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Date:	Wed,  5 Jun 2013 10:23:00 +0800
From:	Robin Dong <robin.k.dong@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Robin Dong <sanbai@...bao.com>,
	Zhu Yanhai <gaoyang.zyh@...bao.com>, Tejun Heo <tj@...nel.org>,
	Vivek Goyal <vgoyal@...hat.com>, Jens Axboe <axboe@...nel.dk>,
	Tao Ma <taoma.tm@...il.com>
Subject: [RFC v1] add new io-scheduler to use cgroup on high-speed device

From: Robin Dong <sanbai@...bao.com>

We want to use blkio.cgroup on high-speed device (like fusionio) for our mysql clusters.
After testing different io-scheduler, we found that  cfq is too slow and deadline can't run on cgroup.
So we developed a new io-scheduler: tpps (Tiny Parallel Proportion Scheduler).It dispatch requests
only by using their individual weight and total weight (proportion) therefore it's simply and efficient.

Test case: fusionio card, 4 cgroups, iodepth-512

groupname  weight
test1      1000
test2      800
test3      600
test4      400

Use tpps, the result is:

groupname  iops    avg-rt(ms)   max-rt(ms)
test1      30220   16           54 
test2      28261   18           56
test3      26333   19           69
test4      20152   25           87

Use cfq, the result is:

groupname  iops    avg-rt(ms)   max-rt(ms)
test1      16478   30           242
test2      13015   39           347
test3       9300   54           371
test4       5806   87           393

Signed-off-by: Robin Dong <sanbai@...bao.com>
Signed-off-by: Zhu Yanhai <gaoyang.zyh@...bao.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: Vivek Goyal <vgoyal@...hat.com>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Tao Ma <taoma.tm@...il.com>
---
 block/Kconfig.iosched  |   13 +
 block/Makefile         |    1 +
 block/tpps-iosched.c   | 1272 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/blkdev.h |    2 +-
 4 files changed, 1287 insertions(+), 1 deletions(-)
 create mode 100644 block/tpps-iosched.c

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 421bef9..e5e28c2 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -21,6 +21,16 @@ config IOSCHED_DEADLINE
 	  a new point in the service tree and doing a batch of IO from there
 	  in case of expiry.
 
+config IOSCHED_TPPS
+	tristate "TPPS I/O scheduler"
+	# If BLK_CGROUP is a module, TPPS has to be built as module.
+	default y
+	---help---
+	  The TPPS I/O scheduler tries to distribute iops proportional
+	  among all cgroups in the system. It should also provide a low
+	  latency working environment, suitable for flash-based device.
+	  Note: If BLK_CGROUP=m, then TPPS can be built only as module.
+
 config IOSCHED_CFQ
 	tristate "CFQ I/O scheduler"
 	default y
@@ -49,6 +59,9 @@ choice
 	config DEFAULT_DEADLINE
 		bool "Deadline" if IOSCHED_DEADLINE=y
 
+	config DEFAULT_TPPS
+		bool "Tiny Parallel Proportion" if IOSCHED_TPPS=y
+
 	config DEFAULT_CFQ
 		bool "CFQ" if IOSCHED_CFQ=y
 
diff --git a/block/Makefile b/block/Makefile
index 39b76ba..6e30ef4 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -15,6 +15,7 @@ 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
+obj-$(CONFIG_IOSCHED_TPPS)	+= tpps-iosched.o
 
 obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o
 obj-$(CONFIG_BLK_DEV_INTEGRITY)	+= blk-integrity.o
diff --git a/block/tpps-iosched.c b/block/tpps-iosched.c
new file mode 100644
index 0000000..981fde2
--- /dev/null
+++ b/block/tpps-iosched.c
@@ -0,0 +1,1272 @@
+/*
+ *  TPPS, or Tiny Parallel Proportion disk Scheduler.
+ *
+ *  Based on ideas from Zhu Yanhai <gaoyang.zyh@...bao.com>
+ *
+ *  Copyright (C) 2013 Robin Dong <sanbai@...bao.com>
+ */
+#include <linux/module.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/jiffies.h>
+#include <linux/rbtree.h>
+#include <linux/ioprio.h>
+#include <linux/blktrace_api.h>
+#include "blk-cgroup.h"
+#include "blk.h"
+
+static struct kmem_cache *tpps_pool;
+
+struct tpps_queue {
+	/* reference count */
+	int ref;
+	/* parent tpps_data */
+	struct tpps_data *tppd;
+	/* tpps_group member */
+	struct list_head tppg_node;
+	/* sorted list of pending requests */
+	struct list_head sort_list;
+	struct tpps_group *tppg;
+	pid_t pid;
+	int online;
+	int rq_queued;
+};
+
+struct tppg_stats {
+	/* total bytes transferred */
+	struct blkg_rwstat		service_bytes;
+	/* total IOs serviced, post merge */
+	struct blkg_rwstat		serviced;
+	/* number of ios merged */
+	struct blkg_rwstat		merged;
+	/* total time spent on device in ns, may not be accurate w/ queueing */
+	struct blkg_rwstat		service_time;
+	/* total time spent waiting in scheduler queue in ns */
+	struct blkg_rwstat		wait_time;
+	/* number of IOs queued up */
+	struct blkg_rwstat		queued;
+	/* total sectors transferred */
+	struct blkg_stat		sectors;
+	/* total disk time and nr sectors dispatched by this group */
+	struct blkg_stat		time;
+};
+
+struct tpps_group {
+	struct blkg_policy_data pd;
+	/* tpps_data member */
+	struct list_head tppd_node;
+	struct list_head *cur_dispatcher;
+
+	unsigned int weight;
+	unsigned int new_weight;
+	unsigned int dev_weight;
+	unsigned int leaf_weight;
+	unsigned int new_leaf_weight;
+	unsigned int dev_leaf_weight;
+
+	bool needs_update;
+
+	/*
+	 * lists of queues with requests.
+	 */
+	struct list_head queue_list;
+	int nr_tppq;
+	int rq_queued;
+	int rq_in_driver;
+
+	struct tppg_stats stats;	/* stats for this tppg */
+	struct tppg_stats dead_stats;	/* stats pushed from dead children */
+};
+
+struct tpps_io_cq {
+	struct io_cq		icq;		/* must be the first member */
+	struct tpps_queue	*tppq;
+	uint64_t			blkcg_id;	/* the current blkcg ID */
+};
+
+struct tpps_data {
+	struct request_queue *queue;
+	struct tpps_group *root_group;
+
+	/* List of tpps groups being managed on this device*/
+	struct list_head group_list;
+
+	unsigned int busy_queues;
+	int dispatched;
+	int rq_in_driver;
+
+	struct work_struct unplug_work;
+
+	/* Number of groups which are on blkcg->blkg_list */
+	unsigned int nr_blkcg_linked_grps;
+
+	unsigned total_weight;
+};
+
+static inline struct blkcg_gq *tppg_to_blkg(struct tpps_group *tppg)
+{
+	return pd_to_blkg(&tppg->pd);
+}
+
+#define tpps_log_tppq(tppd, tppq, fmt, args...)	do {			\
+	char __pbuf[128];						\
+									\
+	blkg_path(tppg_to_blkg((tppq)->tppg), __pbuf, sizeof(__pbuf));	\
+	blk_add_trace_msg((tppd)->queue, "tpps%d %s " fmt, (tppq)->pid, \
+			  __pbuf, ##args);				\
+} while (0)
+
+#define tpps_log_tppg(tppd, tppg, fmt, args...)	do {			\
+	char __pbuf[128];						\
+									\
+	blkg_path(tppg_to_blkg(tppg), __pbuf, sizeof(__pbuf));		\
+	blk_add_trace_msg((tppd)->queue, "%s " fmt, __pbuf, ##args);	\
+} while (0)
+#define tpps_log(tppd, fmt, args...)	\
+	blk_add_trace_msg((tppd)->queue, "tpps " fmt, ##args)
+
+static inline struct tpps_io_cq *icq_to_tic(struct io_cq *icq)
+{
+	/* tic->icq is the first member, %NULL will convert to %NULL */
+	return container_of(icq, struct tpps_io_cq, icq);
+}
+
+#define RQ_TIC(rq)	icq_to_tic((rq)->elv.icq)
+#define RQ_TPPQ(rq)	(struct tpps_queue *) ((rq)->elv.priv[0])
+#define RQ_TPPG(rq)	(struct tpps_group *) ((rq)->elv.priv[1])
+
+#define TPPS_WEIGHT_DEFAULT	(500)
+#define MIN_DISPATCH_RQ		(8)
+
+static struct blkcg_policy blkcg_policy_tpps;
+
+static inline struct tpps_group *pd_to_tppg(struct blkg_policy_data *pd)
+{
+	return pd ? container_of(pd, struct tpps_group, pd) : NULL;
+}
+
+static inline struct tpps_group *blkg_to_tppg(struct blkcg_gq *blkg)
+{
+	return pd_to_tppg(blkg_to_pd(blkg, &blkcg_policy_tpps));
+}
+
+static inline struct tpps_io_cq *
+tpps_tic_lookup(struct tpps_data *tppd, struct io_context *ioc)
+{
+	if (ioc)
+		return icq_to_tic(ioc_lookup_icq(ioc, tppd->queue));
+	return NULL;
+}
+
+static inline struct tpps_queue *tic_to_tppq(struct tpps_io_cq *tic)
+{
+	return tic->tppq;
+}
+
+static inline void tic_set_tppq(struct tpps_io_cq *tic, struct tpps_queue *tppq)
+{
+	tic->tppq = tppq;
+}
+
+static inline struct tpps_data *tic_to_tppd(struct tpps_io_cq *tic)
+{
+	return tic->icq.q->elevator->elevator_data;
+}
+
+static inline void tppg_get(struct tpps_group *tppg)
+{
+	return blkg_get(tppg_to_blkg(tppg));
+}
+
+static inline void tppg_put(struct tpps_group *tppg)
+{
+	return blkg_put(tppg_to_blkg(tppg));
+}
+
+static inline void tppg_stats_update_io_add(struct tpps_group *tppg,
+					    struct tpps_group *curr_tppg, int rw)
+{
+	blkg_rwstat_add(&tppg->stats.queued, rw, 1);
+}
+
+static inline void tppg_stats_update_io_remove(struct tpps_group *tppg, int rw)
+{
+	blkg_rwstat_add(&tppg->stats.queued, rw, -1);
+}
+
+static inline void tppg_stats_update_io_merged(struct tpps_group *tppg, int rw)
+{
+	blkg_rwstat_add(&tppg->stats.merged, rw, 1);
+}
+
+static inline void tppg_stats_update_dispatch(struct tpps_group *tppg,
+					      uint64_t bytes, int rw)
+{
+	blkg_stat_add(&tppg->stats.sectors, bytes >> 9);
+	blkg_rwstat_add(&tppg->stats.serviced, rw, 1);
+	blkg_rwstat_add(&tppg->stats.service_bytes, rw, bytes);
+}
+
+static inline void tppg_stats_update_completion(struct tpps_group *tppg,
+			uint64_t start_time, uint64_t io_start_time, int rw)
+{
+	struct tppg_stats *stats = &tppg->stats;
+	unsigned long long now = sched_clock();
+
+	if (time_after64(now, io_start_time))
+		blkg_rwstat_add(&stats->service_time, rw, now - io_start_time);
+	if (time_after64(io_start_time, start_time))
+		blkg_rwstat_add(&stats->wait_time, rw,
+				io_start_time - start_time);
+}
+
+static void tpps_del_queue(struct tpps_queue *tppq)
+{
+	struct tpps_data *tppd = tppq->tppd;
+	struct tpps_group *tppg = tppq->tppg;
+
+	if (!list_empty(&tppq->tppg_node)) {
+		list_del_init(&tppq->tppg_node);
+		tpps_log_tppq(tppd, tppq, "del queue\n");
+		tppg->cur_dispatcher = NULL;
+		tppq->tppg = NULL;
+	}
+
+	printk("%p nr_tppq:%d\n", tppg, tppg->nr_tppq);
+	BUG_ON(tppg->nr_tppq < 1);
+	tppg->nr_tppq--;
+	if (!tppg->nr_tppq)
+		tppd->total_weight -= tppg->pd.blkg->blkcg->cfq_weight;
+
+	BUG_ON(!tppd->busy_queues);
+	tppd->busy_queues--;
+}
+
+/*
+ * task holds one reference to the queue, dropped when task exits. each rq
+ * in-flight on this queue also holds a reference, dropped when rq is freed.
+ *
+ * Each tpps queue took a reference on the parent group. Drop it now.
+ * queue lock must be held here.
+ */
+static void tpps_put_queue(struct tpps_queue *tppq)
+{
+	struct tpps_data *tppd = tppq->tppd;
+	struct tpps_group *tppg;
+
+	BUG_ON(tppq->ref <= 0);
+
+	tppq->ref--;
+	if (tppq->ref)
+		return;
+
+	tpps_log_tppq(tppd, tppq, "put_queue");
+	BUG_ON(!list_empty(&tppq->sort_list));
+	tppg = tppq->tppg;
+
+	tpps_del_queue(tppq);
+	kmem_cache_free(tpps_pool, tppq);
+	tppg_put(tppg);
+}
+
+static void tpps_init_tppq(struct tpps_data *tppd, struct tpps_queue *tppq,
+			  pid_t pid)
+{
+	INIT_LIST_HEAD(&tppq->tppg_node);
+	INIT_LIST_HEAD(&tppq->sort_list);
+
+	tppq->ref = 0;
+	tppq->tppd = tppd;
+	tppq->pid = pid;
+
+}
+
+static void tpps_link_tppq_tppg(struct tpps_queue *tppq,
+		struct tpps_group *tppg)
+{
+	tppq->tppg = tppg;
+	/* tppq reference on tppg */
+	tppg_get(tppg);
+}
+
+static struct tpps_group *tpps_lookup_create_tppg(struct tpps_data *tppd,
+						struct blkcg *blkcg)
+{
+	struct request_queue *q = tppd->queue;
+	struct tpps_group *tppg = NULL;
+
+	/* avoid lookup for the common case where there's no blkcg */
+	if (blkcg == &blkcg_root) {
+		tppg = tppd->root_group;
+	} else {
+		struct blkcg_gq *blkg;
+
+		blkg = blkg_lookup_create(blkcg, q);
+		if (!IS_ERR(blkg))
+			tppg = blkg_to_tppg(blkg);
+	}
+
+	return tppg;
+}
+
+static struct tpps_queue *
+tpps_find_alloc_queue(struct tpps_data *tppd, struct tpps_io_cq* tic, struct bio *bio,
+		gfp_t gfp_mask)
+{
+	struct tpps_queue *tppq, *new_tppq = NULL;
+	struct tpps_group *tppg;
+	struct blkcg *blkcg;
+
+retry:
+	rcu_read_lock();
+
+	blkcg = bio_blkcg(bio);
+	tppg = tpps_lookup_create_tppg(tppd, blkcg);
+	tppq = tic_to_tppq(tic);
+
+	if (!tppq) {
+		if (new_tppq) {
+			tppq = new_tppq;
+			new_tppq = NULL;
+		} else if (gfp_mask & __GFP_WAIT) {
+			rcu_read_unlock();
+			spin_unlock_irq(tppd->queue->queue_lock);
+			new_tppq = kmem_cache_alloc_node(tpps_pool,
+					gfp_mask | __GFP_ZERO,
+					tppd->queue->node);
+			spin_lock_irq(tppd->queue->queue_lock);
+			if (new_tppq)
+				goto retry;
+		} else
+			tppq = kmem_cache_alloc_node(tpps_pool,
+					gfp_mask | __GFP_ZERO,
+					tppd->queue->node);
+
+		if (tppq) {
+			tpps_init_tppq(tppd, tppq, current->pid);
+			tpps_link_tppq_tppg(tppq, tppg);
+			tpps_log_tppq(tppd, tppq, "alloced");
+		}
+	}
+
+	if (new_tppq)
+		kmem_cache_free(tpps_pool, new_tppq);
+
+	rcu_read_unlock();
+	return tppq;
+}
+
+static struct tpps_queue *
+tpps_get_queue(struct tpps_data *tppd, struct tpps_io_cq *tic, struct bio *bio,
+			gfp_t gfp_mask)
+{
+	struct tpps_queue *tppq;
+
+	tppq = tpps_find_alloc_queue(tppd, tic, bio, gfp_mask);
+	tppq->ref++;
+	return tppq;
+}
+
+/*
+ * scheduler run of queue, if there are requests pending and no one in the
+ * driver that will restart queueing
+ */
+static inline void tpps_schedule_dispatch(struct tpps_data *tppd)
+{
+	if (tppd->busy_queues) {
+		tpps_log(tppd, "schedule dispatch");
+		kblockd_schedule_work(tppd->queue, &tppd->unplug_work);
+	}
+}
+
+static void check_blkcg_changed(struct tpps_io_cq *tic, struct bio *bio)
+{
+	struct tpps_data *tppd = tic_to_tppd(tic);
+	struct tpps_queue *tppq;
+	uint64_t id;
+
+	rcu_read_lock();
+	id = bio_blkcg(bio)->id;
+	rcu_read_unlock();
+
+	/*
+	 * Check whether blkcg has changed.  The condition may trigger
+	 * spuriously on a newly created tic but there's no harm.
+	 */
+	if (unlikely(!tppd) || likely(tic->blkcg_id == id))
+		return;
+
+	tppq = tic_to_tppq(tic);
+	if (tppq) {
+		/*
+		 * Drop reference to sync queue. A new sync queue will be
+		 * assigned in new group upon arrival of a fresh request.
+		 */
+		tpps_log_tppq(tppd, tppq, "changed cgroup");
+		tic_set_tppq(tic, NULL);
+		tpps_put_queue(tppq);
+	}
+
+	tic->blkcg_id = id;
+}
+
+static int
+tpps_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
+			gfp_t gfp_mask)
+{
+	struct tpps_data *tppd = q->elevator->elevator_data;
+	struct tpps_io_cq *tic = icq_to_tic(rq->elv.icq);
+	struct tpps_queue *tppq;
+
+	might_sleep_if(gfp_mask & __GFP_WAIT);
+
+	spin_lock_irq(q->queue_lock);
+
+	check_blkcg_changed(tic, bio);
+
+	tppq = tic_to_tppq(tic);
+	if (!tppq) {
+		tppq = tpps_get_queue(tppd, tic, bio, gfp_mask);
+		tic_set_tppq(tic, tppq);
+	}
+
+	tppq->ref++;
+	tppg_get(tppq->tppg);
+	rq->elv.priv[0] = tppq;
+	rq->elv.priv[1] = tppq->tppg;
+	spin_unlock_irq(q->queue_lock);
+	return 0;
+}
+
+/*
+ * queue lock held here
+ */
+static void tpps_put_request(struct request *rq)
+{
+	struct tpps_queue *tppq = RQ_TPPQ(rq);
+
+	if (tppq) {
+		WARN_ON(tppq->tppg != RQ_TPPG(rq));
+
+		/* Put down rq reference on cfqg */
+		tppg_put(RQ_TPPG(rq));
+		rq->elv.priv[0] = NULL;
+		rq->elv.priv[1] = NULL;
+
+		tpps_put_queue(tppq);
+	}
+}
+
+static void
+tpps_update_group_weight(struct tpps_group *tppg)
+{
+	if (tppg->needs_update) {
+		tppg->weight = tppg->new_weight;
+		tppg->needs_update = false;
+	}
+}
+
+static void tpps_add_queue(struct tpps_data *tppd, struct tpps_queue *tppq)
+{
+	struct tpps_group *tppg;
+
+	if (!tppq->online) {
+		tppq->online = 1;
+		tppg = tppq->tppg;
+		tpps_log_tppq(tppd, tppq, "add queue");
+		tppg->nr_tppq++;
+		tppd->busy_queues++;
+		list_add(&tppq->tppg_node, &tppg->queue_list);
+		printk("add tppq %p to %p\n", tppq, tppg);
+		tpps_update_group_weight(tppg);
+		if (tppg->nr_tppq <= 1) {
+			tppd->total_weight += tppg->pd.blkg->blkcg->cfq_weight;
+			list_add(&tppg->tppd_node, &tppd->group_list);
+			printk("twt:%u, wt:%u %u %d %p\n", tppd->total_weight, tppg->weight,
+					tppg->pd.blkg->blkcg->cfq_weight,
+					tppg->nr_tppq,
+					tppg);
+		}
+	}
+}
+
+static void tpps_insert_request(struct request_queue *q, struct request *rq)
+{
+	struct tpps_data *tppd = q->elevator->elevator_data;
+	struct tpps_queue *tppq = RQ_TPPQ(rq);
+
+	tpps_log_tppq(tppd, tppq, "insert_request");
+
+	list_add_tail(&rq->queuelist, &tppq->sort_list);
+	tppq->rq_queued++;
+	tppq->tppg->rq_queued++;
+	tppd->dispatched++;
+	tpps_add_queue(tppd, tppq);
+	tppg_stats_update_io_add(RQ_TPPG(rq), tppq->tppg, rq->cmd_flags);
+}
+
+static void tpps_remove_request(struct request *rq)
+{
+	struct tpps_queue *tppq = RQ_TPPQ(rq);
+
+	list_del_init(&rq->queuelist);
+	tppq->rq_queued--;
+	tppq->tppg->rq_queued--;
+	tppg_stats_update_io_remove(RQ_TPPG(rq), rq->cmd_flags);
+}
+
+/*
+ * Move request from internal lists to the request queue dispatch list.
+ */
+static int tpps_dispatch_insert(struct request_queue *q,
+				struct tpps_queue *tppq)
+{
+	struct list_head *rbnext = tppq->sort_list.next;
+	struct request *rq;
+
+	if (rbnext == &tppq->sort_list)
+		return 0;
+
+	rq = rq_entry_fifo(rbnext);
+	tpps_remove_request(rq);
+	elv_dispatch_sort(q, rq);
+	tppg_stats_update_dispatch(tppq->tppg, blk_rq_bytes(rq), rq->cmd_flags);
+	return 1;
+}
+
+static int tpps_dispatch_requests_nr(struct tpps_data *tppd,
+				struct tpps_queue *tppq, int count)
+{
+	int cnt = 0, ret;
+
+	if (!tppq->rq_queued)
+		return cnt;
+
+	do {
+		ret = tpps_dispatch_insert(tppd->queue, tppq);
+		if (ret) {
+			cnt++;
+			tppd->dispatched--;
+		}
+	} while (ret && cnt < count);
+
+	return cnt;
+}
+
+static int tpps_dispatch_requests(struct request_queue *q, int force)
+{
+	struct tpps_data *tppd = q->elevator->elevator_data;
+	struct tpps_group *tppg, *group_n;
+	struct tpps_queue *tppq;
+	struct list_head *next;
+	int count = 0, total = 0, ret;
+	int quota, grp_quota;
+
+	if (!tppd->total_weight)
+		return 0;
+
+	quota = q->nr_requests - tppd->rq_in_driver;
+	if (quota < MIN_DISPATCH_RQ && !force)
+		return 0;
+
+	list_for_each_entry_safe(tppg, group_n, &tppd->group_list, tppd_node) {
+		if (!tppg->nr_tppq)
+			continue;
+		grp_quota = (quota * tppg->pd.blkg->blkcg->cfq_weight
+					/ tppd->total_weight) - tppg->rq_in_driver;
+		tpps_log_tppg(tppd, tppg,
+			"nr:%d, wt:%u total_wt:%u in_driver:%d %d quota:%d grp_quota:%d",
+			tppg->nr_tppq, tppg->pd.blkg->blkcg->cfq_weight,
+			tppd->total_weight, tppg->rq_in_driver, tppg->rq_queued,
+			quota, grp_quota);
+		if (grp_quota <= 0 && !force)
+			continue;
+		BUG_ON(tppg->queue_list.next == &tppg->queue_list);
+		if (!tppg->cur_dispatcher)
+			tppg->cur_dispatcher = tppg->queue_list.next;
+		next = tppg->cur_dispatcher;
+		count = 0;
+		do {
+			tppq = list_entry(next, struct tpps_queue, tppg_node);
+			tpps_log_tppq(tppd, tppq, "tppq: %d\n", tppq->rq_queued);
+			if (force)
+				ret = tpps_dispatch_requests_nr(tppd, tppq, -1);
+			else
+				ret = tpps_dispatch_requests_nr(tppd, tppq, 1);
+			count += ret;
+			total += ret;
+			next = next->next;
+			if (next == &tppg->queue_list)
+				next = tppg->queue_list.next;
+			if (count >= grp_quota && !force) {
+				tppg->cur_dispatcher = next;
+				break;
+			}
+			BUG_ON(tppg->cur_dispatcher == &tppg->queue_list);
+		} while (next != tppg->cur_dispatcher);
+	}
+	return total > 0;
+}
+
+static void tpps_kick_queue(struct work_struct *work)
+{
+	struct tpps_data *tppd =
+		container_of(work, struct tpps_data, unplug_work);
+	struct request_queue *q = tppd->queue;
+
+	spin_lock_irq(q->queue_lock);
+	__blk_run_queue(q);
+	spin_unlock_irq(q->queue_lock);
+}
+
+static void tpps_init_tppg_base(struct tpps_group *tppg)
+{
+	INIT_LIST_HEAD(&tppg->tppd_node);
+	INIT_LIST_HEAD(&tppg->queue_list);
+	tppg->cur_dispatcher = NULL;
+
+}
+
+static int tpps_init_queue(struct request_queue *q)
+{
+	struct tpps_data *tppd;
+	struct tpps_group *tppg;
+	int ret;
+
+	tppd = kmalloc_node(sizeof(*tppd), GFP_KERNEL | __GFP_ZERO, q->node);
+	if (!tppd)
+		return -ENOMEM;
+
+	tppd->queue = q;
+	q->elevator->elevator_data = tppd;
+
+	INIT_LIST_HEAD(&tppd->group_list);
+
+	ret = blkcg_activate_policy(q, &blkcg_policy_tpps);
+	if (ret)
+		goto out_free;
+
+	/* Init root group */
+	tppd->root_group = blkg_to_tppg(q->root_blkg);
+	tppg = tppd->root_group;
+	tpps_init_tppg_base(tppg);
+
+	/* Give preference to root group over other groups */
+	tppg->weight = 2 * TPPS_WEIGHT_DEFAULT;
+	tppg->leaf_weight = 2 * TPPS_WEIGHT_DEFAULT;
+
+	INIT_WORK(&tppd->unplug_work, tpps_kick_queue);
+
+	return 0;
+
+out_free:
+	kfree(tppd);
+	return ret;
+}
+
+static void tpps_exit_queue(struct elevator_queue *e)
+{
+	struct tpps_data *tppd = e->elevator_data;
+	struct request_queue *q = tppd->queue;
+
+	cancel_work_sync(&tppd->unplug_work);
+
+	blkcg_deactivate_policy(q, &blkcg_policy_tpps);
+	kfree(tppd->root_group);
+	kfree(tppd);
+}
+
+static void tpps_activate_request(struct request_queue *q, struct request *rq)
+{
+	struct tpps_queue *tppq = RQ_TPPQ(rq);
+	struct tpps_data *tppd = q->elevator->elevator_data;
+	tppd->rq_in_driver++;
+	tppq->tppg->rq_in_driver++;
+	tpps_log_tppq(tppd, RQ_TPPQ(rq), "activate rq, drv=%d",
+						tppd->rq_in_driver);
+}
+
+static void tpps_deactivate_request(struct request_queue *q, struct request *rq)
+{
+	struct tpps_queue *tppq = RQ_TPPQ(rq);
+	struct tpps_data *tppd = q->elevator->elevator_data;
+
+	WARN_ON(!tppd->rq_in_driver);
+	tppd->rq_in_driver--;
+	tppq->tppg->rq_in_driver--;
+	tpps_log_tppq(tppd, RQ_TPPQ(rq), "deactivate rq, drv=%d",
+						tppd->rq_in_driver);
+}
+
+static void tpps_completed_request(struct request_queue *q, struct request *rq)
+{
+	struct tpps_queue *tppq = RQ_TPPQ(rq);
+	struct tpps_data *tppd = tppq->tppd;
+
+	WARN_ON(!tppq);
+	WARN_ON(tppq->tppg != RQ_TPPG(rq));
+
+	tpps_log_tppq(tppd, tppq, "complete rqnoidle %d",
+			!!(rq->cmd_flags & REQ_NOIDLE));
+	WARN_ON(!tppd->rq_in_driver);
+	tppd->rq_in_driver--;
+	tppq->tppg->rq_in_driver--;
+	tppg_stats_update_completion(tppq->tppg,
+			rq_start_time_ns(rq), rq_io_start_time_ns(rq), rq->cmd_flags);
+
+	if (!tppd->rq_in_driver)
+		tpps_schedule_dispatch(tppd);
+}
+
+static void
+tpps_merged_request(struct request_queue *q, struct request *rq, int type)
+{
+	if (type == ELEVATOR_FRONT_MERGE) {
+		struct tpps_queue *tppq = RQ_TPPQ(rq);
+		list_del_init(&rq->queuelist);
+		tppq->rq_queued--;
+		tppg_stats_update_io_remove(RQ_TPPG(rq), rq->cmd_flags);
+		list_add_tail(&rq->queuelist, &tppq->sort_list);
+		tppq->rq_queued++;
+		tppg_stats_update_io_add(RQ_TPPG(rq), tppq->tppg, rq->cmd_flags);
+	}
+}
+
+static void
+tpps_merged_requests(struct request_queue *q, struct request *rq,
+			struct request *next)
+{
+	tpps_remove_request(next);
+	tppg_stats_update_io_merged(RQ_TPPG(rq), rq->cmd_flags);
+}
+
+static void tpps_init_icq(struct io_cq *icq)
+{ }
+
+static void tpps_exit_icq(struct io_cq *icq)
+{
+	struct tpps_io_cq *tic = icq_to_tic(icq);
+
+	if (tic->tppq) {
+		tpps_put_queue(tic->tppq);
+		tic->tppq = NULL;
+	}
+}
+
+static struct elevator_type iosched_tpps = {
+	.ops = {
+		.elevator_merged_fn =		tpps_merged_request,
+		.elevator_merge_req_fn =	tpps_merged_requests,
+		.elevator_dispatch_fn =		tpps_dispatch_requests,
+		.elevator_add_req_fn =		tpps_insert_request,
+		.elevator_activate_req_fn = 	tpps_activate_request,
+		.elevator_deactivate_req_fn = 	tpps_deactivate_request,
+		.elevator_completed_req_fn =	tpps_completed_request,
+		.elevator_init_icq_fn =		tpps_init_icq,
+		.elevator_exit_icq_fn =		tpps_exit_icq,
+		.elevator_set_req_fn =		tpps_set_request,
+		.elevator_put_req_fn =		tpps_put_request,
+		.elevator_init_fn =		tpps_init_queue,
+		.elevator_exit_fn =		tpps_exit_queue,
+	},
+	.icq_size		= sizeof(struct tpps_io_cq),
+	.icq_align		= __alignof__(struct tpps_io_cq),
+	.elevator_name	=	"tpps",
+	.elevator_owner =	THIS_MODULE,
+};
+
+static u64 tppg_prfill_weight_device(struct seq_file *sf,
+				     struct blkg_policy_data *pd, int off)
+{
+	struct tpps_group *tppg = pd_to_tppg(pd);
+
+	if (!tppg->dev_weight)
+		return 0;
+	return __blkg_prfill_u64(sf, pd, tppg->dev_weight);
+}
+
+static int tppg_print_weight_device(struct cgroup *cgrp, struct cftype *cft,
+				    struct seq_file *sf)
+{
+	blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp),
+			  tppg_prfill_weight_device, &blkcg_policy_tpps, 0,
+			  false);
+	return 0;
+}
+
+static u64 tppg_prfill_leaf_weight_device(struct seq_file *sf,
+					  struct blkg_policy_data *pd, int off)
+{
+	struct tpps_group *tppg = pd_to_tppg(pd);
+
+	if (!tppg->dev_leaf_weight)
+		return 0;
+	return __blkg_prfill_u64(sf, pd, tppg->dev_leaf_weight);
+}
+
+static int tppg_print_leaf_weight_device(struct cgroup *cgrp,
+					 struct cftype *cft,
+					 struct seq_file *sf)
+{
+	blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp),
+			  tppg_prfill_leaf_weight_device, &blkcg_policy_tpps, 0,
+			  false);
+	return 0;
+}
+
+static int tppg_print_weight(struct cgroup *cgrp, struct cftype *cft,
+			    struct seq_file *sf)
+{
+	seq_printf(sf, "%u\n", cgroup_to_blkcg(cgrp)->cfq_weight);
+	return 0;
+}
+
+static int tppg_print_leaf_weight(struct cgroup *cgrp, struct cftype *cft,
+				 struct seq_file *sf)
+{
+	seq_printf(sf, "%u\n",
+		   cgroup_to_blkcg(cgrp)->cfq_leaf_weight);
+	return 0;
+}
+
+static int __tppg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
+				    const char *buf, bool is_leaf_weight)
+{
+	struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+	struct blkg_conf_ctx ctx;
+	struct tpps_group *tppg;
+	int ret;
+
+	ret = blkg_conf_prep(blkcg, &blkcg_policy_tpps, buf, &ctx);
+	if (ret)
+		return ret;
+
+	ret = -EINVAL;
+	tppg = blkg_to_tppg(ctx.blkg);
+	if (!ctx.v || (ctx.v >= CFQ_WEIGHT_MIN && ctx.v <= CFQ_WEIGHT_MAX)) {
+		if (!is_leaf_weight) {
+			tppg->dev_weight = ctx.v;
+			tppg->new_weight = ctx.v ?: blkcg->cfq_weight;
+		} else {
+			tppg->dev_leaf_weight = ctx.v;
+			tppg->new_leaf_weight = ctx.v ?: blkcg->cfq_leaf_weight;
+		}
+		ret = 0;
+	}
+
+	blkg_conf_finish(&ctx);
+	return ret;
+}
+
+static int tppg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
+				  const char *buf)
+{
+	return __tppg_set_weight_device(cgrp, cft, buf, false);
+}
+
+static int tppg_set_leaf_weight_device(struct cgroup *cgrp, struct cftype *cft,
+				       const char *buf)
+{
+	return __tppg_set_weight_device(cgrp, cft, buf, true);
+}
+
+static int __tpps_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val,
+			    bool is_leaf_weight)
+{
+	struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+	struct blkcg_gq *blkg;
+
+	if (val < CFQ_WEIGHT_MIN || val > CFQ_WEIGHT_MAX)
+		return -EINVAL;
+
+	spin_lock_irq(&blkcg->lock);
+
+	if (!is_leaf_weight)
+		blkcg->cfq_weight = val;
+	else
+		blkcg->cfq_leaf_weight = val;
+
+	hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
+		struct tpps_group *tppg = blkg_to_tppg(blkg);
+
+		if (!tppg)
+			continue;
+
+		if (!is_leaf_weight) {
+			if (!tppg->dev_weight)
+				tppg->new_weight = blkcg->cfq_weight;
+		} else {
+			if (!tppg->dev_leaf_weight)
+				tppg->new_leaf_weight = blkcg->cfq_leaf_weight;
+		}
+	}
+
+	spin_unlock_irq(&blkcg->lock);
+	return 0;
+}
+
+static int tpps_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+	return __tpps_set_weight(cgrp, cft, val, false);
+}
+
+static int tpps_set_leaf_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+	return __tpps_set_weight(cgrp, cft, val, true);
+}
+
+/* offset delta from tppg->stats to tppg->dead_stats */
+static const int dead_stats_off_delta = offsetof(struct tpps_group, dead_stats) -
+					offsetof(struct tpps_group, stats);
+
+/* to be used by recursive prfill, sums live and dead rwstats recursively */
+static struct blkg_rwstat tppg_rwstat_pd_recursive_sum(struct blkg_policy_data *pd,
+						       int off)
+{
+	struct blkg_rwstat a, b;
+
+	a = blkg_rwstat_recursive_sum(pd, off);
+	b = blkg_rwstat_recursive_sum(pd, off + dead_stats_off_delta);
+	blkg_rwstat_merge(&a, &b);
+	return a;
+}
+
+/* to be used by recursive prfill, sums live and dead stats recursively */
+static u64 tppg_stat_pd_recursive_sum(struct blkg_policy_data *pd, int off)
+{
+	u64 sum = 0;
+
+	sum += blkg_stat_recursive_sum(pd, off);
+	sum += blkg_stat_recursive_sum(pd, off + dead_stats_off_delta);
+	return sum;
+}
+
+static int tppg_print_stat(struct cgroup *cgrp, struct cftype *cft,
+			   struct seq_file *sf)
+{
+	struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+
+	blkcg_print_blkgs(sf, blkcg, blkg_prfill_stat, &blkcg_policy_tpps,
+			  cft->private, false);
+	return 0;
+}
+
+static int tppg_print_rwstat(struct cgroup *cgrp, struct cftype *cft,
+			     struct seq_file *sf)
+{
+	struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+
+	blkcg_print_blkgs(sf, blkcg, blkg_prfill_rwstat, &blkcg_policy_tpps,
+			  cft->private, true);
+	return 0;
+}
+
+static u64 tppg_prfill_stat_recursive(struct seq_file *sf,
+				      struct blkg_policy_data *pd, int off)
+{
+	u64 sum = tppg_stat_pd_recursive_sum(pd, off);
+
+	return __blkg_prfill_u64(sf, pd, sum);
+}
+
+static u64 tppg_prfill_rwstat_recursive(struct seq_file *sf,
+					struct blkg_policy_data *pd, int off)
+{
+	struct blkg_rwstat sum = tppg_rwstat_pd_recursive_sum(pd, off);
+
+	return __blkg_prfill_rwstat(sf, pd, &sum);
+}
+
+static int tppg_print_stat_recursive(struct cgroup *cgrp, struct cftype *cft,
+				     struct seq_file *sf)
+{
+	struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+
+	blkcg_print_blkgs(sf, blkcg, tppg_prfill_stat_recursive,
+			  &blkcg_policy_tpps, cft->private, false);
+	return 0;
+}
+
+static int tppg_print_rwstat_recursive(struct cgroup *cgrp, struct cftype *cft,
+				       struct seq_file *sf)
+{
+	struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+
+	blkcg_print_blkgs(sf, blkcg, tppg_prfill_rwstat_recursive,
+			  &blkcg_policy_tpps, cft->private, true);
+	return 0;
+}
+
+static struct cftype tpps_blkcg_files[] = {
+	/* on root, weight is mapped to leaf_weight */
+	{
+		.name = "tpps.weight_device",
+		.flags = CFTYPE_ONLY_ON_ROOT,
+		.read_seq_string = tppg_print_leaf_weight_device,
+		.write_string = tppg_set_leaf_weight_device,
+		.max_write_len = 256,
+	},
+	{
+		.name = "tpps.weight",
+		.flags = CFTYPE_ONLY_ON_ROOT,
+		.read_seq_string = tppg_print_leaf_weight,
+		.write_u64 = tpps_set_leaf_weight,
+	},
+
+	/* no such mapping necessary for !roots */
+	{
+		.name = "tpps.weight_device",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.read_seq_string = tppg_print_weight_device,
+		.write_string = tppg_set_weight_device,
+		.max_write_len = 256,
+	},
+	{
+		.name = "tpps.weight",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.read_seq_string = tppg_print_weight,
+		.write_u64 = tpps_set_weight,
+	},
+
+	{
+		.name = "tpps.leaf_weight_device",
+		.read_seq_string = tppg_print_leaf_weight_device,
+		.write_string = tppg_set_leaf_weight_device,
+		.max_write_len = 256,
+	},
+	{
+		.name = "tpps.leaf_weight",
+		.read_seq_string = tppg_print_leaf_weight,
+		.write_u64 = tpps_set_leaf_weight,
+	},
+
+	/* statistics, covers only the tasks in the tppg */
+	{
+		.name = "tpps.time",
+		.private = offsetof(struct tpps_group, stats.time),
+		.read_seq_string = tppg_print_stat,
+	},
+	{
+		.name = "tpps.sectors",
+		.private = offsetof(struct tpps_group, stats.sectors),
+		.read_seq_string = tppg_print_stat,
+	},
+	{
+		.name = "tpps.io_service_bytes",
+		.private = offsetof(struct tpps_group, stats.service_bytes),
+		.read_seq_string = tppg_print_rwstat,
+	},
+	{
+		.name = "tpps.io_serviced",
+		.private = offsetof(struct tpps_group, stats.serviced),
+		.read_seq_string = tppg_print_rwstat,
+	},
+	{
+		.name = "tpps.io_service_time",
+		.private = offsetof(struct tpps_group, stats.service_time),
+		.read_seq_string = tppg_print_rwstat,
+	},
+	{
+		.name = "tpps.io_wait_time",
+		.private = offsetof(struct tpps_group, stats.wait_time),
+		.read_seq_string = tppg_print_rwstat,
+	},
+	{
+		.name = "tpps.io_merged",
+		.private = offsetof(struct tpps_group, stats.merged),
+		.read_seq_string = tppg_print_rwstat,
+	},
+	{
+		.name = "tpps.io_queued",
+		.private = offsetof(struct tpps_group, stats.queued),
+		.read_seq_string = tppg_print_rwstat,
+	},
+
+	/* the same statictics which cover the tppg and its descendants */
+	{
+		.name = "tpps.time_recursive",
+		.private = offsetof(struct tpps_group, stats.time),
+		.read_seq_string = tppg_print_stat_recursive,
+	},
+	{
+		.name = "tpps.sectors_recursive",
+		.private = offsetof(struct tpps_group, stats.sectors),
+		.read_seq_string = tppg_print_stat_recursive,
+	},
+	{
+		.name = "tpps.io_service_bytes_recursive",
+		.private = offsetof(struct tpps_group, stats.service_bytes),
+		.read_seq_string = tppg_print_rwstat_recursive,
+	},
+	{
+		.name = "tpps.io_serviced_recursive",
+		.private = offsetof(struct tpps_group, stats.serviced),
+		.read_seq_string = tppg_print_rwstat_recursive,
+	},
+	{
+		.name = "tpps.io_service_time_recursive",
+		.private = offsetof(struct tpps_group, stats.service_time),
+		.read_seq_string = tppg_print_rwstat_recursive,
+	},
+	{
+		.name = "tpps.io_wait_time_recursive",
+		.private = offsetof(struct tpps_group, stats.wait_time),
+		.read_seq_string = tppg_print_rwstat_recursive,
+	},
+	{
+		.name = "tpps.io_merged_recursive",
+		.private = offsetof(struct tpps_group, stats.merged),
+		.read_seq_string = tppg_print_rwstat_recursive,
+	},
+	{
+		.name = "tpps.io_queued_recursive",
+		.private = offsetof(struct tpps_group, stats.queued),
+		.read_seq_string = tppg_print_rwstat_recursive,
+	},
+	{ }	/* terminate */
+};
+
+static void tpps_pd_init(struct blkcg_gq *blkg)
+{
+	struct tpps_group *tppg = blkg_to_tppg(blkg);
+
+	tpps_init_tppg_base(tppg);
+	tppg->weight = blkg->blkcg->cfq_weight;
+	tppg->leaf_weight = blkg->blkcg->cfq_leaf_weight;
+}
+
+static inline struct tpps_group *tppg_parent(struct tpps_group *tppg)
+{
+	struct blkcg_gq *pblkg = tppg_to_blkg(tppg)->parent;
+
+	return pblkg ? blkg_to_tppg(pblkg) : NULL;
+}
+
+static void tppg_stats_reset(struct tppg_stats *stats)
+{
+	/* queued stats shouldn't be cleared */
+	blkg_rwstat_reset(&stats->service_bytes);
+	blkg_rwstat_reset(&stats->serviced);
+	blkg_rwstat_reset(&stats->merged);
+	blkg_rwstat_reset(&stats->service_time);
+	blkg_rwstat_reset(&stats->wait_time);
+	blkg_stat_reset(&stats->time);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+	blkg_stat_reset(&stats->unaccounted_time);
+	blkg_stat_reset(&stats->avg_queue_size_sum);
+	blkg_stat_reset(&stats->avg_queue_size_samples);
+	blkg_stat_reset(&stats->dequeue);
+	blkg_stat_reset(&stats->group_wait_time);
+	blkg_stat_reset(&stats->idle_time);
+	blkg_stat_reset(&stats->empty_time);
+#endif
+}
+
+/* @to += @from */
+static void tppg_stats_merge(struct tppg_stats *to, struct tppg_stats *from)
+{
+	/* queued stats shouldn't be cleared */
+	blkg_rwstat_merge(&to->service_bytes, &from->service_bytes);
+	blkg_rwstat_merge(&to->serviced, &from->serviced);
+	blkg_rwstat_merge(&to->merged, &from->merged);
+	blkg_rwstat_merge(&to->service_time, &from->service_time);
+	blkg_rwstat_merge(&to->wait_time, &from->wait_time);
+	blkg_stat_merge(&from->time, &from->time);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+	blkg_stat_merge(&to->unaccounted_time, &from->unaccounted_time);
+	blkg_stat_merge(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
+	blkg_stat_merge(&to->avg_queue_size_samples, &from->avg_queue_size_samples);
+	blkg_stat_merge(&to->dequeue, &from->dequeue);
+	blkg_stat_merge(&to->group_wait_time, &from->group_wait_time);
+	blkg_stat_merge(&to->idle_time, &from->idle_time);
+	blkg_stat_merge(&to->empty_time, &from->empty_time);
+#endif
+}
+
+static void tppg_stats_xfer_dead(struct tpps_group *tppg)
+{
+	struct tpps_group *parent = tppg_parent(tppg);
+
+	lockdep_assert_held(tppg_to_blkg(tppg)->q->queue_lock);
+
+	if (unlikely(!parent))
+		return;
+
+	tppg_stats_merge(&parent->dead_stats, &tppg->stats);
+	tppg_stats_merge(&parent->dead_stats, &tppg->dead_stats);
+	tppg_stats_reset(&tppg->stats);
+	tppg_stats_reset(&tppg->dead_stats);
+}
+
+static void tpps_pd_offline(struct blkcg_gq *blkg)
+{
+	struct tpps_group *tppg = blkg_to_tppg(blkg);
+	/*
+	 * @blkg is going offline and will be ignored by
+	 * blkg_[rw]stat_recursive_sum().  Transfer stats to the parent so
+	 * that they don't get lost.  If IOs complete after this point, the
+	 * stats for them will be lost.  Oh well...
+	 */
+	tppg_stats_xfer_dead(tppg);
+
+	if (!list_empty(&tppg->tppd_node))
+		list_del_init(&tppg->tppd_node);
+
+	//BUG_ON(!list_empty(&(tppg->queue_list)));
+}
+
+static void tpps_pd_reset_stats(struct blkcg_gq *blkg)
+{
+	struct tpps_group *tppg = blkg_to_tppg(blkg);
+
+	tppg_stats_reset(&tppg->stats);
+	tppg_stats_reset(&tppg->dead_stats);
+}
+
+static struct blkcg_policy blkcg_policy_tpps = {
+	.pd_size			= sizeof(struct tpps_group),
+	.cftypes			= tpps_blkcg_files,
+	.pd_init_fn			= tpps_pd_init,
+	.pd_offline_fn		= tpps_pd_offline,
+	.pd_reset_stats_fn	= tpps_pd_reset_stats,
+};
+
+static int __init tpps_init(void)
+{
+	int ret;
+
+	ret = blkcg_policy_register(&blkcg_policy_tpps);
+	if (ret)
+		return ret;
+
+	ret = -ENOMEM;
+	tpps_pool = KMEM_CACHE(tpps_queue, 0);
+	if (!tpps_pool)
+		goto err_pol_unreg;
+
+	ret = elv_register(&iosched_tpps);
+	if (ret)
+		goto err_free_pool;
+
+	return 0;
+
+err_free_pool:
+	kmem_cache_destroy(tpps_pool);
+err_pol_unreg:
+	blkcg_policy_unregister(&blkcg_policy_tpps);
+	return ret;
+}
+
+static void __exit tpps_exit(void)
+{
+	blkcg_policy_unregister(&blkcg_policy_tpps);
+	elv_unregister(&iosched_tpps);
+	kmem_cache_destroy(tpps_pool);
+}
+
+module_init(tpps_init);
+module_exit(tpps_exit);
+
+MODULE_AUTHOR("Robin Dong");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Tiny Parallel Proportion io Scheduler");
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2fdb4a4..489257a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -42,7 +42,7 @@ struct blkcg_gq;
  * Maximum number of blkcg policies allowed to be registered concurrently.
  * Defined here to simplify include dependency.
  */
-#define BLKCG_MAX_POLS		2
+#define BLKCG_MAX_POLS		3
 
 struct request;
 typedef void (rq_end_io_fn)(struct request *, int);
-- 
1.7.1

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