Initial import

1 files changed, 4671 insertions, 0 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
new file mode 100644
index 000000000..5da8e6e9a
--- /dev/null
+++ b/block/cfq-iosched.c
@@ -0,0 +1,4671 @@
+/*
+ *  CFQ, or complete fairness queueing, disk scheduler.
+ *
+ *  Based on ideas from a previously unfinished io
+ *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
+ *
+ *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
+ */
+#include <linux/module.h>
+#include <linux/slab.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.h"
+#include "blk-cgroup.h"
+
+/*
+ * tunables
+ */
+/* max queue in one round of service */
+static const int cfq_quantum = 8;
+static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
+/* maximum backwards seek, in KiB */
+static const int cfq_back_max = 16 * 1024;
+/* penalty of a backwards seek */
+static const int cfq_back_penalty = 2;
+static const int cfq_slice_sync = HZ / 10;
+static int cfq_slice_async = HZ / 25;
+static const int cfq_slice_async_rq = 2;
+static int cfq_slice_idle = HZ / 125;
+static int cfq_group_idle = HZ / 125;
+static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
+static const int cfq_hist_divisor = 4;
+
+/*
+ * offset from end of service tree
+ */
+#define CFQ_IDLE_DELAY		(HZ / 5)
+
+/*
+ * below this threshold, we consider thinktime immediate
+ */
+#define CFQ_MIN_TT		(2)
+
+#define CFQ_SLICE_SCALE		(5)
+#define CFQ_HW_QUEUE_MIN	(5)
+#define CFQ_SERVICE_SHIFT       12
+
+#define CFQQ_SEEK_THR		(sector_t)(8 * 100)
+#define CFQQ_CLOSE_THR		(sector_t)(8 * 1024)
+#define CFQQ_SECT_THR_NONROT	(sector_t)(2 * 32)
+#define CFQQ_SEEKY(cfqq)	(hweight32(cfqq->seek_history) > 32/8)
+
+#define RQ_CIC(rq)		icq_to_cic((rq)->elv.icq)
+#define RQ_CFQQ(rq)		(struct cfq_queue *) ((rq)->elv.priv[0])
+#define RQ_CFQG(rq)		(struct cfq_group *) ((rq)->elv.priv[1])
+
+static struct kmem_cache *cfq_pool;
+
+#define CFQ_PRIO_LISTS		IOPRIO_BE_NR
+#define cfq_class_idle(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
+#define cfq_class_rt(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
+
+#define sample_valid(samples)	((samples) > 80)
+#define rb_entry_cfqg(node)	rb_entry((node), struct cfq_group, rb_node)
+
+struct cfq_ttime {
+	unsigned long last_end_request;
+
+	unsigned long ttime_total;
+	unsigned long ttime_samples;
+	unsigned long ttime_mean;
+};
+
+/*
+ * Most of our rbtree usage is for sorting with min extraction, so
+ * if we cache the leftmost node we don't have to walk down the tree
+ * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
+ * move this into the elevator for the rq sorting as well.
+ */
+struct cfq_rb_root {
+	struct rb_root rb;
+	struct rb_node *left;
+	unsigned count;
+	u64 min_vdisktime;
+	struct cfq_ttime ttime;
+};
+#define CFQ_RB_ROOT	(struct cfq_rb_root) { .rb = RB_ROOT, \
+			.ttime = {.last_end_request = jiffies,},}
+
+/*
+ * Per process-grouping structure
+ */
+struct cfq_queue {
+	/* reference count */
+	int ref;
+	/* various state flags, see below */
+	unsigned int flags;
+	/* parent cfq_data */
+	struct cfq_data *cfqd;
+	/* service_tree member */
+	struct rb_node rb_node;
+	/* service_tree key */
+	unsigned long rb_key;
+	/* prio tree member */
+	struct rb_node p_node;
+	/* prio tree root we belong to, if any */
+	struct rb_root *p_root;
+	/* sorted list of pending requests */
+	struct rb_root sort_list;
+	/* if fifo isn't expired, next request to serve */
+	struct request *next_rq;
+	/* requests queued in sort_list */
+	int queued[2];
+	/* currently allocated requests */
+	int allocated[2];
+	/* fifo list of requests in sort_list */
+	struct list_head fifo;
+
+	/* time when queue got scheduled in to dispatch first request. */
+	unsigned long dispatch_start;
+	unsigned int allocated_slice;
+	unsigned int slice_dispatch;
+	/* time when first request from queue completed and slice started. */
+	unsigned long slice_start;
+	unsigned long slice_end;
+	long slice_resid;
+
+	/* pending priority requests */
+	int prio_pending;
+	/* number of requests that are on the dispatch list or inside driver */
+	int dispatched;
+
+	/* io prio of this group */
+	unsigned short ioprio, org_ioprio;
+	unsigned short ioprio_class;
+
+	pid_t pid;
+
+	u32 seek_history;
+	sector_t last_request_pos;
+
+	struct cfq_rb_root *service_tree;
+	struct cfq_queue *new_cfqq;
+	struct cfq_group *cfqg;
+	/* Number of sectors dispatched from queue in single dispatch round */
+	unsigned long nr_sectors;
+};
+
+/*
+ * First index in the service_trees.
+ * IDLE is handled separately, so it has negative index
+ */
+enum wl_class_t {
+	BE_WORKLOAD = 0,
+	RT_WORKLOAD = 1,
+	IDLE_WORKLOAD = 2,
+	CFQ_PRIO_NR,
+};
+
+/*
+ * Second index in the service_trees.
+ */
+enum wl_type_t {
+	ASYNC_WORKLOAD = 0,
+	SYNC_NOIDLE_WORKLOAD = 1,
+	SYNC_WORKLOAD = 2
+};
+
+struct cfqg_stats {
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	/* 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;
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+	/* time not charged to this cgroup */
+	struct blkg_stat		unaccounted_time;
+	/* sum of number of ios queued across all samples */
+	struct blkg_stat		avg_queue_size_sum;
+	/* count of samples taken for average */
+	struct blkg_stat		avg_queue_size_samples;
+	/* how many times this group has been removed from service tree */
+	struct blkg_stat		dequeue;
+	/* total time spent waiting for it to be assigned a timeslice. */
+	struct blkg_stat		group_wait_time;
+	/* time spent idling for this blkcg_gq */
+	struct blkg_stat		idle_time;
+	/* total time with empty current active q with other requests queued */
+	struct blkg_stat		empty_time;
+	/* fields after this shouldn't be cleared on stat reset */
+	uint64_t			start_group_wait_time;
+	uint64_t			start_idle_time;
+	uint64_t			start_empty_time;
+	uint16_t			flags;
+#endif	/* CONFIG_DEBUG_BLK_CGROUP */
+#endif	/* CONFIG_CFQ_GROUP_IOSCHED */
+};
+
+/* This is per cgroup per device grouping structure */
+struct cfq_group {
+	/* must be the first member */
+	struct blkg_policy_data pd;
+
+	/* group service_tree member */
+	struct rb_node rb_node;
+
+	/* group service_tree key */
+	u64 vdisktime;
+
+	/*
+	 * The number of active cfqgs and sum of their weights under this
+	 * cfqg.  This covers this cfqg's leaf_weight and all children's
+	 * weights, but does not cover weights of further descendants.
+	 *
+	 * If a cfqg is on the service tree, it's active.  An active cfqg
+	 * also activates its parent and contributes to the children_weight
+	 * of the parent.
+	 */
+	int nr_active;
+	unsigned int children_weight;
+
+	/*
+	 * vfraction is the fraction of vdisktime that the tasks in this
+	 * cfqg are entitled to.  This is determined by compounding the
+	 * ratios walking up from this cfqg to the root.
+	 *
+	 * It is in fixed point w/ CFQ_SERVICE_SHIFT and the sum of all
+	 * vfractions on a service tree is approximately 1.  The sum may
+	 * deviate a bit due to rounding errors and fluctuations caused by
+	 * cfqgs entering and leaving the service tree.
+	 */
+	unsigned int vfraction;
+
+	/*
+	 * There are two weights - (internal) weight is the weight of this
+	 * cfqg against the sibling cfqgs.  leaf_weight is the wight of
+	 * this cfqg against the child cfqgs.  For the root cfqg, both
+	 * weights are kept in sync for backward compatibility.
+	 */
+	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;
+
+	/* number of cfqq currently on this group */
+	int nr_cfqq;
+
+	/*
+	 * Per group busy queues average. Useful for workload slice calc. We
+	 * create the array for each prio class but at run time it is used
+	 * only for RT and BE class and slot for IDLE class remains unused.
+	 * This is primarily done to avoid confusion and a gcc warning.
+	 */
+	unsigned int busy_queues_avg[CFQ_PRIO_NR];
+	/*
+	 * rr lists of queues with requests. We maintain service trees for
+	 * RT and BE classes. These trees are subdivided in subclasses
+	 * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
+	 * class there is no subclassification and all the cfq queues go on
+	 * a single tree service_tree_idle.
+	 * Counts are embedded in the cfq_rb_root
+	 */
+	struct cfq_rb_root service_trees[2][3];
+	struct cfq_rb_root service_tree_idle;
+
+	unsigned long saved_wl_slice;
+	enum wl_type_t saved_wl_type;
+	enum wl_class_t saved_wl_class;
+
+	/* number of requests that are on the dispatch list or inside driver */
+	int dispatched;
+	struct cfq_ttime ttime;
+	struct cfqg_stats stats;	/* stats for this cfqg */
+	struct cfqg_stats dead_stats;	/* stats pushed from dead children */
+};
+
+struct cfq_io_cq {
+	struct io_cq		icq;		/* must be the first member */
+	struct cfq_queue	*cfqq[2];
+	struct cfq_ttime	ttime;
+	int			ioprio;		/* the current ioprio */
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	uint64_t		blkcg_serial_nr; /* the current blkcg serial */
+#endif
+};
+
+/*
+ * Per block device queue structure
+ */
+struct cfq_data {
+	struct request_queue *queue;
+	/* Root service tree for cfq_groups */
+	struct cfq_rb_root grp_service_tree;
+	struct cfq_group *root_group;
+
+	/*
+	 * The priority currently being served
+	 */
+	enum wl_class_t serving_wl_class;
+	enum wl_type_t serving_wl_type;
+	unsigned long workload_expires;
+	struct cfq_group *serving_group;
+
+	/*
+	 * Each priority tree is sorted by next_request position.  These
+	 * trees are used when determining if two or more queues are
+	 * interleaving requests (see cfq_close_cooperator).
+	 */
+	struct rb_root prio_trees[CFQ_PRIO_LISTS];
+
+	unsigned int busy_queues;
+	unsigned int busy_sync_queues;
+
+	int rq_in_driver;
+	int rq_in_flight[2];
+
+	/*
+	 * queue-depth detection
+	 */
+	int rq_queued;
+	int hw_tag;
+	/*
+	 * hw_tag can be
+	 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
+	 *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
+	 *  0 => no NCQ
+	 */
+	int hw_tag_est_depth;
+	unsigned int hw_tag_samples;
+
+	/*
+	 * idle window management
+	 */
+	struct timer_list idle_slice_timer;
+	struct work_struct unplug_work;
+
+	struct cfq_queue *active_queue;
+	struct cfq_io_cq *active_cic;
+
+	/*
+	 * async queue for each priority case
+	 */
+	struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
+	struct cfq_queue *async_idle_cfqq;
+
+	sector_t last_position;
+
+	/*
+	 * tunables, see top of file
+	 */
+	unsigned int cfq_quantum;
+	unsigned int cfq_fifo_expire[2];
+	unsigned int cfq_back_penalty;
+	unsigned int cfq_back_max;
+	unsigned int cfq_slice[2];
+	unsigned int cfq_slice_async_rq;
+	unsigned int cfq_slice_idle;
+	unsigned int cfq_group_idle;
+	unsigned int cfq_latency;
+	unsigned int cfq_target_latency;
+
+	/*
+	 * Fallback dummy cfqq for extreme OOM conditions
+	 */
+	struct cfq_queue oom_cfqq;
+
+	unsigned long last_delayed_sync;
+};
+
+static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
+
+static struct cfq_rb_root *st_for(struct cfq_group *cfqg,
+					    enum wl_class_t class,
+					    enum wl_type_t type)
+{
+	if (!cfqg)
+		return NULL;
+
+	if (class == IDLE_WORKLOAD)
+		return &cfqg->service_tree_idle;
+
+	return &cfqg->service_trees[class][type];
+}
+
+enum cfqq_state_flags {
+	CFQ_CFQQ_FLAG_on_rr = 0,	/* on round-robin busy list */
+	CFQ_CFQQ_FLAG_wait_request,	/* waiting for a request */
+	CFQ_CFQQ_FLAG_must_dispatch,	/* must be allowed a dispatch */
+	CFQ_CFQQ_FLAG_must_alloc_slice,	/* per-slice must_alloc flag */
+	CFQ_CFQQ_FLAG_fifo_expire,	/* FIFO checked in this slice */
+	CFQ_CFQQ_FLAG_idle_window,	/* slice idling enabled */
+	CFQ_CFQQ_FLAG_prio_changed,	/* task priority has changed */
+	CFQ_CFQQ_FLAG_slice_new,	/* no requests dispatched in slice */
+	CFQ_CFQQ_FLAG_sync,		/* synchronous queue */
+	CFQ_CFQQ_FLAG_coop,		/* cfqq is shared */
+	CFQ_CFQQ_FLAG_split_coop,	/* shared cfqq will be splitted */
+	CFQ_CFQQ_FLAG_deep,		/* sync cfqq experienced large depth */
+	CFQ_CFQQ_FLAG_wait_busy,	/* Waiting for next request */
+};
+
+#define CFQ_CFQQ_FNS(name)						\
+static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)		\
+{									\
+	(cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);			\
+}									\
+static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)	\
+{									\
+	(cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);			\
+}									\
+static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)		\
+{									\
+	return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;	\
+}
+
+CFQ_CFQQ_FNS(on_rr);
+CFQ_CFQQ_FNS(wait_request);
+CFQ_CFQQ_FNS(must_dispatch);
+CFQ_CFQQ_FNS(must_alloc_slice);
+CFQ_CFQQ_FNS(fifo_expire);
+CFQ_CFQQ_FNS(idle_window);
+CFQ_CFQQ_FNS(prio_changed);
+CFQ_CFQQ_FNS(slice_new);
+CFQ_CFQQ_FNS(sync);
+CFQ_CFQQ_FNS(coop);
+CFQ_CFQQ_FNS(split_coop);
+CFQ_CFQQ_FNS(deep);
+CFQ_CFQQ_FNS(wait_busy);
+#undef CFQ_CFQQ_FNS
+
+static inline struct cfq_group *pd_to_cfqg(struct blkg_policy_data *pd)
+{
+	return pd ? container_of(pd, struct cfq_group, pd) : NULL;
+}
+
+static inline struct blkcg_gq *cfqg_to_blkg(struct cfq_group *cfqg)
+{
+	return pd_to_blkg(&cfqg->pd);
+}
+
+#if defined(CONFIG_CFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
+
+/* cfqg stats flags */
+enum cfqg_stats_flags {
+	CFQG_stats_waiting = 0,
+	CFQG_stats_idling,
+	CFQG_stats_empty,
+};
+
+#define CFQG_FLAG_FNS(name)						\
+static inline void cfqg_stats_mark_##name(struct cfqg_stats *stats)	\
+{									\
+	stats->flags |= (1 << CFQG_stats_##name);			\
+}									\
+static inline void cfqg_stats_clear_##name(struct cfqg_stats *stats)	\
+{									\
+	stats->flags &= ~(1 << CFQG_stats_##name);			\
+}									\
+static inline int cfqg_stats_##name(struct cfqg_stats *stats)		\
+{									\
+	return (stats->flags & (1 << CFQG_stats_##name)) != 0;		\
+}									\
+
+CFQG_FLAG_FNS(waiting)
+CFQG_FLAG_FNS(idling)
+CFQG_FLAG_FNS(empty)
+#undef CFQG_FLAG_FNS
+
+/* This should be called with the queue_lock held. */
+static void cfqg_stats_update_group_wait_time(struct cfqg_stats *stats)
+{
+	unsigned long long now;
+
+	if (!cfqg_stats_waiting(stats))
+		return;
+
+	now = sched_clock();
+	if (time_after64(now, stats->start_group_wait_time))
+		blkg_stat_add(&stats->group_wait_time,
+			      now - stats->start_group_wait_time);
+	cfqg_stats_clear_waiting(stats);
+}
+
+/* This should be called with the queue_lock held. */
+static void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg,
+						 struct cfq_group *curr_cfqg)
+{
+	struct cfqg_stats *stats = &cfqg->stats;
+
+	if (cfqg_stats_waiting(stats))
+		return;
+	if (cfqg == curr_cfqg)
+		return;
+	stats->start_group_wait_time = sched_clock();
+	cfqg_stats_mark_waiting(stats);
+}
+
+/* This should be called with the queue_lock held. */
+static void cfqg_stats_end_empty_time(struct cfqg_stats *stats)
+{
+	unsigned long long now;
+
+	if (!cfqg_stats_empty(stats))
+		return;
+
+	now = sched_clock();
+	if (time_after64(now, stats->start_empty_time))
+		blkg_stat_add(&stats->empty_time,
+			      now - stats->start_empty_time);
+	cfqg_stats_clear_empty(stats);
+}
+
+static void cfqg_stats_update_dequeue(struct cfq_group *cfqg)
+{
+	blkg_stat_add(&cfqg->stats.dequeue, 1);
+}
+
+static void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg)
+{
+	struct cfqg_stats *stats = &cfqg->stats;
+
+	if (blkg_rwstat_total(&stats->queued))
+		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 (cfqg_stats_empty(stats))
+		return;
+
+	stats->start_empty_time = sched_clock();
+	cfqg_stats_mark_empty(stats);
+}
+
+static void cfqg_stats_update_idle_time(struct cfq_group *cfqg)
+{
+	struct cfqg_stats *stats = &cfqg->stats;
+
+	if (cfqg_stats_idling(stats)) {
+		unsigned long long now = sched_clock();
+
+		if (time_after64(now, stats->start_idle_time))
+			blkg_stat_add(&stats->idle_time,
+				      now - stats->start_idle_time);
+		cfqg_stats_clear_idling(stats);
+	}
+}
+
+static void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg)
+{
+	struct cfqg_stats *stats = &cfqg->stats;
+
+	BUG_ON(cfqg_stats_idling(stats));
+
+	stats->start_idle_time = sched_clock();
+	cfqg_stats_mark_idling(stats);
+}
+
+static void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg)
+{
+	struct cfqg_stats *stats = &cfqg->stats;
+
+	blkg_stat_add(&stats->avg_queue_size_sum,
+		      blkg_rwstat_total(&stats->queued));
+	blkg_stat_add(&stats->avg_queue_size_samples, 1);
+	cfqg_stats_update_group_wait_time(stats);
+}
+
+#else	/* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
+
+static inline void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg, struct cfq_group *curr_cfqg) { }
+static inline void cfqg_stats_end_empty_time(struct cfqg_stats *stats) { }
+static inline void cfqg_stats_update_dequeue(struct cfq_group *cfqg) { }
+static inline void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg) { }
+static inline void cfqg_stats_update_idle_time(struct cfq_group *cfqg) { }
+static inline void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg) { }
+static inline void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg) { }
+
+#endif	/* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+
+static struct blkcg_policy blkcg_policy_cfq;
+
+static inline struct cfq_group *blkg_to_cfqg(struct blkcg_gq *blkg)
+{
+	return pd_to_cfqg(blkg_to_pd(blkg, &blkcg_policy_cfq));
+}
+
+static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg)
+{
+	struct blkcg_gq *pblkg = cfqg_to_blkg(cfqg)->parent;
+
+	return pblkg ? blkg_to_cfqg(pblkg) : NULL;
+}
+
+static inline void cfqg_get(struct cfq_group *cfqg)
+{
+	return blkg_get(cfqg_to_blkg(cfqg));
+}
+
+static inline void cfqg_put(struct cfq_group *cfqg)
+{
+	return blkg_put(cfqg_to_blkg(cfqg));
+}
+
+#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)	do {			\
+	char __pbuf[128];						\
+									\
+	blkg_path(cfqg_to_blkg((cfqq)->cfqg), __pbuf, sizeof(__pbuf));	\
+	blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c %s " fmt, (cfqq)->pid, \
+			cfq_cfqq_sync((cfqq)) ? 'S' : 'A',		\
+			cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
+			  __pbuf, ##args);				\
+} while (0)
+
+#define cfq_log_cfqg(cfqd, cfqg, fmt, args...)	do {			\
+	char __pbuf[128];						\
+									\
+	blkg_path(cfqg_to_blkg(cfqg), __pbuf, sizeof(__pbuf));		\
+	blk_add_trace_msg((cfqd)->queue, "%s " fmt, __pbuf, ##args);	\
+} while (0)
+
+static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
+					    struct cfq_group *curr_cfqg, int rw)
+{
+	blkg_rwstat_add(&cfqg->stats.queued, rw, 1);
+	cfqg_stats_end_empty_time(&cfqg->stats);
+	cfqg_stats_set_start_group_wait_time(cfqg, curr_cfqg);
+}
+
+static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
+			unsigned long time, unsigned long unaccounted_time)
+{
+	blkg_stat_add(&cfqg->stats.time, time);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+	blkg_stat_add(&cfqg->stats.unaccounted_time, unaccounted_time);
+#endif
+}
+
+static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw)
+{
+	blkg_rwstat_add(&cfqg->stats.queued, rw, -1);
+}
+
+static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw)
+{
+	blkg_rwstat_add(&cfqg->stats.merged, rw, 1);
+}
+
+static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
+					      uint64_t bytes, int rw)
+{
+	blkg_stat_add(&cfqg->stats.sectors, bytes >> 9);
+	blkg_rwstat_add(&cfqg->stats.serviced, rw, 1);
+	blkg_rwstat_add(&cfqg->stats.service_bytes, rw, bytes);
+}
+
+static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
+			uint64_t start_time, uint64_t io_start_time, int rw)
+{
+	struct cfqg_stats *stats = &cfqg->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);
+}
+
+/* @stats = 0 */
+static void cfqg_stats_reset(struct cfqg_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 cfqg_stats_merge(struct cfqg_stats *to, struct cfqg_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
+}
+
+/*
+ * Transfer @cfqg's stats to its parent's dead_stats so that the ancestors'
+ * recursive stats can still account for the amount used by this cfqg after
+ * it's gone.
+ */
+static void cfqg_stats_xfer_dead(struct cfq_group *cfqg)
+{
+	struct cfq_group *parent = cfqg_parent(cfqg);
+
+	lockdep_assert_held(cfqg_to_blkg(cfqg)->q->queue_lock);
+
+	if (unlikely(!parent))
+		return;
+
+	cfqg_stats_merge(&parent->dead_stats, &cfqg->stats);
+	cfqg_stats_merge(&parent->dead_stats, &cfqg->dead_stats);
+	cfqg_stats_reset(&cfqg->stats);
+	cfqg_stats_reset(&cfqg->dead_stats);
+}
+
+#else	/* CONFIG_CFQ_GROUP_IOSCHED */
+
+static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg) { return NULL; }
+static inline void cfqg_get(struct cfq_group *cfqg) { }
+static inline void cfqg_put(struct cfq_group *cfqg) { }
+
+#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)	\
+	blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c " fmt, (cfqq)->pid,	\
+			cfq_cfqq_sync((cfqq)) ? 'S' : 'A',		\
+			cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
+				##args)
+#define cfq_log_cfqg(cfqd, cfqg, fmt, args...)		do {} while (0)
+
+static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
+			struct cfq_group *curr_cfqg, int rw) { }
+static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
+			unsigned long time, unsigned long unaccounted_time) { }
+static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw) { }
+static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw) { }
+static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
+					      uint64_t bytes, int rw) { }
+static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
+			uint64_t start_time, uint64_t io_start_time, int rw) { }
+
+#endif	/* CONFIG_CFQ_GROUP_IOSCHED */
+
+#define cfq_log(cfqd, fmt, args...)	\
+	blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
+
+/* Traverses through cfq group service trees */
+#define for_each_cfqg_st(cfqg, i, j, st) \
+	for (i = 0; i <= IDLE_WORKLOAD; i++) \
+		for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
+			: &cfqg->service_tree_idle; \
+			(i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
+			(i == IDLE_WORKLOAD && j == 0); \
+			j++, st = i < IDLE_WORKLOAD ? \
+			&cfqg->service_trees[i][j]: NULL) \
+
+static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
+	struct cfq_ttime *ttime, bool group_idle)
+{
+	unsigned long slice;
+	if (!sample_valid(ttime->ttime_samples))
+		return false;
+	if (group_idle)
+		slice = cfqd->cfq_group_idle;
+	else
+		slice = cfqd->cfq_slice_idle;
+	return ttime->ttime_mean > slice;
+}
+
+static inline bool iops_mode(struct cfq_data *cfqd)
+{
+	/*
+	 * If we are not idling on queues and it is a NCQ drive, parallel
+	 * execution of requests is on and measuring time is not possible
+	 * in most of the cases until and unless we drive shallower queue
+	 * depths and that becomes a performance bottleneck. In such cases
+	 * switch to start providing fairness in terms of number of IOs.
+	 */
+	if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
+		return true;
+	else
+		return false;
+}
+
+static inline enum wl_class_t cfqq_class(struct cfq_queue *cfqq)
+{
+	if (cfq_class_idle(cfqq))
+		return IDLE_WORKLOAD;
+	if (cfq_class_rt(cfqq))
+		return RT_WORKLOAD;
+	return BE_WORKLOAD;
+}
+
+
+static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
+{
+	if (!cfq_cfqq_sync(cfqq))
+		return ASYNC_WORKLOAD;
+	if (!cfq_cfqq_idle_window(cfqq))
+		return SYNC_NOIDLE_WORKLOAD;
+	return SYNC_WORKLOAD;
+}
+
+static inline int cfq_group_busy_queues_wl(enum wl_class_t wl_class,
+					struct cfq_data *cfqd,
+					struct cfq_group *cfqg)
+{
+	if (wl_class == IDLE_WORKLOAD)
+		return cfqg->service_tree_idle.count;
+
+	return cfqg->service_trees[wl_class][ASYNC_WORKLOAD].count +
+		cfqg->service_trees[wl_class][SYNC_NOIDLE_WORKLOAD].count +
+		cfqg->service_trees[wl_class][SYNC_WORKLOAD].count;
+}
+
+static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
+					struct cfq_group *cfqg)
+{
+	return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count +
+		cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
+}
+
+static void cfq_dispatch_insert(struct request_queue *, struct request *);
+static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, bool is_sync,
+				       struct cfq_io_cq *cic, struct bio *bio,
+				       gfp_t gfp_mask);
+
+static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)
+{
+	/* cic->icq is the first member, %NULL will convert to %NULL */
+	return container_of(icq, struct cfq_io_cq, icq);
+}
+
+static inline struct cfq_io_cq *cfq_cic_lookup(struct cfq_data *cfqd,
+					       struct io_context *ioc)
+{
+	if (ioc)
+		return icq_to_cic(ioc_lookup_icq(ioc, cfqd->queue));
+	return NULL;
+}
+
+static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_cq *cic, bool is_sync)
+{
+	return cic->cfqq[is_sync];
+}
+
+static inline void cic_set_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq,
+				bool is_sync)
+{
+	cic->cfqq[is_sync] = cfqq;
+}
+
+static inline struct cfq_data *cic_to_cfqd(struct cfq_io_cq *cic)
+{
+	return cic->icq.q->elevator->elevator_data;
+}
+
+/*
+ * We regard a request as SYNC, if it's either a read or has the SYNC bit
+ * set (in which case it could also be direct WRITE).
+ */
+static inline bool cfq_bio_sync(struct bio *bio)
+{
+	return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
+}
+
+/*
+ * scheduler run of queue, if there are requests pending and no one in the
+ * driver that will restart queueing
+ */
+static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
+{
+	if (cfqd->busy_queues) {
+		cfq_log(cfqd, "schedule dispatch");
+		kblockd_schedule_work(&cfqd->unplug_work);
+	}
+}
+
+/*
+ * Scale schedule slice based on io priority. Use the sync time slice only
+ * if a queue is marked sync and has sync io queued. A sync queue with async
+ * io only, should not get full sync slice length.
+ */
+static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
+				 unsigned short prio)
+{
+	const int base_slice = cfqd->cfq_slice[sync];
+
+	WARN_ON(prio >= IOPRIO_BE_NR);
+
+	return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
+}
+
+static inline int
+cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
+}
+
+/**
+ * cfqg_scale_charge - scale disk time charge according to cfqg weight
+ * @charge: disk time being charged
+ * @vfraction: vfraction of the cfqg, fixed point w/ CFQ_SERVICE_SHIFT
+ *
+ * Scale @charge according to @vfraction, which is in range (0, 1].  The
+ * scaling is inversely proportional.
+ *
+ * scaled = charge / vfraction
+ *
+ * The result is also in fixed point w/ CFQ_SERVICE_SHIFT.
+ */
+static inline u64 cfqg_scale_charge(unsigned long charge,
+				    unsigned int vfraction)
+{
+	u64 c = charge << CFQ_SERVICE_SHIFT;	/* make it fixed point */
+
+	/* charge / vfraction */
+	c <<= CFQ_SERVICE_SHIFT;
+	do_div(c, vfraction);
+	return c;
+}
+
+static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
+{
+	s64 delta = (s64)(vdisktime - min_vdisktime);
+	if (delta > 0)
+		min_vdisktime = vdisktime;
+
+	return min_vdisktime;
+}
+
+static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
+{
+	s64 delta = (s64)(vdisktime - min_vdisktime);
+	if (delta < 0)
+		min_vdisktime = vdisktime;
+
+	return min_vdisktime;
+}
+
+static void update_min_vdisktime(struct cfq_rb_root *st)
+{
+	struct cfq_group *cfqg;
+
+	if (st->left) {
+		cfqg = rb_entry_cfqg(st->left);
+		st->min_vdisktime = max_vdisktime(st->min_vdisktime,
+						  cfqg->vdisktime);
+	}
+}
+
+/*
+ * get averaged number of queues of RT/BE priority.
+ * average is updated, with a formula that gives more weight to higher numbers,
+ * to quickly follows sudden increases and decrease slowly
+ */
+
+static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
+					struct cfq_group *cfqg, bool rt)
+{
+	unsigned min_q, max_q;
+	unsigned mult  = cfq_hist_divisor - 1;
+	unsigned round = cfq_hist_divisor / 2;
+	unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
+
+	min_q = min(cfqg->busy_queues_avg[rt], busy);
+	max_q = max(cfqg->busy_queues_avg[rt], busy);
+	cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
+		cfq_hist_divisor;
+	return cfqg->busy_queues_avg[rt];
+}
+
+static inline unsigned
+cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
+{
+	return cfqd->cfq_target_latency * cfqg->vfraction >> CFQ_SERVICE_SHIFT;
+}
+
+static inline unsigned
+cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
+	if (cfqd->cfq_latency) {
+		/*
+		 * interested queues (we consider only the ones with the same
+		 * priority class in the cfq group)
+		 */
+		unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
+						cfq_class_rt(cfqq));
+		unsigned sync_slice = cfqd->cfq_slice[1];
+		unsigned expect_latency = sync_slice * iq;
+		unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
+
+		if (expect_latency > group_slice) {
+			unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
+			/* scale low_slice according to IO priority
+			 * and sync vs async */
+			unsigned low_slice =
+				min(slice, base_low_slice * slice / sync_slice);
+			/* the adapted slice value is scaled to fit all iqs
+			 * into the target latency */
+			slice = max(slice * group_slice / expect_latency,
+				    low_slice);
+		}
+	}
+	return slice;
+}
+
+static inline void
+cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
+
+	cfqq->slice_start = jiffies;
+	cfqq->slice_end = jiffies + slice;
+	cfqq->allocated_slice = slice;
+	cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
+}
+
+/*
+ * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
+ * isn't valid until the first request from the dispatch is activated
+ * and the slice time set.
+ */
+static inline bool cfq_slice_used(struct cfq_queue *cfqq)
+{
+	if (cfq_cfqq_slice_new(cfqq))
+		return false;
+	if (time_before(jiffies, cfqq->slice_end))
+		return false;
+
+	return true;
+}
+
+/*
+ * Lifted from AS - choose which of rq1 and rq2 that is best served now.
+ * We choose the request that is closest to the head right now. Distance
+ * behind the head is penalized and only allowed to a certain extent.
+ */
+static struct request *
+cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
+{
+	sector_t s1, s2, d1 = 0, d2 = 0;
+	unsigned long back_max;
+#define CFQ_RQ1_WRAP	0x01 /* request 1 wraps */
+#define CFQ_RQ2_WRAP	0x02 /* request 2 wraps */
+	unsigned wrap = 0; /* bit mask: requests behind the disk head? */
+
+	if (rq1 == NULL || rq1 == rq2)
+		return rq2;
+	if (rq2 == NULL)
+		return rq1;
+
+	if (rq_is_sync(rq1) != rq_is_sync(rq2))
+		return rq_is_sync(rq1) ? rq1 : rq2;
+
+	if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_PRIO)
+		return rq1->cmd_flags & REQ_PRIO ? rq1 : rq2;
+
+	s1 = blk_rq_pos(rq1);
+	s2 = blk_rq_pos(rq2);
+
+	/*
+	 * by definition, 1KiB is 2 sectors
+	 */
+	back_max = cfqd->cfq_back_max * 2;
+
+	/*
+	 * Strict one way elevator _except_ in the case where we allow
+	 * short backward seeks which are biased as twice the cost of a
+	 * similar forward seek.
+	 */
+	if (s1 >= last)
+		d1 = s1 - last;
+	else if (s1 + back_max >= last)
+		d1 = (last - s1) * cfqd->cfq_back_penalty;
+	else
+		wrap |= CFQ_RQ1_WRAP;
+
+	if (s2 >= last)
+		d2 = s2 - last;
+	else if (s2 + back_max >= last)
+		d2 = (last - s2) * cfqd->cfq_back_penalty;
+	else
+		wrap |= CFQ_RQ2_WRAP;
+
+	/* Found required data */
+
+	/*
+	 * By doing switch() on the bit mask "wrap" we avoid having to
+	 * check two variables for all permutations: --> faster!
+	 */
+	switch (wrap) {
+	case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
+		if (d1 < d2)
+			return rq1;
+		else if (d2 < d1)
+			return rq2;
+		else {
+			if (s1 >= s2)
+				return rq1;
+			else
+				return rq2;
+		}
+
+	case CFQ_RQ2_WRAP:
+		return rq1;
+	case CFQ_RQ1_WRAP:
+		return rq2;
+	case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
+	default:
+		/*
+		 * Since both rqs are wrapped,
+		 * start with the one that's further behind head
+		 * (--> only *one* back seek required),
+		 * since back seek takes more time than forward.
+		 */
+		if (s1 <= s2)
+			return rq1;
+		else
+			return rq2;
+	}
+}
+
+/*
+ * The below is leftmost cache rbtree addon
+ */
+static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
+{
+	/* Service tree is empty */
+	if (!root->count)
+		return NULL;
+
+	if (!root->left)
+		root->left = rb_first(&root->rb);
+
+	if (root->left)
+		return rb_entry(root->left, struct cfq_queue, rb_node);
+
+	return NULL;
+}
+
+static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
+{
+	if (!root->left)
+		root->left = rb_first(&root->rb);
+
+	if (root->left)
+		return rb_entry_cfqg(root->left);
+
+	return NULL;
+}
+
+static void rb_erase_init(struct rb_node *n, struct rb_root *root)
+{
+	rb_erase(n, root);
+	RB_CLEAR_NODE(n);
+}
+
+static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
+{
+	if (root->left == n)
+		root->left = NULL;
+	rb_erase_init(n, &root->rb);
+	--root->count;
+}
+
+/*
+ * would be nice to take fifo expire time into account as well
+ */
+static struct request *
+cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		  struct request *last)
+{
+	struct rb_node *rbnext = rb_next(&last->rb_node);
+	struct rb_node *rbprev = rb_prev(&last->rb_node);
+	struct request *next = NULL, *prev = NULL;
+
+	BUG_ON(RB_EMPTY_NODE(&last->rb_node));
+
+	if (rbprev)
+		prev = rb_entry_rq(rbprev);
+
+	if (rbnext)
+		next = rb_entry_rq(rbnext);
+	else {
+		rbnext = rb_first(&cfqq->sort_list);
+		if (rbnext && rbnext != &last->rb_node)
+			next = rb_entry_rq(rbnext);
+	}
+
+	return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
+}
+
+static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
+				      struct cfq_queue *cfqq)
+{
+	/*
+	 * just an approximation, should be ok.
+	 */
+	return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
+		       cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
+}
+
+static inline s64
+cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+	return cfqg->vdisktime - st->min_vdisktime;
+}
+
+static void
+__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+	struct rb_node **node = &st->rb.rb_node;
+	struct rb_node *parent = NULL;
+	struct cfq_group *__cfqg;
+	s64 key = cfqg_key(st, cfqg);
+	int left = 1;
+
+	while (*node != NULL) {
+		parent = *node;
+		__cfqg = rb_entry_cfqg(parent);
+
+		if (key < cfqg_key(st, __cfqg))
+			node = &parent->rb_left;
+		else {
+			node = &parent->rb_right;
+			left = 0;
+		}
+	}
+
+	if (left)
+		st->left = &cfqg->rb_node;
+
+	rb_link_node(&cfqg->rb_node, parent, node);
+	rb_insert_color(&cfqg->rb_node, &st->rb);
+}
+
+/*
+ * This has to be called only on activation of cfqg
+ */
+static void
+cfq_update_group_weight(struct cfq_group *cfqg)
+{
+	if (cfqg->new_weight) {
+		cfqg->weight = cfqg->new_weight;
+		cfqg->new_weight = 0;
+	}
+}
+
+static void
+cfq_update_group_leaf_weight(struct cfq_group *cfqg)
+{
+	BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
+
+	if (cfqg->new_leaf_weight) {
+		cfqg->leaf_weight = cfqg->new_leaf_weight;
+		cfqg->new_leaf_weight = 0;
+	}
+}
+
+static void
+cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+	unsigned int vfr = 1 << CFQ_SERVICE_SHIFT;	/* start with 1 */
+	struct cfq_group *pos = cfqg;
+	struct cfq_group *parent;
+	bool propagate;
+
+	/* add to the service tree */
+	BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
+
+	/*
+	 * Update leaf_weight.  We cannot update weight at this point
+	 * because cfqg might already have been activated and is
+	 * contributing its current weight to the parent's child_weight.
+	 */
+	cfq_update_group_leaf_weight(cfqg);
+	__cfq_group_service_tree_add(st, cfqg);
+
+	/*
+	 * Activate @cfqg and calculate the portion of vfraction @cfqg is
+	 * entitled to.  vfraction is calculated by walking the tree
+	 * towards the root calculating the fraction it has at each level.
+	 * The compounded ratio is how much vfraction @cfqg owns.
+	 *
+	 * Start with the proportion tasks in this cfqg has against active
+	 * children cfqgs - its leaf_weight against children_weight.
+	 */
+	propagate = !pos->nr_active++;
+	pos->children_weight += pos->leaf_weight;
+	vfr = vfr * pos->leaf_weight / pos->children_weight;
+
+	/*
+	 * Compound ->weight walking up the tree.  Both activation and
+	 * vfraction calculation are done in the same loop.  Propagation
+	 * stops once an already activated node is met.  vfraction
+	 * calculation should always continue to the root.
+	 */
+	while ((parent = cfqg_parent(pos))) {
+		if (propagate) {
+			cfq_update_group_weight(pos);
+			propagate = !parent->nr_active++;
+			parent->children_weight += pos->weight;
+		}
+		vfr = vfr * pos->weight / parent->children_weight;
+		pos = parent;
+	}
+
+	cfqg->vfraction = max_t(unsigned, vfr, 1);
+}
+
+static void
+cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
+{
+	struct cfq_rb_root *st = &cfqd->grp_service_tree;
+	struct cfq_group *__cfqg;
+	struct rb_node *n;
+
+	cfqg->nr_cfqq++;
+	if (!RB_EMPTY_NODE(&cfqg->rb_node))
+		return;
+
+	/*
+	 * Currently put the group at the end. Later implement something
+	 * so that groups get lesser vtime based on their weights, so that
+	 * if group does not loose all if it was not continuously backlogged.
+	 */
+	n = rb_last(&st->rb);
+	if (n) {
+		__cfqg = rb_entry_cfqg(n);
+		cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
+	} else
+		cfqg->vdisktime = st->min_vdisktime;
+	cfq_group_service_tree_add(st, cfqg);
+}
+
+static void
+cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+	struct cfq_group *pos = cfqg;
+	bool propagate;
+
+	/*
+	 * Undo activation from cfq_group_service_tree_add().  Deactivate
+	 * @cfqg and propagate deactivation upwards.
+	 */
+	propagate = !--pos->nr_active;
+	pos->children_weight -= pos->leaf_weight;
+
+	while (propagate) {
+		struct cfq_group *parent = cfqg_parent(pos);
+
+		/* @pos has 0 nr_active at this point */
+		WARN_ON_ONCE(pos->children_weight);
+		pos->vfraction = 0;
+
+		if (!parent)
+			break;
+
+		propagate = !--parent->nr_active;
+		parent->children_weight -= pos->weight;
+		pos = parent;
+	}
+
+	/* remove from the service tree */
+	if (!RB_EMPTY_NODE(&cfqg->rb_node))
+		cfq_rb_erase(&cfqg->rb_node, st);
+}
+
+static void
+cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
+{
+	struct cfq_rb_root *st = &cfqd->grp_service_tree;
+
+	BUG_ON(cfqg->nr_cfqq < 1);
+	cfqg->nr_cfqq--;
+
+	/* If there are other cfq queues under this group, don't delete it */
+	if (cfqg->nr_cfqq)
+		return;
+
+	cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
+	cfq_group_service_tree_del(st, cfqg);
+	cfqg->saved_wl_slice = 0;
+	cfqg_stats_update_dequeue(cfqg);
+}
+
+static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
+						unsigned int *unaccounted_time)
+{
+	unsigned int slice_used;
+
+	/*
+	 * Queue got expired before even a single request completed or
+	 * got expired immediately after first request completion.
+	 */
+	if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
+		/*
+		 * Also charge the seek time incurred to the group, otherwise
+		 * if there are mutiple queues in the group, each can dispatch
+		 * a single request on seeky media and cause lots of seek time
+		 * and group will never know it.
+		 */
+		slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
+					1);
+	} else {
+		slice_used = jiffies - cfqq->slice_start;
+		if (slice_used > cfqq->allocated_slice) {
+			*unaccounted_time = slice_used - cfqq->allocated_slice;
+			slice_used = cfqq->allocated_slice;
+		}
+		if (time_after(cfqq->slice_start, cfqq->dispatch_start))
+			*unaccounted_time += cfqq->slice_start -
+					cfqq->dispatch_start;
+	}
+
+	return slice_used;
+}
+
+static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
+				struct cfq_queue *cfqq)
+{
+	struct cfq_rb_root *st = &cfqd->grp_service_tree;
+	unsigned int used_sl, charge, unaccounted_sl = 0;
+	int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
+			- cfqg->service_tree_idle.count;
+	unsigned int vfr;
+
+	BUG_ON(nr_sync < 0);
+	used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
+
+	if (iops_mode(cfqd))
+		charge = cfqq->slice_dispatch;
+	else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
+		charge = cfqq->allocated_slice;
+
+	/*
+	 * Can't update vdisktime while on service tree and cfqg->vfraction
+	 * is valid only while on it.  Cache vfr, leave the service tree,
+	 * update vdisktime and go back on.  The re-addition to the tree
+	 * will also update the weights as necessary.
+	 */
+	vfr = cfqg->vfraction;
+	cfq_group_service_tree_del(st, cfqg);
+	cfqg->vdisktime += cfqg_scale_charge(charge, vfr);
+	cfq_group_service_tree_add(st, cfqg);
+
+	/* This group is being expired. Save the context */
+	if (time_after(cfqd->workload_expires, jiffies)) {
+		cfqg->saved_wl_slice = cfqd->workload_expires
+						- jiffies;
+		cfqg->saved_wl_type = cfqd->serving_wl_type;
+		cfqg->saved_wl_class = cfqd->serving_wl_class;
+	} else
+		cfqg->saved_wl_slice = 0;
+
+	cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
+					st->min_vdisktime);
+	cfq_log_cfqq(cfqq->cfqd, cfqq,
+		     "sl_used=%u disp=%u charge=%u iops=%u sect=%lu",
+		     used_sl, cfqq->slice_dispatch, charge,
+		     iops_mode(cfqd), cfqq->nr_sectors);
+	cfqg_stats_update_timeslice_used(cfqg, used_sl, unaccounted_sl);
+	cfqg_stats_set_start_empty_time(cfqg);
+}
+
+/**
+ * cfq_init_cfqg_base - initialize base part of a cfq_group
+ * @cfqg: cfq_group to initialize
+ *
+ * Initialize the base part which is used whether %CONFIG_CFQ_GROUP_IOSCHED
+ * is enabled or not.
+ */
+static void cfq_init_cfqg_base(struct cfq_group *cfqg)
+{
+	struct cfq_rb_root *st;
+	int i, j;
+
+	for_each_cfqg_st(cfqg, i, j, st)
+		*st = CFQ_RB_ROOT;
+	RB_CLEAR_NODE(&cfqg->rb_node);
+
+	cfqg->ttime.last_end_request = jiffies;
+}
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+static void cfqg_stats_init(struct cfqg_stats *stats)
+{
+	blkg_rwstat_init(&stats->service_bytes);
+	blkg_rwstat_init(&stats->serviced);
+	blkg_rwstat_init(&stats->merged);
+	blkg_rwstat_init(&stats->service_time);
+	blkg_rwstat_init(&stats->wait_time);
+	blkg_rwstat_init(&stats->queued);
+
+	blkg_stat_init(&stats->sectors);
+	blkg_stat_init(&stats->time);
+
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+	blkg_stat_init(&stats->unaccounted_time);
+	blkg_stat_init(&stats->avg_queue_size_sum);
+	blkg_stat_init(&stats->avg_queue_size_samples);
+	blkg_stat_init(&stats->dequeue);
+	blkg_stat_init(&stats->group_wait_time);
+	blkg_stat_init(&stats->idle_time);
+	blkg_stat_init(&stats->empty_time);
+#endif
+}
+
+static void cfq_pd_init(struct blkcg_gq *blkg)
+{
+	struct cfq_group *cfqg = blkg_to_cfqg(blkg);
+
+	cfq_init_cfqg_base(cfqg);
+	cfqg->weight = blkg->blkcg->cfq_weight;
+	cfqg->leaf_weight = blkg->blkcg->cfq_leaf_weight;
+	cfqg_stats_init(&cfqg->stats);
+	cfqg_stats_init(&cfqg->dead_stats);
+}
+
+static void cfq_pd_offline(struct blkcg_gq *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...
+	 */
+	cfqg_stats_xfer_dead(blkg_to_cfqg(blkg));
+}
+
+/* offset delta from cfqg->stats to cfqg->dead_stats */
+static const int dead_stats_off_delta = offsetof(struct cfq_group, dead_stats) -
+					offsetof(struct cfq_group, stats);
+
+/* to be used by recursive prfill, sums live and dead stats recursively */
+static u64 cfqg_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;
+}
+
+/* to be used by recursive prfill, sums live and dead rwstats recursively */
+static struct blkg_rwstat cfqg_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;
+}
+
+static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
+{
+	struct cfq_group *cfqg = blkg_to_cfqg(blkg);
+
+	cfqg_stats_reset(&cfqg->stats);
+	cfqg_stats_reset(&cfqg->dead_stats);
+}
+
+/*
+ * Search for the cfq group current task belongs to. request_queue lock must
+ * be held.
+ */
+static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
+						struct blkcg *blkcg)
+{
+	struct request_queue *q = cfqd->queue;
+	struct cfq_group *cfqg = NULL;
+
+	/* avoid lookup for the common case where there's no blkcg */
+	if (blkcg == &blkcg_root) {
+		cfqg = cfqd->root_group;
+	} else {
+		struct blkcg_gq *blkg;
+
+		blkg = blkg_lookup_create(blkcg, q);
+		if (!IS_ERR(blkg))
+			cfqg = blkg_to_cfqg(blkg);
+	}
+
+	return cfqg;
+}
+
+static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
+{
+	/* Currently, all async queues are mapped to root group */
+	if (!cfq_cfqq_sync(cfqq))
+		cfqg = cfqq->cfqd->root_group;
+
+	cfqq->cfqg = cfqg;
+	/* cfqq reference on cfqg */
+	cfqg_get(cfqg);
+}
+
+static u64 cfqg_prfill_weight_device(struct seq_file *sf,
+				     struct blkg_policy_data *pd, int off)
+{
+	struct cfq_group *cfqg = pd_to_cfqg(pd);
+
+	if (!cfqg->dev_weight)
+		return 0;
+	return __blkg_prfill_u64(sf, pd, cfqg->dev_weight);
+}
+
+static int cfqg_print_weight_device(struct seq_file *sf, void *v)
+{
+	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+			  cfqg_prfill_weight_device, &blkcg_policy_cfq,
+			  0, false);
+	return 0;
+}
+
+static u64 cfqg_prfill_leaf_weight_device(struct seq_file *sf,
+					  struct blkg_policy_data *pd, int off)
+{
+	struct cfq_group *cfqg = pd_to_cfqg(pd);
+
+	if (!cfqg->dev_leaf_weight)
+		return 0;
+	return __blkg_prfill_u64(sf, pd, cfqg->dev_leaf_weight);
+}
+
+static int cfqg_print_leaf_weight_device(struct seq_file *sf, void *v)
+{
+	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+			  cfqg_prfill_leaf_weight_device, &blkcg_policy_cfq,
+			  0, false);
+	return 0;
+}
+
+static int cfq_print_weight(struct seq_file *sf, void *v)
+{
+	seq_printf(sf, "%u\n", css_to_blkcg(seq_css(sf))->cfq_weight);
+	return 0;
+}
+
+static int cfq_print_leaf_weight(struct seq_file *sf, void *v)
+{
+	seq_printf(sf, "%u\n", css_to_blkcg(seq_css(sf))->cfq_leaf_weight);
+	return 0;
+}
+
+static ssize_t __cfqg_set_weight_device(struct kernfs_open_file *of,
+					char *buf, size_t nbytes, loff_t off,
+					bool is_leaf_weight)
+{
+	struct blkcg *blkcg = css_to_blkcg(of_css(of));
+	struct blkg_conf_ctx ctx;
+	struct cfq_group *cfqg;
+	int ret;
+
+	ret = blkg_conf_prep(blkcg, &blkcg_policy_cfq, buf, &ctx);
+	if (ret)
+		return ret;
+
+	ret = -EINVAL;
+	cfqg = blkg_to_cfqg(ctx.blkg);
+	if (!ctx.v || (ctx.v >= CFQ_WEIGHT_MIN && ctx.v <= CFQ_WEIGHT_MAX)) {
+		if (!is_leaf_weight) {
+			cfqg->dev_weight = ctx.v;
+			cfqg->new_weight = ctx.v ?: blkcg->cfq_weight;
+		} else {
+			cfqg->dev_leaf_weight = ctx.v;
+			cfqg->new_leaf_weight = ctx.v ?: blkcg->cfq_leaf_weight;
+		}
+		ret = 0;
+	}
+
+	blkg_conf_finish(&ctx);
+	return ret ?: nbytes;
+}
+
+static ssize_t cfqg_set_weight_device(struct kernfs_open_file *of,
+				      char *buf, size_t nbytes, loff_t off)
+{
+	return __cfqg_set_weight_device(of, buf, nbytes, off, false);
+}
+
+static ssize_t cfqg_set_leaf_weight_device(struct kernfs_open_file *of,
+					   char *buf, size_t nbytes, loff_t off)
+{
+	return __cfqg_set_weight_device(of, buf, nbytes, off, true);
+}
+
+static int __cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
+			    u64 val, bool is_leaf_weight)
+{
+	struct blkcg *blkcg = css_to_blkcg(css);
+	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 cfq_group *cfqg = blkg_to_cfqg(blkg);
+
+		if (!cfqg)
+			continue;
+
+		if (!is_leaf_weight) {
+			if (!cfqg->dev_weight)
+				cfqg->new_weight = blkcg->cfq_weight;
+		} else {
+			if (!cfqg->dev_leaf_weight)
+				cfqg->new_leaf_weight = blkcg->cfq_leaf_weight;
+		}
+	}
+
+	spin_unlock_irq(&blkcg->lock);
+	return 0;
+}
+
+static int cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
+			  u64 val)
+{
+	return __cfq_set_weight(css, cft, val, false);
+}
+
+static int cfq_set_leaf_weight(struct cgroup_subsys_state *css,
+			       struct cftype *cft, u64 val)
+{
+	return __cfq_set_weight(css, cft, val, true);
+}
+
+static int cfqg_print_stat(struct seq_file *sf, void *v)
+{
+	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
+			  &blkcg_policy_cfq, seq_cft(sf)->private, false);
+	return 0;
+}
+
+static int cfqg_print_rwstat(struct seq_file *sf, void *v)
+{
+	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
+			  &blkcg_policy_cfq, seq_cft(sf)->private, true);
+	return 0;
+}
+
+static u64 cfqg_prfill_stat_recursive(struct seq_file *sf,
+				      struct blkg_policy_data *pd, int off)
+{
+	u64 sum = cfqg_stat_pd_recursive_sum(pd, off);
+
+	return __blkg_prfill_u64(sf, pd, sum);
+}
+
+static u64 cfqg_prfill_rwstat_recursive(struct seq_file *sf,
+					struct blkg_policy_data *pd, int off)
+{
+	struct blkg_rwstat sum = cfqg_rwstat_pd_recursive_sum(pd, off);
+
+	return __blkg_prfill_rwstat(sf, pd, &sum);
+}
+
+static int cfqg_print_stat_recursive(struct seq_file *sf, void *v)
+{
+	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+			  cfqg_prfill_stat_recursive, &blkcg_policy_cfq,
+			  seq_cft(sf)->private, false);
+	return 0;
+}
+
+static int cfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
+{
+	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+			  cfqg_prfill_rwstat_recursive, &blkcg_policy_cfq,
+			  seq_cft(sf)->private, true);
+	return 0;
+}
+
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,
+				      struct blkg_policy_data *pd, int off)
+{
+	struct cfq_group *cfqg = pd_to_cfqg(pd);
+	u64 samples = blkg_stat_read(&cfqg->stats.avg_queue_size_samples);
+	u64 v = 0;
+
+	if (samples) {
+		v = blkg_stat_read(&cfqg->stats.avg_queue_size_sum);
+		v = div64_u64(v, samples);
+	}
+	__blkg_prfill_u64(sf, pd, v);
+	return 0;
+}
+
+/* print avg_queue_size */
+static int cfqg_print_avg_queue_size(struct seq_file *sf, void *v)
+{
+	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+			  cfqg_prfill_avg_queue_size, &blkcg_policy_cfq,
+			  0, false);
+	return 0;
+}
+#endif	/* CONFIG_DEBUG_BLK_CGROUP */
+
+static struct cftype cfq_blkcg_files[] = {
+	/* on root, weight is mapped to leaf_weight */
+	{
+		.name = "weight_device",
+		.flags = CFTYPE_ONLY_ON_ROOT,
+		.seq_show = cfqg_print_leaf_weight_device,
+		.write = cfqg_set_leaf_weight_device,
+	},
+	{
+		.name = "weight",
+		.flags = CFTYPE_ONLY_ON_ROOT,
+		.seq_show = cfq_print_leaf_weight,
+		.write_u64 = cfq_set_leaf_weight,
+	},
+
+	/* no such mapping necessary for !roots */
+	{
+		.name = "weight_device",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = cfqg_print_weight_device,
+		.write = cfqg_set_weight_device,
+	},
+	{
+		.name = "weight",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = cfq_print_weight,
+		.write_u64 = cfq_set_weight,
+	},
+
+	{
+		.name = "leaf_weight_device",
+		.seq_show = cfqg_print_leaf_weight_device,
+		.write = cfqg_set_leaf_weight_device,
+	},
+	{
+		.name = "leaf_weight",
+		.seq_show = cfq_print_leaf_weight,
+		.write_u64 = cfq_set_leaf_weight,
+	},
+
+	/* statistics, covers only the tasks in the cfqg */
+	{
+		.name = "time",
+		.private = offsetof(struct cfq_group, stats.time),
+		.seq_show = cfqg_print_stat,
+	},
+	{
+		.name = "sectors",
+		.private = offsetof(struct cfq_group, stats.sectors),
+		.seq_show = cfqg_print_stat,
+	},
+	{
+		.name = "io_service_bytes",
+		.private = offsetof(struct cfq_group, stats.service_bytes),
+		.seq_show = cfqg_print_rwstat,
+	},
+	{
+		.name = "io_serviced",
+		.private = offsetof(struct cfq_group, stats.serviced),
+		.seq_show = cfqg_print_rwstat,
+	},
+	{
+		.name = "io_service_time",
+		.private = offsetof(struct cfq_group, stats.service_time),
+		.seq_show = cfqg_print_rwstat,
+	},
+	{
+		.name = "io_wait_time",
+		.private = offsetof(struct cfq_group, stats.wait_time),
+		.seq_show = cfqg_print_rwstat,
+	},
+	{
+		.name = "io_merged",
+		.private = offsetof(struct cfq_group, stats.merged),
+		.seq_show = cfqg_print_rwstat,
+	},
+	{
+		.name = "io_queued",
+		.private = offsetof(struct cfq_group, stats.queued),
+		.seq_show = cfqg_print_rwstat,
+	},
+
+	/* the same statictics which cover the cfqg and its descendants */
+	{
+		.name = "time_recursive",
+		.private = offsetof(struct cfq_group, stats.time),
+		.seq_show = cfqg_print_stat_recursive,
+	},
+	{
+		.name = "sectors_recursive",
+		.private = offsetof(struct cfq_group, stats.sectors),
+		.seq_show = cfqg_print_stat_recursive,
+	},
+	{
+		.name = "io_service_bytes_recursive",
+		.private = offsetof(struct cfq_group, stats.service_bytes),
+		.seq_show = cfqg_print_rwstat_recursive,
+	},
+	{
+		.name = "io_serviced_recursive",
+		.private = offsetof(struct cfq_group, stats.serviced),
+		.seq_show = cfqg_print_rwstat_recursive,
+	},
+	{
+		.name = "io_service_time_recursive",
+		.private = offsetof(struct cfq_group, stats.service_time),
+		.seq_show = cfqg_print_rwstat_recursive,
+	},
+	{
+		.name = "io_wait_time_recursive",
+		.private = offsetof(struct cfq_group, stats.wait_time),
+		.seq_show = cfqg_print_rwstat_recursive,
+	},
+	{
+		.name = "io_merged_recursive",
+		.private = offsetof(struct cfq_group, stats.merged),
+		.seq_show = cfqg_print_rwstat_recursive,
+	},
+	{
+		.name = "io_queued_recursive",
+		.private = offsetof(struct cfq_group, stats.queued),
+		.seq_show = cfqg_print_rwstat_recursive,
+	},
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+	{
+		.name = "avg_queue_size",
+		.seq_show = cfqg_print_avg_queue_size,
+	},
+	{
+		.name = "group_wait_time",
+		.private = offsetof(struct cfq_group, stats.group_wait_time),
+		.seq_show = cfqg_print_stat,
+	},
+	{
+		.name = "idle_time",
+		.private = offsetof(struct cfq_group, stats.idle_time),
+		.seq_show = cfqg_print_stat,
+	},
+	{
+		.name = "empty_time",
+		.private = offsetof(struct cfq_group, stats.empty_time),
+		.seq_show = cfqg_print_stat,
+	},
+	{
+		.name = "dequeue",
+		.private = offsetof(struct cfq_group, stats.dequeue),
+		.seq_show = cfqg_print_stat,
+	},
+	{
+		.name = "unaccounted_time",
+		.private = offsetof(struct cfq_group, stats.unaccounted_time),
+		.seq_show = cfqg_print_stat,
+	},
+#endif	/* CONFIG_DEBUG_BLK_CGROUP */
+	{ }	/* terminate */
+};
+#else /* GROUP_IOSCHED */
+static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
+						struct blkcg *blkcg)
+{
+	return cfqd->root_group;
+}
+
+static inline void
+cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
+	cfqq->cfqg = cfqg;
+}
+
+#endif /* GROUP_IOSCHED */
+
+/*
+ * The cfqd->service_trees holds all pending cfq_queue's that have
+ * requests waiting to be processed. It is sorted in the order that
+ * we will service the queues.
+ */
+static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+				 bool add_front)
+{
+	struct rb_node **p, *parent;
+	struct cfq_queue *__cfqq;
+	unsigned long rb_key;
+	struct cfq_rb_root *st;
+	int left;
+	int new_cfqq = 1;
+
+	st = st_for(cfqq->cfqg, cfqq_class(cfqq), cfqq_type(cfqq));
+	if (cfq_class_idle(cfqq)) {
+		rb_key = CFQ_IDLE_DELAY;
+		parent = rb_last(&st->rb);
+		if (parent && parent != &cfqq->rb_node) {
+			__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
+			rb_key += __cfqq->rb_key;
+		} else
+			rb_key += jiffies;
+	} else if (!add_front) {
+		/*
+		 * Get our rb key offset. Subtract any residual slice
+		 * value carried from last service. A negative resid
+		 * count indicates slice overrun, and this should position
+		 * the next service time further away in the tree.
+		 */
+		rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
+		rb_key -= cfqq->slice_resid;
+		cfqq->slice_resid = 0;
+	} else {
+		rb_key = -HZ;
+		__cfqq = cfq_rb_first(st);
+		rb_key += __cfqq ? __cfqq->rb_key : jiffies;
+	}
+
+	if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
+		new_cfqq = 0;
+		/*
+		 * same position, nothing more to do
+		 */
+		if (rb_key == cfqq->rb_key && cfqq->service_tree == st)
+			return;
+
+		cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
+		cfqq->service_tree = NULL;
+	}
+
+	left = 1;
+	parent = NULL;
+	cfqq->service_tree = st;
+	p = &st->rb.rb_node;
+	while (*p) {
+		parent = *p;
+		__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
+
+		/*
+		 * sort by key, that represents service time.
+		 */
+		if (time_before(rb_key, __cfqq->rb_key))
+			p = &parent->rb_left;
+		else {
+			p = &parent->rb_right;
+			left = 0;
+		}
+	}
+
+	if (left)
+		st->left = &cfqq->rb_node;
+
+	cfqq->rb_key = rb_key;
+	rb_link_node(&cfqq->rb_node, parent, p);
+	rb_insert_color(&cfqq->rb_node, &st->rb);
+	st->count++;
+	if (add_front || !new_cfqq)
+		return;
+	cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
+}
+
+static struct cfq_queue *
+cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
+		     sector_t sector, struct rb_node **ret_parent,
+		     struct rb_node ***rb_link)
+{
+	struct rb_node **p, *parent;
+	struct cfq_queue *cfqq = NULL;
+
+	parent = NULL;
+	p = &root->rb_node;
+	while (*p) {
+		struct rb_node **n;
+
+		parent = *p;
+		cfqq = rb_entry(parent, struct cfq_queue, p_node);
+
+		/*
+		 * Sort strictly based on sector.  Smallest to the left,
+		 * largest to the right.
+		 */
+		if (sector > blk_rq_pos(cfqq->next_rq))
+			n = &(*p)->rb_right;
+		else if (sector < blk_rq_pos(cfqq->next_rq))
+			n = &(*p)->rb_left;
+		else
+			break;
+		p = n;
+		cfqq = NULL;
+	}
+
+	*ret_parent = parent;
+	if (rb_link)
+		*rb_link = p;
+	return cfqq;
+}
+
+static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	struct rb_node **p, *parent;
+	struct cfq_queue *__cfqq;
+
+	if (cfqq->p_root) {
+		rb_erase(&cfqq->p_node, cfqq->p_root);
+		cfqq->p_root = NULL;
+	}
+
+	if (cfq_class_idle(cfqq))
+		return;
+	if (!cfqq->next_rq)
+		return;
+
+	cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
+	__cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
+				      blk_rq_pos(cfqq->next_rq), &parent, &p);
+	if (!__cfqq) {
+		rb_link_node(&cfqq->p_node, parent, p);
+		rb_insert_color(&cfqq->p_node, cfqq->p_root);
+	} else
+		cfqq->p_root = NULL;
+}
+
+/*
+ * Update cfqq's position in the service tree.
+ */
+static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	/*
+	 * Resorting requires the cfqq to be on the RR list already.
+	 */
+	if (cfq_cfqq_on_rr(cfqq)) {
+		cfq_service_tree_add(cfqd, cfqq, 0);
+		cfq_prio_tree_add(cfqd, cfqq);
+	}
+}
+
+/*
+ * add to busy list of queues for service, trying to be fair in ordering
+ * the pending list according to last request service
+ */
+static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
+	BUG_ON(cfq_cfqq_on_rr(cfqq));
+	cfq_mark_cfqq_on_rr(cfqq);
+	cfqd->busy_queues++;
+	if (cfq_cfqq_sync(cfqq))
+		cfqd->busy_sync_queues++;
+
+	cfq_resort_rr_list(cfqd, cfqq);
+}
+
+/*
+ * Called when the cfqq no longer has requests pending, remove it from
+ * the service tree.
+ */
+static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
+	BUG_ON(!cfq_cfqq_on_rr(cfqq));
+	cfq_clear_cfqq_on_rr(cfqq);
+
+	if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
+		cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
+		cfqq->service_tree = NULL;
+	}
+	if (cfqq->p_root) {
+		rb_erase(&cfqq->p_node, cfqq->p_root);
+		cfqq->p_root = NULL;
+	}
+
+	cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
+	BUG_ON(!cfqd->busy_queues);
+	cfqd->busy_queues--;
+	if (cfq_cfqq_sync(cfqq))
+		cfqd->busy_sync_queues--;
+}
+
+/*
+ * rb tree support functions
+ */
+static void cfq_del_rq_rb(struct request *rq)
+{
+	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+	const int sync = rq_is_sync(rq);
+
+	BUG_ON(!cfqq->queued[sync]);
+	cfqq->queued[sync]--;
+
+	elv_rb_del(&cfqq->sort_list, rq);
+
+	if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
+		/*
+		 * Queue will be deleted from service tree when we actually
+		 * expire it later. Right now just remove it from prio tree
+		 * as it is empty.
+		 */
+		if (cfqq->p_root) {
+			rb_erase(&cfqq->p_node, cfqq->p_root);
+			cfqq->p_root = NULL;
+		}
+	}
+}
+
+static void cfq_add_rq_rb(struct request *rq)
+{
+	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+	struct cfq_data *cfqd = cfqq->cfqd;
+	struct request *prev;
+
+	cfqq->queued[rq_is_sync(rq)]++;
+
+	elv_rb_add(&cfqq->sort_list, rq);
+
+	if (!cfq_cfqq_on_rr(cfqq))
+		cfq_add_cfqq_rr(cfqd, cfqq);
+
+	/*
+	 * check if this request is a better next-serve candidate
+	 */
+	prev = cfqq->next_rq;
+	cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
+
+	/*
+	 * adjust priority tree position, if ->next_rq changes
+	 */
+	if (prev != cfqq->next_rq)
+		cfq_prio_tree_add(cfqd, cfqq);
+
+	BUG_ON(!cfqq->next_rq);
+}
+
+static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
+{
+	elv_rb_del(&cfqq->sort_list, rq);
+	cfqq->queued[rq_is_sync(rq)]--;
+	cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
+	cfq_add_rq_rb(rq);
+	cfqg_stats_update_io_add(RQ_CFQG(rq), cfqq->cfqd->serving_group,
+				 rq->cmd_flags);
+}
+
+static struct request *
+cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
+{
+	struct task_struct *tsk = current;
+	struct cfq_io_cq *cic;
+	struct cfq_queue *cfqq;
+
+	cic = cfq_cic_lookup(cfqd, tsk->io_context);
+	if (!cic)
+		return NULL;
+
+	cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
+	if (cfqq)
+		return elv_rb_find(&cfqq->sort_list, bio_end_sector(bio));
+
+	return NULL;
+}
+
+static void cfq_activate_request(struct request_queue *q, struct request *rq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+
+	cfqd->rq_in_driver++;
+	cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
+						cfqd->rq_in_driver);
+
+	cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
+}
+
+static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+
+	WARN_ON(!cfqd->rq_in_driver);
+	cfqd->rq_in_driver--;
+	cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
+						cfqd->rq_in_driver);
+}
+
+static void cfq_remove_request(struct request *rq)
+{
+	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+
+	if (cfqq->next_rq == rq)
+		cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
+
+	list_del_init(&rq->queuelist);
+	cfq_del_rq_rb(rq);
+
+	cfqq->cfqd->rq_queued--;
+	cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
+	if (rq->cmd_flags & REQ_PRIO) {
+		WARN_ON(!cfqq->prio_pending);
+		cfqq->prio_pending--;
+	}
+}
+
+static int cfq_merge(struct request_queue *q, struct request **req,
+		     struct bio *bio)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct request *__rq;
+
+	__rq = cfq_find_rq_fmerge(cfqd, bio);
+	if (__rq && elv_rq_merge_ok(__rq, bio)) {
+		*req = __rq;
+		return ELEVATOR_FRONT_MERGE;
+	}
+
+	return ELEVATOR_NO_MERGE;
+}
+
+static void cfq_merged_request(struct request_queue *q, struct request *req,
+			       int type)
+{
+	if (type == ELEVATOR_FRONT_MERGE) {
+		struct cfq_queue *cfqq = RQ_CFQQ(req);
+
+		cfq_reposition_rq_rb(cfqq, req);
+	}
+}
+
+static void cfq_bio_merged(struct request_queue *q, struct request *req,
+				struct bio *bio)
+{
+	cfqg_stats_update_io_merged(RQ_CFQG(req), bio->bi_rw);
+}
+
+static void
+cfq_merged_requests(struct request_queue *q, struct request *rq,
+		    struct request *next)
+{
+	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+
+	/*
+	 * reposition in fifo if next is older than rq
+	 */
+	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
+	    time_before(next->fifo_time, rq->fifo_time) &&
+	    cfqq == RQ_CFQQ(next)) {
+		list_move(&rq->queuelist, &next->queuelist);
+		rq->fifo_time = next->fifo_time;
+	}
+
+	if (cfqq->next_rq == next)
+		cfqq->next_rq = rq;
+	cfq_remove_request(next);
+	cfqg_stats_update_io_merged(RQ_CFQG(rq), next->cmd_flags);
+
+	cfqq = RQ_CFQQ(next);
+	/*
+	 * all requests of this queue are merged to other queues, delete it
+	 * from the service tree. If it's the active_queue,
+	 * cfq_dispatch_requests() will choose to expire it or do idle
+	 */
+	if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list) &&
+	    cfqq != cfqd->active_queue)
+		cfq_del_cfqq_rr(cfqd, cfqq);
+}
+
+static int cfq_allow_merge(struct request_queue *q, struct request *rq,
+			   struct bio *bio)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_io_cq *cic;
+	struct cfq_queue *cfqq;
+
+	/*
+	 * Disallow merge of a sync bio into an async request.
+	 */
+	if (cfq_bio_sync(bio) && !rq_is_sync(rq))
+		return false;
+
+	/*
+	 * Lookup the cfqq that this bio will be queued with and allow
+	 * merge only if rq is queued there.
+	 */
+	cic = cfq_cic_lookup(cfqd, current->io_context);
+	if (!cic)
+		return false;
+
+	cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
+	return cfqq == RQ_CFQQ(rq);
+}
+
+static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	del_timer(&cfqd->idle_slice_timer);
+	cfqg_stats_update_idle_time(cfqq->cfqg);
+}
+
+static void __cfq_set_active_queue(struct cfq_data *cfqd,
+				   struct cfq_queue *cfqq)
+{
+	if (cfqq) {
+		cfq_log_cfqq(cfqd, cfqq, "set_active wl_class:%d wl_type:%d",
+				cfqd->serving_wl_class, cfqd->serving_wl_type);
+		cfqg_stats_update_avg_queue_size(cfqq->cfqg);
+		cfqq->slice_start = 0;
+		cfqq->dispatch_start = jiffies;
+		cfqq->allocated_slice = 0;
+		cfqq->slice_end = 0;
+		cfqq->slice_dispatch = 0;
+		cfqq->nr_sectors = 0;
+
+		cfq_clear_cfqq_wait_request(cfqq);
+		cfq_clear_cfqq_must_dispatch(cfqq);
+		cfq_clear_cfqq_must_alloc_slice(cfqq);
+		cfq_clear_cfqq_fifo_expire(cfqq);
+		cfq_mark_cfqq_slice_new(cfqq);
+
+		cfq_del_timer(cfqd, cfqq);
+	}
+
+	cfqd->active_queue = cfqq;
+}
+
+/*
+ * current cfqq expired its slice (or was too idle), select new one
+ */
+static void
+__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		    bool timed_out)
+{
+	cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
+
+	if (cfq_cfqq_wait_request(cfqq))
+		cfq_del_timer(cfqd, cfqq);
+
+	cfq_clear_cfqq_wait_request(cfqq);
+	cfq_clear_cfqq_wait_busy(cfqq);
+
+	/*
+	 * If this cfqq is shared between multiple processes, check to
+	 * make sure that those processes are still issuing I/Os within
+	 * the mean seek distance.  If not, it may be time to break the
+	 * queues apart again.
+	 */
+	if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
+		cfq_mark_cfqq_split_coop(cfqq);
+
+	/*
+	 * store what was left of this slice, if the queue idled/timed out
+	 */
+	if (timed_out) {
+		if (cfq_cfqq_slice_new(cfqq))
+			cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
+		else
+			cfqq->slice_resid = cfqq->slice_end - jiffies;
+		cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
+	}
+
+	cfq_group_served(cfqd, cfqq->cfqg, cfqq);
+
+	if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
+		cfq_del_cfqq_rr(cfqd, cfqq);
+
+	cfq_resort_rr_list(cfqd, cfqq);
+
+	if (cfqq == cfqd->active_queue)
+		cfqd->active_queue = NULL;
+
+	if (cfqd->active_cic) {
+		put_io_context(cfqd->active_cic->icq.ioc);
+		cfqd->active_cic = NULL;
+	}
+}
+
+static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
+{
+	struct cfq_queue *cfqq = cfqd->active_queue;
+
+	if (cfqq)
+		__cfq_slice_expired(cfqd, cfqq, timed_out);
+}
+
+/*
+ * Get next queue for service. Unless we have a queue preemption,
+ * we'll simply select the first cfqq in the service tree.
+ */
+static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
+{
+	struct cfq_rb_root *st = st_for(cfqd->serving_group,
+			cfqd->serving_wl_class, cfqd->serving_wl_type);
+
+	if (!cfqd->rq_queued)
+		return NULL;
+
+	/* There is nothing to dispatch */
+	if (!st)
+		return NULL;
+	if (RB_EMPTY_ROOT(&st->rb))
+		return NULL;
+	return cfq_rb_first(st);
+}
+
+static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
+{
+	struct cfq_group *cfqg;
+	struct cfq_queue *cfqq;
+	int i, j;
+	struct cfq_rb_root *st;
+
+	if (!cfqd->rq_queued)
+		return NULL;
+
+	cfqg = cfq_get_next_cfqg(cfqd);
+	if (!cfqg)
+		return NULL;
+
+	for_each_cfqg_st(cfqg, i, j, st)
+		if ((cfqq = cfq_rb_first(st)) != NULL)
+			return cfqq;
+	return NULL;
+}
+
+/*
+ * Get and set a new active queue for service.
+ */
+static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
+					      struct cfq_queue *cfqq)
+{
+	if (!cfqq)
+		cfqq = cfq_get_next_queue(cfqd);
+
+	__cfq_set_active_queue(cfqd, cfqq);
+	return cfqq;
+}
+
+static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
+					  struct request *rq)
+{
+	if (blk_rq_pos(rq) >= cfqd->last_position)
+		return blk_rq_pos(rq) - cfqd->last_position;
+	else
+		return cfqd->last_position - blk_rq_pos(rq);
+}
+
+static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+			       struct request *rq)
+{
+	return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
+}
+
+static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
+				    struct cfq_queue *cur_cfqq)
+{
+	struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
+	struct rb_node *parent, *node;
+	struct cfq_queue *__cfqq;
+	sector_t sector = cfqd->last_position;
+
+	if (RB_EMPTY_ROOT(root))
+		return NULL;
+
+	/*
+	 * First, if we find a request starting at the end of the last
+	 * request, choose it.
+	 */
+	__cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
+	if (__cfqq)
+		return __cfqq;
+
+	/*
+	 * If the exact sector wasn't found, the parent of the NULL leaf
+	 * will contain the closest sector.
+	 */
+	__cfqq = rb_entry(parent, struct cfq_queue, p_node);
+	if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
+		return __cfqq;
+
+	if (blk_rq_pos(__cfqq->next_rq) < sector)
+		node = rb_next(&__cfqq->p_node);
+	else
+		node = rb_prev(&__cfqq->p_node);
+	if (!node)
+		return NULL;
+
+	__cfqq = rb_entry(node, struct cfq_queue, p_node);
+	if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
+		return __cfqq;
+
+	return NULL;
+}
+
+/*
+ * cfqd - obvious
+ * cur_cfqq - passed in so that we don't decide that the current queue is
+ * 	      closely cooperating with itself.
+ *
+ * So, basically we're assuming that that cur_cfqq has dispatched at least
+ * one request, and that cfqd->last_position reflects a position on the disk
+ * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
+ * assumption.
+ */
+static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
+					      struct cfq_queue *cur_cfqq)
+{
+	struct cfq_queue *cfqq;
+
+	if (cfq_class_idle(cur_cfqq))
+		return NULL;
+	if (!cfq_cfqq_sync(cur_cfqq))
+		return NULL;
+	if (CFQQ_SEEKY(cur_cfqq))
+		return NULL;
+
+	/*
+	 * Don't search priority tree if it's the only queue in the group.
+	 */
+	if (cur_cfqq->cfqg->nr_cfqq == 1)
+		return NULL;
+
+	/*
+	 * We should notice if some of the queues are cooperating, eg
+	 * working closely on the same area of the disk. In that case,
+	 * we can group them together and don't waste time idling.
+	 */
+	cfqq = cfqq_close(cfqd, cur_cfqq);
+	if (!cfqq)
+		return NULL;
+
+	/* If new queue belongs to different cfq_group, don't choose it */
+	if (cur_cfqq->cfqg != cfqq->cfqg)
+		return NULL;
+
+	/*
+	 * It only makes sense to merge sync queues.
+	 */
+	if (!cfq_cfqq_sync(cfqq))
+		return NULL;
+	if (CFQQ_SEEKY(cfqq))
+		return NULL;
+
+	/*
+	 * Do not merge queues of different priority classes
+	 */
+	if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
+		return NULL;
+
+	return cfqq;
+}
+
+/*
+ * Determine whether we should enforce idle window for this queue.
+ */
+
+static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	enum wl_class_t wl_class = cfqq_class(cfqq);
+	struct cfq_rb_root *st = cfqq->service_tree;
+
+	BUG_ON(!st);
+	BUG_ON(!st->count);
+
+	if (!cfqd->cfq_slice_idle)
+		return false;
+
+	/* We never do for idle class queues. */
+	if (wl_class == IDLE_WORKLOAD)
+		return false;
+
+	/* We do for queues that were marked with idle window flag. */
+	if (cfq_cfqq_idle_window(cfqq) &&
+	   !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
+		return true;
+
+	/*
+	 * Otherwise, we do only if they are the last ones
+	 * in their service tree.
+	 */
+	if (st->count == 1 && cfq_cfqq_sync(cfqq) &&
+	   !cfq_io_thinktime_big(cfqd, &st->ttime, false))
+		return true;
+	cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d", st->count);
+	return false;
+}
+
+static void cfq_arm_slice_timer(struct cfq_data *cfqd)
+{
+	struct cfq_queue *cfqq = cfqd->active_queue;
+	struct cfq_io_cq *cic;
+	unsigned long sl, group_idle = 0;
+
+	/*
+	 * SSD device without seek penalty, disable idling. But only do so
+	 * for devices that support queuing, otherwise we still have a problem
+	 * with sync vs async workloads.
+	 */
+	if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
+		return;
+
+	WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
+	WARN_ON(cfq_cfqq_slice_new(cfqq));
+
+	/*
+	 * idle is disabled, either manually or by past process history
+	 */
+	if (!cfq_should_idle(cfqd, cfqq)) {
+		/* no queue idling. Check for group idling */
+		if (cfqd->cfq_group_idle)
+			group_idle = cfqd->cfq_group_idle;
+		else
+			return;
+	}
+
+	/*
+	 * still active requests from this queue, don't idle
+	 */
+	if (cfqq->dispatched)
+		return;
+
+	/*
+	 * task has exited, don't wait
+	 */
+	cic = cfqd->active_cic;
+	if (!cic || !atomic_read(&cic->icq.ioc->active_ref))
+		return;
+
+	/*
+	 * If our average think time is larger than the remaining time
+	 * slice, then don't idle. This avoids overrunning the allotted
+	 * time slice.
+	 */
+	if (sample_valid(cic->ttime.ttime_samples) &&
+	    (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) {
+		cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%lu",
+			     cic->ttime.ttime_mean);
+		return;
+	}
+
+	/* There are other queues in the group, don't do group idle */
+	if (group_idle && cfqq->cfqg->nr_cfqq > 1)
+		return;
+
+	cfq_mark_cfqq_wait_request(cfqq);
+
+	if (group_idle)
+		sl = cfqd->cfq_group_idle;
+	else
+		sl = cfqd->cfq_slice_idle;
+
+	mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
+	cfqg_stats_set_start_idle_time(cfqq->cfqg);
+	cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
+			group_idle ? 1 : 0);
+}
+
+/*
+ * Move request from internal lists to the request queue dispatch list.
+ */
+static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+
+	cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
+
+	cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
+	cfq_remove_request(rq);
+	cfqq->dispatched++;
+	(RQ_CFQG(rq))->dispatched++;
+	elv_dispatch_sort(q, rq);
+
+	cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
+	cfqq->nr_sectors += blk_rq_sectors(rq);
+	cfqg_stats_update_dispatch(cfqq->cfqg, blk_rq_bytes(rq), rq->cmd_flags);
+}
+
+/*
+ * return expired entry, or NULL to just start from scratch in rbtree
+ */
+static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
+{
+	struct request *rq = NULL;
+
+	if (cfq_cfqq_fifo_expire(cfqq))
+		return NULL;
+
+	cfq_mark_cfqq_fifo_expire(cfqq);
+
+	if (list_empty(&cfqq->fifo))
+		return NULL;
+
+	rq = rq_entry_fifo(cfqq->fifo.next);
+	if (time_before(jiffies, rq->fifo_time))
+		rq = NULL;
+
+	cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
+	return rq;
+}
+
+static inline int
+cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	const int base_rq = cfqd->cfq_slice_async_rq;
+
+	WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
+
+	return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
+}
+
+/*
+ * Must be called with the queue_lock held.
+ */
+static int cfqq_process_refs(struct cfq_queue *cfqq)
+{
+	int process_refs, io_refs;
+
+	io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
+	process_refs = cfqq->ref - io_refs;
+	BUG_ON(process_refs < 0);
+	return process_refs;
+}
+
+static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
+{
+	int process_refs, new_process_refs;
+	struct cfq_queue *__cfqq;
+
+	/*
+	 * If there are no process references on the new_cfqq, then it is
+	 * unsafe to follow the ->new_cfqq chain as other cfqq's in the
+	 * chain may have dropped their last reference (not just their
+	 * last process reference).
+	 */
+	if (!cfqq_process_refs(new_cfqq))
+		return;
+
+	/* Avoid a circular list and skip interim queue merges */
+	while ((__cfqq = new_cfqq->new_cfqq)) {
+		if (__cfqq == cfqq)
+			return;
+		new_cfqq = __cfqq;
+	}
+
+	process_refs = cfqq_process_refs(cfqq);
+	new_process_refs = cfqq_process_refs(new_cfqq);
+	/*
+	 * If the process for the cfqq has gone away, there is no
+	 * sense in merging the queues.
+	 */
+	if (process_refs == 0 || new_process_refs == 0)
+		return;
+
+	/*
+	 * Merge in the direction of the lesser amount of work.
+	 */
+	if (new_process_refs >= process_refs) {
+		cfqq->new_cfqq = new_cfqq;
+		new_cfqq->ref += process_refs;
+	} else {
+		new_cfqq->new_cfqq = cfqq;
+		cfqq->ref += new_process_refs;
+	}
+}
+
+static enum wl_type_t cfq_choose_wl_type(struct cfq_data *cfqd,
+			struct cfq_group *cfqg, enum wl_class_t wl_class)
+{
+	struct cfq_queue *queue;
+	int i;
+	bool key_valid = false;
+	unsigned long lowest_key = 0;
+	enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
+
+	for (i = 0; i <= SYNC_WORKLOAD; ++i) {
+		/* select the one with lowest rb_key */
+		queue = cfq_rb_first(st_for(cfqg, wl_class, i));
+		if (queue &&
+		    (!key_valid || time_before(queue->rb_key, lowest_key))) {
+			lowest_key = queue->rb_key;
+			cur_best = i;
+			key_valid = true;
+		}
+	}
+
+	return cur_best;
+}
+
+static void
+choose_wl_class_and_type(struct cfq_data *cfqd, struct cfq_group *cfqg)
+{
+	unsigned slice;
+	unsigned count;
+	struct cfq_rb_root *st;
+	unsigned group_slice;
+	enum wl_class_t original_class = cfqd->serving_wl_class;
+
+	/* Choose next priority. RT > BE > IDLE */
+	if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
+		cfqd->serving_wl_class = RT_WORKLOAD;
+	else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
+		cfqd->serving_wl_class = BE_WORKLOAD;
+	else {
+		cfqd->serving_wl_class = IDLE_WORKLOAD;
+		cfqd->workload_expires = jiffies + 1;
+		return;
+	}
+
+	if (original_class != cfqd->serving_wl_class)
+		goto new_workload;
+
+	/*
+	 * For RT and BE, we have to choose also the type
+	 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
+	 * expiration time
+	 */
+	st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
+	count = st->count;
+
+	/*
+	 * check workload expiration, and that we still have other queues ready
+	 */
+	if (count && !time_after(jiffies, cfqd->workload_expires))
+		return;
+
+new_workload:
+	/* otherwise select new workload type */
+	cfqd->serving_wl_type = cfq_choose_wl_type(cfqd, cfqg,
+					cfqd->serving_wl_class);
+	st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
+	count = st->count;
+
+	/*
+	 * the workload slice is computed as a fraction of target latency
+	 * proportional to the number of queues in that workload, over
+	 * all the queues in the same priority class
+	 */
+	group_slice = cfq_group_slice(cfqd, cfqg);
+
+	slice = group_slice * count /
+		max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_wl_class],
+		      cfq_group_busy_queues_wl(cfqd->serving_wl_class, cfqd,
+					cfqg));
+
+	if (cfqd->serving_wl_type == ASYNC_WORKLOAD) {
+		unsigned int tmp;
+
+		/*
+		 * Async queues are currently system wide. Just taking
+		 * proportion of queues with-in same group will lead to higher
+		 * async ratio system wide as generally root group is going
+		 * to have higher weight. A more accurate thing would be to
+		 * calculate system wide asnc/sync ratio.
+		 */
+		tmp = cfqd->cfq_target_latency *
+			cfqg_busy_async_queues(cfqd, cfqg);
+		tmp = tmp/cfqd->busy_queues;
+		slice = min_t(unsigned, slice, tmp);
+
+		/* async workload slice is scaled down according to
+		 * the sync/async slice ratio. */
+		slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
+	} else
+		/* sync workload slice is at least 2 * cfq_slice_idle */
+		slice = max(slice, 2 * cfqd->cfq_slice_idle);
+
+	slice = max_t(unsigned, slice, CFQ_MIN_TT);
+	cfq_log(cfqd, "workload slice:%d", slice);
+	cfqd->workload_expires = jiffies + slice;
+}
+
+static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
+{
+	struct cfq_rb_root *st = &cfqd->grp_service_tree;
+	struct cfq_group *cfqg;
+
+	if (RB_EMPTY_ROOT(&st->rb))
+		return NULL;
+	cfqg = cfq_rb_first_group(st);
+	update_min_vdisktime(st);
+	return cfqg;
+}
+
+static void cfq_choose_cfqg(struct cfq_data *cfqd)
+{
+	struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
+
+	cfqd->serving_group = cfqg;
+
+	/* Restore the workload type data */
+	if (cfqg->saved_wl_slice) {
+		cfqd->workload_expires = jiffies + cfqg->saved_wl_slice;
+		cfqd->serving_wl_type = cfqg->saved_wl_type;
+		cfqd->serving_wl_class = cfqg->saved_wl_class;
+	} else
+		cfqd->workload_expires = jiffies - 1;
+
+	choose_wl_class_and_type(cfqd, cfqg);
+}
+
+/*
+ * Select a queue for service. If we have a current active queue,
+ * check whether to continue servicing it, or retrieve and set a new one.
+ */
+static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
+{
+	struct cfq_queue *cfqq, *new_cfqq = NULL;
+
+	cfqq = cfqd->active_queue;
+	if (!cfqq)
+		goto new_queue;
+
+	if (!cfqd->rq_queued)
+		return NULL;
+
+	/*
+	 * We were waiting for group to get backlogged. Expire the queue
+	 */
+	if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
+		goto expire;
+
+	/*
+	 * The active queue has run out of time, expire it and select new.
+	 */
+	if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
+		/*
+		 * If slice had not expired at the completion of last request
+		 * we might not have turned on wait_busy flag. Don't expire
+		 * the queue yet. Allow the group to get backlogged.
+		 *
+		 * The very fact that we have used the slice, that means we
+		 * have been idling all along on this queue and it should be
+		 * ok to wait for this request to complete.
+		 */
+		if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
+		    && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
+			cfqq = NULL;
+			goto keep_queue;
+		} else
+			goto check_group_idle;
+	}
+
+	/*
+	 * The active queue has requests and isn't expired, allow it to
+	 * dispatch.
+	 */
+	if (!RB_EMPTY_ROOT(&cfqq->sort_list))
+		goto keep_queue;
+
+	/*
+	 * If another queue has a request waiting within our mean seek
+	 * distance, let it run.  The expire code will check for close
+	 * cooperators and put the close queue at the front of the service
+	 * tree.  If possible, merge the expiring queue with the new cfqq.
+	 */
+	new_cfqq = cfq_close_cooperator(cfqd, cfqq);
+	if (new_cfqq) {
+		if (!cfqq->new_cfqq)
+			cfq_setup_merge(cfqq, new_cfqq);
+		goto expire;
+	}
+
+	/*
+	 * No requests pending. If the active queue still has requests in
+	 * flight or is idling for a new request, allow either of these
+	 * conditions to happen (or time out) before selecting a new queue.
+	 */
+	if (timer_pending(&cfqd->idle_slice_timer)) {
+		cfqq = NULL;
+		goto keep_queue;
+	}
+
+	/*
+	 * This is a deep seek queue, but the device is much faster than
+	 * the queue can deliver, don't idle
+	 **/
+	if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
+	    (cfq_cfqq_slice_new(cfqq) ||
+	    (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
+		cfq_clear_cfqq_deep(cfqq);
+		cfq_clear_cfqq_idle_window(cfqq);
+	}
+
+	if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
+		cfqq = NULL;
+		goto keep_queue;
+	}
+
+	/*
+	 * If group idle is enabled and there are requests dispatched from
+	 * this group, wait for requests to complete.
+	 */
+check_group_idle:
+	if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 &&
+	    cfqq->cfqg->dispatched &&
+	    !cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true)) {
+		cfqq = NULL;
+		goto keep_queue;
+	}
+
+expire:
+	cfq_slice_expired(cfqd, 0);
+new_queue:
+	/*
+	 * Current queue expired. Check if we have to switch to a new
+	 * service tree
+	 */
+	if (!new_cfqq)
+		cfq_choose_cfqg(cfqd);
+
+	cfqq = cfq_set_active_queue(cfqd, new_cfqq);
+keep_queue:
+	return cfqq;
+}
+
+static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
+{
+	int dispatched = 0;
+
+	while (cfqq->next_rq) {
+		cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
+		dispatched++;
+	}
+
+	BUG_ON(!list_empty(&cfqq->fifo));
+
+	/* By default cfqq is not expired if it is empty. Do it explicitly */
+	__cfq_slice_expired(cfqq->cfqd, cfqq, 0);
+	return dispatched;
+}
+
+/*
+ * Drain our current requests. Used for barriers and when switching
+ * io schedulers on-the-fly.
+ */
+static int cfq_forced_dispatch(struct cfq_data *cfqd)
+{
+	struct cfq_queue *cfqq;
+	int dispatched = 0;
+
+	/* Expire the timeslice of the current active queue first */
+	cfq_slice_expired(cfqd, 0);
+	while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
+		__cfq_set_active_queue(cfqd, cfqq);
+		dispatched += __cfq_forced_dispatch_cfqq(cfqq);
+	}
+
+	BUG_ON(cfqd->busy_queues);
+
+	cfq_log(cfqd, "forced_dispatch=%d", dispatched);
+	return dispatched;
+}
+
+static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
+	struct cfq_queue *cfqq)
+{
+	/* the queue hasn't finished any request, can't estimate */
+	if (cfq_cfqq_slice_new(cfqq))
+		return true;
+	if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
+		cfqq->slice_end))
+		return true;
+
+	return false;
+}
+
+static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	unsigned int max_dispatch;
+
+	/*
+	 * Drain async requests before we start sync IO
+	 */
+	if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
+		return false;
+
+	/*
+	 * If this is an async queue and we have sync IO in flight, let it wait
+	 */
+	if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
+		return false;
+
+	max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
+	if (cfq_class_idle(cfqq))
+		max_dispatch = 1;
+
+	/*
+	 * Does this cfqq already have too much IO in flight?
+	 */
+	if (cfqq->dispatched >= max_dispatch) {
+		bool promote_sync = false;
+		/*
+		 * idle queue must always only have a single IO in flight
+		 */
+		if (cfq_class_idle(cfqq))
+			return false;
+
+		/*
+		 * If there is only one sync queue
+		 * we can ignore async queue here and give the sync
+		 * queue no dispatch limit. The reason is a sync queue can
+		 * preempt async queue, limiting the sync queue doesn't make
+		 * sense. This is useful for aiostress test.
+		 */
+		if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
+			promote_sync = true;
+
+		/*
+		 * We have other queues, don't allow more IO from this one
+		 */
+		if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
+				!promote_sync)
+			return false;
+
+		/*
+		 * Sole queue user, no limit
+		 */
+		if (cfqd->busy_queues == 1 || promote_sync)
+			max_dispatch = -1;
+		else
+			/*
+			 * Normally we start throttling cfqq when cfq_quantum/2
+			 * requests have been dispatched. But we can drive
+			 * deeper queue depths at the beginning of slice
+			 * subjected to upper limit of cfq_quantum.
+			 * */
+			max_dispatch = cfqd->cfq_quantum;
+	}
+
+	/*
+	 * Async queues must wait a bit before being allowed dispatch.
+	 * We also ramp up the dispatch depth gradually for async IO,
+	 * based on the last sync IO we serviced
+	 */
+	if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
+		unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
+		unsigned int depth;
+
+		depth = last_sync / cfqd->cfq_slice[1];
+		if (!depth && !cfqq->dispatched)
+			depth = 1;
+		if (depth < max_dispatch)
+			max_dispatch = depth;
+	}
+
+	/*
+	 * If we're below the current max, allow a dispatch
+	 */
+	return cfqq->dispatched < max_dispatch;
+}
+
+/*
+ * Dispatch a request from cfqq, moving them to the request queue
+ * dispatch list.
+ */
+static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	struct request *rq;
+
+	BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
+
+	if (!cfq_may_dispatch(cfqd, cfqq))
+		return false;
+
+	/*
+	 * follow expired path, else get first next available
+	 */
+	rq = cfq_check_fifo(cfqq);
+	if (!rq)
+		rq = cfqq->next_rq;
+
+	/*
+	 * insert request into driver dispatch list
+	 */
+	cfq_dispatch_insert(cfqd->queue, rq);
+
+	if (!cfqd->active_cic) {
+		struct cfq_io_cq *cic = RQ_CIC(rq);
+
+		atomic_long_inc(&cic->icq.ioc->refcount);
+		cfqd->active_cic = cic;
+	}
+
+	return true;
+}
+
+/*
+ * Find the cfqq that we need to service and move a request from that to the
+ * dispatch list
+ */
+static int cfq_dispatch_requests(struct request_queue *q, int force)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_queue *cfqq;
+
+	if (!cfqd->busy_queues)
+		return 0;
+
+	if (unlikely(force))
+		return cfq_forced_dispatch(cfqd);
+
+	cfqq = cfq_select_queue(cfqd);
+	if (!cfqq)
+		return 0;
+
+	/*
+	 * Dispatch a request from this cfqq, if it is allowed
+	 */
+	if (!cfq_dispatch_request(cfqd, cfqq))
+		return 0;
+
+	cfqq->slice_dispatch++;
+	cfq_clear_cfqq_must_dispatch(cfqq);
+
+	/*
+	 * expire an async queue immediately if it has used up its slice. idle
+	 * queue always expire after 1 dispatch round.
+	 */
+	if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
+	    cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
+	    cfq_class_idle(cfqq))) {
+		cfqq->slice_end = jiffies + 1;
+		cfq_slice_expired(cfqd, 0);
+	}
+
+	cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
+	return 1;
+}
+
+/*
+ * 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 cfq queue took a reference on the parent group. Drop it now.
+ * queue lock must be held here.
+ */
+static void cfq_put_queue(struct cfq_queue *cfqq)
+{
+	struct cfq_data *cfqd = cfqq->cfqd;
+	struct cfq_group *cfqg;
+
+	BUG_ON(cfqq->ref <= 0);
+
+	cfqq->ref--;
+	if (cfqq->ref)
+		return;
+
+	cfq_log_cfqq(cfqd, cfqq, "put_queue");
+	BUG_ON(rb_first(&cfqq->sort_list));
+	BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
+	cfqg = cfqq->cfqg;
+
+	if (unlikely(cfqd->active_queue == cfqq)) {
+		__cfq_slice_expired(cfqd, cfqq, 0);
+		cfq_schedule_dispatch(cfqd);
+	}
+
+	BUG_ON(cfq_cfqq_on_rr(cfqq));
+	kmem_cache_free(cfq_pool, cfqq);
+	cfqg_put(cfqg);
+}
+
+static void cfq_put_cooperator(struct cfq_queue *cfqq)
+{
+	struct cfq_queue *__cfqq, *next;
+
+	/*
+	 * If this queue was scheduled to merge with another queue, be
+	 * sure to drop the reference taken on that queue (and others in
+	 * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
+	 */
+	__cfqq = cfqq->new_cfqq;
+	while (__cfqq) {
+		if (__cfqq == cfqq) {
+			WARN(1, "cfqq->new_cfqq loop detected\n");
+			break;
+		}
+		next = __cfqq->new_cfqq;
+		cfq_put_queue(__cfqq);
+		__cfqq = next;
+	}
+}
+
+static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	if (unlikely(cfqq == cfqd->active_queue)) {
+		__cfq_slice_expired(cfqd, cfqq, 0);
+		cfq_schedule_dispatch(cfqd);
+	}
+
+	cfq_put_cooperator(cfqq);
+
+	cfq_put_queue(cfqq);
+}
+
+static void cfq_init_icq(struct io_cq *icq)
+{
+	struct cfq_io_cq *cic = icq_to_cic(icq);
+
+	cic->ttime.last_end_request = jiffies;
+}
+
+static void cfq_exit_icq(struct io_cq *icq)
+{
+	struct cfq_io_cq *cic = icq_to_cic(icq);
+	struct cfq_data *cfqd = cic_to_cfqd(cic);
+
+	if (cic->cfqq[BLK_RW_ASYNC]) {
+		cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
+		cic->cfqq[BLK_RW_ASYNC] = NULL;
+	}
+
+	if (cic->cfqq[BLK_RW_SYNC]) {
+		cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
+		cic->cfqq[BLK_RW_SYNC] = NULL;
+	}
+}
+
+static void cfq_init_prio_data(struct cfq_queue *cfqq, struct cfq_io_cq *cic)
+{
+	struct task_struct *tsk = current;
+	int ioprio_class;
+
+	if (!cfq_cfqq_prio_changed(cfqq))
+		return;
+
+	ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
+	switch (ioprio_class) {
+	default:
+		printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
+	case IOPRIO_CLASS_NONE:
+		/*
+		 * no prio set, inherit CPU scheduling settings
+		 */
+		cfqq->ioprio = task_nice_ioprio(tsk);
+		cfqq->ioprio_class = task_nice_ioclass(tsk);
+		break;
+	case IOPRIO_CLASS_RT:
+		cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
+		cfqq->ioprio_class = IOPRIO_CLASS_RT;
+		break;
+	case IOPRIO_CLASS_BE:
+		cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
+		cfqq->ioprio_class = IOPRIO_CLASS_BE;
+		break;
+	case IOPRIO_CLASS_IDLE:
+		cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
+		cfqq->ioprio = 7;
+		cfq_clear_cfqq_idle_window(cfqq);
+		break;
+	}
+
+	/*
+	 * keep track of original prio settings in case we have to temporarily
+	 * elevate the priority of this queue
+	 */
+	cfqq->org_ioprio = cfqq->ioprio;
+	cfq_clear_cfqq_prio_changed(cfqq);
+}
+
+static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio)
+{
+	int ioprio = cic->icq.ioc->ioprio;
+	struct cfq_data *cfqd = cic_to_cfqd(cic);
+	struct cfq_queue *cfqq;
+
+	/*
+	 * Check whether ioprio has changed.  The condition may trigger
+	 * spuriously on a newly created cic but there's no harm.
+	 */
+	if (unlikely(!cfqd) || likely(cic->ioprio == ioprio))
+		return;
+
+	cfqq = cic->cfqq[BLK_RW_ASYNC];
+	if (cfqq) {
+		struct cfq_queue *new_cfqq;
+		new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio,
+					 GFP_ATOMIC);
+		if (new_cfqq) {
+			cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
+			cfq_put_queue(cfqq);
+		}
+	}
+
+	cfqq = cic->cfqq[BLK_RW_SYNC];
+	if (cfqq)
+		cfq_mark_cfqq_prio_changed(cfqq);
+
+	cic->ioprio = ioprio;
+}
+
+static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+			  pid_t pid, bool is_sync)
+{
+	RB_CLEAR_NODE(&cfqq->rb_node);
+	RB_CLEAR_NODE(&cfqq->p_node);
+	INIT_LIST_HEAD(&cfqq->fifo);
+
+	cfqq->ref = 0;
+	cfqq->cfqd = cfqd;
+
+	cfq_mark_cfqq_prio_changed(cfqq);
+
+	if (is_sync) {
+		if (!cfq_class_idle(cfqq))
+			cfq_mark_cfqq_idle_window(cfqq);
+		cfq_mark_cfqq_sync(cfqq);
+	}
+	cfqq->pid = pid;
+}
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
+{
+	struct cfq_data *cfqd = cic_to_cfqd(cic);
+	struct cfq_queue *sync_cfqq;
+	uint64_t serial_nr;
+
+	rcu_read_lock();
+	serial_nr = bio_blkcg(bio)->css.serial_nr;
+	rcu_read_unlock();
+
+	/*
+	 * Check whether blkcg has changed.  The condition may trigger
+	 * spuriously on a newly created cic but there's no harm.
+	 */
+	if (unlikely(!cfqd) || likely(cic->blkcg_serial_nr == serial_nr))
+		return;
+
+	sync_cfqq = cic_to_cfqq(cic, 1);
+	if (sync_cfqq) {
+		/*
+		 * Drop reference to sync queue. A new sync queue will be
+		 * assigned in new group upon arrival of a fresh request.
+		 */
+		cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
+		cic_set_cfqq(cic, NULL, 1);
+		cfq_put_queue(sync_cfqq);
+	}
+
+	cic->blkcg_serial_nr = serial_nr;
+}
+#else
+static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { }
+#endif  /* CONFIG_CFQ_GROUP_IOSCHED */
+
+static struct cfq_queue *
+cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
+		     struct bio *bio, gfp_t gfp_mask)
+{
+	struct blkcg *blkcg;
+	struct cfq_queue *cfqq, *new_cfqq = NULL;
+	struct cfq_group *cfqg;
+
+retry:
+	rcu_read_lock();
+
+	blkcg = bio_blkcg(bio);
+	cfqg = cfq_lookup_create_cfqg(cfqd, blkcg);
+	if (!cfqg) {
+		cfqq = &cfqd->oom_cfqq;
+		goto out;
+	}
+
+	cfqq = cic_to_cfqq(cic, is_sync);
+
+	/*
+	 * Always try a new alloc if we fell back to the OOM cfqq
+	 * originally, since it should just be a temporary situation.
+	 */
+	if (!cfqq || cfqq == &cfqd->oom_cfqq) {
+		cfqq = NULL;
+		if (new_cfqq) {
+			cfqq = new_cfqq;
+			new_cfqq = NULL;
+		} else if (gfp_mask & __GFP_WAIT) {
+			rcu_read_unlock();
+			spin_unlock_irq(cfqd->queue->queue_lock);
+			new_cfqq = kmem_cache_alloc_node(cfq_pool,
+					gfp_mask | __GFP_ZERO,
+					cfqd->queue->node);
+			spin_lock_irq(cfqd->queue->queue_lock);
+			if (new_cfqq)
+				goto retry;
+			else
+				return &cfqd->oom_cfqq;
+		} else {
+			cfqq = kmem_cache_alloc_node(cfq_pool,
+					gfp_mask | __GFP_ZERO,
+					cfqd->queue->node);
+		}
+
+		if (cfqq) {
+			cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
+			cfq_init_prio_data(cfqq, cic);
+			cfq_link_cfqq_cfqg(cfqq, cfqg);
+			cfq_log_cfqq(cfqd, cfqq, "alloced");
+		} else
+			cfqq = &cfqd->oom_cfqq;
+	}
+out:
+	if (new_cfqq)
+		kmem_cache_free(cfq_pool, new_cfqq);
+
+	rcu_read_unlock();
+	return cfqq;
+}
+
+static struct cfq_queue **
+cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
+{
+	switch (ioprio_class) {
+	case IOPRIO_CLASS_RT:
+		return &cfqd->async_cfqq[0][ioprio];
+	case IOPRIO_CLASS_NONE:
+		ioprio = IOPRIO_NORM;
+		/* fall through */
+	case IOPRIO_CLASS_BE:
+		return &cfqd->async_cfqq[1][ioprio];
+	case IOPRIO_CLASS_IDLE:
+		return &cfqd->async_idle_cfqq;
+	default:
+		BUG();
+	}
+}
+
+static struct cfq_queue *
+cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
+	      struct bio *bio, gfp_t gfp_mask)
+{
+	int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
+	int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
+	struct cfq_queue **async_cfqq = NULL;
+	struct cfq_queue *cfqq = NULL;
+
+	if (!is_sync) {
+		if (!ioprio_valid(cic->ioprio)) {
+			struct task_struct *tsk = current;
+			ioprio = task_nice_ioprio(tsk);
+			ioprio_class = task_nice_ioclass(tsk);
+		}
+		async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
+		cfqq = *async_cfqq;
+	}
+
+	if (!cfqq)
+		cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic, bio, gfp_mask);
+
+	/*
+	 * pin the queue now that it's allocated, scheduler exit will prune it
+	 */
+	if (!is_sync && !(*async_cfqq)) {
+		cfqq->ref++;
+		*async_cfqq = cfqq;
+	}
+
+	cfqq->ref++;
+	return cfqq;
+}
+
+static void
+__cfq_update_io_thinktime(struct cfq_ttime *ttime, unsigned long slice_idle)
+{
+	unsigned long elapsed = jiffies - ttime->last_end_request;
+	elapsed = min(elapsed, 2UL * slice_idle);
+
+	ttime->ttime_samples = (7*ttime->ttime_samples + 256) / 8;
+	ttime->ttime_total = (7*ttime->ttime_total + 256*elapsed) / 8;
+	ttime->ttime_mean = (ttime->ttime_total + 128) / ttime->ttime_samples;
+}
+
+static void
+cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+			struct cfq_io_cq *cic)
+{
+	if (cfq_cfqq_sync(cfqq)) {
+		__cfq_update_io_thinktime(&cic->ttime, cfqd->cfq_slice_idle);
+		__cfq_update_io_thinktime(&cfqq->service_tree->ttime,
+			cfqd->cfq_slice_idle);
+	}
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	__cfq_update_io_thinktime(&cfqq->cfqg->ttime, cfqd->cfq_group_idle);
+#endif
+}
+
+static void
+cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		       struct request *rq)
+{
+	sector_t sdist = 0;
+	sector_t n_sec = blk_rq_sectors(rq);
+	if (cfqq->last_request_pos) {
+		if (cfqq->last_request_pos < blk_rq_pos(rq))
+			sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
+		else
+			sdist = cfqq->last_request_pos - blk_rq_pos(rq);
+	}
+
+	cfqq->seek_history <<= 1;
+	if (blk_queue_nonrot(cfqd->queue))
+		cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
+	else
+		cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
+}
+
+/*
+ * Disable idle window if the process thinks too long or seeks so much that
+ * it doesn't matter
+ */
+static void
+cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		       struct cfq_io_cq *cic)
+{
+	int old_idle, enable_idle;
+
+	/*
+	 * Don't idle for async or idle io prio class
+	 */
+	if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
+		return;
+
+	enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
+
+	if (cfqq->queued[0] + cfqq->queued[1] >= 4)
+		cfq_mark_cfqq_deep(cfqq);
+
+	if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
+		enable_idle = 0;
+	else if (!atomic_read(&cic->icq.ioc->active_ref) ||
+		 !cfqd->cfq_slice_idle ||
+		 (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
+		enable_idle = 0;
+	else if (sample_valid(cic->ttime.ttime_samples)) {
+		if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle)
+			enable_idle = 0;
+		else
+			enable_idle = 1;
+	}
+
+	if (old_idle != enable_idle) {
+		cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
+		if (enable_idle)
+			cfq_mark_cfqq_idle_window(cfqq);
+		else
+			cfq_clear_cfqq_idle_window(cfqq);
+	}
+}
+
+/*
+ * Check if new_cfqq should preempt the currently active queue. Return 0 for
+ * no or if we aren't sure, a 1 will cause a preempt.
+ */
+static bool
+cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
+		   struct request *rq)
+{
+	struct cfq_queue *cfqq;
+
+	cfqq = cfqd->active_queue;
+	if (!cfqq)
+		return false;
+
+	if (cfq_class_idle(new_cfqq))
+		return false;
+
+	if (cfq_class_idle(cfqq))
+		return true;
+
+	/*
+	 * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
+	 */
+	if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
+		return false;
+
+	/*
+	 * if the new request is sync, but the currently running queue is
+	 * not, let the sync request have priority.
+	 */
+	if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
+		return true;
+
+	if (new_cfqq->cfqg != cfqq->cfqg)
+		return false;
+
+	if (cfq_slice_used(cfqq))
+		return true;
+
+	/* Allow preemption only if we are idling on sync-noidle tree */
+	if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD &&
+	    cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
+	    new_cfqq->service_tree->count == 2 &&
+	    RB_EMPTY_ROOT(&cfqq->sort_list))
+		return true;
+
+	/*
+	 * So both queues are sync. Let the new request get disk time if
+	 * it's a metadata request and the current queue is doing regular IO.
+	 */
+	if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending)
+		return true;
+
+	/*
+	 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
+	 */
+	if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
+		return true;
+
+	/* An idle queue should not be idle now for some reason */
+	if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
+		return true;
+
+	if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
+		return false;
+
+	/*
+	 * if this request is as-good as one we would expect from the
+	 * current cfqq, let it preempt
+	 */
+	if (cfq_rq_close(cfqd, cfqq, rq))
+		return true;
+
+	return false;
+}
+
+/*
+ * cfqq preempts the active queue. if we allowed preempt with no slice left,
+ * let it have half of its nominal slice.
+ */
+static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	enum wl_type_t old_type = cfqq_type(cfqd->active_queue);
+
+	cfq_log_cfqq(cfqd, cfqq, "preempt");
+	cfq_slice_expired(cfqd, 1);
+
+	/*
+	 * workload type is changed, don't save slice, otherwise preempt
+	 * doesn't happen
+	 */
+	if (old_type != cfqq_type(cfqq))
+		cfqq->cfqg->saved_wl_slice = 0;
+
+	/*
+	 * Put the new queue at the front of the of the current list,
+	 * so we know that it will be selected next.
+	 */
+	BUG_ON(!cfq_cfqq_on_rr(cfqq));
+
+	cfq_service_tree_add(cfqd, cfqq, 1);
+
+	cfqq->slice_end = 0;
+	cfq_mark_cfqq_slice_new(cfqq);
+}
+
+/*
+ * Called when a new fs request (rq) is added (to cfqq). Check if there's
+ * something we should do about it
+ */
+static void
+cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		struct request *rq)
+{
+	struct cfq_io_cq *cic = RQ_CIC(rq);
+
+	cfqd->rq_queued++;
+	if (rq->cmd_flags & REQ_PRIO)
+		cfqq->prio_pending++;
+
+	cfq_update_io_thinktime(cfqd, cfqq, cic);
+	cfq_update_io_seektime(cfqd, cfqq, rq);
+	cfq_update_idle_window(cfqd, cfqq, cic);
+
+	cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
+
+	if (cfqq == cfqd->active_queue) {
+		/*
+		 * Remember that we saw a request from this process, but
+		 * don't start queuing just yet. Otherwise we risk seeing lots
+		 * of tiny requests, because we disrupt the normal plugging
+		 * and merging. If the request is already larger than a single
+		 * page, let it rip immediately. For that case we assume that
+		 * merging is already done. Ditto for a busy system that
+		 * has other work pending, don't risk delaying until the
+		 * idle timer unplug to continue working.
+		 */
+		if (cfq_cfqq_wait_request(cfqq)) {
+			if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
+			    cfqd->busy_queues > 1) {
+				cfq_del_timer(cfqd, cfqq);
+				cfq_clear_cfqq_wait_request(cfqq);
+				__blk_run_queue(cfqd->queue);
+			} else {
+				cfqg_stats_update_idle_time(cfqq->cfqg);
+				cfq_mark_cfqq_must_dispatch(cfqq);
+			}
+		}
+	} else if (cfq_should_preempt(cfqd, cfqq, rq)) {
+		/*
+		 * not the active queue - expire current slice if it is
+		 * idle and has expired it's mean thinktime or this new queue
+		 * has some old slice time left and is of higher priority or
+		 * this new queue is RT and the current one is BE
+		 */
+		cfq_preempt_queue(cfqd, cfqq);
+		__blk_run_queue(cfqd->queue);
+	}
+}
+
+static void cfq_insert_request(struct request_queue *q, struct request *rq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+
+	cfq_log_cfqq(cfqd, cfqq, "insert_request");
+	cfq_init_prio_data(cfqq, RQ_CIC(rq));
+
+	rq->fifo_time = jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)];
+	list_add_tail(&rq->queuelist, &cfqq->fifo);
+	cfq_add_rq_rb(rq);
+	cfqg_stats_update_io_add(RQ_CFQG(rq), cfqd->serving_group,
+				 rq->cmd_flags);
+	cfq_rq_enqueued(cfqd, cfqq, rq);
+}
+
+/*
+ * Update hw_tag based on peak queue depth over 50 samples under
+ * sufficient load.
+ */
+static void cfq_update_hw_tag(struct cfq_data *cfqd)
+{
+	struct cfq_queue *cfqq = cfqd->active_queue;
+
+	if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
+		cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
+
+	if (cfqd->hw_tag == 1)
+		return;
+
+	if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
+	    cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
+		return;
+
+	/*
+	 * If active queue hasn't enough requests and can idle, cfq might not
+	 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
+	 * case
+	 */
+	if (cfqq && cfq_cfqq_idle_window(cfqq) &&
+	    cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
+	    CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
+		return;
+
+	if (cfqd->hw_tag_samples++ < 50)
+		return;
+
+	if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
+		cfqd->hw_tag = 1;
+	else
+		cfqd->hw_tag = 0;
+}
+
+static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	struct cfq_io_cq *cic = cfqd->active_cic;
+
+	/* If the queue already has requests, don't wait */
+	if (!RB_EMPTY_ROOT(&cfqq->sort_list))
+		return false;
+
+	/* If there are other queues in the group, don't wait */
+	if (cfqq->cfqg->nr_cfqq > 1)
+		return false;
+
+	/* the only queue in the group, but think time is big */
+	if (cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true))
+		return false;
+
+	if (cfq_slice_used(cfqq))
+		return true;
+
+	/* if slice left is less than think time, wait busy */
+	if (cic && sample_valid(cic->ttime.ttime_samples)
+	    && (cfqq->slice_end - jiffies < cic->ttime.ttime_mean))
+		return true;
+
+	/*
+	 * If think times is less than a jiffy than ttime_mean=0 and above
+	 * will not be true. It might happen that slice has not expired yet
+	 * but will expire soon (4-5 ns) during select_queue(). To cover the
+	 * case where think time is less than a jiffy, mark the queue wait
+	 * busy if only 1 jiffy is left in the slice.
+	 */
+	if (cfqq->slice_end - jiffies == 1)
+		return true;
+
+	return false;
+}
+
+static void cfq_completed_request(struct request_queue *q, struct request *rq)
+{
+	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+	struct cfq_data *cfqd = cfqq->cfqd;
+	const int sync = rq_is_sync(rq);
+	unsigned long now;
+
+	now = jiffies;
+	cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
+		     !!(rq->cmd_flags & REQ_NOIDLE));
+
+	cfq_update_hw_tag(cfqd);
+
+	WARN_ON(!cfqd->rq_in_driver);
+	WARN_ON(!cfqq->dispatched);
+	cfqd->rq_in_driver--;
+	cfqq->dispatched--;
+	(RQ_CFQG(rq))->dispatched--;
+	cfqg_stats_update_completion(cfqq->cfqg, rq_start_time_ns(rq),
+				     rq_io_start_time_ns(rq), rq->cmd_flags);
+
+	cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
+
+	if (sync) {
+		struct cfq_rb_root *st;
+
+		RQ_CIC(rq)->ttime.last_end_request = now;
+
+		if (cfq_cfqq_on_rr(cfqq))
+			st = cfqq->service_tree;
+		else
+			st = st_for(cfqq->cfqg, cfqq_class(cfqq),
+					cfqq_type(cfqq));
+
+		st->ttime.last_end_request = now;
+		if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
+			cfqd->last_delayed_sync = now;
+	}
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	cfqq->cfqg->ttime.last_end_request = now;
+#endif
+
+	/*
+	 * If this is the active queue, check if it needs to be expired,
+	 * or if we want to idle in case it has no pending requests.
+	 */
+	if (cfqd->active_queue == cfqq) {
+		const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
+
+		if (cfq_cfqq_slice_new(cfqq)) {
+			cfq_set_prio_slice(cfqd, cfqq);
+			cfq_clear_cfqq_slice_new(cfqq);
+		}
+
+		/*
+		 * Should we wait for next request to come in before we expire
+		 * the queue.
+		 */
+		if (cfq_should_wait_busy(cfqd, cfqq)) {
+			unsigned long extend_sl = cfqd->cfq_slice_idle;
+			if (!cfqd->cfq_slice_idle)
+				extend_sl = cfqd->cfq_group_idle;
+			cfqq->slice_end = jiffies + extend_sl;
+			cfq_mark_cfqq_wait_busy(cfqq);
+			cfq_log_cfqq(cfqd, cfqq, "will busy wait");
+		}
+
+		/*
+		 * Idling is not enabled on:
+		 * - expired queues
+		 * - idle-priority queues
+		 * - async queues
+		 * - queues with still some requests queued
+		 * - when there is a close cooperator
+		 */
+		if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
+			cfq_slice_expired(cfqd, 1);
+		else if (sync && cfqq_empty &&
+			 !cfq_close_cooperator(cfqd, cfqq)) {
+			cfq_arm_slice_timer(cfqd);
+		}
+	}
+
+	if (!cfqd->rq_in_driver)
+		cfq_schedule_dispatch(cfqd);
+}
+
+static inline int __cfq_may_queue(struct cfq_queue *cfqq)
+{
+	if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
+		cfq_mark_cfqq_must_alloc_slice(cfqq);
+		return ELV_MQUEUE_MUST;
+	}
+
+	return ELV_MQUEUE_MAY;
+}
+
+static int cfq_may_queue(struct request_queue *q, int rw)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct task_struct *tsk = current;
+	struct cfq_io_cq *cic;
+	struct cfq_queue *cfqq;
+
+	/*
+	 * don't force setup of a queue from here, as a call to may_queue
+	 * does not necessarily imply that a request actually will be queued.
+	 * so just lookup a possibly existing queue, or return 'may queue'
+	 * if that fails
+	 */
+	cic = cfq_cic_lookup(cfqd, tsk->io_context);
+	if (!cic)
+		return ELV_MQUEUE_MAY;
+
+	cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
+	if (cfqq) {
+		cfq_init_prio_data(cfqq, cic);
+
+		return __cfq_may_queue(cfqq);
+	}
+
+	return ELV_MQUEUE_MAY;
+}
+
+/*
+ * queue lock held here
+ */
+static void cfq_put_request(struct request *rq)
+{
+	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+
+	if (cfqq) {
+		const int rw = rq_data_dir(rq);
+
+		BUG_ON(!cfqq->allocated[rw]);
+		cfqq->allocated[rw]--;
+
+		/* Put down rq reference on cfqg */
+		cfqg_put(RQ_CFQG(rq));
+		rq->elv.priv[0] = NULL;
+		rq->elv.priv[1] = NULL;
+
+		cfq_put_queue(cfqq);
+	}
+}
+
+static struct cfq_queue *
+cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_cq *cic,
+		struct cfq_queue *cfqq)
+{
+	cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
+	cic_set_cfqq(cic, cfqq->new_cfqq, 1);
+	cfq_mark_cfqq_coop(cfqq->new_cfqq);
+	cfq_put_queue(cfqq);
+	return cic_to_cfqq(cic, 1);
+}
+
+/*
+ * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
+ * was the last process referring to said cfqq.
+ */
+static struct cfq_queue *
+split_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq)
+{
+	if (cfqq_process_refs(cfqq) == 1) {
+		cfqq->pid = current->pid;
+		cfq_clear_cfqq_coop(cfqq);
+		cfq_clear_cfqq_split_coop(cfqq);
+		return cfqq;
+	}
+
+	cic_set_cfqq(cic, NULL, 1);
+
+	cfq_put_cooperator(cfqq);
+
+	cfq_put_queue(cfqq);
+	return NULL;
+}
+/*
+ * Allocate cfq data structures associated with this request.
+ */
+static int
+cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
+		gfp_t gfp_mask)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_io_cq *cic = icq_to_cic(rq->elv.icq);
+	const int rw = rq_data_dir(rq);
+	const bool is_sync = rq_is_sync(rq);
+	struct cfq_queue *cfqq;
+
+	might_sleep_if(gfp_mask & __GFP_WAIT);
+
+	spin_lock_irq(q->queue_lock);
+
+	check_ioprio_changed(cic, bio);
+	check_blkcg_changed(cic, bio);
+new_queue:
+	cfqq = cic_to_cfqq(cic, is_sync);
+	if (!cfqq || cfqq == &cfqd->oom_cfqq) {
+		cfqq = cfq_get_queue(cfqd, is_sync, cic, bio, gfp_mask);
+		cic_set_cfqq(cic, cfqq, is_sync);
+	} else {
+		/*
+		 * If the queue was seeky for too long, break it apart.
+		 */
+		if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
+			cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
+			cfqq = split_cfqq(cic, cfqq);
+			if (!cfqq)
+				goto new_queue;
+		}
+
+		/*
+		 * Check to see if this queue is scheduled to merge with
+		 * another, closely cooperating queue.  The merging of
+		 * queues happens here as it must be done in process context.
+		 * The reference on new_cfqq was taken in merge_cfqqs.
+		 */
+		if (cfqq->new_cfqq)
+			cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
+	}
+
+	cfqq->allocated[rw]++;
+
+	cfqq->ref++;
+	cfqg_get(cfqq->cfqg);
+	rq->elv.priv[0] = cfqq;
+	rq->elv.priv[1] = cfqq->cfqg;
+	spin_unlock_irq(q->queue_lock);
+	return 0;
+}
+
+static void cfq_kick_queue(struct work_struct *work)
+{
+	struct cfq_data *cfqd =
+		container_of(work, struct cfq_data, unplug_work);
+	struct request_queue *q = cfqd->queue;
+
+	spin_lock_irq(q->queue_lock);
+	__blk_run_queue(cfqd->queue);
+	spin_unlock_irq(q->queue_lock);
+}
+
+/*
+ * Timer running if the active_queue is currently idling inside its time slice
+ */
+static void cfq_idle_slice_timer(unsigned long data)
+{
+	struct cfq_data *cfqd = (struct cfq_data *) data;
+	struct cfq_queue *cfqq;
+	unsigned long flags;
+	int timed_out = 1;
+
+	cfq_log(cfqd, "idle timer fired");
+
+	spin_lock_irqsave(cfqd->queue->queue_lock, flags);
+
+	cfqq = cfqd->active_queue;
+	if (cfqq) {
+		timed_out = 0;
+
+		/*
+		 * We saw a request before the queue expired, let it through
+		 */
+		if (cfq_cfqq_must_dispatch(cfqq))
+			goto out_kick;
+
+		/*
+		 * expired
+		 */
+		if (cfq_slice_used(cfqq))
+			goto expire;
+
+		/*
+		 * only expire and reinvoke request handler, if there are
+		 * other queues with pending requests
+		 */
+		if (!cfqd->busy_queues)
+			goto out_cont;
+
+		/*
+		 * not expired and it has a request pending, let it dispatch
+		 */
+		if (!RB_EMPTY_ROOT(&cfqq->sort_list))
+			goto out_kick;
+
+		/*
+		 * Queue depth flag is reset only when the idle didn't succeed
+		 */
+		cfq_clear_cfqq_deep(cfqq);
+	}
+expire:
+	cfq_slice_expired(cfqd, timed_out);
+out_kick:
+	cfq_schedule_dispatch(cfqd);
+out_cont:
+	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+}
+
+static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
+{
+	del_timer_sync(&cfqd->idle_slice_timer);
+	cancel_work_sync(&cfqd->unplug_work);
+}
+
+static void cfq_put_async_queues(struct cfq_data *cfqd)
+{
+	int i;
+
+	for (i = 0; i < IOPRIO_BE_NR; i++) {
+		if (cfqd->async_cfqq[0][i])
+			cfq_put_queue(cfqd->async_cfqq[0][i]);
+		if (cfqd->async_cfqq[1][i])
+			cfq_put_queue(cfqd->async_cfqq[1][i]);
+	}
+
+	if (cfqd->async_idle_cfqq)
+		cfq_put_queue(cfqd->async_idle_cfqq);
+}
+
+static void cfq_exit_queue(struct elevator_queue *e)
+{
+	struct cfq_data *cfqd = e->elevator_data;
+	struct request_queue *q = cfqd->queue;
+
+	cfq_shutdown_timer_wq(cfqd);
+
+	spin_lock_irq(q->queue_lock);
+
+	if (cfqd->active_queue)
+		__cfq_slice_expired(cfqd, cfqd->active_queue, 0);
+
+	cfq_put_async_queues(cfqd);
+
+	spin_unlock_irq(q->queue_lock);
+
+	cfq_shutdown_timer_wq(cfqd);
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	blkcg_deactivate_policy(q, &blkcg_policy_cfq);
+#else
+	kfree(cfqd->root_group);
+#endif
+	kfree(cfqd);
+}
+
+static int cfq_init_queue(struct request_queue *q, struct elevator_type *e)
+{
+	struct cfq_data *cfqd;
+	struct blkcg_gq *blkg __maybe_unused;
+	int i, ret;
+	struct elevator_queue *eq;
+
+	eq = elevator_alloc(q, e);
+	if (!eq)
+		return -ENOMEM;
+
+	cfqd = kzalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
+	if (!cfqd) {
+		kobject_put(&eq->kobj);
+		return -ENOMEM;
+	}
+	eq->elevator_data = cfqd;
+
+	cfqd->queue = q;
+	spin_lock_irq(q->queue_lock);
+	q->elevator = eq;
+	spin_unlock_irq(q->queue_lock);
+
+	/* Init root service tree */
+	cfqd->grp_service_tree = CFQ_RB_ROOT;
+
+	/* Init root group and prefer root group over other groups by default */
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	ret = blkcg_activate_policy(q, &blkcg_policy_cfq);
+	if (ret)
+		goto out_free;
+
+	cfqd->root_group = blkg_to_cfqg(q->root_blkg);
+#else
+	ret = -ENOMEM;
+	cfqd->root_group = kzalloc_node(sizeof(*cfqd->root_group),
+					GFP_KERNEL, cfqd->queue->node);
+	if (!cfqd->root_group)
+		goto out_free;
+
+	cfq_init_cfqg_base(cfqd->root_group);
+#endif
+	cfqd->root_group->weight = 2 * CFQ_WEIGHT_DEFAULT;
+	cfqd->root_group->leaf_weight = 2 * CFQ_WEIGHT_DEFAULT;
+
+	/*
+	 * Not strictly needed (since RB_ROOT just clears the node and we
+	 * zeroed cfqd on alloc), but better be safe in case someone decides
+	 * to add magic to the rb code
+	 */
+	for (i = 0; i < CFQ_PRIO_LISTS; i++)
+		cfqd->prio_trees[i] = RB_ROOT;
+
+	/*
+	 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
+	 * Grab a permanent reference to it, so that the normal code flow
+	 * will not attempt to free it.  oom_cfqq is linked to root_group
+	 * but shouldn't hold a reference as it'll never be unlinked.  Lose
+	 * the reference from linking right away.
+	 */
+	cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
+	cfqd->oom_cfqq.ref++;
+
+	spin_lock_irq(q->queue_lock);
+	cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, cfqd->root_group);
+	cfqg_put(cfqd->root_group);
+	spin_unlock_irq(q->queue_lock);
+
+	init_timer(&cfqd->idle_slice_timer);
+	cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
+	cfqd->idle_slice_timer.data = (unsigned long) cfqd;
+
+	INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
+
+	cfqd->cfq_quantum = cfq_quantum;
+	cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
+	cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
+	cfqd->cfq_back_max = cfq_back_max;
+	cfqd->cfq_back_penalty = cfq_back_penalty;
+	cfqd->cfq_slice[0] = cfq_slice_async;
+	cfqd->cfq_slice[1] = cfq_slice_sync;
+	cfqd->cfq_target_latency = cfq_target_latency;
+	cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
+	cfqd->cfq_slice_idle = cfq_slice_idle;
+	cfqd->cfq_group_idle = cfq_group_idle;
+	cfqd->cfq_latency = 1;
+	cfqd->hw_tag = -1;
+	/*
+	 * we optimistically start assuming sync ops weren't delayed in last
+	 * second, in order to have larger depth for async operations.
+	 */
+	cfqd->last_delayed_sync = jiffies - HZ;
+	return 0;
+
+out_free:
+	kfree(cfqd);
+	kobject_put(&eq->kobj);
+	return ret;
+}
+
+/*
+ * sysfs parts below -->
+ */
+static ssize_t
+cfq_var_show(unsigned int var, char *page)
+{
+	return sprintf(page, "%u\n", var);
+}
+
+static ssize_t
+cfq_var_store(unsigned int *var, const char *page, size_t count)
+{
+	char *p = (char *) page;
+
+	*var = simple_strtoul(p, &p, 10);
+	return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
+static ssize_t __FUNC(struct elevator_queue *e, char *page)		\
+{									\
+	struct cfq_data *cfqd = e->elevator_data;			\
+	unsigned int __data = __VAR;					\
+	if (__CONV)							\
+		__data = jiffies_to_msecs(__data);			\
+	return cfq_var_show(__data, (page));				\
+}
+SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
+SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
+SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
+SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
+SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
+SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
+SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
+SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
+SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
+SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
+SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
+SHOW_FUNCTION(cfq_target_latency_show, cfqd->cfq_target_latency, 1);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
+static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)	\
+{									\
+	struct cfq_data *cfqd = e->elevator_data;			\
+	unsigned int __data;						\
+	int ret = cfq_var_store(&__data, (page), count);		\
+	if (__data < (MIN))						\
+		__data = (MIN);						\
+	else if (__data > (MAX))					\
+		__data = (MAX);						\
+	if (__CONV)							\
+		*(__PTR) = msecs_to_jiffies(__data);			\
+	else								\
+		*(__PTR) = __data;					\
+	return ret;							\
+}
+STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
+STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
+		UINT_MAX, 1);
+STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
+		UINT_MAX, 1);
+STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
+STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
+		UINT_MAX, 0);
+STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
+STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
+STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
+STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
+STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
+		UINT_MAX, 0);
+STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
+STORE_FUNCTION(cfq_target_latency_store, &cfqd->cfq_target_latency, 1, UINT_MAX, 1);
+#undef STORE_FUNCTION
+
+#define CFQ_ATTR(name) \
+	__ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
+
+static struct elv_fs_entry cfq_attrs[] = {
+	CFQ_ATTR(quantum),
+	CFQ_ATTR(fifo_expire_sync),
+	CFQ_ATTR(fifo_expire_async),
+	CFQ_ATTR(back_seek_max),
+	CFQ_ATTR(back_seek_penalty),
+	CFQ_ATTR(slice_sync),
+	CFQ_ATTR(slice_async),
+	CFQ_ATTR(slice_async_rq),
+	CFQ_ATTR(slice_idle),
+	CFQ_ATTR(group_idle),
+	CFQ_ATTR(low_latency),
+	CFQ_ATTR(target_latency),
+	__ATTR_NULL
+};
+
+static struct elevator_type iosched_cfq = {
+	.ops = {
+		.elevator_merge_fn = 		cfq_merge,
+		.elevator_merged_fn =		cfq_merged_request,
+		.elevator_merge_req_fn =	cfq_merged_requests,
+		.elevator_allow_merge_fn =	cfq_allow_merge,
+		.elevator_bio_merged_fn =	cfq_bio_merged,
+		.elevator_dispatch_fn =		cfq_dispatch_requests,
+		.elevator_add_req_fn =		cfq_insert_request,
+		.elevator_activate_req_fn =	cfq_activate_request,
+		.elevator_deactivate_req_fn =	cfq_deactivate_request,
+		.elevator_completed_req_fn =	cfq_completed_request,
+		.elevator_former_req_fn =	elv_rb_former_request,
+		.elevator_latter_req_fn =	elv_rb_latter_request,
+		.elevator_init_icq_fn =		cfq_init_icq,
+		.elevator_exit_icq_fn =		cfq_exit_icq,
+		.elevator_set_req_fn =		cfq_set_request,
+		.elevator_put_req_fn =		cfq_put_request,
+		.elevator_may_queue_fn =	cfq_may_queue,
+		.elevator_init_fn =		cfq_init_queue,
+		.elevator_exit_fn =		cfq_exit_queue,
+	},
+	.icq_size	=	sizeof(struct cfq_io_cq),
+	.icq_align	=	__alignof__(struct cfq_io_cq),
+	.elevator_attrs =	cfq_attrs,
+	.elevator_name	=	"cfq",
+	.elevator_owner =	THIS_MODULE,
+};
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+static struct blkcg_policy blkcg_policy_cfq = {
+	.pd_size		= sizeof(struct cfq_group),
+	.cftypes		= cfq_blkcg_files,
+
+	.pd_init_fn		= cfq_pd_init,
+	.pd_offline_fn		= cfq_pd_offline,
+	.pd_reset_stats_fn	= cfq_pd_reset_stats,
+};
+#endif
+
+static int __init cfq_init(void)
+{
+	int ret;
+
+	/*
+	 * could be 0 on HZ < 1000 setups
+	 */
+	if (!cfq_slice_async)
+		cfq_slice_async = 1;
+	if (!cfq_slice_idle)
+		cfq_slice_idle = 1;
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	if (!cfq_group_idle)
+		cfq_group_idle = 1;
+
+	ret = blkcg_policy_register(&blkcg_policy_cfq);
+	if (ret)
+		return ret;
+#else
+	cfq_group_idle = 0;
+#endif
+
+	ret = -ENOMEM;
+	cfq_pool = KMEM_CACHE(cfq_queue, 0);
+	if (!cfq_pool)
+		goto err_pol_unreg;
+
+	ret = elv_register(&iosched_cfq);
+	if (ret)
+		goto err_free_pool;
+
+	return 0;
+
+err_free_pool:
+	kmem_cache_destroy(cfq_pool);
+err_pol_unreg:
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	blkcg_policy_unregister(&blkcg_policy_cfq);
+#endif
+	return ret;
+}
+
+static void __exit cfq_exit(void)
+{
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+	blkcg_policy_unregister(&blkcg_policy_cfq);
+#endif
+	elv_unregister(&iosched_cfq);
+	kmem_cache_destroy(cfq_pool);
+}
+
+module_init(cfq_init);
+module_exit(cfq_exit);
+
+MODULE_AUTHOR("Jens Axboe");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");