ops.blkio_update_group_weight_fn(blkg, weight);
+	}
+}
+
+static inline void blkio_update_group_bps(struct blkio_group *blkg, u64 bps,
+				enum blkio_rule_type rulet)
+{
+	struct blkio_policy_type *blkiop;
+
+	list_for_each_entry(blkiop, &blkio_list, list) {
+		if (rulet == BLKIO_RULE_READ
+		    && blkiop->ops.blkio_update_group_read_bps_fn)
+			blkiop->ops.blkio_update_group_read_bps_fn(blkg, bps);
+
+		if (rulet == BLKIO_RULE_WRITE
+		    && blkiop->ops.blkio_update_group_write_bps_fn)
+			blkiop->ops.blkio_update_group_write_bps_fn(blkg, bps);
+	}
+}
+
 /*
  * Add to the appropriate stat variable depending on the request type.
  * This should be called with the blkg->stats_lock held.
@@ -341,7 +415,8 @@ void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
 EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);
 
 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-			struct blkio_group *blkg, void *key, dev_t dev)
+		struct blkio_group *blkg, void *key, dev_t dev,
+		enum blkio_policy_id plid)
 {
 	unsigned long flags;
 
@@ -350,6 +425,7 @@ void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
 	rcu_assign_pointer(blkg->key, key);
 	blkg->blkcg_id = css_id(&blkcg->css);
 	hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
+	blkg->plid = plid;
 	spin_unlock_irqrestore(&blkcg->lock, flags);
 	/* Need to take css reference ? */
 	cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
@@ -408,51 +484,6 @@ struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
 }
 EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
 
-#define SHOW_FUNCTION(__VAR)						\
-static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup,		\
-				       struct cftype *cftype)		\
-{									\
-	struct blkio_cgroup *blkcg;					\
-									\
-	blkcg = cgroup_to_blkio_cgroup(cgroup);				\
-	return (u64)blkcg->__VAR;					\
-}
-
-SHOW_FUNCTION(weight);
-#undef SHOW_FUNCTION
-
-static int
-blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
-{
-	struct blkio_cgroup *blkcg;
-	struct blkio_group *blkg;
-	struct hlist_node *n;
-	struct blkio_policy_type *blkiop;
-	struct blkio_policy_node *pn;
-
-	if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
-		return -EINVAL;
-
-	blkcg = cgroup_to_blkio_cgroup(cgroup);
-	spin_lock(&blkio_list_lock);
-	spin_lock_irq(&blkcg->lock);
-	blkcg->weight = (unsigned int)val;
-
-	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
-		pn = blkio_policy_search_node(blkcg, blkg->dev);
-
-		if (pn)
-			continue;
-
-		list_for_each_entry(blkiop, &blkio_list, list)
-			blkiop->ops.blkio_update_group_weight_fn(blkg,
-					blkcg->weight);
-	}
-	spin_unlock_irq(&blkcg->lock);
-	spin_unlock(&blkio_list_lock);
-	return 0;
-}
-
 static int
 blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 {
@@ -593,52 +624,6 @@ static uint64_t blkio_get_stat(struct blkio_group *blkg,
 	return disk_total;
 }
 
-#define SHOW_FUNCTION_PER_GROUP(__VAR, type, show_total)		\
-static int blkiocg_##__VAR##_read(struct cgroup *cgroup,		\
-		struct cftype *cftype, struct cgroup_map_cb *cb)	\
-{									\
-	struct blkio_cgroup *blkcg;					\
-	struct blkio_group *blkg;					\
-	struct hlist_node *n;						\
-	uint64_t cgroup_total = 0;					\
-									\
-	if (!cgroup_lock_live_group(cgroup))				\
-		return -ENODEV;						\
-									\
-	blkcg = cgroup_to_blkio_cgroup(cgroup);				\
-	rcu_read_lock();						\
-	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
-		if (blkg->dev) {					\
-			spin_lock_irq(&blkg->stats_lock);		\
-			cgroup_total += blkio_get_stat(blkg, cb,	\
-						blkg->dev, type);	\
-			spin_unlock_irq(&blkg->stats_lock);		\
-		}							\
-	}								\
-	if (show_total)							\
-		cb->fill(cb, "Total", cgroup_total);			\
-	rcu_read_unlock();						\
-	cgroup_unlock();						\
-	return 0;							\
-}
-
-SHOW_FUNCTION_PER_GROUP(time, BLKIO_STAT_TIME, 0);
-SHOW_FUNCTION_PER_GROUP(sectors, BLKIO_STAT_SECTORS, 0);
-SHOW_FUNCTION_PER_GROUP(io_service_bytes, BLKIO_STAT_SERVICE_BYTES, 1);
-SHOW_FUNCTION_PER_GROUP(io_serviced, BLKIO_STAT_SERVICED, 1);
-SHOW_FUNCTION_PER_GROUP(io_service_time, BLKIO_STAT_SERVICE_TIME, 1);
-SHOW_FUNCTION_PER_GROUP(io_wait_time, BLKIO_STAT_WAIT_TIME, 1);
-SHOW_FUNCTION_PER_GROUP(io_merged, BLKIO_STAT_MERGED, 1);
-SHOW_FUNCTION_PER_GROUP(io_queued, BLKIO_STAT_QUEUED, 1);
-#ifdef CONFIG_DEBUG_BLK_CGROUP
-SHOW_FUNCTION_PER_GROUP(dequeue, BLKIO_STAT_DEQUEUE, 0);
-SHOW_FUNCTION_PER_GROUP(avg_queue_size, BLKIO_STAT_AVG_QUEUE_SIZE, 0);
-SHOW_FUNCTION_PER_GROUP(group_wait_time, BLKIO_STAT_GROUP_WAIT_TIME, 0);
-SHOW_FUNCTION_PER_GROUP(idle_time, BLKIO_STAT_IDLE_TIME, 0);
-SHOW_FUNCTION_PER_GROUP(empty_time, BLKIO_STAT_EMPTY_TIME, 0);
-#endif
-#undef SHOW_FUNCTION_PER_GROUP
-
 static int blkio_check_dev_num(dev_t dev)
 {
 	int part = 0;
@@ -652,11 +637,13 @@ static int blkio_check_dev_num(dev_t dev)
 }
 
 static int blkio_policy_parse_and_set(char *buf,
-				      struct blkio_policy_node *newpn)
+	struct blkio_policy_node *newpn, enum blkio_policy_id plid,
+	enum blkio_rule_type rulet)
 {
 	char *s[4], *p, *major_s = NULL, *minor_s = NULL;
 	int ret;
 	unsigned long major, minor, temp;
+	u64 bps;
 	int i = 0;
 	dev_t dev;
 
@@ -705,12 +692,26 @@ static int blkio_policy_parse_and_set(char *buf,
 	if (s[1] == NULL)
 		return -EINVAL;
 
-	ret = strict_strtoul(s[1], 10, &temp);
-	if (ret || (temp < BLKIO_WEIGHT_MIN && temp > 0) ||
-	    temp > BLKIO_WEIGHT_MAX)
-		return -EINVAL;
+	switch (plid) {
+	case BLKIO_POLICY_PROP:
+		ret = strict_strtoul(s[1], 10, &temp);
+		if (ret || (temp < BLKIO_WEIGHT_MIN && temp > 0) ||
+	    	    temp > BLKIO_WEIGHT_MAX)
+			return -EINVAL;
 
-	newpn->weight =  temp;
+		newpn->plid = plid;
+		newpn->rulet = rulet;
+		newpn->val.weight = temp;
+		break;
+	case BLKIO_POLICY_THROTL:
+		ret = strict_strtoull(s[1], 10, &bps);
+		if (ret)
+			return -EINVAL;
+
+		newpn->plid = plid;
+		newpn->rulet = rulet;
+		newpn->val.bps = bps;
+	}
 
 	return 0;
 }
@@ -720,26 +721,121 @@ unsigned int blkcg_get_weight(struct blkio_cgroup *blkcg,
 {
 	struct blkio_policy_node *pn;
 
-	pn = blkio_policy_search_node(blkcg, dev);
+	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_PROP,
+				BLKIO_RULE_WEIGHT);
 	if (pn)
-		return pn->weight;
+		return pn->val.weight;
 	else
 		return blkcg->weight;
 }
 EXPORT_SYMBOL_GPL(blkcg_get_weight);
 
+uint64_t blkcg_get_read_bps(struct blkio_cgroup *blkcg, dev_t dev)
+{
+	struct blkio_policy_node *pn;
+
+	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
+				BLKIO_RULE_READ);
+	if (pn)
+		return pn->val.bps;
+	else
+		return -1;
+}
+EXPORT_SYMBOL_GPL(blkcg_get_read_bps);
 
-static int blkiocg_weight_device_write(struct cgroup *cgrp, struct cftype *cft,
-				       const char *buffer)
+uint64_t blkcg_get_write_bps(struct blkio_cgroup *blkcg, dev_t dev)
+{
+	struct blkio_policy_node *pn;
+	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
+				BLKIO_RULE_WRITE);
+	if (pn)
+		return pn->val.bps;
+	else
+		return -1;
+}
+EXPORT_SYMBOL_GPL(blkcg_get_write_bps);
+
+/* Checks whether user asked for deleting a policy rule */
+static bool blkio_delete_rule_command(struct blkio_policy_node *pn)
+{
+	switch(pn->plid) {
+	case BLKIO_POLICY_PROP:
+		if (pn->val.weight == 0)
+			return 1;
+		break;
+	case BLKIO_POLICY_THROTL:
+		if (pn->val.bps == 0)
+			return 1;
+		break;
+	default:
+		BUG();
+	}
+
+	return 0;
+}
+
+static void blkio_update_policy_rule(struct blkio_policy_node *oldpn,
+					struct blkio_policy_node *newpn)
+{
+	switch(oldpn->plid) {
+	case BLKIO_POLICY_PROP:
+		oldpn->val.weight = newpn->val.weight;
+		break;
+	case BLKIO_POLICY_THROTL:
+		oldpn->val.bps = newpn->val.bps;
+		break;
+	default:
+		BUG();
+	}
+}
+
+/*
+ * A policy node rule has been updated. Propogate this update to all the
+ * block groups which might be affected by this update.
+ */
+static void blkio_update_policy_node_blkg(struct blkio_cgroup *blkcg,
+				struct blkio_policy_node *pn)
+{
+	struct blkio_group *blkg;
+	struct hlist_node *n;
+	enum blkio_rule_type rulet = pn->rulet;
+	unsigned int weight;
+	u64 bps;
+
+	spin_lock(&blkio_list_lock);
+	spin_lock_irq(&blkcg->lock);
+
+	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
+		if (pn->dev == blkg->dev) {
+			if (pn->plid == BLKIO_POLICY_PROP) {
+				weight = pn->val.weight ? pn->val.weight :
+						blkcg->weight;
+				blkio_update_group_weight(blkg, weight);
+			} else {
+
+				bps = pn->val.bps ? pn->val.bps : (-1);
+				blkio_update_group_bps(blkg, bps, rulet);
+			}
+		}
+	}
+
+	spin_unlock_irq(&blkcg->lock);
+	spin_unlock(&blkio_list_lock);
+
+}
+
+
+static int blkiocg_file_write(struct cgroup *cgrp, struct cftype *cft,
+ 				       const char *buffer)
 {
 	int ret = 0;
 	char *buf;
 	struct blkio_policy_node *newpn, *pn;
 	struct blkio_cgroup *blkcg;
-	struct blkio_group *blkg;
 	int keep_newpn = 0;
-	struct hlist_node *n;
-	struct blkio_policy_type *blkiop;
+	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
+	int name = BLKIOFILE_ATTR(cft->private);
+	enum blkio_rule_type rulet;
 
 	buf = kstrdup(buffer, GFP_KERNEL);
 	if (!buf)
@@ -751,7 +847,30 @@ static int blkiocg_weight_device_write(struct cgroup *cgrp, struct cftype *cft,
 		goto free_buf;
 	}
 
-	ret = blkio_policy_parse_and_set(buf, newpn);
+	switch (plid) {
+	case BLKIO_POLICY_PROP:
+		if (name == BLKIO_PROP_weight_device) {
+			rulet = BLKIO_RULE_WEIGHT;
+			ret = blkio_policy_parse_and_set(buf, newpn, plid, 0);
+		} else
+			BUG();
+		break;
+	case BLKIO_POLICY_THROTL:
+		if (name == BLKIO_THROTL_read_bps_device) {
+			rulet = BLKIO_RULE_READ;
+			ret = blkio_policy_parse_and_set(buf, newpn, plid,
+					rulet);
+		} else if (name == BLKIO_THROTL_write_bps_device) {
+			rulet = BLKIO_RULE_WRITE;
+			ret = blkio_policy_parse_and_set(buf, newpn, plid,
+					rulet);
+		} else
+			BUG();
+		break;
+	default:
+		BUG();
+	}
+
 	if (ret)
 		goto free_newpn;
 
@@ -759,9 +878,9 @@ static int blkiocg_weight_device_write(struct cgroup *cgrp, struct cftype *cft,
 
 	spin_lock_irq(&blkcg->lock);
 
-	pn = blkio_policy_search_node(blkcg, newpn->dev);
+	pn = blkio_policy_search_node(blkcg, newpn->dev, plid, rulet);
 	if (!pn) {
-		if (newpn->weight != 0) {
+		if (!blkio_delete_rule_command(newpn)) {
 			blkio_policy_insert_node(blkcg, newpn);
 			keep_newpn = 1;
 		}
@@ -769,33 +888,17 @@ static int blkiocg_weight_device_write(struct cgroup *cgrp, struct cftype *cft,
 		goto update_io_group;
 	}
 
-	if (newpn->weight == 0) {
-		/* weight == 0 means deleteing a specific weight */
+	if (blkio_delete_rule_command(newpn)) {
 		blkio_policy_delete_node(pn);
 		spin_unlock_irq(&blkcg->lock);
 		goto update_io_group;
 	}
 	spin_unlock_irq(&blkcg->lock);
 
-	pn->weight = newpn->weight;
+	blkio_update_policy_rule(pn, newpn);
 
 update_io_group:
-	/* update weight for each cfqg */
-	spin_lock(&blkio_list_lock);
-	spin_lock_irq(&blkcg->lock);
-
-	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
-		if (newpn->dev == blkg->dev) {
-			list_for_each_entry(blkiop, &blkio_list, list)
-				blkiop->ops.blkio_update_group_weight_fn(blkg,
-							 newpn->weight ?
-							 newpn->weight :
-							 blkcg->weight);
-		}
-	}
-
-	spin_unlock_irq(&blkcg->lock);
-	spin_unlock(&blkio_list_lock);
+	blkio_update_policy_node_blkg(blkcg, newpn);
 
 free_newpn:
 	if (!keep_newpn)
@@ -805,21 +908,251 @@ free_buf:
 	return ret;
 }
 
-static int blkiocg_weight_device_read(struct cgroup *cgrp, struct cftype *cft,
-				      struct seq_file *m)
+static void
+blkio_print_policy_node(struct seq_file *m, struct blkio_policy_node *pn)
+{
+	switch(pn->plid) {
+		case BLKIO_POLICY_PROP:
+			if (pn->rulet == BLKIO_RULE_WEIGHT)
+				seq_printf(m, "%u:%u\t%u\n", MAJOR(pn->dev),
+					MINOR(pn->dev), pn->val.weight);
+			break;
+		case BLKIO_POLICY_THROTL:
+			if (pn->rulet == BLKIO_RULE_READ)
+				seq_printf(m, "%u:%u\t%llu\n", MAJOR(pn->dev),
+					MINOR(pn->dev), pn->val.bps);
+			else if (pn->rulet == BLKIO_RULE_WRITE)
+				seq_printf(m, "%u:%u\t%llu\n", MAJOR(pn->dev),
+					MINOR(pn->dev), pn->val.bps);
+			else
+				BUG();
+			break;
+		default:
+			BUG();
+	}
+}
+
+/* cgroup files which read their data from policy nodes end up here */
+static void blkio_read_policy_node_files(struct cftype *cft,
+			struct blkio_cgroup *blkcg, struct seq_file *m)
 {
-	struct blkio_cgroup *blkcg;
 	struct blkio_policy_node *pn;
 
-	blkcg = cgroup_to_blkio_cgroup(cgrp);
 	if (!list_empty(&blkcg->policy_list)) {
 		spin_lock_irq(&blkcg->lock);
 		list_for_each_entry(pn, &blkcg->policy_list, node) {
-			seq_printf(m, "%u:%u\t%u\n", MAJOR(pn->dev),
-				   MINOR(pn->dev), pn->weight);
+			if (!pn_matches_cftype(cft, pn))
+				continue;
+			blkio_print_policy_node(m, pn);
 		}
 		spin_unlock_irq(&blkcg->lock);
 	}
+}
+
+static int blkiocg_file_read(struct cgroup *cgrp, struct cftype *cft,
+				struct seq_file *m)
+{
+	struct blkio_cgroup *blkcg;
+	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
+	int name = BLKIOFILE_ATTR(cft->private);
+
+	blkcg = cgroup_to_blkio_cgroup(cgrp);
+
+	switch(plid) {
+	case BLKIO_POLICY_PROP:
+		switch(name) {
+		case BLKIO_PROP_weight_device:
+			blkio_read_policy_node_files(cft, blkcg, m);
+			return 0;
+		default:
+			BUG();
+		}
+		break;
+	case BLKIO_POLICY_THROTL:
+		switch(name){
+		case BLKIO_THROTL_read_bps_device:
+		case BLKIO_THROTL_write_bps_device:
+			blkio_read_policy_node_files(cft, blkcg, m);
+			return 0;
+		default:
+			BUG();
+		}
+		break;
+	default:
+		BUG();
+	}
+
+	return 0;
+}
+
+static int blkio_read_blkg_stats(struct blkio_cgroup *blkcg,
+		struct cftype *cft, struct cgroup_map_cb *cb, enum stat_type type,
+		bool show_total)
+{
+	struct blkio_group *blkg;
+	struct hlist_node *n;
+	uint64_t cgroup_total = 0;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
+		if (blkg->dev) {
+			if (!cftype_blkg_same_policy(cft, blkg))
+				continue;
+			spin_lock_irq(&blkg->stats_lock);
+			cgroup_total += blkio_get_stat(blkg, cb, blkg->dev,
+						type);
+			spin_unlock_irq(&blkg->stats_lock);
+		}
+	}
+	if (show_total)
+		cb->fill(cb, "Total", cgroup_total);
+	rcu_read_unlock();
+	return 0;
+}
+
+/* All map kind of cgroup file get serviced by this function */
+static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
+				struct cgroup_map_cb *cb)
+{
+	struct blkio_cgroup *blkcg;
+	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
+	int name = BLKIOFILE_ATTR(cft->private);
+
+	blkcg = cgroup_to_blkio_cgroup(cgrp);
+
+	switch(plid) {
+	case BLKIO_POLICY_PROP:
+		switch(name) {
+		case BLKIO_PROP_time:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_TIME, 0);
+		case BLKIO_PROP_sectors:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_SECTORS, 0);
+		case BLKIO_PROP_io_service_bytes:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_SERVICE_BYTES, 1);
+		case BLKIO_PROP_io_serviced:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_SERVICED, 1);
+		case BLKIO_PROP_io_service_time:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_SERVICE_TIME, 1);
+		case BLKIO_PROP_io_wait_time:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_WAIT_TIME, 1);
+		case BLKIO_PROP_io_merged:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_MERGED, 1);
+		case BLKIO_PROP_io_queued:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_QUEUED, 1);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+		case BLKIO_PROP_dequeue:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_DEQUEUE, 0);
+		case BLKIO_PROP_avg_queue_size:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_AVG_QUEUE_SIZE, 0);
+		case BLKIO_PROP_group_wait_time:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_GROUP_WAIT_TIME, 0);
+		case BLKIO_PROP_idle_time:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_IDLE_TIME, 0);
+		case BLKIO_PROP_empty_time:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_EMPTY_TIME, 0);
+#endif
+		default:
+			BUG();
+		}
+		break;
+
+	case BLKIO_POLICY_THROTL:
+		switch(name){
+		case BLKIO_THROTL_io_service_bytes:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_SERVICE_BYTES, 1);
+		case BLKIO_THROTL_io_serviced:
+			return blkio_read_blkg_stats(blkcg, cft, cb,
+						BLKIO_STAT_SERVICED, 1);
+		default:
+			BUG();
+		}
+		break;
+	default:
+		BUG();
+	}
+
+	return 0;
+}
+
+static int blkio_weight_write(struct blkio_cgroup *blkcg, u64 val)
+{
+	struct blkio_group *blkg;
+	struct hlist_node *n;
+	struct blkio_policy_node *pn;
+
+	if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
+		return -EINVAL;
+
+	spin_lock(&blkio_list_lock);
+	spin_lock_irq(&blkcg->lock);
+	blkcg->weight = (unsigned int)val;
+
+	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
+		pn = blkio_policy_search_node(blkcg, blkg->dev,
+					BLKIO_POLICY_PROP, BLKIO_RULE_WEIGHT);
+		if (pn)
+			continue;
+
+		blkio_update_group_weight(blkg, blkcg->weight);
+	}
+	spin_unlock_irq(&blkcg->lock);
+	spin_unlock(&blkio_list_lock);
+	return 0;
+}
+
+static u64 blkiocg_file_read_u64 (struct cgroup *cgrp, struct cftype *cft) {
+	struct blkio_cgroup *blkcg;
+	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
+	int name = BLKIOFILE_ATTR(cft->private);
+
+	blkcg = cgroup_to_blkio_cgroup(cgrp);
+
+	switch(plid) {
+	case BLKIO_POLICY_PROP:
+		switch(name) {
+		case BLKIO_PROP_weight:
+			return (u64)blkcg->weight;
+		}
+		break;
+	default:
+		BUG();
+	}
+	return 0;
+}
+
+static int
+blkiocg_file_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+	struct blkio_cgroup *blkcg;
+	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
+	int name = BLKIOFILE_ATTR(cft->private);
+
+	blkcg = cgroup_to_blkio_cgroup(cgrp);
+
+	switch(plid) {
+	case BLKIO_POLICY_PROP:
+		switch(name) {
+		case BLKIO_PROP_weight:
+			return blkio_weight_write(blkcg, val);
+		}
+		break;
+	default:
+		BUG();
+	}
 
 	return 0;
 }
@@ -827,46 +1160,96 @@ static int blkiocg_weight_device_read(struct cgroup *cgrp, struct cftype *cft,
 struct cftype blkio_files[] = {
 	{
 		.name = "weight_device",
-		.read_seq_string = blkiocg_weight_device_read,
-		.write_string = blkiocg_weight_device_write,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_weight_device),
+		.read_seq_string = blkiocg_file_read,
+		.write_string = blkiocg_file_write,
 		.max_write_len = 256,
 	},
 	{
 		.name = "weight",
-		.read_u64 = blkiocg_weight_read,
-		.write_u64 = blkiocg_weight_write,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_weight),
+		.read_u64 = blkiocg_file_read_u64,
+		.write_u64 = blkiocg_file_write_u64,
+	},
+
+	{
+		.name = "throttle.read_bps_device",
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
+				BLKIO_THROTL_read_bps_device),
+		.read_seq_string = blkiocg_file_read,
+		.write_string = blkiocg_file_write,
+		.max_write_len = 256,
+	},
+
+	{
+		.name = "throttle.write_bps_device",
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
+				BLKIO_THROTL_write_bps_device),
+		.read_seq_string = blkiocg_file_read,
+		.write_string = blkiocg_file_write,
+		.max_write_len = 256,
 	},
 	{
 		.name = "time",
-		.read_map = blkiocg_time_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_time),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "sectors",
-		.read_map = blkiocg_sectors_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_sectors),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "io_service_bytes",
-		.read_map = blkiocg_io_service_bytes_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_io_service_bytes),
+		.read_map = blkiocg_file_read_map,
+	},
+	{
+		.name = "throttle.io_service_bytes",
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
+				BLKIO_THROTL_io_service_bytes),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "io_serviced",
-		.read_map = blkiocg_io_serviced_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_io_serviced),
+		.read_map = blkiocg_file_read_map,
+	},
+	{
+		.name = "throttle.io_serviced",
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
+				BLKIO_THROTL_io_serviced),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "io_service_time",
-		.read_map = blkiocg_io_service_time_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_io_service_time),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "io_wait_time",
-		.read_map = blkiocg_io_wait_time_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_io_wait_time),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "io_merged",
-		.read_map = blkiocg_io_merged_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_io_merged),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "io_queued",
-		.read_map = blkiocg_io_queued_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_io_queued),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "reset_stats",
@@ -875,23 +1258,33 @@ struct cftype blkio_files[] = {
 #ifdef CONFIG_DEBUG_BLK_CGROUP
 	{
 		.name = "avg_queue_size",
-		.read_map = blkiocg_avg_queue_size_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_avg_queue_size),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "group_wait_time",
-		.read_map = blkiocg_group_wait_time_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_group_wait_time),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "idle_time",
-		.read_map = blkiocg_idle_time_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_idle_time),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "empty_time",
-		.read_map = blkiocg_empty_time_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_empty_time),
+		.read_map = blkiocg_file_read_map,
 	},
 	{
 		.name = "dequeue",
-		.read_map = blkiocg_dequeue_read,
+		.private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+				BLKIO_PROP_dequeue),
+		.read_map = blkiocg_file_read_map,
 	},
 #endif
 };
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 2b866ec..aa8f0ea 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -15,6 +15,11 @@
 
 #include <linux/cgroup.h>
 
+enum blkio_policy_id {
+	BLKIO_POLICY_PROP = 0,		/* Proportional Bandwidth division */
+	BLKIO_POLICY_THROTL,		/* Throttling */
+};
+
 #if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
 
 #ifndef CONFIG_BLK_CGROUP
@@ -65,6 +70,39 @@ enum blkg_state_flags {
 	BLKG_empty,
 };
 
+/* cgroup files owned by proportional weight policy */
+enum blkcg_file_name_prop {
+	BLKIO_PROP_weight = 1,
+	BLKIO_PROP_weight_device,
+	BLKIO_PROP_io_service_bytes,
+	BLKIO_PROP_io_serviced,
+	BLKIO_PROP_time,
+	BLKIO_PROP_sectors,
+	BLKIO_PROP_io_service_time,
+	BLKIO_PROP_io_wait_time,
+	BLKIO_PROP_io_merged,
+	BLKIO_PROP_io_queued,
+	BLKIO_PROP_avg_queue_size,
+	BLKIO_PROP_group_wait_time,
+	BLKIO_PROP_idle_time,
+	BLKIO_PROP_empty_time,
+	BLKIO_PROP_dequeue,
+};
+
+/* cgroup files owned by throttle policy */
+enum blkcg_file_name_throtl {
+	BLKIO_THROTL_read_bps_device,
+	BLKIO_THROTL_write_bps_device,
+	BLKIO_THROTL_io_service_bytes,
+	BLKIO_THROTL_io_serviced,
+};
+
+enum blkio_rule_type {
+	BLKIO_RULE_WEIGHT = 0,
+	BLKIO_RULE_READ,
+	BLKIO_RULE_WRITE,
+};
+
 struct blkio_cgroup {
 	struct cgroup_subsys_state css;
 	unsigned int weight;
@@ -113,6 +151,10 @@ struct blkio_group {
 	/* The device MKDEV(major, minor), this group has been created for */
 	dev_t dev;
 
+	/* policy which owns this blk group */
+	enum blkio_policy_id plid;
+
+
 	/* Need to serialize the stats in the case of reset/update */
 	spinlock_t stats_lock;
 	struct blkio_group_stats stats;
@@ -121,19 +163,44 @@ struct blkio_group {
 struct blkio_policy_node {
 	struct list_head node;
 	dev_t dev;
-	unsigned int weight;
+
+	/* This node belongs to max bw policy or porportional weight policy */
+	enum blkio_policy_id plid;
+
+	/* Whether a read or write rule */
+	enum blkio_rule_type rulet;
+
+	union {
+		unsigned int weight;
+		/*
+		 * Rate read/write in terms of byptes per second
+		 * Whether this rate represents read or write is determined
+		 * by rule type "rulet"
+		 */
+		u64 bps;
+	} val;
 };
 
 extern unsigned int blkcg_get_weight(struct blkio_cgroup *blkcg,
 				     dev_t dev);
+extern uint64_t blkcg_get_read_bps(struct blkio_cgroup *blkcg,
+				     dev_t dev);
+extern uint64_t blkcg_get_write_bps(struct blkio_cgroup *blkcg,
+				     dev_t dev);
 
 typedef void (blkio_unlink_group_fn) (void *key, struct blkio_group *blkg);
 typedef void (blkio_update_group_weight_fn) (struct blkio_group *blkg,
 						unsigned int weight);
+typedef void (blkio_update_group_read_bps_fn) (struct blkio_group *blkg,
+						u64 read_bps);
+typedef void (blkio_update_group_write_bps_fn) (struct blkio_group *blkg,
+						u64 write_bps);
 
 struct blkio_policy_ops {
 	blkio_unlink_group_fn *blkio_unlink_group_fn;
 	blkio_update_group_weight_fn *blkio_update_group_weight_fn;
+	blkio_update_group_read_bps_fn *blkio_update_group_read_bps_fn;
+	blkio_update_group_write_bps_fn *blkio_update_group_write_bps_fn;
 };
 
 struct blkio_policy_type {
@@ -212,7 +279,8 @@ static inline void blkiocg_set_start_empty_time(struct blkio_group *blkg) {}
 extern struct blkio_cgroup blkio_root_cgroup;
 extern struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup);
 extern void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-			struct blkio_group *blkg, void *key, dev_t dev);
+	struct blkio_group *blkg, void *key, dev_t dev,
+	enum blkio_policy_id plid);
 extern int blkiocg_del_blkio_group(struct blkio_group *blkg);
 extern struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg,
 						void *key);
@@ -234,7 +302,8 @@ static inline struct blkio_cgroup *
 cgroup_to_blkio_cgroup(struct cgroup *cgroup) { return NULL; }
 
 static inline void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-			struct blkio_group *blkg, void *key, dev_t dev) {}
+		struct blkio_group *blkg, void *key, dev_t dev,
+		enum blkio_policy_id plid) {}
 
 static inline int
 blkiocg_del_blkio_group(struct blkio_group *blkg) { return 0; }
diff --git a/block/cfq.h b/block/cfq.h
index 93448e5..54a6d90 100644
--- a/block/cfq.h
+++ b/block/cfq.h
@@ -69,7 +69,7 @@ static inline void cfq_blkiocg_update_completion_stats(struct blkio_group *blkg,
 
 static inline void cfq_blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
 			struct blkio_group *blkg, void *key, dev_t dev) {
-	blkiocg_add_blkio_group(blkcg, blkg, key, dev);
+	blkiocg_add_blkio_group(blkcg, blkg, key, dev, BLKIO_POLICY_PROP);
 }
 
 static inline int cfq_blkiocg_del_blkio_group(struct blkio_group *blkg)
-- 
1.7.2.2

[PATCH 3/4] block: Core throttling logic implementation

[Vivek Goyal]

o Actual implementation of throttling policy.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 block/Kconfig             |   12 +
 block/Makefile            |    1 +
 block/blk-core.c          |   24 ++
 block/blk-throttle.c      |  946 +++++++++++++++++++++++++++++++++++++++++++++
 block/blk.h               |    4 +-
 block/cfq-iosched.c       |    4 +
 include/linux/blk_types.h |    3 +
 include/linux/blkdev.h    |   24 ++
 init/Kconfig              |    9 +-
 9 files changed, 1023 insertions(+), 4 deletions(-)
 create mode 100644 block/blk-throttle.c

diff --git a/block/Kconfig b/block/Kconfig
index 9be0b56..6c9213e 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -77,6 +77,18 @@ config BLK_DEV_INTEGRITY
 	T10/SCSI Data Integrity Field or the T13/ATA External Path
 	Protection.  If in doubt, say N.
 
+config BLK_DEV_THROTTLING
+	bool "Block layer bio throttling support"
+	depends on BLK_CGROUP=y && EXPERIMENTAL
+	default n
+	---help---
+	Block layer bio throttling support. It can be used to limit
+	the IO rate to a device. IO rate policies are per cgroup and
+	one needs to mount and use blkio cgroup controller for creating
+	cgroups and specifying per device IO rate policies.
+
+	See Documentation/cgroups/blkio-controller.txt for more information.
+
 endif # BLOCK
 
 config BLOCK_COMPAT
diff --git a/block/Makefile b/block/Makefile
index 0bb499a..c850d5e 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_BLOCK) := elevator.o blk-core.o blk-tag.o blk-sysfs.o \
 
 obj-$(CONFIG_BLK_DEV_BSG)	+= bsg.o
 obj-$(CONFIG_BLK_CGROUP)	+= blk-cgroup.o
+obj-$(CONFIG_BLK_DEV_THROTTLING)	+= blk-throttle.o
 obj-$(CONFIG_IOSCHED_NOOP)	+= noop-iosched.o
 obj-$(CONFIG_IOSCHED_DEADLINE)	+= deadline-iosched.o
 obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o
diff --git a/block/blk-core.c b/block/blk-core.c
index ee1a1e7..c4831b6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -382,6 +382,7 @@ void blk_sync_queue(struct request_queue *q)
 	del_timer_sync(&q->unplug_timer);
 	del_timer_sync(&q->timeout);
 	cancel_work_sync(&q->unplug_work);
+	throtl_shutdown_timer_wq(q);
 }
 EXPORT_SYMBOL(blk_sync_queue);
 
@@ -459,6 +460,8 @@ void blk_cleanup_queue(struct request_queue *q)
 	if (q->elevator)
 		elevator_exit(q->elevator);
 
+	blk_throtl_exit(q);
+
 	blk_put_queue(q);
 }
 EXPORT_SYMBOL(blk_cleanup_queue);
@@ -515,6 +518,11 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 		return NULL;
 	}
 
+	if (blk_throtl_init(q)) {
+		kmem_cache_free(blk_requestq_cachep, q);
+		return NULL;
+	}
+
 	setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
 		    laptop_mode_timer_fn, (unsigned long) q);
 	init_timer(&q->unplug_timer);
@@ -1522,6 +1530,15 @@ static inline void __generic_make_request(struct bio *bio)
 			goto end_io;
 		}
 
+		blk_throtl_bio(q, &bio);
+
+		/*
+		 * If bio = NULL, bio has been throttled and will be submitted
+		 * later.
+		 */
+		if (!bio)
+			break;
+
 		trace_block_bio_queue(q, bio);
 
 		ret = q->make_request_fn(q, bio);
@@ -2579,6 +2596,13 @@ int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
 }
 EXPORT_SYMBOL(kblockd_schedule_work);
 
+int kblockd_schedule_delayed_work(struct request_queue *q,
+			struct delayed_work *dwork, unsigned long delay)
+{
+	return queue_delayed_work(kblockd_workqueue, dwork, delay);
+}
+EXPORT_SYMBOL(kblockd_schedule_delayed_work);
+
 int __init blk_dev_init(void)
 {
 	BUILD_BUG_ON(__REQ_NR_BITS > 8 *
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
new file mode 100644
index 0000000..77ea2cf
--- /dev/null
+++ b/block/blk-throttle.c
@@ -0,0 +1,946 @@
+/*
+ * Interface for controlling IO bandwidth on a request queue
+ *
+ * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/blktrace_api.h>
+#include "blk-cgroup.h"
+
+/* Max dispatch from a group in 1 round */
+static int throtl_grp_quantum = 8;
+
+/* Total max dispatch from all groups in one round */
+static int throtl_quantum = 32;
+
+/* Throttling is performed over 100ms slice and after that slice is renewed */
+static unsigned long throtl_slice = HZ/10;	/* 100 ms */
+
+struct throtl_rb_root {
+	struct rb_root rb;
+	struct rb_node *left;
+	unsigned int count;
+	unsigned long min_disptime;
+};
+
+#define THROTL_RB_ROOT	(struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
+			.count = 0, .min_disptime = 0}
+
+#define rb_entry_tg(node)	rb_entry((node), struct throtl_grp, rb_node)
+
+struct throtl_grp {
+	/* List of throtl groups on the request queue*/
+	struct hlist_node tg_node;
+
+	/* active throtl group service_tree member */
+	struct rb_node rb_node;
+
+	/*
+	 * Dispatch time in jiffies. This is the estimated time when group
+	 * will unthrottle and is ready to dispatch more bio. It is used as
+	 * key to sort active groups in service tree.
+	 */
+	unsigned long disptime;
+
+	struct blkio_group blkg;
+	atomic_t ref;
+	unsigned int flags;
+
+	/* Two lists for READ and WRITE */
+	struct bio_list bio_lists[2];
+
+	/* Number of queued bios on READ and WRITE lists */
+	unsigned int nr_queued[2];
+
+	/* bytes per second rate limits */
+	uint64_t bps[2];
+
+	/* Number of bytes disptached in current slice */
+	uint64_t bytes_disp[2];
+
+	/* When did we start a new slice */
+	unsigned long slice_start[2];
+	unsigned long slice_end[2];
+};
+
+struct throtl_data
+{
+	/* List of throtl groups */
+	struct hlist_head tg_list;
+
+	/* service tree for active throtl groups */
+	struct throtl_rb_root tg_service_tree;
+
+	struct throtl_grp root_tg;
+	struct request_queue *queue;
+
+	/* Total Number of queued bios on READ and WRITE lists */
+	unsigned int nr_queued[2];
+
+	/* How many bios are on disp_list */
+	int nr_disp_list;
+
+	/*
+	 * number of total undestroyed groups (excluding root group)
+	 */
+	unsigned int nr_undestroyed_grps;
+
+	/* Bios queued for dispatch */
+	struct bio_list disp_list;
+
+	/* Work for dispatching throttled bios */
+	struct delayed_work throtl_work;
+};
+
+enum tg_state_flags {
+	THROTL_TG_FLAG_on_rr = 0,	/* on round-robin busy list */
+};
+
+#define THROTL_TG_FNS(name)						\
+static inline void throtl_mark_tg_##name(struct throtl_grp *tg)		\
+{									\
+	(tg)->flags |= (1 << THROTL_TG_FLAG_##name);			\
+}									\
+static inline void throtl_clear_tg_##name(struct throtl_grp *tg)	\
+{									\
+	(tg)->flags &= ~(1 << THROTL_TG_FLAG_##name);			\
+}									\
+static inline int throtl_tg_##name(const struct throtl_grp *tg)		\
+{									\
+	return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0;	\
+}
+
+THROTL_TG_FNS(on_rr);
+
+#define throtl_log_tg(td, tg, fmt, args...)				\
+	blk_add_trace_msg((td)->queue, "%s throtl " fmt,		\
+				blkg_path(&(tg)->blkg), ##args);      	\
+
+#define throtl_log(td, fmt, args...)	\
+	blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
+
+static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg)
+{
+	if (blkg)
+		return container_of(blkg, struct throtl_grp, blkg);
+
+	return NULL;
+}
+
+static inline int total_nr_queued(struct throtl_data *td)
+{
+	return (td->nr_disp_list + td->nr_queued[0] + td->nr_queued[1]);
+}
+
+static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
+{
+	atomic_inc(&tg->ref);
+	return tg;
+}
+
+static void throtl_put_tg(struct throtl_grp *tg)
+{
+	BUG_ON(atomic_read(&tg->ref) <= 0);
+	if (!atomic_dec_and_test(&tg->ref))
+		return;
+	kfree(tg);
+}
+
+static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td,
+			struct cgroup *cgroup)
+{
+	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
+	struct throtl_grp *tg = NULL;
+	void *key = td;
+	struct backing_dev_info *bdi = &td->queue->backing_dev_info;
+	unsigned int major, minor;
+
+	/*
+	 * TODO: Speed up blkiocg_lookup_group() by maintaining a radix
+	 * tree of blkg (instead of traversing through hash list all
+	 * the time.
+	 */
+	tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
+
+	/* Fill in device details for root group */
+	if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
+		sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
+		tg->blkg.dev = MKDEV(major, minor);
+		goto done;
+	}
+
+	if (tg)
+		goto done;
+
+	tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node);
+	if (!tg)
+		goto done;
+
+	INIT_HLIST_NODE(&tg->tg_node);
+	RB_CLEAR_NODE(&tg->rb_node);
+	bio_list_init(&tg->bio_lists[0]);
+	bio_list_init(&tg->bio_lists[1]);
+
+	/*
+	 * Take the initial reference that will be released on destroy
+	 * This can be thought of a joint reference by cgroup and
+	 * request queue which will be dropped by either request queue
+	 * exit or cgroup deletion path depending on who is exiting first.
+	 */
+	atomic_set(&tg->ref, 1);
+
+	/* Add group onto cgroup list */
+	sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
+	blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td,
+				MKDEV(major, minor), BLKIO_POLICY_THROTL);
+
+	tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
+	tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
+
+	hlist_add_head(&tg->tg_node, &td->tg_list);
+	td->nr_undestroyed_grps++;
+done:
+	return tg;
+}
+
+static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
+{
+	struct cgroup *cgroup;
+	struct throtl_grp *tg = NULL;
+
+	rcu_read_lock();
+	cgroup = task_cgroup(current, blkio_subsys_id);
+	tg = throtl_find_alloc_tg(td, cgroup);
+	if (!tg)
+		tg = &td->root_tg;
+	rcu_read_unlock();
+	return tg;
+}
+
+static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
+{
+	/* Service tree is empty */
+	if (!root->count)
+		return NULL;
+
+	if (!root->left)
+		root->left = rb_first(&root->rb);
+
+	if (root->left)
+		return rb_entry_tg(root->left);
+
+	return NULL;
+}
+
+static void rb_erase_init(struct rb_node *n, struct rb_root *root)
+{
+	rb_erase(n, root);
+	RB_CLEAR_NODE(n);
+}
+
+static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
+{
+	if (root->left == n)
+		root->left = NULL;
+	rb_erase_init(n, &root->rb);
+	--root->count;
+}
+
+static void update_min_dispatch_time(struct throtl_rb_root *st)
+{
+	struct throtl_grp *tg;
+
+	tg = throtl_rb_first(st);
+	if (!tg)
+		return;
+
+	st->min_disptime = tg->disptime;
+}
+
+static void
+tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
+{
+	struct rb_node **node = &st->rb.rb_node;
+	struct rb_node *parent = NULL;
+	struct throtl_grp *__tg;
+	unsigned long key = tg->disptime;
+	int left = 1;
+
+	while (*node != NULL) {
+		parent = *node;
+		__tg = rb_entry_tg(parent);
+
+		if (time_before(key, __tg->disptime))
+			node = &parent->rb_left;
+		else {
+			node = &parent->rb_right;
+			left = 0;
+		}
+	}
+
+	if (left)
+		st->left = &tg->rb_node;
+
+	rb_link_node(&tg->rb_node, parent, node);
+	rb_insert_color(&tg->rb_node, &st->rb);
+}
+
+static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
+{
+	struct throtl_rb_root *st = &td->tg_service_tree;
+
+	tg_service_tree_add(st, tg);
+	throtl_mark_tg_on_rr(tg);
+	st->count++;
+}
+
+static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
+{
+	if (!throtl_tg_on_rr(tg))
+		__throtl_enqueue_tg(td, tg);
+}
+
+static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
+{
+	throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
+	throtl_clear_tg_on_rr(tg);
+}
+
+static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
+{
+	if (throtl_tg_on_rr(tg))
+		__throtl_dequeue_tg(td, tg);
+}
+
+static void throtl_schedule_next_dispatch(struct throtl_data *td)
+{
+	struct throtl_rb_root *st = &td->tg_service_tree;
+
+	/*
+	 * If there are more bios pending, schedule more work.
+	 */
+	if (!total_nr_queued(td))
+		return;
+
+	BUG_ON(!st->count);
+
+	update_min_dispatch_time(st);
+
+	if (time_before_eq(st->min_disptime, jiffies))
+		throtl_schedule_delayed_work(td->queue, 0);
+	else
+		throtl_schedule_delayed_work(td->queue,
+				(st->min_disptime - jiffies));
+}
+
+static inline void
+throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
+{
+	tg->bytes_disp[rw] = 0;
+	tg->slice_start[rw] = jiffies;
+	tg->slice_end[rw] = jiffies + throtl_slice;
+	throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
+			rw == READ ? 'R' : 'W', tg->slice_start[rw],
+			tg->slice_end[rw], jiffies);
+}
+
+static inline void throtl_extend_slice(struct throtl_data *td,
+		struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
+{
+	tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
+	throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
+			rw == READ ? 'R' : 'W', tg->slice_start[rw],
+			tg->slice_end[rw], jiffies);
+}
+
+/* Trim the used slices and adjust slice start accordingly */
+static inline void
+throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
+{
+	unsigned long nr_slices, bytes_trim, time_elapsed;
+
+	BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
+
+	time_elapsed = jiffies - tg->slice_start[rw];
+
+	nr_slices = time_elapsed / throtl_slice;
+
+	if (!nr_slices)
+		return;
+
+	bytes_trim = (tg->bps[rw] * throtl_slice * nr_slices)/HZ;
+
+	if (!bytes_trim)
+		return;
+
+	if (tg->bytes_disp[rw] >= bytes_trim)
+		tg->bytes_disp[rw] -= bytes_trim;
+	else
+		tg->bytes_disp[rw] = 0;
+
+	tg->slice_start[rw] += nr_slices * throtl_slice;
+
+	throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%lu"
+			" start=%lu end=%lu jiffies=%lu",
+			rw == READ ? 'R' : 'W', nr_slices, bytes_trim,
+			tg->slice_start[rw], tg->slice_end[rw], jiffies);
+}
+
+/* Determine if previously allocated or extended slice is complete or not */
+static bool throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
+{
+	if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
+		return 0;
+
+	return 1;
+}
+
+/*
+ * Returns whether one can dispatch a bio or not. Also returns approx number
+ * of jiffies to wait before this bio is with-in IO rate and can be dispatched
+ */
+static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
+				struct bio *bio, unsigned long *wait)
+{
+	bool rw = bio_data_dir(bio);
+	u64 bytes_allowed, extra_bytes;
+	unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
+
+	/*
+ 	 * Currently whole state machine of group depends on first bio
+	 * queued in the group bio list. So one should not be calling
+	 * this function with a different bio if there are other bios
+	 * queued.
+	 */
+	BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
+
+	/* If tg->bps = -1, then BW is unlimited */
+	if (tg->bps[rw] == -1)
+		return 1;
+
+	/*
+	 * If previous slice expired, start a new one otherwise renew/extend
+	 * existing slice to make sure it is at least throtl_slice interval
+	 * long since now.
+	 */
+	if (throtl_slice_used(td, tg, rw))
+		throtl_start_new_slice(td, tg, rw);
+	else {
+		if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
+			throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
+	}
+
+	jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
+
+	/* Slice has just started. Consider one slice interval */
+	if (!jiffy_elapsed)
+		jiffy_elapsed_rnd = throtl_slice;
+
+	jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
+
+	bytes_allowed = (tg->bps[rw] * jiffies_to_msecs(jiffy_elapsed_rnd))
+				/ MSEC_PER_SEC;
+
+	if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
+		if (wait)
+			*wait = 0;
+		return 1;
+	}
+
+	/* Calc approx time to dispatch */
+	extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
+	jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
+
+	if (!jiffy_wait)
+		jiffy_wait = 1;
+
+	/*
+	 * This wait time is without taking into consideration the rounding
+	 * up we did. Add that time also.
+	 */
+	jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
+
+	if (wait)
+		*wait = jiffy_wait;
+
+	if (time_before(tg->slice_end[rw], jiffies + jiffy_wait))
+		throtl_extend_slice(td, tg, rw, jiffies + jiffy_wait);
+
+	return 0;
+}
+
+static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
+{
+	bool rw = bio_data_dir(bio);
+	bool sync = bio->bi_rw & REQ_SYNC;
+
+	/* Charge the bio to the group */
+	tg->bytes_disp[rw] += bio->bi_size;
+
+	/*
+	 * TODO: This will take blkg->stats_lock. Figure out a way
+	 * to avoid this cost.
+	 */
+	blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);
+
+}
+
+static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
+			struct bio *bio)
+{
+	bool rw = bio_data_dir(bio);
+
+	bio_list_add(&tg->bio_lists[rw], bio);
+	/* Take a bio reference on tg */
+	throtl_ref_get_tg(tg);
+	tg->nr_queued[rw]++;
+	td->nr_queued[rw]++;
+	throtl_enqueue_tg(td, tg);
+}
+
+static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
+{
+	unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
+	struct bio *bio;
+
+	if ((bio = bio_list_peek(&tg->bio_lists[READ])))
+		tg_may_dispatch(td, tg, bio, &read_wait);
+
+	if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
+		tg_may_dispatch(td, tg, bio, &write_wait);
+
+	min_wait = min(read_wait, write_wait);
+	disptime = jiffies + min_wait;
+
+	/*
+	 * If group is already on active tree, then update dispatch time
+	 * only if it is lesser than existing dispatch time. Otherwise
+	 * always update the dispatch time
+	 */
+
+	if (throtl_tg_on_rr(tg) && time_before(disptime, tg->disptime))
+		return;
+
+	/* Update dispatch time */
+	throtl_dequeue_tg(td, tg);
+	tg->disptime = disptime;
+	throtl_enqueue_tg(td, tg);
+}
+
+static void
+tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg, bool rw)
+{
+	struct bio *bio;
+
+	bio = bio_list_pop(&tg->bio_lists[rw]);
+	tg->nr_queued[rw]--;
+	/* Drop bio reference on tg */
+	throtl_put_tg(tg);
+
+	BUG_ON(td->nr_queued[rw] <= 0);
+	td->nr_queued[rw]--;
+
+	throtl_charge_bio(tg, bio);
+	bio_list_add(&td->disp_list, bio);
+	td->nr_disp_list++;
+
+	throtl_trim_slice(td, tg, rw);
+}
+
+/*
+ * Enter with queue lock held spin_lock_irq(). Returns with queue lock unlocked  */
+static int release_from_disp_list(struct throtl_data *td)
+{
+	struct bio *bio;
+	unsigned int nr_disp = 0;
+
+	if (!td->nr_disp_list)
+		goto out;
+
+	while (!bio_list_empty(&td->disp_list)) {
+		bio = bio_list_pop(&td->disp_list);
+		bio->bi_rw |= REQ_THROTTLED;
+		BUG_ON(td->nr_disp_list <= 0);
+		td->nr_disp_list--;
+		nr_disp++;
+		/*
+		 * Drop the spin lock and submit bio.
+		 */
+		spin_unlock_irq(td->queue->queue_lock);
+		generic_make_request(bio);
+		spin_lock_irq(td->queue->queue_lock);
+	}
+
+out:
+	spin_unlock_irq(td->queue->queue_lock);
+	return nr_disp;
+}
+
+static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg)
+{
+	unsigned int nr_reads = 0, nr_writes = 0;
+	unsigned int max_nr_reads = throtl_grp_quantum*3/4;
+	unsigned int max_nr_writes = throtl_grp_quantum - nr_reads;
+	struct bio *bio;
+
+	/* Try to dispatch 75% READS and 25% WRITES */
+
+	while ((bio = bio_list_peek(&tg->bio_lists[READ]))
+		&& tg_may_dispatch(td, tg, bio, NULL)) {
+
+		tg_dispatch_one_bio(td, tg, bio_data_dir(bio));
+		nr_reads++;
+
+		if (nr_reads >= max_nr_reads)
+			break;
+	}
+
+	while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
+		&& tg_may_dispatch(td, tg, bio, NULL)) {
+
+		tg_dispatch_one_bio(td, tg, bio_data_dir(bio));
+		nr_writes++;
+
+		if (nr_writes >= max_nr_writes)
+			break;
+	}
+
+	return nr_reads + nr_writes;
+}
+
+static int throtl_select_dispatch(struct throtl_data *td)
+{
+	unsigned int nr_disp = 0;
+	struct throtl_grp *tg;
+	struct throtl_rb_root *st = &td->tg_service_tree;
+
+	while (1) {
+		tg = throtl_rb_first(st);
+
+		if (!tg)
+			break;
+
+		if (time_before(jiffies, tg->disptime))
+			break;
+
+		throtl_dequeue_tg(td, tg);
+
+		nr_disp += throtl_dispatch_tg(td, tg);
+
+		if (tg->nr_queued[0] || tg->nr_queued[1]) {
+			tg_update_disptime(td, tg);
+			throtl_enqueue_tg(td, tg);
+		}
+
+		if (nr_disp >= throtl_quantum)
+			break;
+	}
+
+	return nr_disp;
+}
+
+/* Dispatch throttled bios. Should be called without queue lock held. */
+static int throtl_dispatch(struct request_queue *q)
+{
+	struct throtl_data *td = q->td;
+	unsigned int nr_disp = 0, temp_disp = 0;
+
+	spin_lock_irq(q->queue_lock);
+
+	if (!total_nr_queued(td))
+		goto out;
+
+	throtl_log(td, "dispatch nr_queued=%lu", total_nr_queued(td));
+
+	while(1) {
+		temp_disp = 0;
+		temp_disp = release_from_disp_list(q->td);
+		nr_disp += temp_disp;
+
+		if (nr_disp >= throtl_quantum)
+			break;
+
+		/*
+		 * release_from_disp_list returns with queue lock unlocked.
+		 * acquire the lock again.
+		 */
+		spin_lock_irq(q->queue_lock);
+		temp_disp = throtl_select_dispatch(td);
+		if (!temp_disp)
+			break;
+	}
+
+	throtl_schedule_next_dispatch(td);
+out:
+	spin_unlock_irq(q->queue_lock);
+	/*
+	 * If we dispatched some requests, unplug the queue to make sure
+	 * immediate dispatch
+	 */
+	if (nr_disp) {
+		throtl_log(td, "bios disp=%u", nr_disp);
+		blk_unplug(q);
+	}
+	return nr_disp;
+}
+
+void blk_throtl_work(struct work_struct *work)
+{
+	struct throtl_data *td = container_of(work, struct throtl_data,
+					throtl_work.work);
+	struct request_queue *q = td->queue;
+
+	throtl_dispatch(q);
+}
+
+/* Call with queue lock held */
+void throtl_schedule_delayed_work(struct request_queue *q, unsigned long delay)
+{
+
+	struct throtl_data *td = q->td;
+	struct delayed_work *dwork = &td->throtl_work;
+
+	if (total_nr_queued(td) > 0) {
+		/*
+		 * We might have a work scheduled to be executed in future.
+		 * Cancel that and schedule a new one.
+		 */
+		__cancel_delayed_work(dwork);
+		kblockd_schedule_delayed_work(q, dwork, delay);
+		throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
+				delay, jiffies);
+	}
+}
+EXPORT_SYMBOL(throtl_schedule_delayed_work);
+
+static void
+throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
+{
+	/* Something wrong if we are trying to remove same group twice */
+	BUG_ON(hlist_unhashed(&tg->tg_node));
+
+	hlist_del_init(&tg->tg_node);
+
+	/*
+	 * Put the reference taken at the time of creation so that when all
+	 * queues are gone, group can be destroyed.
+	 */
+	throtl_put_tg(tg);
+	td->nr_undestroyed_grps--;
+}
+
+static void throtl_release_tgs(struct throtl_data *td)
+{
+	struct hlist_node *pos, *n;
+	struct throtl_grp *tg;
+
+	hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
+		/*
+		 * If cgroup removal path got to blk_group first and removed
+		 * it from cgroup list, then it will take care of destroying
+		 * cfqg also.
+		 */
+		if (!blkiocg_del_blkio_group(&tg->blkg))
+			throtl_destroy_tg(td, tg);
+	}
+}
+
+static void throtl_td_free(struct throtl_data *td)
+{
+	kfree(td);
+}
+
+/*
+ * Blk cgroup controller notification saying that blkio_group object is being
+ * delinked as associated cgroup object is going away. That also means that
+ * no new IO will come in this group. So get rid of this group as soon as
+ * any pending IO in the group is finished.
+ *
+ * This function is called under rcu_read_lock(). key is the rcu protected
+ * pointer. That means "key" is a valid throtl_data pointer as long as we are
+ * rcu read lock.
+ *
+ * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
+ * it should not be NULL as even if queue was going away, cgroup deltion
+ * path got to it first.
+ */
+void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg)
+{
+	unsigned long flags;
+	struct throtl_data *td = key;
+
+	spin_lock_irqsave(td->queue->queue_lock, flags);
+	throtl_destroy_tg(td, tg_of_blkg(blkg));
+	spin_unlock_irqrestore(td->queue->queue_lock, flags);
+}
+
+static void throtl_update_blkio_group_read_bps (struct blkio_group *blkg,
+			u64 read_bps)
+{
+	tg_of_blkg(blkg)->bps[READ] = read_bps;
+}
+
+static void throtl_update_blkio_group_write_bps (struct blkio_group *blkg,
+			u64 write_bps)
+{
+	tg_of_blkg(blkg)->bps[WRITE] = write_bps;
+}
+
+void throtl_shutdown_timer_wq(struct request_queue *q)
+{
+	struct throtl_data *td = q->td;
+
+	cancel_delayed_work_sync(&td->throtl_work);
+}
+
+static struct blkio_policy_type blkio_policy_throtl = {
+	.ops = {
+		.blkio_unlink_group_fn = throtl_unlink_blkio_group,
+		.blkio_update_group_read_bps_fn =
+					throtl_update_blkio_group_read_bps,
+		.blkio_update_group_write_bps_fn =
+					throtl_update_blkio_group_write_bps,
+	},
+};
+
+int blk_throtl_bio(struct request_queue *q, struct bio **biop)
+{
+	struct throtl_data *td = q->td;
+	struct throtl_grp *tg;
+	struct bio *bio = *biop;
+	bool rw = bio_data_dir(bio), update_disptime = true;
+
+	if (bio->bi_rw & REQ_THROTTLED) {
+		bio->bi_rw &= ~REQ_THROTTLED;
+		return 0;
+	}
+
+	/*
+	 * Do not throttle barriers. Upstream work is on to get rid of
+	 * hard barriers and block layer will not gurantee ordering of
+	 * barrier w.r.t other bios, hence no need to flush all the
+	 * queued/throttled bios.
+	 */
+	if (unlikely((bio->bi_rw & REQ_HARDBARRIER)))
+		return 0;
+
+	spin_lock_irq(q->queue_lock);
+	tg = throtl_get_tg(td);
+
+	if (tg->nr_queued[rw]) {
+		/*
+		 * There is already another bio queued in same dir. No
+		 * need to update dispatch time.
+		 */
+		update_disptime = false;
+		goto queue_bio;
+	}
+
+	/* Bio is with-in rate limit of group */
+	if (tg_may_dispatch(td, tg, bio, NULL)) {
+		throtl_charge_bio(tg, bio);
+		goto out;
+	}
+
+queue_bio:
+	throtl_log_tg(td, tg, "[%c] bio. disp=%u sz=%u bps=%llu"
+			" queued=%d/%d", rw == READ ? 'R' : 'W',
+			tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
+			tg->nr_queued[READ], tg->nr_queued[WRITE]);
+
+	throtl_add_bio_tg(q->td, tg, bio);
+	*biop = NULL;
+
+	if (update_disptime) {
+		tg_update_disptime(td, tg);
+		throtl_schedule_next_dispatch(td);
+	}
+
+out:
+	spin_unlock_irq(q->queue_lock);
+	return 0;
+}
+
+int blk_throtl_init(struct request_queue *q)
+{
+	struct throtl_data *td;
+	struct throtl_grp *tg;
+
+	td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
+	if (!td)
+		return -ENOMEM;
+
+	INIT_HLIST_HEAD(&td->tg_list);
+	td->tg_service_tree = THROTL_RB_ROOT;
+	bio_list_init(&td->disp_list);
+
+	/* Init root group */
+	tg = &td->root_tg;
+	INIT_HLIST_NODE(&tg->tg_node);
+	RB_CLEAR_NODE(&tg->rb_node);
+	bio_list_init(&tg->bio_lists[0]);
+	bio_list_init(&tg->bio_lists[1]);
+
+	/* Practically unlimited BW */
+	tg->bps[0] = tg->bps[1] = -1;
+	atomic_set(&tg->ref, 1);
+
+	INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
+
+	rcu_read_lock();
+	blkiocg_add_blkio_group(&blkio_root_cgroup, &tg->blkg, (void *)td,
+					0, BLKIO_POLICY_THROTL);
+	rcu_read_unlock();
+
+	/* Attach throtl data to request queue */
+	td->queue = q;
+	q->td = td;
+	return 0;
+}
+
+void blk_throtl_exit(struct request_queue *q)
+{
+	struct throtl_data *td = q->td;
+	bool wait = false;
+
+	BUG_ON(!td);
+
+	throtl_shutdown_timer_wq(q);
+
+	spin_lock_irq(q->queue_lock);
+	throtl_release_tgs(td);
+	blkiocg_del_blkio_group(&td->root_tg.blkg);
+
+	/* If there are other groups */
+	if (td->nr_undestroyed_grps >= 1)
+		wait = true;
+
+	spin_unlock_irq(q->queue_lock);
+
+	/*
+	 * Wait for tg->blkg->key accessors to exit their grace periods.
+	 * Do this wait only if there are other undestroyed groups out
+	 * there (other than root group). This can happen if cgroup deletion
+	 * path claimed the responsibility of cleaning up a group before
+	 * queue cleanup code get to the group.
+	 *
+	 * Do not call synchronize_rcu() unconditionally as there are drivers
+	 * which create/delete request queue hundreds of times during scan/boot
+	 * and synchronize_rcu() can take significant time and slow down boot.
+	 */
+	if (wait)
+		synchronize_rcu();
+	throtl_td_free(td);
+}
+
+static int __init throtl_init(void)
+{
+	blkio_policy_register(&blkio_policy_throtl);
+	return 0;
+}
+
+module_init(throtl_init);
diff --git a/block/blk.h b/block/blk.h
index 6e7dc87..e836e64 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -62,8 +62,10 @@ static inline struct request *__elv_next_request(struct request_queue *q)
 				return rq;
 		}
 
-		if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
+		if (!q->elevator->ops->elevator_dispatch_fn(q, 0)) {
+			throtl_schedule_delayed_work(q, 0);
 			return NULL;
+		}
 	}
 }
 
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index eb4086f..8cec3a8 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -467,10 +467,14 @@ static inline bool cfq_bio_sync(struct bio *bio)
  */
 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
 {
+	struct request_queue *q = cfqd->queue;
+
 	if (cfqd->busy_queues) {
 		cfq_log(cfqd, "schedule dispatch");
 		kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
 	}
+
+	throtl_schedule_delayed_work(q, 0);
 }
 
 static int cfq_queue_empty(struct request_queue *q)
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index ca83a97..10a0c29 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -130,6 +130,8 @@ enum rq_flag_bits {
 	/* bio only flags */
 	__REQ_UNPLUG,		/* unplug the immediately after submission */
 	__REQ_RAHEAD,		/* read ahead, can fail anytime */
+	__REQ_THROTTLED,	/* This bio has already been subjected to
+				 * throttling rules. Don't do it again. */
 
 	/* request only flags */
 	__REQ_SORTED,		/* elevator knows about this request */
@@ -172,6 +174,7 @@ enum rq_flag_bits {
 
 #define REQ_UNPLUG		(1 << __REQ_UNPLUG)
 #define REQ_RAHEAD		(1 << __REQ_RAHEAD)
+#define REQ_THROTTLED		(1 << __REQ_THROTTLED)
 
 #define REQ_SORTED		(1 << __REQ_SORTED)
 #define REQ_SOFTBARRIER		(1 << __REQ_SOFTBARRIER)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2c54906..66bca1a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -367,6 +367,11 @@ struct request_queue
 #if defined(CONFIG_BLK_DEV_BSG)
 	struct bsg_class_device bsg_dev;
 #endif
+
+#ifdef CONFIG_BLK_DEV_THROTTLING
+	/* Throttle data */
+	struct throtl_data *td;
+#endif
 };
 
 #define QUEUE_FLAG_CLUSTER	0	/* cluster several segments into 1 */
@@ -1127,6 +1132,7 @@ static inline void put_dev_sector(Sector p)
 
 struct work_struct;
 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work);
+int kblockd_schedule_delayed_work(struct request_queue *q, struct delayed_work *dwork, unsigned long delay);
 
 #ifdef CONFIG_BLK_CGROUP
 /*
@@ -1170,6 +1176,24 @@ static inline uint64_t rq_io_start_time_ns(struct request *req)
 }
 #endif
 
+#ifdef CONFIG_BLK_DEV_THROTTLING
+extern int blk_throtl_init(struct request_queue *q);
+extern void blk_throtl_exit(struct request_queue *q);
+extern int blk_throtl_bio(struct request_queue *q, struct bio **bio);
+extern void throtl_schedule_delayed_work(struct request_queue *q, unsigned long delay);
+extern void throtl_shutdown_timer_wq(struct request_queue *q);
+#else /* CONFIG_BLK_DEV_THROTTLING */
+static inline int blk_throtl_bio(struct request_queue *q, struct bio **bio)
+{
+	return 0;
+}
+
+static inline int blk_throtl_init(struct request_queue *q) { return 0; }
+static inline int blk_throtl_exit(struct request_queue *q) { return 0; }
+static inline void throtl_schedule_delayed_work(struct request_queue *q, unsigned long delay) {}
+static inline void throtl_shutdown_timer_wq(struct request_queue *q) {}
+#endif /* CONFIG_BLK_DEV_THROTTLING */
+
 #define MODULE_ALIAS_BLOCKDEV(major,minor) \
 	MODULE_ALIAS("block-major-" __stringify(major) "-" __stringify(minor))
 #define MODULE_ALIAS_BLOCKDEV_MAJOR(major) \
diff --git a/init/Kconfig b/init/Kconfig
index 2de5b1c..950ba26 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -634,11 +634,14 @@ config BLK_CGROUP
 
 	Currently, CFQ IO scheduler uses it to recognize task groups and
 	control disk bandwidth allocation (proportional time slice allocation)
-	to such task groups.
+	to such task groups. It is also used by bio throttling logic in
+	block layer to implement upper limit in IO rates on a device.
 
 	This option only enables generic Block IO controller infrastructure.
-	One needs to also enable actual IO controlling logic in CFQ for it
-	to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
+	One needs to also enable actual IO controlling logic/policy. For
+	enabling proportional weight division of disk bandwidth in CFQ seti
+	CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
+	CONFIG_BLK_THROTTLE=y.
 
 	See Documentation/cgroups/blkio-controller.txt for more information.
 
-- 
1.7.2.2

[PATCH 4/4] blkio: Documentation update

[Vivek Goyal]

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 Documentation/cgroups/blkio-controller.txt |   89 +++++++++++++++++++++++++++-
 1 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index 48e0b21..ba895f0 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -8,12 +8,17 @@ both at leaf nodes as well as at intermediate nodes in a storage hierarchy.
 Plan is to use the same cgroup based management interface for blkio controller
 and based on user options switch IO policies in the background.
 
-In the first phase, this patchset implements proportional weight time based
-division of disk policy. It is implemented in CFQ. Hence this policy takes
-effect only on leaf nodes when CFQ is being used.
+Currently two IO control policies are implemented. First one is proportional
+weight time based division of disk policy. It is implemented in CFQ. Hence
+this policy takes effect only on leaf nodes when CFQ is being used. The second
+one is throttling policy which can be used to specify upper IO rate limits
+on devices. This policy is implemented in generic block layer and can be
+used on leaf nodes as well as higher level logical devices like device mapper.
 
 HOWTO
 =====
+Proportional Weight division of bandwidth
+-----------------------------------------
 You can do a very simple testing of running two dd threads in two different
 cgroups. Here is what you can do.
 
@@ -55,6 +60,35 @@ cgroups. Here is what you can do.
   group dispatched to the disk. We provide fairness in terms of disk time, so
   ideally io.disk_time of cgroups should be in proportion to the weight.
 
+Throttling/Upper Limit policy
+-----------------------------
+- Enable Block IO controller
+	CONFIG_BLK_CGROUP=y
+
+- Enable throttling in block layer
+	CONFIG_BLK_DEV_THROTTLING=y
+
+- Mount blkio controller
+        mount -t cgroup -o blkio none /cgroup/blkio
+
+- Specify a bandwidth rate on particular device for root group. The format
+  for policy is "<major>:<minor>  <byes_per_second>".
+
+        echo "8:16  1048576" > /cgroup/blkio/blkio.read_bps_device
+
+  Above will put a limit of 1MB/second on reads happening for root group
+  on device having major/minor number 8:16.
+
+- Run dd to read a file and see if rate is throttled to 1MB/s or not.
+
+       	# dd if=/mnt/common/zerofile of=/dev/null bs=4K count=1024
+       	# iflag=direct
+        1024+0 records in
+        1024+0 records out
+        4194304 bytes (4.2 MB) copied, 4.0001 s, 1.0 MB/s
+
+ Limits for writes can be put using blkio.write_bps_device file.
+
 Various user visible config options
 ===================================
 CONFIG_BLK_CGROUP
@@ -68,8 +102,13 @@ CONFIG_CFQ_GROUP_IOSCHED
 	- Enables group scheduling in CFQ. Currently only 1 level of group
 	  creation is allowed.
 
+CONFIG_BLK_DEV_THROTTLING
+	- Enable block device throttling support in block layer.
+
 Details of cgroup files
 =======================
+Proportional weight policy files
+--------------------------------
 - blkio.weight
 	- Specifies per cgroup weight. This is default weight of the group
 	  on all the devices until and unless overridden by per device rule.
@@ -210,6 +249,50 @@ Details of cgroup files
 	  and minor number of the device and third field specifies the number
 	  of times a group was dequeued from a particular device.
 
+Throttling/Upper limit policy files
+-----------------------------------
+- blkio.throttle.read_bps_device
+	- Specifies upper limit on READ rate from the device. IO rate is
+	  specified in bytes per second. Rules are per deivce. Following is
+	  the format.
+
+  echo "<major>:<minor>  <rate_bytes_per_second>" > /cgrp/blkio.read_bps_device
+
+- blkio.throttle.write_bps_device
+	- Specifies upper limit on WRITE rate to the device. IO rate is
+	  specified in bytes per second. Rules are per deivce. Following is
+	  the format.
+
+  echo "<major>:<minor>  <rate_bytes_per_second>" > /cgrp/blkio.write_bps_device
+
+- blkio.throttle.io_serviced
+	- Number of IOs (bio) completed to/from the disk by the group (as
+	  seen by throttling policy). These are further divided by the type
+	  of operation - read or write, sync or async. First two fields specify
+	  the major and minor number of the device, third field specifies the
+	  operation type and the fourth field specifies the number of IOs.
+
+	  blkio.io_serviced does accounting as seen by CFQ and counts are in
+	  number of requests (struct request). On the other hand,
+	  blkio.throttle.io_serviced counts number of IO in terms of number
+	  of bios as seen by throttling policy.  These bios can later be
+	  merged by elevator and total number of requests completed can be
+	  lesser.
+
+- blkio.throttle.io_service_bytes
+	- Number of bytes transferred to/from the disk by the group. These
+	  are further divided by the type of operation - read or write, sync
+	  or async. First two fields specify the major and minor number of the
+	  device, third field specifies the operation type and the fourth field
+	  specifies the number of bytes.
+
+	  These numbers should roughly be same as blkio.io_service_bytes as
+	  updated by CFQ. The difference between two is that
+	  blkio.io_service_bytes will not be updated if CFQ is not operating
+	  on request queue.
+
+Common files among various policies
+-----------------------------------
 - blkio.reset_stats
 	- Writing an int to this file will result in resetting all the stats
 	  for that cgroup.
-- 
1.7.2.2