text: /*
   * Header file for the BFQ I/O scheduler: data structures and
   * prototypes of interface functions among BFQ components.
   *
   *  This program is free software; you can redistribute it and/or
   *  modify it under the terms of the GNU General Public License as
   *  published by the Free Software Foundation; either version 2 of the
   *  License, or (at your option) any later version.
   *
   *  This program is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   *  General Public License for more details.
   */
  #ifndef _BFQ_H
  #define _BFQ_H
  
  #include <linux/blktrace_api.h>
  #include <linux/hrtimer.h>
  #include <linux/blk-cgroup.h>
  
  #define BFQ_IOPRIO_CLASSES	3
  #define BFQ_CL_IDLE_TIMEOUT	(HZ/5)
  
  #define BFQ_MIN_WEIGHT			1
  #define BFQ_MAX_WEIGHT			1000
  #define BFQ_WEIGHT_CONVERSION_COEFF	10
  
  #define BFQ_DEFAULT_QUEUE_IOPRIO	4
  
  #define BFQ_WEIGHT_LEGACY_DFL	100
  #define BFQ_DEFAULT_GRP_IOPRIO	0
  #define BFQ_DEFAULT_GRP_CLASS	IOPRIO_CLASS_BE
  
  /*
   * Soft real-time applications are extremely more latency sensitive
   * than interactive ones. Over-raise the weight of the former to
   * privilege them against the latter.
   */
  #define BFQ_SOFTRT_WEIGHT_FACTOR	100
  
  struct bfq_entity;
  
  /**
   * struct bfq_service_tree - per ioprio_class service tree.
   *
   * Each service tree represents a B-WF2Q+ scheduler on its own.  Each
   * ioprio_class has its own independent scheduler, and so its own
   * bfq_service_tree.  All the fields are protected by the queue lock
   * of the containing bfqd.
   */
  struct bfq_service_tree {
  	/* tree for active entities (i.e., those backlogged) */
  	struct rb_root active;
  	/* tree for idle entities (i.e., not backlogged, with V < F_i)*/
  	struct rb_root idle;
  
  	/* idle entity with minimum F_i */
  	struct bfq_entity *first_idle;
  	/* idle entity with maximum F_i */
  	struct bfq_entity *last_idle;
  
  	/* scheduler virtual time */
  	u64 vtime;
  	/* scheduler weight sum; active and idle entities contribute to it */
  	unsigned long wsum;
  };
  
  /**
   * struct bfq_sched_data - multi-class scheduler.
   *
   * bfq_sched_data is the basic scheduler queue.  It supports three
   * ioprio_classes, and can be used either as a toplevel queue or as an
   * intermediate queue in a hierarchical setup.
   *
   * The supported ioprio_classes are the same as in CFQ, in descending
   * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
   * Requests from higher priority queues are served before all the
   * requests from lower priority queues; among requests of the same
   * queue requests are served according to B-WF2Q+.
   *
   * The schedule is implemented by the service trees, plus the field
   * @next_in_service, which points to the entity on the active trees
   * that will be served next, if 1) no changes in the schedule occurs
   * before the current in-service entity is expired, 2) the in-service
   * queue becomes idle when it expires, and 3) if the entity pointed by
   * in_service_entity is not a queue, then the in-service child entity
   * of the entity pointed by in_service_entity becomes idle on
   * expiration. This peculiar definition allows for the following
   * optimization, not yet exploited: while a given entity is still in
   * service, we already know which is the best candidate for next
   * service among the other active entitities in the same parent
   * entity. We can then quickly compare the timestamps of the
   * in-service entity with those of such best candidate.
   *
   * All fields are protected by the lock of the containing bfqd.
   */
  struct bfq_sched_data {
  	/* entity in service */
  	struct bfq_entity *in_service_entity;
  	/* head-of-line entity (see comments above) */
  	struct bfq_entity *next_in_service;
  	/* array of service trees, one per ioprio_class */
  	struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
  	/* last time CLASS_IDLE was served */
  	unsigned long bfq_class_idle_last_service;
  
  };
  
  /**
   * struct bfq_weight_counter - counter of the number of all active queues
   *                             with a given weight.
   */
  struct bfq_weight_counter {
  	unsigned int weight; /* weight of the queues this counter refers to */
  	unsigned int num_active; /* nr of active queues with this weight */
  	/*
  	 * Weights tree member (see bfq_data's @queue_weights_tree)
  	 */
  	struct rb_node weights_node;
  };
  
  /**
   * struct bfq_entity - schedulable entity.
   *
   * A bfq_entity is used to represent either a bfq_queue (leaf node in the
   * cgroup hierarchy) or a bfq_group into the upper level scheduler.  Each
   * entity belongs to the sched_data of the parent group in the cgroup
   * hierarchy.  Non-leaf entities have also their own sched_data, stored
   * in @my_sched_data.
   *
   * Each entity stores independently its priority values; this would
   * allow different weights on different devices, but this
   * functionality is not exported to userspace by now.  Priorities and
   * weights are updated lazily, first storing the new values into the
   * new_* fields, then setting the @prio_changed flag.  As soon as
   * there is a transition in the entity state that allows the priority
   * update to take place the effective and the requested priority
   * values are synchronized.
   *
   * Unless cgroups are used, the weight value is calculated from the
   * ioprio to export the same interface as CFQ.  When dealing with
   * ``well-behaved'' queues (i.e., queues that do not spend too much
   * time to consume their budget and have true sequential behavior, and
   * when there are no external factors breaking anticipation) the
   * relative weights at each level of the cgroups hierarchy should be
   * guaranteed.  All the fields are protected by the queue lock of the
   * containing bfqd.
   */
  struct bfq_entity {
  	/* service_tree member */
  	struct rb_node rb_node;
  
  	/*
  	 * Flag, true if the entity is on a tree (either the active or
  	 * the idle one of its service_tree) or is in service.
  	 */
  	bool on_st;
  
  	/* B-WF2Q+ start and finish timestamps [sectors/weight] */
  	u64 start, finish;
  
  	/* tree the entity is enqueued into; %NULL if not on a tree */
  	struct rb_root *tree;
  
  	/*
  	 * minimum start time of the (active) subtree rooted at this
  	 * entity; used for O(log N) lookups into active trees
  	 */
  	u64 min_start;
  
  	/* amount of service received during the last service slot */
  	int service;
  
  	/* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */
  	int budget;
  
  	/* weight of the queue */
  	int weight;
  	/* next weight if a change is in progress */
  	int new_weight;
  
  	/* original weight, used to implement weight boosting */
  	int orig_weight;
  
  	/* parent entity, for hierarchical scheduling */
  	struct bfq_entity *parent;
  
  	/*
  	 * For non-leaf nodes in the hierarchy, the associated
  	 * scheduler queue, %NULL on leaf nodes.
  	 */
  	struct bfq_sched_data *my_sched_data;
  	/* the scheduler queue this entity belongs to */
  	struct bfq_sched_data *sched_data;
  
  	/* flag, set to request a weight, ioprio or ioprio_class change  */
  	int prio_changed;
  
  	/* flag, set if the entity is counted in groups_with_pending_reqs */
  	bool in_groups_with_pending_reqs;
  };
  
  struct bfq_group;
  
  /**
   * struct bfq_ttime - per process thinktime stats.
   */
  struct bfq_ttime {
  	/* completion time of the last request */
  	u64 last_end_request;
  
  	/* total process thinktime */
  	u64 ttime_total;
  	/* number of thinktime samples */
  	unsigned long ttime_samples;
  	/* average process thinktime */
  	u64 ttime_mean;
  };
  
  /**
   * struct bfq_queue - leaf schedulable entity.
   *
   * A bfq_queue is a leaf request queue; it can be associated with an
   * io_context or more, if it  is  async or shared  between  cooperating
   * processes. @cgroup holds a reference to the cgroup, to be sure that it
   * does not disappear while a bfqq still references it (mostly to avoid
   * races between request issuing and task migration followed by cgroup
   * destruction).
   * All the fields are protected by the queue lock of the containing bfqd.
   */
  struct bfq_queue {
  	/* reference counter */
  	int ref;
  	/* parent bfq_data */
  	struct bfq_data *bfqd;
  
  	/* current ioprio and ioprio class */
  	unsigned short ioprio, ioprio_class;
  	/* next ioprio and ioprio class if a change is in progress */
  	unsigned short new_ioprio, new_ioprio_class;
  
  	/*
  	 * Shared bfq_queue if queue is cooperating with one or more
  	 * other queues.
  	 */
  	struct bfq_queue *new_bfqq;
  	/* request-position tree member (see bfq_group's @rq_pos_tree) */
  	struct rb_node pos_node;
  	/* request-position tree root (see bfq_group's @rq_pos_tree) */
  	struct rb_root *pos_root;
  
  	/* sorted list of pending requests */
  	struct rb_root sort_list;
  	/* if fifo isn't expired, next request to serve */
  	struct request *next_rq;
  	/* number of sync and async requests queued */
  	int queued[2];
  	/* number of requests currently allocated */
  	int allocated;
  	/* number of pending metadata requests */
  	int meta_pending;
  	/* fifo list of requests in sort_list */
  	struct list_head fifo;
  
  	/* entity representing this queue in the scheduler */
  	struct bfq_entity entity;
  
  	/* pointer to the weight counter associated with this entity */
  	struct bfq_weight_counter *weight_counter;
  
  	/* maximum budget allowed from the feedback mechanism */
  	int max_budget;
  	/* budget expiration (in jiffies) */
  	unsigned long budget_timeout;
  
  	/* number of requests on the dispatch list or inside driver */
  	int dispatched;
  
  	/* status flags */
  	unsigned long flags;
  
  	/* node for active/idle bfqq list inside parent bfqd */
  	struct list_head bfqq_list;
  
  	/* associated @bfq_ttime struct */
  	struct bfq_ttime ttime;
  
  	/* bit vector: a 1 for each seeky requests in history */
  	u32 seek_history;
  
  	/* node for the device's burst list */
  	struct hlist_node burst_list_node;
  
  	/* position of the last request enqueued */
  	sector_t last_request_pos;
  
  	/* Number of consecutive pairs of request completion and
  	 * arrival, such that the queue becomes idle after the
  	 * completion, but the next request arrives within an idle
  	 * time slice; used only if the queue's IO_bound flag has been
  	 * cleared.
  	 */
  	unsigned int requests_within_timer;
  
  	/* pid of the process owning the queue, used for logging purposes */
  	pid_t pid;
  
  	/*
  	 * Pointer to the bfq_io_cq owning the bfq_queue, set to %NULL
  	 * if the queue is shared.
  	 */
  	struct bfq_io_cq *bic;
  
  	/* current maximum weight-raising time for this queue */
  	unsigned long wr_cur_max_time;
  	/*
  	 * Minimum time instant such that, only if a new request is
  	 * enqueued after this time instant in an idle @bfq_queue with
  	 * no outstanding requests, then the task associated with the
  	 * queue it is deemed as soft real-time (see the comments on
  	 * the function bfq_bfqq_softrt_next_start())
  	 */
  	unsigned long soft_rt_next_start;
  	/*
  	 * Start time of the current weight-raising period if
  	 * the @bfq-queue is being weight-raised, otherwise
  	 * finish time of the last weight-raising period.
  	 */
  	unsigned long last_wr_start_finish;
  	/* factor by which the weight of this queue is multiplied */
  	unsigned int wr_coeff;
  	/*
  	 * Time of the last transition of the @bfq_queue from idle to
  	 * backlogged.
  	 */
  	unsigned long last_idle_bklogged;
  	/*
  	 * Cumulative service received from the @bfq_queue since the
  	 * last transition from idle to backlogged.
  	 */
  	unsigned long service_from_backlogged;
  	/*
  	 * Cumulative service received from the @bfq_queue since its
  	 * last transition to weight-raised state.
  	 */
  	unsigned long service_from_wr;
  
  	/*
  	 * Value of wr start time when switching to soft rt
  	 */
  	unsigned long wr_start_at_switch_to_srt;
  
  	unsigned long split_time; /* time of last split */
  
  	unsigned long first_IO_time; /* time of first I/O for this queue */
  
  	/* max service rate measured so far */
  	u32 max_service_rate;
  	/*
  	 * Ratio between the service received by bfqq while it is in
  	 * service, and the cumulative service (of requests of other
  	 * queues) that may be injected while bfqq is empty but still
  	 * in service. To increase precision, the coefficient is
  	 * measured in tenths of unit. Here are some example of (1)
  	 * ratios, (2) resulting percentages of service injected
  	 * w.r.t. to the total service dispatched while bfqq is in
  	 * service, and (3) corresponding values of the coefficient:
  	 * 1 (50%) -> 10
  	 * 2 (33%) -> 20
  	 * 10 (9%) -> 100
  	 * 9.9 (9%) -> 99
  	 * 1.5 (40%) -> 15
  	 * 0.5 (66%) -> 5
  	 * 0.1 (90%) -> 1
  	 *
  	 * So, if the coefficient is lower than 10, then
  	 * injected service is more than bfqq service.
  	 */
  	unsigned int inject_coeff;
  	/* amount of service injected in current service slot */
  	unsigned int injected_service;
  };
  
  /**
   * struct bfq_io_cq - per (request_queue, io_context) structure.
   */
  struct bfq_io_cq {
  	/* associated io_cq structure */
  	struct io_cq icq; /* must be the first member */
  	/* array of two process queues, the sync and the async */
  	struct bfq_queue *bfqq[2];
  	/* per (request_queue, blkcg) ioprio */
  	int ioprio;
  #ifdef CONFIG_BFQ_GROUP_IOSCHED
  	uint64_t blkcg_serial_nr; /* the current blkcg serial */
  #endif
  	/*
  	 * Snapshot of the has_short_time flag before merging; taken
  	 * to remember its value while the queue is merged, so as to
  	 * be able to restore it in case of split.
  	 */
  	bool saved_has_short_ttime;
  	/*
  	 * Same purpose as the previous two fields for the I/O bound
  	 * classification of a queue.
  	 */
  	bool saved_IO_bound;
  
  	/*
  	 * Same purpose as the previous fields for the value of the
  	 * field keeping the queue's belonging to a large burst
  	 */
  	bool saved_in_large_burst;
  	/*
  	 * True if the queue belonged to a burst list before its merge
  	 * with another cooperating queue.
  	 */
  	bool was_in_burst_list;
  
  	/*
  	 * Similar to previous fields: save wr information.
  	 */
  	unsigned long saved_wr_coeff;
  	unsigned long saved_last_wr_start_finish;
  	unsigned long saved_wr_start_at_switch_to_srt;
  	unsigned int saved_wr_cur_max_time;
  	struct bfq_ttime saved_ttime;
  };
  
  /**
   * struct bfq_data - per-device data structure.
   *
   * All the fields are protected by @lock.
   */
  struct bfq_data {
  	/* device request queue */
  	struct request_queue *queue;
  	/* dispatch queue */
  	struct list_head dispatch;
  
  	/* root bfq_group for the device */
  	struct bfq_group *root_group;
  
  	/*
  	 * rbtree of weight counters of @bfq_queues, sorted by
  	 * weight. Used to keep track of whether all @bfq_queues have
  	 * the same weight. The tree contains one counter for each
  	 * distinct weight associated to some active and not
  	 * weight-raised @bfq_queue (see the comments to the functions
  	 * bfq_weights_tree_[add|remove] for further details).
  	 */
  	struct rb_root queue_weights_tree;
  
  	/*
  	 * Number of groups with at least one descendant process that
  	 * has at least one request waiting for completion. Note that
  	 * this accounts for also requests already dispatched, but not
  	 * yet completed. Therefore this number of groups may differ
  	 * (be larger) than the number of active groups, as a group is
  	 * considered active only if its corresponding entity has
  	 * descendant queues with at least one request queued. This
  	 * number is used to decide whether a scenario is symmetric.
  	 * For a detailed explanation see comments on the computation
  	 * of the variable asymmetric_scenario in the function
  	 * bfq_better_to_idle().
  	 *
  	 * However, it is hard to compute this number exactly, for
  	 * groups with multiple descendant processes. Consider a group
  	 * that is inactive, i.e., that has no descendant process with
  	 * pending I/O inside BFQ queues. Then suppose that
  	 * num_groups_with_pending_reqs is still accounting for this
  	 * group, because the group has descendant processes with some
  	 * I/O request still in flight. num_groups_with_pending_reqs
  	 * should be decremented when the in-flight request of the
  	 * last descendant process is finally completed (assuming that
  	 * nothing else has changed for the group in the meantime, in
  	 * terms of composition of the group and active/inactive state of child
  	 * groups and processes). To accomplish this, an additional
  	 * pending-request counter must be added to entities, and must
  	 * be updated correctly. To avoid this additional field and operations,
  	 * we resort to the following tradeoff between simplicity and
  	 * accuracy: for an inactive group that is still counted in
  	 * num_groups_with_pending_reqs, we decrement
  	 * num_groups_with_pending_reqs when the first descendant
  	 * process of the group remains with no request waiting for
  	 * completion.
  	 *
  	 * Even this simpler decrement strategy requires a little
  	 * carefulness: to avoid multiple decrements, we flag a group,
  	 * more precisely an entity representing a group, as still
  	 * counted in num_groups_with_pending_reqs when it becomes
  	 * inactive. Then, when the first descendant queue of the
  	 * entity remains with no request waiting for completion,
  	 * num_groups_with_pending_reqs is decremented, and this flag
  	 * is reset. After this flag is reset for the entity,
  	 * num_groups_with_pending_reqs won't be decremented any
  	 * longer in case a new descendant queue of the entity remains
  	 * with no request waiting for completion.
  	 */
  	unsigned int num_groups_with_pending_reqs;
  
  	/*
  	 * Per-class (RT, BE, IDLE) number of bfq_queues containing
  	 * requests (including the queue in service, even if it is
  	 * idling).
  	 */
  	unsigned int busy_queues[3];
  	/* number of weight-raised busy @bfq_queues */
  	int wr_busy_queues;
  	/* number of queued requests */
  	int queued;
  	/* number of requests dispatched and waiting for completion */
  	int rq_in_driver;
  
  	/*
  	 * Maximum number of requests in driver in the last
  	 * @hw_tag_samples completed requests.
  	 */
  	int max_rq_in_driver;
  	/* number of samples used to calculate hw_tag */
  	int hw_tag_samples;
  	/* flag set to one if the driver is showing a queueing behavior */
  	int hw_tag;
  
  	/* number of budgets assigned */
  	int budgets_assigned;
  
  	/*
  	 * Timer set when idling (waiting) for the next request from
  	 * the queue in service.
  	 */
  	struct hrtimer idle_slice_timer;
  
  	/* bfq_queue in service */
  	struct bfq_queue *in_service_queue;
  
  	/* on-disk position of the last served request */
  	sector_t last_position;
  
  	/* position of the last served request for the in-service queue */
  	sector_t in_serv_last_pos;
  
  	/* time of last request completion (ns) */
  	u64 last_completion;
  
  	/* time of first rq dispatch in current observation interval (ns) */
  	u64 first_dispatch;
  	/* time of last rq dispatch in current observation interval (ns) */
  	u64 last_dispatch;
  
  	/* beginning of the last budget */
  	ktime_t last_budget_start;
  	/* beginning of the last idle slice */
  	ktime_t last_idling_start;
  
  	/* number of samples in current observation interval */
  	int peak_rate_samples;
  	/* num of samples of seq dispatches in current observation interval */
  	u32 sequential_samples;
  	/* total num of sectors transferred in current observation interval */
  	u64 tot_sectors_dispatched;
  	/* max rq size seen during current observation interval (sectors) */
  	u32 last_rq_max_size;
  	/* time elapsed from first dispatch in current observ. interval (us) */
  	u64 delta_from_first;
  	/*
  	 * Current estimate of the device peak rate, measured in
  	 * [(sectors/usec) / 2^BFQ_RATE_SHIFT]. The left-shift by
  	 * BFQ_RATE_SHIFT is performed to increase precision in
  	 * fixed-point calculations.
  	 */
  	u32 peak_rate;
  
  	/* maximum budget allotted to a bfq_queue before rescheduling */
  	int bfq_max_budget;
  
  	/* list of all the bfq_queues active on the device */
  	struct list_head active_list;
  	/* list of all the bfq_queues idle on the device */
  	struct list_head idle_list;
  
  	/*
  	 * Timeout for async/sync requests; when it fires, requests
  	 * are served in fifo order.
  	 */
  	u64 bfq_fifo_expire[2];
  	/* weight of backward seeks wrt forward ones */
  	unsigned int bfq_back_penalty;
  	/* maximum allowed backward seek */
  	unsigned int bfq_back_max;
  	/* maximum idling time */
  	u32 bfq_slice_idle;
  
  	/* user-configured max budget value (0 for auto-tuning) */
  	int bfq_user_max_budget;
  	/*
  	 * Timeout for bfq_queues to consume their budget; used to
  	 * prevent seeky queues from imposing long latencies to
  	 * sequential or quasi-sequential ones (this also implies that
  	 * seeky queues cannot receive guarantees in the service
  	 * domain; after a timeout they are charged for the time they
  	 * have been in service, to preserve fairness among them, but
  	 * without service-domain guarantees).
  	 */
  	unsigned int bfq_timeout;
  
  	/*
  	 * Number of consecutive requests that must be issued within
  	 * the idle time slice to set again idling to a queue which
  	 * was marked as non-I/O-bound (see the definition of the
  	 * IO_bound flag for further details).
  	 */
  	unsigned int bfq_requests_within_timer;
  
  	/*
  	 * Force device idling whenever needed to provide accurate
  	 * service guarantees, without caring about throughput
  	 * issues. CAVEAT: this may even increase latencies, in case
  	 * of useless idling for processes that did stop doing I/O.
  	 */
  	bool strict_guarantees;
  
  	/*
  	 * Last time at which a queue entered the current burst of
  	 * queues being activated shortly after each other; for more
  	 * details about this and the following parameters related to
  	 * a burst of activations, see the comments on the function
  	 * bfq_handle_burst.
  	 */
  	unsigned long last_ins_in_burst;
  	/*
  	 * Reference time interval used to decide whether a queue has
  	 * been activated shortly after @last_ins_in_burst.
  	 */
  	unsigned long bfq_burst_interval;
  	/* number of queues in the current burst of queue activations */
  	int burst_size;
  
  	/* common parent entity for the queues in the burst */
  	struct bfq_entity *burst_parent_entity;
  	/* Maximum burst size above which the current queue-activation
  	 * burst is deemed as 'large'.
  	 */
  	unsigned long bfq_large_burst_thresh;
  	/* true if a large queue-activation burst is in progress */
  	bool large_burst;
  	/*
  	 * Head of the burst list (as for the above fields, more
  	 * details in the comments on the function bfq_handle_burst).
  	 */
  	struct hlist_head burst_list;
  
  	/* if set to true, low-latency heuristics are enabled */
  	bool low_latency;
  	/*
  	 * Maximum factor by which the weight of a weight-raised queue
  	 * is multiplied.
  	 */
  	unsigned int bfq_wr_coeff;
  	/* maximum duration of a weight-raising period (jiffies) */
  	unsigned int bfq_wr_max_time;
  
  	/* Maximum weight-raising duration for soft real-time processes */
  	unsigned int bfq_wr_rt_max_time;
  	/*
  	 * Minimum idle period after which weight-raising may be
  	 * reactivated for a queue (in jiffies).
  	 */
  	unsigned int bfq_wr_min_idle_time;
  	/*
  	 * Minimum period between request arrivals after which
  	 * weight-raising may be reactivated for an already busy async
  	 * queue (in jiffies).
  	 */
  	unsigned long bfq_wr_min_inter_arr_async;
  
  	/* Max service-rate for a soft real-time queue, in sectors/sec */
  	unsigned int bfq_wr_max_softrt_rate;
  	/*
  	 * Cached value of the product ref_rate*ref_wr_duration, used
  	 * for computing the maximum duration of weight raising
  	 * automatically.
  	 */
  	u64 rate_dur_prod;
  
  	/* fallback dummy bfqq for extreme OOM conditions */
  	struct bfq_queue oom_bfqq;
  
  	spinlock_t lock;
  
  	/*
  	 * bic associated with the task issuing current bio for
  	 * merging. This and the next field are used as a support to
  	 * be able to perform the bic lookup, needed by bio-merge
  	 * functions, before the scheduler lock is taken, and thus
  	 * avoid taking the request-queue lock while the scheduler
  	 * lock is being held.
  	 */
  	struct bfq_io_cq *bio_bic;
  	/* bfqq associated with the task issuing current bio for merging */
  	struct bfq_queue *bio_bfqq;
  
  	/*
  	 * Depth limits used in bfq_limit_depth (see comments on the
  	 * function)
  	 */
  	unsigned int word_depths[2][2];
  };
  
  enum bfqq_state_flags {
  	BFQQF_just_created = 0,	/* queue just allocated */
  	BFQQF_busy,		/* has requests or is in service */
  	BFQQF_wait_request,	/* waiting for a request */
  	BFQQF_non_blocking_wait_rq, /*
  				     * waiting for a request
  				     * without idling the device
  				     */
  	BFQQF_fifo_expire,	/* FIFO checked in this slice */
  	BFQQF_has_short_ttime,	/* queue has a short think time */
  	BFQQF_sync,		/* synchronous queue */
  	BFQQF_IO_bound,		/*
  				 * bfqq has timed-out at least once
  				 * having consumed at most 2/10 of
  				 * its budget
  				 */
  	BFQQF_in_large_burst,	/*
  				 * bfqq activated in a large burst,
  				 * see comments to bfq_handle_burst.
  				 */
  	BFQQF_softrt_update,	/*
  				 * may need softrt-next-start
  				 * update
  				 */
  	BFQQF_coop,		/* bfqq is shared */
  	BFQQF_split_coop	/* shared bfqq will be split */
  };
  
  #define BFQ_BFQQ_FNS(name)						\
  void bfq_mark_bfqq_##name(struct bfq_queue *bfqq);			\
  void bfq_clear_bfqq_##name(struct bfq_queue *bfqq);			\
  int bfq_bfqq_##name(const struct bfq_queue *bfqq);
  
  BFQ_BFQQ_FNS(just_created);
  BFQ_BFQQ_FNS(busy);
  BFQ_BFQQ_FNS(wait_request);
  BFQ_BFQQ_FNS(non_blocking_wait_rq);
  BFQ_BFQQ_FNS(fifo_expire);
  BFQ_BFQQ_FNS(has_short_ttime);
  BFQ_BFQQ_FNS(sync);
  BFQ_BFQQ_FNS(IO_bound);
  BFQ_BFQQ_FNS(in_large_burst);
  BFQ_BFQQ_FNS(coop);
  BFQ_BFQQ_FNS(split_coop);
  BFQ_BFQQ_FNS(softrt_update);
  #undef BFQ_BFQQ_FNS
  
  /* Expiration reasons. */
  enum bfqq_expiration {
  	BFQQE_TOO_IDLE = 0,		/*
  					 * queue has been idling for
  					 * too long
  					 */
  	BFQQE_BUDGET_TIMEOUT,	/* budget took too long to be used */
  	BFQQE_BUDGET_EXHAUSTED,	/* budget consumed */
  	BFQQE_NO_MORE_REQUESTS,	/* the queue has no more requests */
  	BFQQE_PREEMPTED		/* preemption in progress */
  };
  
  struct bfqg_stats {
  #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
  	/* 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 disk time and nr sectors dispatched by this group */
  	struct blkg_stat		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 */
  	u64				start_group_wait_time;
  	u64				start_idle_time;
  	u64				start_empty_time;
  	uint16_t			flags;
  #endif	/* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
  };
  
  #ifdef CONFIG_BFQ_GROUP_IOSCHED
  
  /*
   * struct bfq_group_data - per-blkcg storage for the blkio subsystem.
   *
   * @ps: @blkcg_policy_storage that this structure inherits
   * @weight: weight of the bfq_group
   */
  struct bfq_group_data {
  	/* must be the first member */
  	struct blkcg_policy_data pd;
  
  	unsigned int weight;
  };
  
  /**
   * struct bfq_group - per (device, cgroup) data structure.
   * @entity: schedulable entity to insert into the parent group sched_data.
   * @sched_data: own sched_data, to contain child entities (they may be
   *              both bfq_queues and bfq_groups).
   * @bfqd: the bfq_data for the device this group acts upon.
   * @async_bfqq: array of async queues for all the tasks belonging to
   *              the group, one queue per ioprio value per ioprio_class,
   *              except for the idle class that has only one queue.
   * @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
   * @my_entity: pointer to @entity, %NULL for the toplevel group; used
   *             to avoid too many special cases during group creation/
   *             migration.
   * @stats: stats for this bfqg.
   * @active_entities: number of active entities belonging to the group;
   *                   unused for the root group. Used to know whether there
   *                   are groups with more than one active @bfq_entity
   *                   (see the comments to the function
   *                   bfq_bfqq_may_idle()).
   * @rq_pos_tree: rbtree sorted by next_request position, used when
   *               determining if two or more queues have interleaving
   *               requests (see bfq_find_close_cooperator()).
   *
   * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
   * there is a set of bfq_groups, each one collecting the lower-level
   * entities belonging to the group that are acting on the same device.
   *
   * Locking works as follows:
   *    o @bfqd is protected by the queue lock, RCU is used to access it
   *      from the readers.
   *    o All the other fields are protected by the @bfqd queue lock.
   */
  struct bfq_group {
  	/* must be the first member */
  	struct blkg_policy_data pd;
  
  	/* cached path for this blkg (see comments in bfq_bic_update_cgroup) */
  	char blkg_path[128];
  
  	/* reference counter (see comments in bfq_bic_update_cgroup) */
  	int ref;
  
  	struct bfq_entity entity;
  	struct bfq_sched_data sched_data;
  
  	void *bfqd;
  
  	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
  	struct bfq_queue *async_idle_bfqq;
  
  	struct bfq_entity *my_entity;
  
  	int active_entities;
  
  	struct rb_root rq_pos_tree;
  
  	struct bfqg_stats stats;
  };
  
  #else
  struct bfq_group {
  	struct bfq_sched_data sched_data;
  
  	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
  	struct bfq_queue *async_idle_bfqq;
  
  	struct rb_root rq_pos_tree;
  };
  #endif
  
  struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
  
  /* --------------- main algorithm interface ----------------- */
  
  #define BFQ_SERVICE_TREE_INIT	((struct bfq_service_tree)		\
  				{ RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
  
  extern const int bfq_timeout;
  
  struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync);
  void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync);
  struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic);
  void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq);
  void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  			  struct rb_root *root);
  void __bfq_weights_tree_remove(struct bfq_data *bfqd,
  			       struct bfq_queue *bfqq,
  			       struct rb_root *root);
  void bfq_weights_tree_remove(struct bfq_data *bfqd,
  			     struct bfq_queue *bfqq);
  void bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  		     bool compensate, enum bfqq_expiration reason);
  void bfq_put_queue(struct bfq_queue *bfqq);
  void bfq_end_wr_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
  void bfq_schedule_dispatch(struct bfq_data *bfqd);
  void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
  
  /* ------------ end of main algorithm interface -------------- */
  
  /* ---------------- cgroups-support interface ---------------- */
  
  void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
  			      unsigned int op);
  void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op);
  void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op);
  void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
  				  u64 io_start_time_ns, unsigned int op);
  void bfqg_stats_update_dequeue(struct bfq_group *bfqg);
  void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg);
  void bfqg_stats_update_idle_time(struct bfq_group *bfqg);
  void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg);
  void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg);
  void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  		   struct bfq_group *bfqg);
  
  void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg);
  void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio);
  void bfq_end_wr_async(struct bfq_data *bfqd);
  struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
  				     struct blkcg *blkcg);
  struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg);
  struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
  struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node);
  void bfqg_and_blkg_put(struct bfq_group *bfqg);
  
  #ifdef CONFIG_BFQ_GROUP_IOSCHED
  extern struct cftype bfq_blkcg_legacy_files[];
  extern struct cftype bfq_blkg_files[];
  extern struct blkcg_policy blkcg_policy_bfq;
  #endif
  
  /* ------------- end of cgroups-support interface ------------- */
  
  /* - interface of the internal hierarchical B-WF2Q+ scheduler - */
  
  #ifdef CONFIG_BFQ_GROUP_IOSCHED
  /* both next loops stop at one of the child entities of the root group */
  #define for_each_entity(entity)	\
  	for (; entity ; entity = entity->parent)
  
  /*
   * For each iteration, compute parent in advance, so as to be safe if
   * entity is deallocated during the iteration. Such a deallocation may
   * happen as a consequence of a bfq_put_queue that frees the bfq_queue
   * containing entity.
   */
  #define for_each_entity_safe(entity, parent) \
  	for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
  
  #else /* CONFIG_BFQ_GROUP_IOSCHED */
  /*
   * Next two macros are fake loops when cgroups support is not
   * enabled. I fact, in such a case, there is only one level to go up
   * (to reach the root group).
   */
  #define for_each_entity(entity)	\
  	for (; entity ; entity = NULL)
  
  #define for_each_entity_safe(entity, parent) \
  	for (parent = NULL; entity ; entity = parent)
  #endif /* CONFIG_BFQ_GROUP_IOSCHED */
  
  struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq);
  struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
  unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd);
  struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity);
  struct bfq_entity *bfq_entity_of(struct rb_node *node);
  unsigned short bfq_ioprio_to_weight(int ioprio);
  void bfq_put_idle_entity(struct bfq_service_tree *st,
  			 struct bfq_entity *entity);
  struct bfq_service_tree *
  __bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
  				struct bfq_entity *entity,
  				bool update_class_too);
  void bfq_bfqq_served(struct bfq_queue *bfqq, int served);
  void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  			  unsigned long time_ms);
  bool __bfq_deactivate_entity(struct bfq_entity *entity,
  			     bool ins_into_idle_tree);
  bool next_queue_may_preempt(struct bfq_data *bfqd);
  struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd);
  void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd);
  void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  			 bool ins_into_idle_tree, bool expiration);
  void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq);
  void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  		      bool expiration);
  void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
  		       bool expiration);
  void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq);
  
  /* --------------- end of interface of B-WF2Q+ ---------------- */
  
  /* Logging facilities. */
  #ifdef CONFIG_BFQ_GROUP_IOSCHED
  struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
  
  #define bfq_log_bfqq(bfqd, bfqq, fmt, args...)	do {			\
  	blk_add_cgroup_trace_msg((bfqd)->queue,				\
  			bfqg_to_blkg(bfqq_group(bfqq))->blkcg,		\
  			"bfq%d%c " fmt, (bfqq)->pid,			\
  			bfq_bfqq_sync((bfqq)) ? 'S' : 'A', ##args);	\
  } while (0)
  
  #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)	do {			\
  	blk_add_cgroup_trace_msg((bfqd)->queue,				\
  		bfqg_to_blkg(bfqg)->blkcg, fmt, ##args);		\
  } while (0)
  
  #else /* CONFIG_BFQ_GROUP_IOSCHED */
  
  #define bfq_log_bfqq(bfqd, bfqq, fmt, args...)	\
  	blk_add_trace_msg((bfqd)->queue, "bfq%d%c " fmt, (bfqq)->pid,	\
  			bfq_bfqq_sync((bfqq)) ? 'S' : 'A',		\
  				##args)
  #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)		do {} while (0)
  
  #endif /* CONFIG_BFQ_GROUP_IOSCHED */
  
  #define bfq_log(bfqd, fmt, args...) \
  	blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)
  
  #endif /* _BFQ_H */
  