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 /* SPDX-License-Identifier: GPL-2.0-or-later */
 /*
  * Header file for the BFQ I/O scheduler: data structures and
  * prototypes of interface functions among BFQ components.
  */
 #ifndef _BFQ_H
 #define _BFQ_H
 
 #include <linux/blktrace_api.h>
 #include <linux/hrtimer.h>
 
 #include "blk-cgroup-rwstat.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
 
 #define MAX_BFQQ_NAME_LENGTH 16
 
 /*
  * 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 entities 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_or_in_serv;
 
     /* 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;
 
     /* Number of requests allocated in the subtree of this entity */
     int allocated;
 
     /* device weight, if non-zero, it overrides the default weight of
      * bfq_group_data */
     int dev_weight;
     /* 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;
 
     /* last child queue of entity created (for non-leaf entities) */
     struct bfq_queue *last_bfqq_created;
 };
 
 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;
     /* counter of references from other queues for delayed stable merge */
     int stable_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;
 
     /* last total-service-time sample, see bfq_update_inject_limit() */
     u64 last_serv_time_ns;
     /* limit for request injection */
     unsigned int inject_limit;
     /* last time the inject limit has been decreased, in jiffies */
     unsigned long decrease_time_jif;
 
     /*
      * 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 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;
 
     /* when bfqq started to do I/O within the last observation window */
     u64 io_start_time;
     /* how long bfqq has remained empty during the last observ. window */
     u64 tot_idle_time;
 
     /* 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 */
 
     unsigned long creation_time; /* when this queue is created */
 
     /* max service rate measured so far */
     u32 max_service_rate;
 
     /*
      * Pointer to the waker queue for this queue, i.e., to the
      * queue Q such that this queue happens to get new I/O right
      * after some I/O request of Q is completed. For details, see
      * the comments on the choice of the queue for injection in
      * bfq_select_queue().
      */
     struct bfq_queue *waker_bfqq;
     /* pointer to the curr. tentative waker queue, see bfq_check_waker() */
     struct bfq_queue *tentative_waker_bfqq;
     /* number of times the same tentative waker has been detected */
     unsigned int num_waker_detections;
     /* time when we started considering this waker */
     u64 waker_detection_started;
 
     /* node for woken_list, see below */
     struct hlist_node woken_list_node;
     /*
      * Head of the list of the woken queues for this queue, i.e.,
      * of the list of the queues for which this queue is a waker
      * queue. This list is used to reset the waker_bfqq pointer in
      * the woken queues when this queue exits.
      */
     struct hlist_head woken_list;
 };
 
 /**
  * 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;
 
     u64 saved_io_start_time;
     u64 saved_tot_idle_time;
 
     /*
      * 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;
 
     /*
      * Save the weight when a merge occurs, to be able
      * to restore it in case of split. If the weight is not
      * correctly resumed when the queue is recycled,
      * then the weight of the recycled queue could differ
      * from the weight of the original queue.
      */
     unsigned int saved_weight;
 
     /*
      * Similar to previous fields: save wr information.
      */
     unsigned long saved_wr_coeff;
     unsigned long saved_last_wr_start_finish;
     unsigned long saved_service_from_wr;
     unsigned long saved_wr_start_at_switch_to_srt;
     unsigned int saved_wr_cur_max_time;
     struct bfq_ttime saved_ttime;
 
     /* Save also injection state */
     u64 saved_last_serv_time_ns;
     unsigned int saved_inject_limit;
     unsigned long saved_decrease_time_jif;
 
     /* candidate queue for a stable merge (due to close creation time) */
     struct bfq_queue *stable_merge_bfqq;
 
     bool stably_merged; /* non splittable if true */
     unsigned int requests;  /* Number of requests this process has in flight */
 };
 
 /**
  * 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_cached 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;
 
     /* true if the device is non rotational and performs queueing */
     bool nonrot_with_queueing;
 
     /*
      * 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;
 
     /* bfqq owning the last completed rq */
     struct bfq_queue *last_completed_rq_bfqq;
 
     /* last bfqq created, among those in the root group */
     struct bfq_queue *last_bfqq_created;
 
     /* time of last transition from empty to non-empty (ns) */
     u64 last_empty_occupied_ns;
 
     /*
      * Flag set to activate the sampling of the total service time
      * of a just-arrived first I/O request (see
      * bfq_update_inject_limit()). This will cause the setting of
      * waited_rq when the request is finally dispatched.
      */
     bool wait_dispatch;
     /*
      *  If set, then bfq_update_inject_limit() is invoked when
      *  waited_rq is eventually completed.
      */
     struct request *waited_rq;
     /*
      * True if some request has been injected during the last service hole.
      */
     bool rqs_injected;
 
     /* 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;
     unsigned long last_idling_start_jiffies;
 
     /* 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;
 
     /*
      * 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];
     unsigned int full_depth_shift;
 };
 
 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 bfq_stat {
     struct percpu_counter       cpu_cnt;
     atomic64_t          aux_cnt;
 };
 
 struct bfqg_stats {
     /* basic stats */
     struct blkg_rwstat      bytes;
     struct blkg_rwstat      ios;
 #ifdef CONFIG_BFQ_CGROUP_DEBUG
     /* 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 bfq_stat     time;
     /* sum of number of ios queued across all samples */
     struct bfq_stat     avg_queue_size_sum;
     /* count of samples taken for average */
     struct bfq_stat     avg_queue_size_samples;
     /* how many times this group has been removed from service tree */
     struct bfq_stat     dequeue;
     /* total time spent waiting for it to be assigned a timeslice. */
     struct bfq_stat     group_wait_time;
     /* time spent idling for this blkcg_gq */
     struct bfq_stat     idle_time;
     /* total time with empty current active q with other requests queued */
     struct bfq_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_CGROUP_DEBUG */
 };
 
 #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;
     /* Is bfq_group still online? */
     bool online;
 
     struct bfq_entity entity;
     struct bfq_sched_data sched_data;
 
     void *bfqd;
 
     struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
     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_entity entity;
     struct bfq_sched_data sched_data;
 
     struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
     struct bfq_queue *async_idle_bfqq;
 
     struct rb_root rq_pos_tree;
 };
 #endif
 
 /* --------------- 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_cached *root);
 void __bfq_weights_tree_remove(struct bfq_data *bfqd,
                    struct bfq_queue *bfqq,
                    struct rb_root_cached *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_put_cooperator(struct bfq_queue *bfqq);
 void bfq_end_wr_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
 void bfq_release_process_ref(struct bfq_data *bfqd, struct bfq_queue *bfqq);
 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_legacy_io(struct request_queue *q, struct request *rq);
 void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
                   blk_opf_t opf);
 void bfqg_stats_update_io_remove(struct bfq_group *bfqg, blk_opf_t opf);
 void bfqg_stats_update_io_merged(struct bfq_group *bfqg, blk_opf_t opf);
 void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
                   u64 io_start_time_ns, blk_opf_t opf);
 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_bio_bfqg(struct bfq_data *bfqd, struct bio *bio);
 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_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);
 bool __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. */
 static inline void bfq_bfqq_name(struct bfq_queue *bfqq, char *str, int len)
 {
     char type = bfq_bfqq_sync(bfqq) ? 'S' : 'A';
 
     if (bfqq->pid != -1)
         snprintf(str, len, "bfq%d%c", bfqq->pid, type);
     else
         snprintf(str, len, "bfqSHARED-%c", type);
 }
 
 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
 
 #define bfq_log_bfqq(bfqd, bfqq, fmt, args...)  do {            \
     char pid_str[MAX_BFQQ_NAME_LENGTH];             \
     if (likely(!blk_trace_note_message_enabled((bfqd)->queue))) \
         break;                          \
     bfq_bfqq_name((bfqq), pid_str, MAX_BFQQ_NAME_LENGTH);       \
     blk_add_cgroup_trace_msg((bfqd)->queue,             \
             &bfqg_to_blkg(bfqq_group(bfqq))->blkcg->css,    \
             "%s " fmt, pid_str, ##args);            \
 } while (0)
 
 #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)  do {            \
     blk_add_cgroup_trace_msg((bfqd)->queue,             \
         &bfqg_to_blkg(bfqg)->blkcg->css, fmt, ##args);      \
 } while (0)
 
 #else /* CONFIG_BFQ_GROUP_IOSCHED */
 
 #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \
     char pid_str[MAX_BFQQ_NAME_LENGTH];             \
     if (likely(!blk_trace_note_message_enabled((bfqd)->queue))) \
         break;                          \
     bfq_bfqq_name((bfqq), pid_str, MAX_BFQQ_NAME_LENGTH);       \
     blk_add_trace_msg((bfqd)->queue, "%s " fmt, pid_str, ##args);   \
 } while (0)
 #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 */

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