1 files changed, 799 insertions, 707 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 126c341955de..4fdeb46b4436 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -17,71 +17,38 @@
 #include <linux/err.h>
 #include <linux/blkdev.h>
 #include <linux/slab.h>
-#include "blk-cgroup.h"
 #include <linux/genhd.h>
+#include <linux/delay.h>
+#include <linux/atomic.h>
+#include "blk-cgroup.h"
+#include "blk.h"
 
 #define MAX_KEY_LEN 100
 
 static DEFINE_SPINLOCK(blkio_list_lock);
 static LIST_HEAD(blkio_list);
 
+static DEFINE_MUTEX(all_q_mutex);
+static LIST_HEAD(all_q_list);
+
+/* List of groups pending per cpu stats allocation */
+static DEFINE_SPINLOCK(alloc_list_lock);
+static LIST_HEAD(alloc_list);
+
+static void blkio_stat_alloc_fn(struct work_struct *);
+static DECLARE_DELAYED_WORK(blkio_stat_alloc_work, blkio_stat_alloc_fn);
+
 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
 
+static struct blkio_policy_type *blkio_policy[BLKIO_NR_POLICIES];
+
 /* 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)
 
-static inline void blkio_policy_insert_node(struct blkio_cgroup *blkcg,
-					    struct blkio_policy_node *pn)
-{
-	list_add(&pn->node, &blkcg->policy_list);
-}
-
-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 fileid = BLKIOFILE_ATTR(cft->private);
-
-	return (plid == pn->plid && fileid == pn->fileid);
-}
-
-/* Must be called with blkcg->lock held */
-static inline void blkio_policy_delete_node(struct blkio_policy_node *pn)
-{
-	list_del(&pn->node);
-}
-
-/* Must be called with blkcg->lock held */
-static struct blkio_policy_node *
-blkio_policy_search_node(const struct blkio_cgroup *blkcg, dev_t dev,
-		enum blkio_policy_id plid, int fileid)
-{
-	struct blkio_policy_node *pn;
-
-	list_for_each_entry(pn, &blkcg->policy_list, node) {
-		if (pn->dev == dev && pn->plid == plid && pn->fileid == fileid)
-			return pn;
-	}
-
-	return NULL;
-}
-
 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
 {
 	return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
@@ -89,77 +56,85 @@ struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
 }
 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
 
-struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk)
+static struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk)
 {
 	return container_of(task_subsys_state(tsk, blkio_subsys_id),
 			    struct blkio_cgroup, css);
 }
-EXPORT_SYMBOL_GPL(task_blkio_cgroup);
 
-static inline void
-blkio_update_group_weight(struct blkio_group *blkg, unsigned int weight)
+struct blkio_cgroup *bio_blkio_cgroup(struct bio *bio)
+{
+	if (bio && bio->bi_css)
+		return container_of(bio->bi_css, struct blkio_cgroup, css);
+	return task_blkio_cgroup(current);
+}
+EXPORT_SYMBOL_GPL(bio_blkio_cgroup);
+
+static inline void blkio_update_group_weight(struct blkio_group *blkg,
+					     int plid, unsigned int weight)
 {
 	struct blkio_policy_type *blkiop;
 
 	list_for_each_entry(blkiop, &blkio_list, list) {
 		/* If this policy does not own the blkg, do not send updates */
-		if (blkiop->plid != blkg->plid)
+		if (blkiop->plid != plid)
 			continue;
 		if (blkiop->ops.blkio_update_group_weight_fn)
-			blkiop->ops.blkio_update_group_weight_fn(blkg->key,
+			blkiop->ops.blkio_update_group_weight_fn(blkg->q,
 							blkg, weight);
 	}
 }
 
-static inline void blkio_update_group_bps(struct blkio_group *blkg, u64 bps,
-				int fileid)
+static inline void blkio_update_group_bps(struct blkio_group *blkg, int plid,
+					  u64 bps, int fileid)
 {
 	struct blkio_policy_type *blkiop;
 
 	list_for_each_entry(blkiop, &blkio_list, list) {
 
 		/* If this policy does not own the blkg, do not send updates */
-		if (blkiop->plid != blkg->plid)
+		if (blkiop->plid != plid)
 			continue;
 
 		if (fileid == BLKIO_THROTL_read_bps_device
 		    && blkiop->ops.blkio_update_group_read_bps_fn)
-			blkiop->ops.blkio_update_group_read_bps_fn(blkg->key,
+			blkiop->ops.blkio_update_group_read_bps_fn(blkg->q,
 								blkg, bps);
 
 		if (fileid == BLKIO_THROTL_write_bps_device
 		    && blkiop->ops.blkio_update_group_write_bps_fn)
-			blkiop->ops.blkio_update_group_write_bps_fn(blkg->key,
+			blkiop->ops.blkio_update_group_write_bps_fn(blkg->q,
 								blkg, bps);
 	}
 }
 
 static inline void blkio_update_group_iops(struct blkio_group *blkg,
-			unsigned int iops, int fileid)
+					   int plid, unsigned int iops,
+					   int fileid)
 {
 	struct blkio_policy_type *blkiop;
 
 	list_for_each_entry(blkiop, &blkio_list, list) {
 
 		/* If this policy does not own the blkg, do not send updates */
-		if (blkiop->plid != blkg->plid)
+		if (blkiop->plid != plid)
 			continue;
 
 		if (fileid == BLKIO_THROTL_read_iops_device
 		    && blkiop->ops.blkio_update_group_read_iops_fn)
-			blkiop->ops.blkio_update_group_read_iops_fn(blkg->key,
+			blkiop->ops.blkio_update_group_read_iops_fn(blkg->q,
 								blkg, iops);
 
 		if (fileid == BLKIO_THROTL_write_iops_device
 		    && blkiop->ops.blkio_update_group_write_iops_fn)
-			blkiop->ops.blkio_update_group_write_iops_fn(blkg->key,
+			blkiop->ops.blkio_update_group_write_iops_fn(blkg->q,
 								blkg,iops);
 	}
 }
 
 /*
  * Add to the appropriate stat variable depending on the request type.
- * This should be called with the blkg->stats_lock held.
+ * This should be called with queue_lock held.
  */
 static void blkio_add_stat(uint64_t *stat, uint64_t add, bool direction,
 				bool sync)
@@ -177,7 +152,7 @@ static void blkio_add_stat(uint64_t *stat, uint64_t add, bool direction,
 /*
  * Decrements the appropriate stat variable if non-zero depending on the
  * request type. Panics on value being zero.
- * This should be called with the blkg->stats_lock held.
+ * This should be called with the queue_lock held.
  */
 static void blkio_check_and_dec_stat(uint64_t *stat, bool direction, bool sync)
 {
@@ -198,19 +173,22 @@ static void blkio_check_and_dec_stat(uint64_t *stat, bool direction, bool sync)
 }
 
 #ifdef CONFIG_DEBUG_BLK_CGROUP
-/* This should be called with the blkg->stats_lock held. */
+/* This should be called with the queue_lock held. */
 static void blkio_set_start_group_wait_time(struct blkio_group *blkg,
-						struct blkio_group *curr_blkg)
+					    struct blkio_policy_type *pol,
+					    struct blkio_group *curr_blkg)
 {
-	if (blkio_blkg_waiting(&blkg->stats))
+	struct blkg_policy_data *pd = blkg->pd[pol->plid];
+
+	if (blkio_blkg_waiting(&pd->stats))
 		return;
 	if (blkg == curr_blkg)
 		return;
-	blkg->stats.start_group_wait_time = sched_clock();
-	blkio_mark_blkg_waiting(&blkg->stats);
+	pd->stats.start_group_wait_time = sched_clock();
+	blkio_mark_blkg_waiting(&pd->stats);
 }
 
-/* This should be called with the blkg->stats_lock held. */
+/* This should be called with the queue_lock held. */
 static void blkio_update_group_wait_time(struct blkio_group_stats *stats)
 {
 	unsigned long long now;
@@ -224,7 +202,7 @@ static void blkio_update_group_wait_time(struct blkio_group_stats *stats)
 	blkio_clear_blkg_waiting(stats);
 }
 
-/* This should be called with the blkg->stats_lock held. */
+/* This should be called with the queue_lock held. */
 static void blkio_end_empty_time(struct blkio_group_stats *stats)
 {
 	unsigned long long now;
@@ -238,132 +216,146 @@ static void blkio_end_empty_time(struct blkio_group_stats *stats)
 	blkio_clear_blkg_empty(stats);
 }
 
-void blkiocg_update_set_idle_time_stats(struct blkio_group *blkg)
+void blkiocg_update_set_idle_time_stats(struct blkio_group *blkg,
+					struct blkio_policy_type *pol)
 {
-	unsigned long flags;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+
+	lockdep_assert_held(blkg->q->queue_lock);
+	BUG_ON(blkio_blkg_idling(stats));
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	BUG_ON(blkio_blkg_idling(&blkg->stats));
-	blkg->stats.start_idle_time = sched_clock();
-	blkio_mark_blkg_idling(&blkg->stats);
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
+	stats->start_idle_time = sched_clock();
+	blkio_mark_blkg_idling(stats);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_set_idle_time_stats);
 
-void blkiocg_update_idle_time_stats(struct blkio_group *blkg)
+void blkiocg_update_idle_time_stats(struct blkio_group *blkg,
+				    struct blkio_policy_type *pol)
 {
-	unsigned long flags;
-	unsigned long long now;
-	struct blkio_group_stats *stats;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+
+	lockdep_assert_held(blkg->q->queue_lock);
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	stats = &blkg->stats;
 	if (blkio_blkg_idling(stats)) {
-		now = sched_clock();
-		if (time_after64(now, stats->start_idle_time))
+		unsigned long long now = sched_clock();
+
+		if (time_after64(now, stats->start_idle_time)) {
+			u64_stats_update_begin(&stats->syncp);
 			stats->idle_time += now - stats->start_idle_time;
+			u64_stats_update_end(&stats->syncp);
+		}
 		blkio_clear_blkg_idling(stats);
 	}
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_idle_time_stats);
 
-void blkiocg_update_avg_queue_size_stats(struct blkio_group *blkg)
+void blkiocg_update_avg_queue_size_stats(struct blkio_group *blkg,
+					 struct blkio_policy_type *pol)
 {
-	unsigned long flags;
-	struct blkio_group_stats *stats;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+
+	lockdep_assert_held(blkg->q->queue_lock);
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	stats = &blkg->stats;
+	u64_stats_update_begin(&stats->syncp);
 	stats->avg_queue_size_sum +=
 			stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_READ] +
 			stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE];
 	stats->avg_queue_size_samples++;
 	blkio_update_group_wait_time(stats);
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
+	u64_stats_update_end(&stats->syncp);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_avg_queue_size_stats);
 
-void blkiocg_set_start_empty_time(struct blkio_group *blkg)
+void blkiocg_set_start_empty_time(struct blkio_group *blkg,
+				  struct blkio_policy_type *pol)
 {
-	unsigned long flags;
-	struct blkio_group_stats *stats;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	stats = &blkg->stats;
+	lockdep_assert_held(blkg->q->queue_lock);
 
 	if (stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_READ] ||
-			stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE]) {
-		spin_unlock_irqrestore(&blkg->stats_lock, flags);
+			stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE])
 		return;
-	}
 
 	/*
 	 * group is already marked empty. This can happen if cfqq got new
 	 * request in parent group and moved to this group while being added
 	 * to service tree. Just ignore the event and move on.
 	 */
-	if(blkio_blkg_empty(stats)) {
-		spin_unlock_irqrestore(&blkg->stats_lock, flags);
+	if (blkio_blkg_empty(stats))
 		return;
-	}
 
 	stats->start_empty_time = sched_clock();
 	blkio_mark_blkg_empty(stats);
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
 }
 EXPORT_SYMBOL_GPL(blkiocg_set_start_empty_time);
 
 void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
-			unsigned long dequeue)
+				  struct blkio_policy_type *pol,
+				  unsigned long dequeue)
 {
-	blkg->stats.dequeue += dequeue;
+	struct blkg_policy_data *pd = blkg->pd[pol->plid];
+
+	lockdep_assert_held(blkg->q->queue_lock);
+
+	pd->stats.dequeue += dequeue;
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_dequeue_stats);
 #else
 static inline void blkio_set_start_group_wait_time(struct blkio_group *blkg,
-					struct blkio_group *curr_blkg) {}
-static inline void blkio_end_empty_time(struct blkio_group_stats *stats) {}
+					struct blkio_policy_type *pol,
+					struct blkio_group *curr_blkg) { }
+static inline void blkio_end_empty_time(struct blkio_group_stats *stats) { }
 #endif
 
 void blkiocg_update_io_add_stats(struct blkio_group *blkg,
-			struct blkio_group *curr_blkg, bool direction,
-			bool sync)
+				 struct blkio_policy_type *pol,
+				 struct blkio_group *curr_blkg, bool direction,
+				 bool sync)
 {
-	unsigned long flags;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+
+	lockdep_assert_held(blkg->q->queue_lock);
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	blkio_add_stat(blkg->stats.stat_arr[BLKIO_STAT_QUEUED], 1, direction,
-			sync);
-	blkio_end_empty_time(&blkg->stats);
-	blkio_set_start_group_wait_time(blkg, curr_blkg);
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
+	u64_stats_update_begin(&stats->syncp);
+	blkio_add_stat(stats->stat_arr[BLKIO_STAT_QUEUED], 1, direction, sync);
+	blkio_end_empty_time(stats);
+	u64_stats_update_end(&stats->syncp);
+
+	blkio_set_start_group_wait_time(blkg, pol, curr_blkg);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_io_add_stats);
 
 void blkiocg_update_io_remove_stats(struct blkio_group *blkg,
-						bool direction, bool sync)
+				    struct blkio_policy_type *pol,
+				    bool direction, bool sync)
 {
-	unsigned long flags;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	blkio_check_and_dec_stat(blkg->stats.stat_arr[BLKIO_STAT_QUEUED],
-					direction, sync);
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
+	lockdep_assert_held(blkg->q->queue_lock);
+
+	u64_stats_update_begin(&stats->syncp);
+	blkio_check_and_dec_stat(stats->stat_arr[BLKIO_STAT_QUEUED], direction,
+				 sync);
+	u64_stats_update_end(&stats->syncp);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_io_remove_stats);
 
-void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time,
-				unsigned long unaccounted_time)
+void blkiocg_update_timeslice_used(struct blkio_group *blkg,
+				   struct blkio_policy_type *pol,
+				   unsigned long time,
+				   unsigned long unaccounted_time)
 {
-	unsigned long flags;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	blkg->stats.time += time;
+	lockdep_assert_held(blkg->q->queue_lock);
+
+	u64_stats_update_begin(&stats->syncp);
+	stats->time += time;
 #ifdef CONFIG_DEBUG_BLK_CGROUP
-	blkg->stats.unaccounted_time += unaccounted_time;
+	stats->unaccounted_time += unaccounted_time;
 #endif
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
+	u64_stats_update_end(&stats->syncp);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used);
 
@@ -372,11 +364,17 @@ EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used);
  * is valid.
  */
 void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
-				uint64_t bytes, bool direction, bool sync)
+				   struct blkio_policy_type *pol,
+				   uint64_t bytes, bool direction, bool sync)
 {
+	struct blkg_policy_data *pd = blkg->pd[pol->plid];
 	struct blkio_group_stats_cpu *stats_cpu;
 	unsigned long flags;
 
+	/* If per cpu stats are not allocated yet, don't do any accounting. */
+	if (pd->stats_cpu == NULL)
+		return;
+
 	/*
 	 * Disabling interrupts to provide mutual exclusion between two
 	 * writes on same cpu. It probably is not needed for 64bit. Not
@@ -384,7 +382,7 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
 	 */
 	local_irq_save(flags);
 
-	stats_cpu = this_cpu_ptr(blkg->stats_cpu);
+	stats_cpu = this_cpu_ptr(pd->stats_cpu);
 
 	u64_stats_update_begin(&stats_cpu->syncp);
 	stats_cpu->sectors += bytes >> 9;
@@ -398,213 +396,419 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
 EXPORT_SYMBOL_GPL(blkiocg_update_dispatch_stats);
 
 void blkiocg_update_completion_stats(struct blkio_group *blkg,
-	uint64_t start_time, uint64_t io_start_time, bool direction, bool sync)
+				     struct blkio_policy_type *pol,
+				     uint64_t start_time,
+				     uint64_t io_start_time, bool direction,
+				     bool sync)
 {
-	struct blkio_group_stats *stats;
-	unsigned long flags;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
 	unsigned long long now = sched_clock();
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	stats = &blkg->stats;
+	lockdep_assert_held(blkg->q->queue_lock);
+
+	u64_stats_update_begin(&stats->syncp);
 	if (time_after64(now, io_start_time))
 		blkio_add_stat(stats->stat_arr[BLKIO_STAT_SERVICE_TIME],
 				now - io_start_time, direction, sync);
 	if (time_after64(io_start_time, start_time))
 		blkio_add_stat(stats->stat_arr[BLKIO_STAT_WAIT_TIME],
 				io_start_time - start_time, direction, sync);
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
+	u64_stats_update_end(&stats->syncp);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);
 
 /*  Merged stats are per cpu.  */
-void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
-					bool sync)
+void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
+				    struct blkio_policy_type *pol,
+				    bool direction, bool sync)
 {
-	struct blkio_group_stats_cpu *stats_cpu;
-	unsigned long flags;
+	struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
 
-	/*
-	 * Disabling interrupts to provide mutual exclusion between two
-	 * writes on same cpu. It probably is not needed for 64bit. Not
-	 * optimizing that case yet.
-	 */
-	local_irq_save(flags);
+	lockdep_assert_held(blkg->q->queue_lock);
 
-	stats_cpu = this_cpu_ptr(blkg->stats_cpu);
-
-	u64_stats_update_begin(&stats_cpu->syncp);
-	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_MERGED], 1,
-				direction, sync);
-	u64_stats_update_end(&stats_cpu->syncp);
-	local_irq_restore(flags);
+	u64_stats_update_begin(&stats->syncp);
+	blkio_add_stat(stats->stat_arr[BLKIO_STAT_MERGED], 1, direction, sync);
+	u64_stats_update_end(&stats->syncp);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);
 
 /*
- * This function allocates the per cpu stats for blkio_group. Should be called
- * from sleepable context as alloc_per_cpu() requires that.
+ * Worker for allocating per cpu stat for blk groups. This is scheduled on
+ * the system_nrt_wq once there are some groups on the alloc_list waiting
+ * for allocation.
  */
-int blkio_alloc_blkg_stats(struct blkio_group *blkg)
+static void blkio_stat_alloc_fn(struct work_struct *work)
 {
-	/* Allocate memory for per cpu stats */
-	blkg->stats_cpu = alloc_percpu(struct blkio_group_stats_cpu);
-	if (!blkg->stats_cpu)
-		return -ENOMEM;
-	return 0;
-}
-EXPORT_SYMBOL_GPL(blkio_alloc_blkg_stats);
+	static void *pcpu_stats[BLKIO_NR_POLICIES];
+	struct delayed_work *dwork = to_delayed_work(work);
+	struct blkio_group *blkg;
+	int i;
+	bool empty = false;
 
-void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-		struct blkio_group *blkg, void *key, dev_t dev,
-		enum blkio_policy_id plid)
-{
-	unsigned long flags;
+alloc_stats:
+	for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+		if (pcpu_stats[i] != NULL)
+			continue;
 
-	spin_lock_irqsave(&blkcg->lock, flags);
-	spin_lock_init(&blkg->stats_lock);
-	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));
-	blkg->dev = dev;
+		pcpu_stats[i] = alloc_percpu(struct blkio_group_stats_cpu);
+
+		/* Allocation failed. Try again after some time. */
+		if (pcpu_stats[i] == NULL) {
+			queue_delayed_work(system_nrt_wq, dwork,
+						msecs_to_jiffies(10));
+			return;
+		}
+	}
+
+	spin_lock_irq(&blkio_list_lock);
+	spin_lock(&alloc_list_lock);
+
+	/* cgroup got deleted or queue exited. */
+	if (!list_empty(&alloc_list)) {
+		blkg = list_first_entry(&alloc_list, struct blkio_group,
+						alloc_node);
+		for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+			struct blkg_policy_data *pd = blkg->pd[i];
+
+			if (blkio_policy[i] && pd && !pd->stats_cpu)
+				swap(pd->stats_cpu, pcpu_stats[i]);
+		}
+
+		list_del_init(&blkg->alloc_node);
+	}
+
+	empty = list_empty(&alloc_list);
+
+	spin_unlock(&alloc_list_lock);
+	spin_unlock_irq(&blkio_list_lock);
+
+	if (!empty)
+		goto alloc_stats;
 }
-EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
 
-static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
+/**
+ * blkg_free - free a blkg
+ * @blkg: blkg to free
+ *
+ * Free @blkg which may be partially allocated.
+ */
+static void blkg_free(struct blkio_group *blkg)
 {
-	hlist_del_init_rcu(&blkg->blkcg_node);
-	blkg->blkcg_id = 0;
+	int i;
+
+	if (!blkg)
+		return;
+
+	for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+		struct blkg_policy_data *pd = blkg->pd[i];
+
+		if (pd) {
+			free_percpu(pd->stats_cpu);
+			kfree(pd);
+		}
+	}
+
+	kfree(blkg);
 }
 
-/*
- * returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
- * indicating that blk_group was unhashed by the time we got to it.
+/**
+ * blkg_alloc - allocate a blkg
+ * @blkcg: block cgroup the new blkg is associated with
+ * @q: request_queue the new blkg is associated with
+ *
+ * Allocate a new blkg assocating @blkcg and @q.
  */
-int blkiocg_del_blkio_group(struct blkio_group *blkg)
+static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
+				      struct request_queue *q)
 {
-	struct blkio_cgroup *blkcg;
-	unsigned long flags;
-	struct cgroup_subsys_state *css;
-	int ret = 1;
+	struct blkio_group *blkg;
+	int i;
 
-	rcu_read_lock();
-	css = css_lookup(&blkio_subsys, blkg->blkcg_id);
-	if (css) {
-		blkcg = container_of(css, struct blkio_cgroup, css);
-		spin_lock_irqsave(&blkcg->lock, flags);
-		if (!hlist_unhashed(&blkg->blkcg_node)) {
-			__blkiocg_del_blkio_group(blkg);
-			ret = 0;
+	/* alloc and init base part */
+	blkg = kzalloc_node(sizeof(*blkg), GFP_ATOMIC, q->node);
+	if (!blkg)
+		return NULL;
+
+	blkg->q = q;
+	INIT_LIST_HEAD(&blkg->q_node);
+	INIT_LIST_HEAD(&blkg->alloc_node);
+	blkg->blkcg = blkcg;
+	blkg->refcnt = 1;
+	cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
+
+	for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+		struct blkio_policy_type *pol = blkio_policy[i];
+		struct blkg_policy_data *pd;
+
+		if (!pol)
+			continue;
+
+		/* alloc per-policy data and attach it to blkg */
+		pd = kzalloc_node(sizeof(*pd) + pol->pdata_size, GFP_ATOMIC,
+				  q->node);
+		if (!pd) {
+			blkg_free(blkg);
+			return NULL;
 		}
-		spin_unlock_irqrestore(&blkcg->lock, flags);
+
+		blkg->pd[i] = pd;
+		pd->blkg = blkg;
 	}
 
-	rcu_read_unlock();
-	return ret;
+	/* invoke per-policy init */
+	for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+		struct blkio_policy_type *pol = blkio_policy[i];
+
+		if (pol)
+			pol->ops.blkio_init_group_fn(blkg);
+	}
+
+	return blkg;
+}
+
+struct blkio_group *blkg_lookup_create(struct blkio_cgroup *blkcg,
+				       struct request_queue *q,
+				       enum blkio_policy_id plid,
+				       bool for_root)
+	__releases(q->queue_lock) __acquires(q->queue_lock)
+{
+	struct blkio_group *blkg;
+
+	WARN_ON_ONCE(!rcu_read_lock_held());
+	lockdep_assert_held(q->queue_lock);
+
+	/*
+	 * This could be the first entry point of blkcg implementation and
+	 * we shouldn't allow anything to go through for a bypassing queue.
+	 * The following can be removed if blkg lookup is guaranteed to
+	 * fail on a bypassing queue.
+	 */
+	if (unlikely(blk_queue_bypass(q)) && !for_root)
+		return ERR_PTR(blk_queue_dead(q) ? -EINVAL : -EBUSY);
+
+	blkg = blkg_lookup(blkcg, q);
+	if (blkg)
+		return blkg;
+
+	/* blkg holds a reference to blkcg */
+	if (!css_tryget(&blkcg->css))
+		return ERR_PTR(-EINVAL);
+
+	/*
+	 * Allocate and initialize.
+	 */
+	blkg = blkg_alloc(blkcg, q);
+
+	/* did alloc fail? */
+	if (unlikely(!blkg)) {
+		blkg = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	/* insert */
+	spin_lock(&blkcg->lock);
+	hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
+	list_add(&blkg->q_node, &q->blkg_list);
+	spin_unlock(&blkcg->lock);
+
+	spin_lock(&alloc_list_lock);
+	list_add(&blkg->alloc_node, &alloc_list);
+	/* Queue per cpu stat allocation from worker thread. */
+	queue_delayed_work(system_nrt_wq, &blkio_stat_alloc_work, 0);
+	spin_unlock(&alloc_list_lock);
+out:
+	return blkg;
 }
-EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);
+EXPORT_SYMBOL_GPL(blkg_lookup_create);
 
 /* called under rcu_read_lock(). */
-struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
+struct blkio_group *blkg_lookup(struct blkio_cgroup *blkcg,
+				struct request_queue *q)
 {
 	struct blkio_group *blkg;
 	struct hlist_node *n;
-	void *__key;
 
-	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
-		__key = blkg->key;
-		if (__key == key)
+	hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node)
+		if (blkg->q == q)
 			return blkg;
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(blkg_lookup);
+
+static void blkg_destroy(struct blkio_group *blkg)
+{
+	struct request_queue *q = blkg->q;
+	struct blkio_cgroup *blkcg = blkg->blkcg;
+
+	lockdep_assert_held(q->queue_lock);
+	lockdep_assert_held(&blkcg->lock);
+
+	/* Something wrong if we are trying to remove same group twice */
+	WARN_ON_ONCE(list_empty(&blkg->q_node));
+	WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
+	list_del_init(&blkg->q_node);
+	hlist_del_init_rcu(&blkg->blkcg_node);
+
+	spin_lock(&alloc_list_lock);
+	list_del_init(&blkg->alloc_node);
+	spin_unlock(&alloc_list_lock);
+
+	/*
+	 * Put the reference taken at the time of creation so that when all
+	 * queues are gone, group can be destroyed.
+	 */
+	blkg_put(blkg);
+}
+
+/*
+ * XXX: This updates blkg policy data in-place for root blkg, which is
+ * necessary across elevator switch and policy registration as root blkgs
+ * aren't shot down.  This broken and racy implementation is temporary.
+ * Eventually, blkg shoot down will be replaced by proper in-place update.
+ */
+void update_root_blkg_pd(struct request_queue *q, enum blkio_policy_id plid)
+{
+	struct blkio_policy_type *pol = blkio_policy[plid];
+	struct blkio_group *blkg = blkg_lookup(&blkio_root_cgroup, q);
+	struct blkg_policy_data *pd;
+
+	if (!blkg)
+		return;
+
+	kfree(blkg->pd[plid]);
+	blkg->pd[plid] = NULL;
+
+	if (!pol)
+		return;
+
+	pd = kzalloc(sizeof(*pd) + pol->pdata_size, GFP_KERNEL);
+	WARN_ON_ONCE(!pd);
+
+	pd->stats_cpu = alloc_percpu(struct blkio_group_stats_cpu);
+	WARN_ON_ONCE(!pd->stats_cpu);
+
+	blkg->pd[plid] = pd;
+	pd->blkg = blkg;
+	pol->ops.blkio_init_group_fn(blkg);
+}
+EXPORT_SYMBOL_GPL(update_root_blkg_pd);
+
+/**
+ * blkg_destroy_all - destroy all blkgs associated with a request_queue
+ * @q: request_queue of interest
+ * @destroy_root: whether to destroy root blkg or not
+ *
+ * Destroy blkgs associated with @q.  If @destroy_root is %true, all are
+ * destroyed; otherwise, root blkg is left alone.
+ */
+void blkg_destroy_all(struct request_queue *q, bool destroy_root)
+{
+	struct blkio_group *blkg, *n;
+
+	spin_lock_irq(q->queue_lock);
+
+	list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
+		struct blkio_cgroup *blkcg = blkg->blkcg;
+
+		/* skip root? */
+		if (!destroy_root && blkg->blkcg == &blkio_root_cgroup)
+			continue;
+
+		spin_lock(&blkcg->lock);
+		blkg_destroy(blkg);
+		spin_unlock(&blkcg->lock);
 	}
 
-	return NULL;
+	spin_unlock_irq(q->queue_lock);
 }
-EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
+EXPORT_SYMBOL_GPL(blkg_destroy_all);
 
-static void blkio_reset_stats_cpu(struct blkio_group *blkg)
+static void blkg_rcu_free(struct rcu_head *rcu_head)
 {
-	struct blkio_group_stats_cpu *stats_cpu;
-	int i, j, k;
+	blkg_free(container_of(rcu_head, struct blkio_group, rcu_head));
+}
+
+void __blkg_release(struct blkio_group *blkg)
+{
+	/* release the extra blkcg reference this blkg has been holding */
+	css_put(&blkg->blkcg->css);
+
 	/*
-	 * Note: On 64 bit arch this should not be an issue. This has the
-	 * possibility of returning some inconsistent value on 32bit arch
-	 * as 64bit update on 32bit is non atomic. Taking care of this
-	 * corner case makes code very complicated, like sending IPIs to
-	 * cpus, taking care of stats of offline cpus etc.
+	 * A group is freed in rcu manner. But having an rcu lock does not
+	 * mean that one can access all the fields of blkg and assume these
+	 * are valid. For example, don't try to follow throtl_data and
+	 * request queue links.
 	 *
-	 * reset stats is anyway more of a debug feature and this sounds a
-	 * corner case. So I am not complicating the code yet until and
-	 * unless this becomes a real issue.
+	 * Having a reference to blkg under an rcu allows acess to only
+	 * values local to groups like group stats and group rate limits
 	 */
-	for_each_possible_cpu(i) {
-		stats_cpu = per_cpu_ptr(blkg->stats_cpu, i);
-		stats_cpu->sectors = 0;
-		for(j = 0; j < BLKIO_STAT_CPU_NR; j++)
-			for (k = 0; k < BLKIO_STAT_TOTAL; k++)
-				stats_cpu->stat_arr_cpu[j][k] = 0;
+	call_rcu(&blkg->rcu_head, blkg_rcu_free);
+}
+EXPORT_SYMBOL_GPL(__blkg_release);
+
+static void blkio_reset_stats_cpu(struct blkio_group *blkg, int plid)
+{
+	struct blkg_policy_data *pd = blkg->pd[plid];
+	int cpu;
+
+	if (pd->stats_cpu == NULL)
+		return;
+
+	for_each_possible_cpu(cpu) {
+		struct blkio_group_stats_cpu *sc =
+			per_cpu_ptr(pd->stats_cpu, cpu);
+
+		sc->sectors = 0;
+		memset(sc->stat_arr_cpu, 0, sizeof(sc->stat_arr_cpu));
 	}
 }
 
 static int
 blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 {
-	struct blkio_cgroup *blkcg;
+	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
 	struct blkio_group *blkg;
-	struct blkio_group_stats *stats;
 	struct hlist_node *n;
-	uint64_t queued[BLKIO_STAT_TOTAL];
 	int i;
-#ifdef CONFIG_DEBUG_BLK_CGROUP
-	bool idling, waiting, empty;
-	unsigned long long now = sched_clock();
-#endif
 
-	blkcg = cgroup_to_blkio_cgroup(cgroup);
+	spin_lock(&blkio_list_lock);
 	spin_lock_irq(&blkcg->lock);
+
+	/*
+	 * Note that stat reset is racy - it doesn't synchronize against
+	 * stat updates.  This is a debug feature which shouldn't exist
+	 * anyway.  If you get hit by a race, retry.
+	 */
 	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
-		spin_lock(&blkg->stats_lock);
-		stats = &blkg->stats;
+		struct blkio_policy_type *pol;
+
+		list_for_each_entry(pol, &blkio_list, list) {
+			struct blkg_policy_data *pd = blkg->pd[pol->plid];
+			struct blkio_group_stats *stats = &pd->stats;
+
+			/* queued stats shouldn't be cleared */
+			for (i = 0; i < ARRAY_SIZE(stats->stat_arr); i++)
+				if (i != BLKIO_STAT_QUEUED)
+					memset(stats->stat_arr[i], 0,
+					       sizeof(stats->stat_arr[i]));
+			stats->time = 0;
 #ifdef CONFIG_DEBUG_BLK_CGROUP
-		idling = blkio_blkg_idling(stats);
-		waiting = blkio_blkg_waiting(stats);
-		empty = blkio_blkg_empty(stats);
+			memset((void *)stats + BLKG_STATS_DEBUG_CLEAR_START, 0,
+			       BLKG_STATS_DEBUG_CLEAR_SIZE);
 #endif
-		for (i = 0; i < BLKIO_STAT_TOTAL; i++)
-			queued[i] = stats->stat_arr[BLKIO_STAT_QUEUED][i];
-		memset(stats, 0, sizeof(struct blkio_group_stats));
-		for (i = 0; i < BLKIO_STAT_TOTAL; i++)
-			stats->stat_arr[BLKIO_STAT_QUEUED][i] = queued[i];
-#ifdef CONFIG_DEBUG_BLK_CGROUP
-		if (idling) {
-			blkio_mark_blkg_idling(stats);
-			stats->start_idle_time = now;
-		}
-		if (waiting) {
-			blkio_mark_blkg_waiting(stats);
-			stats->start_group_wait_time = now;
-		}
-		if (empty) {
-			blkio_mark_blkg_empty(stats);
-			stats->start_empty_time = now;
+			blkio_reset_stats_cpu(blkg, pol->plid);
 		}
-#endif
-		spin_unlock(&blkg->stats_lock);
-
-		/* Reset Per cpu stats which don't take blkg->stats_lock */
-		blkio_reset_stats_cpu(blkg);
 	}
 
 	spin_unlock_irq(&blkcg->lock);
+	spin_unlock(&blkio_list_lock);
 	return 0;
 }
 
-static void blkio_get_key_name(enum stat_sub_type type, dev_t dev, char *str,
-				int chars_left, bool diskname_only)
+static void blkio_get_key_name(enum stat_sub_type type, const char *dname,
+			       char *str, int chars_left, bool diskname_only)
 {
-	snprintf(str, chars_left, "%d:%d", MAJOR(dev), MINOR(dev));
+	snprintf(str, chars_left, "%s", dname);
 	chars_left -= strlen(str);
 	if (chars_left <= 0) {
 		printk(KERN_WARNING
@@ -634,25 +838,20 @@ static void blkio_get_key_name(enum stat_sub_type type, dev_t dev, char *str,
 	}
 }
 
-static uint64_t blkio_fill_stat(char *str, int chars_left, uint64_t val,
-				struct cgroup_map_cb *cb, dev_t dev)
-{
-	blkio_get_key_name(0, dev, str, chars_left, true);
-	cb->fill(cb, str, val);
-	return val;
-}
-
-
-static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg,
+static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg, int plid,
 			enum stat_type_cpu type, enum stat_sub_type sub_type)
 {
+	struct blkg_policy_data *pd = blkg->pd[plid];
 	int cpu;
 	struct blkio_group_stats_cpu *stats_cpu;
 	u64 val = 0, tval;
 
+	if (pd->stats_cpu == NULL)
+		return val;
+
 	for_each_possible_cpu(cpu) {
 		unsigned int start;
-		stats_cpu  = per_cpu_ptr(blkg->stats_cpu, cpu);
+		stats_cpu = per_cpu_ptr(pd->stats_cpu, cpu);
 
 		do {
 			start = u64_stats_fetch_begin(&stats_cpu->syncp);
@@ -668,87 +867,115 @@ static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg,
 	return val;
 }
 
-static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg,
-		struct cgroup_map_cb *cb, dev_t dev, enum stat_type_cpu type)
+static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg, int plid,
+				   struct cgroup_map_cb *cb, const char *dname,
+				   enum stat_type_cpu type)
 {
 	uint64_t disk_total, val;
 	char key_str[MAX_KEY_LEN];
 	enum stat_sub_type sub_type;
 
 	if (type == BLKIO_STAT_CPU_SECTORS) {
-		val = blkio_read_stat_cpu(blkg, type, 0);
-		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1, val, cb, dev);
+		val = blkio_read_stat_cpu(blkg, plid, type, 0);
+		blkio_get_key_name(0, dname, key_str, MAX_KEY_LEN, true);
+		cb->fill(cb, key_str, val);
+		return val;
 	}
 
 	for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
 			sub_type++) {
-		blkio_get_key_name(sub_type, dev, key_str, MAX_KEY_LEN, false);
-		val = blkio_read_stat_cpu(blkg, type, sub_type);
+		blkio_get_key_name(sub_type, dname, key_str, MAX_KEY_LEN,
+				   false);
+		val = blkio_read_stat_cpu(blkg, plid, type, sub_type);
 		cb->fill(cb, key_str, val);
 	}
 
-	disk_total = blkio_read_stat_cpu(blkg, type, BLKIO_STAT_READ) +
-			blkio_read_stat_cpu(blkg, type, BLKIO_STAT_WRITE);
+	disk_total = blkio_read_stat_cpu(blkg, plid, type, BLKIO_STAT_READ) +
+		blkio_read_stat_cpu(blkg, plid, type, BLKIO_STAT_WRITE);
 
-	blkio_get_key_name(BLKIO_STAT_TOTAL, dev, key_str, MAX_KEY_LEN, false);
+	blkio_get_key_name(BLKIO_STAT_TOTAL, dname, key_str, MAX_KEY_LEN,
+			   false);
 	cb->fill(cb, key_str, disk_total);
 	return disk_total;
 }
 
-/* This should be called with blkg->stats_lock held */
-static uint64_t blkio_get_stat(struct blkio_group *blkg,
-		struct cgroup_map_cb *cb, dev_t dev, enum stat_type type)
+static uint64_t blkio_get_stat(struct blkio_group *blkg, int plid,
+			       struct cgroup_map_cb *cb, const char *dname,
+			       enum stat_type type)
 {
-	uint64_t disk_total;
+	struct blkio_group_stats *stats = &blkg->pd[plid]->stats;
+	uint64_t v = 0, disk_total = 0;
 	char key_str[MAX_KEY_LEN];
-	enum stat_sub_type sub_type;
+	unsigned int sync_start;
+	int st;
 
-	if (type == BLKIO_STAT_TIME)
-		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-					blkg->stats.time, cb, dev);
+	if (type >= BLKIO_STAT_ARR_NR) {
+		do {
+			sync_start = u64_stats_fetch_begin(&stats->syncp);
+			switch (type) {
+			case BLKIO_STAT_TIME:
+				v = stats->time;
+				break;
 #ifdef CONFIG_DEBUG_BLK_CGROUP
-	if (type == BLKIO_STAT_UNACCOUNTED_TIME)
-		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-					blkg->stats.unaccounted_time, cb, dev);
-	if (type == BLKIO_STAT_AVG_QUEUE_SIZE) {
-		uint64_t sum = blkg->stats.avg_queue_size_sum;
-		uint64_t samples = blkg->stats.avg_queue_size_samples;
-		if (samples)
-			do_div(sum, samples);
-		else
-			sum = 0;
-		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1, sum, cb, dev);
-	}
-	if (type == BLKIO_STAT_GROUP_WAIT_TIME)
-		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-					blkg->stats.group_wait_time, cb, dev);
-	if (type == BLKIO_STAT_IDLE_TIME)
-		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-					blkg->stats.idle_time, cb, dev);
-	if (type == BLKIO_STAT_EMPTY_TIME)
-		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-					blkg->stats.empty_time, cb, dev);
-	if (type == BLKIO_STAT_DEQUEUE)
-		return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-					blkg->stats.dequeue, cb, dev);
+			case BLKIO_STAT_UNACCOUNTED_TIME:
+				v = stats->unaccounted_time;
+				break;
+			case BLKIO_STAT_AVG_QUEUE_SIZE: {
+				uint64_t samples = stats->avg_queue_size_samples;
+
+				if (samples) {
+					v = stats->avg_queue_size_sum;
+					do_div(v, samples);
+				}
+				break;
+			}
+			case BLKIO_STAT_IDLE_TIME:
+				v = stats->idle_time;
+				break;
+			case BLKIO_STAT_EMPTY_TIME:
+				v = stats->empty_time;
+				break;
+			case BLKIO_STAT_DEQUEUE:
+				v = stats->dequeue;
+				break;
+			case BLKIO_STAT_GROUP_WAIT_TIME:
+				v = stats->group_wait_time;
+				break;
 #endif
+			default:
+				WARN_ON_ONCE(1);
+			}
+		} while (u64_stats_fetch_retry(&stats->syncp, sync_start));
 
-	for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
-			sub_type++) {
-		blkio_get_key_name(sub_type, dev, key_str, MAX_KEY_LEN, false);
-		cb->fill(cb, key_str, blkg->stats.stat_arr[type][sub_type]);
+		blkio_get_key_name(0, dname, key_str, MAX_KEY_LEN, true);
+		cb->fill(cb, key_str, v);
+		return v;
+	}
+
+	for (st = BLKIO_STAT_READ; st < BLKIO_STAT_TOTAL; st++) {
+		do {
+			sync_start = u64_stats_fetch_begin(&stats->syncp);
+			v = stats->stat_arr[type][st];
+		} while (u64_stats_fetch_retry(&stats->syncp, sync_start));
+
+		blkio_get_key_name(st, dname, key_str, MAX_KEY_LEN, false);
+		cb->fill(cb, key_str, v);
+		if (st == BLKIO_STAT_READ || st == BLKIO_STAT_WRITE)
+			disk_total += v;
 	}
-	disk_total = blkg->stats.stat_arr[type][BLKIO_STAT_READ] +
-			blkg->stats.stat_arr[type][BLKIO_STAT_WRITE];
-	blkio_get_key_name(BLKIO_STAT_TOTAL, dev, key_str, MAX_KEY_LEN, false);
+
+	blkio_get_key_name(BLKIO_STAT_TOTAL, dname, key_str, MAX_KEY_LEN,
+			   false);
 	cb->fill(cb, key_str, disk_total);
 	return disk_total;
 }
 
-static int blkio_policy_parse_and_set(char *buf,
-	struct blkio_policy_node *newpn, enum blkio_policy_id plid, int fileid)
+static int blkio_policy_parse_and_set(char *buf, enum blkio_policy_id plid,
+				      int fileid, struct blkio_cgroup *blkcg)
 {
 	struct gendisk *disk = NULL;
+	struct blkio_group *blkg = NULL;
+	struct blkg_policy_data *pd;
 	char *s[4], *p, *major_s = NULL, *minor_s = NULL;
 	unsigned long major, minor;
 	int i = 0, ret = -EINVAL;
@@ -793,43 +1020,53 @@ static int blkio_policy_parse_and_set(char *buf,
 	if (strict_strtoull(s[1], 10, &temp))
 		goto out;
 
-	/* For rule removal, do not check for device presence. */
-	if (temp) {
-		disk = get_gendisk(dev, &part);
-		if (!disk || part) {
-			ret = -ENODEV;
-			goto out;
-		}
+	disk = get_gendisk(dev, &part);
+	if (!disk || part)
+		goto out;
+
+	rcu_read_lock();
+
+	spin_lock_irq(disk->queue->queue_lock);
+	blkg = blkg_lookup_create(blkcg, disk->queue, plid, false);
+	spin_unlock_irq(disk->queue->queue_lock);
+
+	if (IS_ERR(blkg)) {
+		ret = PTR_ERR(blkg);
+		goto out_unlock;
 	}
 
-	newpn->dev = dev;
+	pd = blkg->pd[plid];
 
 	switch (plid) {
 	case BLKIO_POLICY_PROP:
 		if ((temp < BLKIO_WEIGHT_MIN && temp > 0) ||
 		     temp > BLKIO_WEIGHT_MAX)
-			goto out;
+			goto out_unlock;
 
-		newpn->plid = plid;
-		newpn->fileid = fileid;
-		newpn->val.weight = temp;
+		pd->conf.weight = temp;
+		blkio_update_group_weight(blkg, plid, temp ?: blkcg->weight);
 		break;
 	case BLKIO_POLICY_THROTL:
 		switch(fileid) {
 		case BLKIO_THROTL_read_bps_device:
+			pd->conf.bps[READ] = temp;
+			blkio_update_group_bps(blkg, plid, temp ?: -1, fileid);
+			break;
 		case BLKIO_THROTL_write_bps_device:
-			newpn->plid = plid;
-			newpn->fileid = fileid;
-			newpn->val.bps = temp;
+			pd->conf.bps[WRITE] = temp;
+			blkio_update_group_bps(blkg, plid, temp ?: -1, fileid);
 			break;
 		case BLKIO_THROTL_read_iops_device:
+			if (temp > THROTL_IOPS_MAX)
+				goto out_unlock;
+			pd->conf.iops[READ] = temp;
+			blkio_update_group_iops(blkg, plid, temp ?: -1, fileid);
+			break;
 		case BLKIO_THROTL_write_iops_device:
 			if (temp > THROTL_IOPS_MAX)
-				goto out;
-
-			newpn->plid = plid;
-			newpn->fileid = fileid;
-			newpn->val.iops = (unsigned int)temp;
+				goto out_unlock;
+			pd->conf.iops[WRITE] = temp;
+			blkio_update_group_iops(blkg, plid, temp ?: -1, fileid);
 			break;
 		}
 		break;
@@ -837,204 +1074,22 @@ static int blkio_policy_parse_and_set(char *buf,
 		BUG();
 	}
 	ret = 0;
+out_unlock:
+	rcu_read_unlock();
 out:
 	put_disk(disk);
-	return ret;
-}
-
-unsigned int blkcg_get_weight(struct blkio_cgroup *blkcg,
-			      dev_t dev)
-{
-	struct blkio_policy_node *pn;
-	unsigned long flags;
-	unsigned int weight;
-
-	spin_lock_irqsave(&blkcg->lock, flags);
-
-	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_PROP,
-				BLKIO_PROP_weight_device);
-	if (pn)
-		weight = pn->val.weight;
-	else
-		weight = blkcg->weight;
-
-	spin_unlock_irqrestore(&blkcg->lock, flags);
-
-	return 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;
-	unsigned long flags;
-	uint64_t bps = -1;
-
-	spin_lock_irqsave(&blkcg->lock, flags);
-	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
-				BLKIO_THROTL_read_bps_device);
-	if (pn)
-		bps = pn->val.bps;
-	spin_unlock_irqrestore(&blkcg->lock, flags);
-
-	return bps;
-}
-
-uint64_t blkcg_get_write_bps(struct blkio_cgroup *blkcg, dev_t dev)
-{
-	struct blkio_policy_node *pn;
-	unsigned long flags;
-	uint64_t bps = -1;
-
-	spin_lock_irqsave(&blkcg->lock, flags);
-	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
-				BLKIO_THROTL_write_bps_device);
-	if (pn)
-		bps = pn->val.bps;
-	spin_unlock_irqrestore(&blkcg->lock, flags);
-
-	return bps;
-}
-
-unsigned int blkcg_get_read_iops(struct blkio_cgroup *blkcg, dev_t dev)
-{
-	struct blkio_policy_node *pn;
-	unsigned long flags;
-	unsigned int iops = -1;
-
-	spin_lock_irqsave(&blkcg->lock, flags);
-	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
-				BLKIO_THROTL_read_iops_device);
-	if (pn)
-		iops = pn->val.iops;
-	spin_unlock_irqrestore(&blkcg->lock, flags);
-
-	return iops;
-}
-
-unsigned int blkcg_get_write_iops(struct blkio_cgroup *blkcg, dev_t dev)
-{
-	struct blkio_policy_node *pn;
-	unsigned long flags;
-	unsigned int iops = -1;
-
-	spin_lock_irqsave(&blkcg->lock, flags);
-	pn = blkio_policy_search_node(blkcg, dev, BLKIO_POLICY_THROTL,
-				BLKIO_THROTL_write_iops_device);
-	if (pn)
-		iops = pn->val.iops;
-	spin_unlock_irqrestore(&blkcg->lock, flags);
-
-	return iops;
-}
-
-/* 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:
-		switch(pn->fileid) {
-		case BLKIO_THROTL_read_bps_device:
-		case BLKIO_THROTL_write_bps_device:
-			if (pn->val.bps == 0)
-				return 1;
-			break;
-		case BLKIO_THROTL_read_iops_device:
-		case BLKIO_THROTL_write_iops_device:
-			if (pn->val.iops == 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:
-		switch(newpn->fileid) {
-		case BLKIO_THROTL_read_bps_device:
-		case BLKIO_THROTL_write_bps_device:
-			oldpn->val.bps = newpn->val.bps;
-			break;
-		case BLKIO_THROTL_read_iops_device:
-		case BLKIO_THROTL_write_iops_device:
-			oldpn->val.iops = newpn->val.iops;
-		}
-		break;
-	default:
-		BUG();
-	}
-}
-
-/*
- * Some rules/values in blkg have changed. Propagate those to respective
- * policies.
- */
-static void blkio_update_blkg_policy(struct blkio_cgroup *blkcg,
-		struct blkio_group *blkg, struct blkio_policy_node *pn)
-{
-	unsigned int weight, iops;
-	u64 bps;
-
-	switch(pn->plid) {
-	case BLKIO_POLICY_PROP:
-		weight = pn->val.weight ? pn->val.weight :
-				blkcg->weight;
-		blkio_update_group_weight(blkg, weight);
-		break;
-	case BLKIO_POLICY_THROTL:
-		switch(pn->fileid) {
-		case BLKIO_THROTL_read_bps_device:
-		case BLKIO_THROTL_write_bps_device:
-			bps = pn->val.bps ? pn->val.bps : (-1);
-			blkio_update_group_bps(blkg, bps, pn->fileid);
-			break;
-		case BLKIO_THROTL_read_iops_device:
-		case BLKIO_THROTL_write_iops_device:
-			iops = pn->val.iops ? pn->val.iops : (-1);
-			blkio_update_group_iops(blkg, iops, pn->fileid);
-			break;
-		}
-		break;
-	default:
-		BUG();
-	}
-}
-
-/*
- * A policy node rule has been updated. Propagate 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;
-
-	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 || pn->plid != blkg->plid)
-			continue;
-		blkio_update_blkg_policy(blkcg, blkg, pn);
+	/*
+	 * If queue was bypassing, we should retry.  Do so after a short
+	 * msleep().  It isn't strictly necessary but queue can be
+	 * bypassing for some time and it's always nice to avoid busy
+	 * looping.
+	 */
+	if (ret == -EBUSY) {
+		msleep(10);
+		return restart_syscall();
 	}
-
-	spin_unlock_irq(&blkcg->lock);
-	spin_unlock(&blkio_list_lock);
+	return ret;
 }
 
 static int blkiocg_file_write(struct cgroup *cgrp, struct cftype *cft,
@@ -1042,9 +1097,7 @@ static int blkiocg_file_write(struct cgroup *cgrp, struct cftype *cft,
 {
 	int ret = 0;
 	char *buf;
-	struct blkio_policy_node *newpn, *pn;
-	struct blkio_cgroup *blkcg;
-	int keep_newpn = 0;
+	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
 	enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
 	int fileid = BLKIOFILE_ATTR(cft->private);
 
@@ -1052,71 +1105,52 @@ static int blkiocg_file_write(struct cgroup *cgrp, struct cftype *cft,
 	if (!buf)
 		return -ENOMEM;
 
-	newpn = kzalloc(sizeof(*newpn), GFP_KERNEL);
-	if (!newpn) {
-		ret = -ENOMEM;
-		goto free_buf;
-	}
-
-	ret = blkio_policy_parse_and_set(buf, newpn, plid, fileid);
-	if (ret)
-		goto free_newpn;
-
-	blkcg = cgroup_to_blkio_cgroup(cgrp);
-
-	spin_lock_irq(&blkcg->lock);
-
-	pn = blkio_policy_search_node(blkcg, newpn->dev, plid, fileid);
-	if (!pn) {
-		if (!blkio_delete_rule_command(newpn)) {
-			blkio_policy_insert_node(blkcg, newpn);
-			keep_newpn = 1;
-		}
-		spin_unlock_irq(&blkcg->lock);
-		goto update_io_group;
-	}
-
-	if (blkio_delete_rule_command(newpn)) {
-		blkio_policy_delete_node(pn);
-		kfree(pn);
-		spin_unlock_irq(&blkcg->lock);
-		goto update_io_group;
-	}
-	spin_unlock_irq(&blkcg->lock);
-
-	blkio_update_policy_rule(pn, newpn);
-
-update_io_group:
-	blkio_update_policy_node_blkg(blkcg, newpn);
-
-free_newpn:
-	if (!keep_newpn)
-		kfree(newpn);
-free_buf:
+	ret = blkio_policy_parse_and_set(buf, plid, fileid, blkcg);
 	kfree(buf);
 	return ret;
 }
 
-static void
-blkio_print_policy_node(struct seq_file *m, struct blkio_policy_node *pn)
+static const char *blkg_dev_name(struct blkio_group *blkg)
+{
+	/* some drivers (floppy) instantiate a queue w/o disk registered */
+	if (blkg->q->backing_dev_info.dev)
+		return dev_name(blkg->q->backing_dev_info.dev);
+	return NULL;
+}
+
+static void blkio_print_group_conf(struct cftype *cft, struct blkio_group *blkg,
+				   struct seq_file *m)
 {
-	switch(pn->plid) {
+	int plid = BLKIOFILE_POLICY(cft->private);
+	int fileid = BLKIOFILE_ATTR(cft->private);
+	struct blkg_policy_data *pd = blkg->pd[plid];
+	const char *dname = blkg_dev_name(blkg);
+	int rw = WRITE;
+
+	if (!dname)
+		return;
+
+	switch (plid) {
 		case BLKIO_POLICY_PROP:
-			if (pn->fileid == BLKIO_PROP_weight_device)
-				seq_printf(m, "%u:%u\t%u\n", MAJOR(pn->dev),
-					MINOR(pn->dev), pn->val.weight);
+			if (pd->conf.weight)
+				seq_printf(m, "%s\t%u\n",
+					   dname, pd->conf.weight);
 			break;
 		case BLKIO_POLICY_THROTL:
-			switch(pn->fileid) {
+			switch (fileid) {
 			case BLKIO_THROTL_read_bps_device:
+				rw = READ;
 			case BLKIO_THROTL_write_bps_device:
-				seq_printf(m, "%u:%u\t%llu\n", MAJOR(pn->dev),
-					MINOR(pn->dev), pn->val.bps);
+				if (pd->conf.bps[rw])
+					seq_printf(m, "%s\t%llu\n",
+						   dname, pd->conf.bps[rw]);
 				break;
 			case BLKIO_THROTL_read_iops_device:
+				rw = READ;
 			case BLKIO_THROTL_write_iops_device:
-				seq_printf(m, "%u:%u\t%u\n", MAJOR(pn->dev),
-					MINOR(pn->dev), pn->val.iops);
+				if (pd->conf.iops[rw])
+					seq_printf(m, "%s\t%u\n",
+						   dname, pd->conf.iops[rw]);
 				break;
 			}
 			break;
@@ -1126,20 +1160,16 @@ blkio_print_policy_node(struct seq_file *m, struct blkio_policy_node *pn)
 }
 
 /* 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)
+static void blkio_read_conf(struct cftype *cft, struct blkio_cgroup *blkcg,
+			    struct seq_file *m)
 {
-	struct blkio_policy_node *pn;
-
-	if (!list_empty(&blkcg->policy_list)) {
-		spin_lock_irq(&blkcg->lock);
-		list_for_each_entry(pn, &blkcg->policy_list, node) {
-			if (!pn_matches_cftype(cft, pn))
-				continue;
-			blkio_print_policy_node(m, pn);
-		}
-		spin_unlock_irq(&blkcg->lock);
-	}
+	struct blkio_group *blkg;
+	struct hlist_node *n;
+
+	spin_lock_irq(&blkcg->lock);
+	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
+		blkio_print_group_conf(cft, blkg, m);
+	spin_unlock_irq(&blkcg->lock);
 }
 
 static int blkiocg_file_read(struct cgroup *cgrp, struct cftype *cft,
@@ -1155,7 +1185,7 @@ static int blkiocg_file_read(struct cgroup *cgrp, struct cftype *cft,
 	case BLKIO_POLICY_PROP:
 		switch(name) {
 		case BLKIO_PROP_weight_device:
-			blkio_read_policy_node_files(cft, blkcg, m);
+			blkio_read_conf(cft, blkcg, m);
 			return 0;
 		default:
 			BUG();
@@ -1167,7 +1197,7 @@ static int blkiocg_file_read(struct cgroup *cgrp, struct cftype *cft,
 		case BLKIO_THROTL_write_bps_device:
 		case BLKIO_THROTL_read_iops_device:
 		case BLKIO_THROTL_write_iops_device:
-			blkio_read_policy_node_files(cft, blkcg, m);
+			blkio_read_conf(cft, blkcg, m);
 			return 0;
 		default:
 			BUG();
@@ -1188,25 +1218,25 @@ static int blkio_read_blkg_stats(struct blkio_cgroup *blkcg,
 	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;
-			if (pcpu)
-				cgroup_total += blkio_get_stat_cpu(blkg, cb,
-						blkg->dev, type);
-			else {
-				spin_lock_irq(&blkg->stats_lock);
-				cgroup_total += blkio_get_stat(blkg, cb,
-						blkg->dev, type);
-				spin_unlock_irq(&blkg->stats_lock);
-			}
-		}
+	spin_lock_irq(&blkcg->lock);
+
+	hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
+		const char *dname = blkg_dev_name(blkg);
+		int plid = BLKIOFILE_POLICY(cft->private);
+
+		if (!dname)
+			continue;
+		if (pcpu)
+			cgroup_total += blkio_get_stat_cpu(blkg, plid,
+							   cb, dname, type);
+		else
+			cgroup_total += blkio_get_stat(blkg, plid,
+						       cb, dname, type);
 	}
 	if (show_total)
 		cb->fill(cb, "Total", cgroup_total);
-	rcu_read_unlock();
+
+	spin_unlock_irq(&blkcg->lock);
 	return 0;
 }
 
@@ -1243,7 +1273,7 @@ static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
 						BLKIO_STAT_WAIT_TIME, 1, 0);
 		case BLKIO_PROP_io_merged:
 			return blkio_read_blkg_stats(blkcg, cft, cb,
-						BLKIO_STAT_CPU_MERGED, 1, 1);
+						BLKIO_STAT_MERGED, 1, 0);
 		case BLKIO_PROP_io_queued:
 			return blkio_read_blkg_stats(blkcg, cft, cb,
 						BLKIO_STAT_QUEUED, 1, 0);
@@ -1290,11 +1320,10 @@ static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
 	return 0;
 }
 
-static int blkio_weight_write(struct blkio_cgroup *blkcg, u64 val)
+static int blkio_weight_write(struct blkio_cgroup *blkcg, int plid, 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;
@@ -1304,13 +1333,12 @@ static int blkio_weight_write(struct blkio_cgroup *blkcg, u64 val)
 	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_PROP_weight_device);
-		if (pn)
-			continue;
+		struct blkg_policy_data *pd = blkg->pd[plid];
 
-		blkio_update_group_weight(blkg, blkcg->weight);
+		if (!pd->conf.weight)
+			blkio_update_group_weight(blkg, plid, blkcg->weight);
 	}
+
 	spin_unlock_irq(&blkcg->lock);
 	spin_unlock(&blkio_list_lock);
 	return 0;
@@ -1349,7 +1377,7 @@ blkiocg_file_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
 	case BLKIO_POLICY_PROP:
 		switch(name) {
 		case BLKIO_PROP_weight:
-			return blkio_weight_write(blkcg, val);
+			return blkio_weight_write(blkcg, plid, val);
 		}
 		break;
 	default:
@@ -1518,58 +1546,53 @@ struct cftype blkio_files[] = {
 	{ }	/* terminate */
 };
 
-static void blkiocg_destroy(struct cgroup *cgroup)
+/**
+ * blkiocg_pre_destroy - cgroup pre_destroy callback
+ * @cgroup: cgroup of interest
+ *
+ * This function is called when @cgroup is about to go away and responsible
+ * for shooting down all blkgs associated with @cgroup.  blkgs should be
+ * removed while holding both q and blkcg locks.  As blkcg lock is nested
+ * inside q lock, this function performs reverse double lock dancing.
+ *
+ * This is the blkcg counterpart of ioc_release_fn().
+ */
+static int blkiocg_pre_destroy(struct cgroup *cgroup)
 {
 	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
-	unsigned long flags;
-	struct blkio_group *blkg;
-	void *key;
-	struct blkio_policy_type *blkiop;
-	struct blkio_policy_node *pn, *pntmp;
 
-	rcu_read_lock();
-	do {
-		spin_lock_irqsave(&blkcg->lock, flags);
+	spin_lock_irq(&blkcg->lock);
 
-		if (hlist_empty(&blkcg->blkg_list)) {
-			spin_unlock_irqrestore(&blkcg->lock, flags);
-			break;
+	while (!hlist_empty(&blkcg->blkg_list)) {
+		struct blkio_group *blkg = hlist_entry(blkcg->blkg_list.first,
+						struct blkio_group, blkcg_node);
+		struct request_queue *q = blkg->q;
+
+		if (spin_trylock(q->queue_lock)) {
+			blkg_destroy(blkg);
+			spin_unlock(q->queue_lock);
+		} else {
+			spin_unlock_irq(&blkcg->lock);
+			cpu_relax();
+			spin_lock_irq(&blkcg->lock);
 		}
+	}
 
-		blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
-					blkcg_node);
-		key = rcu_dereference(blkg->key);
-		__blkiocg_del_blkio_group(blkg);
-
-		spin_unlock_irqrestore(&blkcg->lock, flags);
-
-		/*
-		 * This blkio_group is being unlinked as associated cgroup is
-		 * going away. Let all the IO controlling policies know about
-		 * this event.
-		 */
-		spin_lock(&blkio_list_lock);
-		list_for_each_entry(blkiop, &blkio_list, list) {
-			if (blkiop->plid != blkg->plid)
-				continue;
-			blkiop->ops.blkio_unlink_group_fn(key, blkg);
-		}
-		spin_unlock(&blkio_list_lock);
-	} while (1);
+	spin_unlock_irq(&blkcg->lock);
+	return 0;
+}
 
-	list_for_each_entry_safe(pn, pntmp, &blkcg->policy_list, node) {
-		blkio_policy_delete_node(pn);
-		kfree(pn);
-	}
+static void blkiocg_destroy(struct cgroup *cgroup)
+{
+	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
 
-	free_css_id(&blkio_subsys, &blkcg->css);
-	rcu_read_unlock();
 	if (blkcg != &blkio_root_cgroup)
 		kfree(blkcg);
 }
 
 static struct cgroup_subsys_state *blkiocg_create(struct cgroup *cgroup)
 {
+	static atomic64_t id_seq = ATOMIC64_INIT(0);
 	struct blkio_cgroup *blkcg;
 	struct cgroup *parent = cgroup->parent;
 
@@ -1583,14 +1606,72 @@ static struct cgroup_subsys_state *blkiocg_create(struct cgroup *cgroup)
 		return ERR_PTR(-ENOMEM);
 
 	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
+	blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
 done:
 	spin_lock_init(&blkcg->lock);
 	INIT_HLIST_HEAD(&blkcg->blkg_list);
 
-	INIT_LIST_HEAD(&blkcg->policy_list);
 	return &blkcg->css;
 }
 
+/**
+ * blkcg_init_queue - initialize blkcg part of request queue
+ * @q: request_queue to initialize
+ *
+ * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
+ * part of new request_queue @q.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int blkcg_init_queue(struct request_queue *q)
+{
+	int ret;
+
+	might_sleep();
+
+	ret = blk_throtl_init(q);
+	if (ret)
+		return ret;
+
+	mutex_lock(&all_q_mutex);
+	INIT_LIST_HEAD(&q->all_q_node);
+	list_add_tail(&q->all_q_node, &all_q_list);
+	mutex_unlock(&all_q_mutex);
+
+	return 0;
+}
+
+/**
+ * blkcg_drain_queue - drain blkcg part of request_queue
+ * @q: request_queue to drain
+ *
+ * Called from blk_drain_queue().  Responsible for draining blkcg part.
+ */
+void blkcg_drain_queue(struct request_queue *q)
+{
+	lockdep_assert_held(q->queue_lock);
+
+	blk_throtl_drain(q);
+}
+
+/**
+ * blkcg_exit_queue - exit and release blkcg part of request_queue
+ * @q: request_queue being released
+ *
+ * Called from blk_release_queue().  Responsible for exiting blkcg part.
+ */
+void blkcg_exit_queue(struct request_queue *q)
+{
+	mutex_lock(&all_q_mutex);
+	list_del_init(&q->all_q_node);
+	mutex_unlock(&all_q_mutex);
+
+	blkg_destroy_all(q, true);
+
+	blk_throtl_exit(q);
+}
+
 /*
  * We cannot support shared io contexts, as we have no mean to support
  * two tasks with the same ioc in two different groups without major rework
@@ -1616,63 +1697,74 @@ static int blkiocg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 	return ret;
 }
 
-static void blkiocg_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
+static void blkcg_bypass_start(void)
+	__acquires(&all_q_mutex)
 {
-	struct task_struct *task;
-	struct io_context *ioc;
+	struct request_queue *q;
 
-	cgroup_taskset_for_each(task, cgrp, tset) {
-		/* we don't lose anything even if ioc allocation fails */
-		ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
-		if (ioc) {
-			ioc_cgroup_changed(ioc);
-			put_io_context(ioc);
-		}
+	mutex_lock(&all_q_mutex);
+
+	list_for_each_entry(q, &all_q_list, all_q_node) {
+		blk_queue_bypass_start(q);
+		blkg_destroy_all(q, false);
 	}
 }
 
+static void blkcg_bypass_end(void)
+	__releases(&all_q_mutex)
+{
+	struct request_queue *q;
+
+	list_for_each_entry(q, &all_q_list, all_q_node)
+		blk_queue_bypass_end(q);
+
+	mutex_unlock(&all_q_mutex);
+}
+
 struct cgroup_subsys blkio_subsys = {
 	.name = "blkio",
 	.create = blkiocg_create,
 	.can_attach = blkiocg_can_attach,
-	.attach = blkiocg_attach,
+	.pre_destroy = blkiocg_pre_destroy,
 	.destroy = blkiocg_destroy,
-#ifdef CONFIG_BLK_CGROUP
-	/* note: blkio_subsys_id is otherwise defined in blk-cgroup.h */
 	.subsys_id = blkio_subsys_id,
-#endif
 	.base_cftypes = blkio_files,
-	.use_id = 1,
 	.module = THIS_MODULE,
 };
 EXPORT_SYMBOL_GPL(blkio_subsys);
 
 void blkio_policy_register(struct blkio_policy_type *blkiop)
 {
+	struct request_queue *q;
+
+	blkcg_bypass_start();
 	spin_lock(&blkio_list_lock);
+
+	BUG_ON(blkio_policy[blkiop->plid]);
+	blkio_policy[blkiop->plid] = blkiop;
 	list_add_tail(&blkiop->list, &blkio_list);
+
 	spin_unlock(&blkio_list_lock);
+	list_for_each_entry(q, &all_q_list, all_q_node)
+		update_root_blkg_pd(q, blkiop->plid);
+	blkcg_bypass_end();
 }
 EXPORT_SYMBOL_GPL(blkio_policy_register);
 
 void blkio_policy_unregister(struct blkio_policy_type *blkiop)
 {
+	struct request_queue *q;
+
+	blkcg_bypass_start();
 	spin_lock(&blkio_list_lock);
+
+	BUG_ON(blkio_policy[blkiop->plid] != blkiop);
+	blkio_policy[blkiop->plid] = NULL;
 	list_del_init(&blkiop->list);
+
 	spin_unlock(&blkio_list_lock);
+	list_for_each_entry(q, &all_q_list, all_q_node)
+		update_root_blkg_pd(q, blkiop->plid);
+	blkcg_bypass_end();
 }
 EXPORT_SYMBOL_GPL(blkio_policy_unregister);
-
-static int __init init_cgroup_blkio(void)
-{
-	return cgroup_load_subsys(&blkio_subsys);
-}
-
-static void __exit exit_cgroup_blkio(void)
-{
-	cgroup_unload_subsys(&blkio_subsys);
-}
-
-module_init(init_cgroup_blkio);
-module_exit(exit_cgroup_blkio);
-MODULE_LICENSE("GPL");