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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef BLK_MQ_H
 #define BLK_MQ_H
 
 #include <linux/blkdev.h>
 #include <linux/sbitmap.h>
 #include <linux/lockdep.h>
 #include <linux/scatterlist.h>
 #include <linux/prefetch.h>
 
 struct blk_mq_tags;
 struct blk_flush_queue;
 
 #define BLKDEV_MIN_RQ   4
 #define BLKDEV_DEFAULT_RQ   128
 
 typedef void (rq_end_io_fn)(struct request *, blk_status_t);
 
 /*
  * request flags */
 typedef __u32 __bitwise req_flags_t;
 
 /* drive already may have started this one */
 #define RQF_STARTED     ((__force req_flags_t)(1 << 1))
 /* may not be passed by ioscheduler */
 #define RQF_SOFTBARRIER     ((__force req_flags_t)(1 << 3))
 /* request for flush sequence */
 #define RQF_FLUSH_SEQ       ((__force req_flags_t)(1 << 4))
 /* merge of different types, fail separately */
 #define RQF_MIXED_MERGE     ((__force req_flags_t)(1 << 5))
 /* track inflight for MQ */
 #define RQF_MQ_INFLIGHT     ((__force req_flags_t)(1 << 6))
 /* don't call prep for this one */
 #define RQF_DONTPREP        ((__force req_flags_t)(1 << 7))
 /* vaguely specified driver internal error.  Ignored by the block layer */
 #define RQF_FAILED      ((__force req_flags_t)(1 << 10))
 /* don't warn about errors */
 #define RQF_QUIET       ((__force req_flags_t)(1 << 11))
 /* elevator private data attached */
 #define RQF_ELVPRIV     ((__force req_flags_t)(1 << 12))
 /* account into disk and partition IO statistics */
 #define RQF_IO_STAT     ((__force req_flags_t)(1 << 13))
 /* runtime pm request */
 #define RQF_PM          ((__force req_flags_t)(1 << 15))
 /* on IO scheduler merge hash */
 #define RQF_HASHED      ((__force req_flags_t)(1 << 16))
 /* track IO completion time */
 #define RQF_STATS       ((__force req_flags_t)(1 << 17))
 /* Look at ->special_vec for the actual data payload instead of the
    bio chain. */
 #define RQF_SPECIAL_PAYLOAD ((__force req_flags_t)(1 << 18))
 /* The per-zone write lock is held for this request */
 #define RQF_ZONE_WRITE_LOCKED   ((__force req_flags_t)(1 << 19))
 /* already slept for hybrid poll */
 #define RQF_MQ_POLL_SLEPT   ((__force req_flags_t)(1 << 20))
 /* ->timeout has been called, don't expire again */
 #define RQF_TIMED_OUT       ((__force req_flags_t)(1 << 21))
 /* queue has elevator attached */
 #define RQF_ELV         ((__force req_flags_t)(1 << 22))
 #define RQF_RESV            ((__force req_flags_t)(1 << 23))
 
 /* flags that prevent us from merging requests: */
 #define RQF_NOMERGE_FLAGS \
     (RQF_STARTED | RQF_SOFTBARRIER | RQF_FLUSH_SEQ | RQF_SPECIAL_PAYLOAD)
 
 enum mq_rq_state {
     MQ_RQ_IDLE      = 0,
     MQ_RQ_IN_FLIGHT     = 1,
     MQ_RQ_COMPLETE      = 2,
 };
 
 /*
  * Try to put the fields that are referenced together in the same cacheline.
  *
  * If you modify this structure, make sure to update blk_rq_init() and
  * especially blk_mq_rq_ctx_init() to take care of the added fields.
  */
 struct request {
     struct request_queue *q;
     struct blk_mq_ctx *mq_ctx;
     struct blk_mq_hw_ctx *mq_hctx;
 
     blk_opf_t cmd_flags;        /* op and common flags */
     req_flags_t rq_flags;
 
     int tag;
     int internal_tag;
 
     unsigned int timeout;
 
     /* the following two fields are internal, NEVER access directly */
     unsigned int __data_len;    /* total data len */
     sector_t __sector;      /* sector cursor */
 
     struct bio *bio;
     struct bio *biotail;
 
     union {
         struct list_head queuelist;
         struct request *rq_next;
     };
 
     struct block_device *part;
 #ifdef CONFIG_BLK_RQ_ALLOC_TIME
     /* Time that the first bio started allocating this request. */
     u64 alloc_time_ns;
 #endif
     /* Time that this request was allocated for this IO. */
     u64 start_time_ns;
     /* Time that I/O was submitted to the device. */
     u64 io_start_time_ns;
 
 #ifdef CONFIG_BLK_WBT
     unsigned short wbt_flags;
 #endif
     /*
      * rq sectors used for blk stats. It has the same value
      * with blk_rq_sectors(rq), except that it never be zeroed
      * by completion.
      */
     unsigned short stats_sectors;
 
     /*
      * Number of scatter-gather DMA addr+len pairs after
      * physical address coalescing is performed.
      */
     unsigned short nr_phys_segments;
 
 #ifdef CONFIG_BLK_DEV_INTEGRITY
     unsigned short nr_integrity_segments;
 #endif
 
 #ifdef CONFIG_BLK_INLINE_ENCRYPTION
     struct bio_crypt_ctx *crypt_ctx;
     struct blk_crypto_keyslot *crypt_keyslot;
 #endif
 
     unsigned short write_hint;
     unsigned short ioprio;
 
     enum mq_rq_state state;
     atomic_t ref;
 
     unsigned long deadline;
 
     /*
      * The hash is used inside the scheduler, and killed once the
      * request reaches the dispatch list. The ipi_list is only used
      * to queue the request for softirq completion, which is long
      * after the request has been unhashed (and even removed from
      * the dispatch list).
      */
     union {
         struct hlist_node hash; /* merge hash */
         struct llist_node ipi_list;
     };
 
     /*
      * The rb_node is only used inside the io scheduler, requests
      * are pruned when moved to the dispatch queue. So let the
      * completion_data share space with the rb_node.
      */
     union {
         struct rb_node rb_node; /* sort/lookup */
         struct bio_vec special_vec;
         void *completion_data;
     };
 
 
     /*
      * Three pointers are available for the IO schedulers, if they need
      * more they have to dynamically allocate it.  Flush requests are
      * never put on the IO scheduler. So let the flush fields share
      * space with the elevator data.
      */
     union {
         struct {
             struct io_cq        *icq;
             void            *priv[2];
         } elv;
 
         struct {
             unsigned int        seq;
             struct list_head    list;
             rq_end_io_fn        *saved_end_io;
         } flush;
     };
 
     union {
         struct __call_single_data csd;
         u64 fifo_time;
     };
 
     /*
      * completion callback.
      */
     rq_end_io_fn *end_io;
     void *end_io_data;
 };
 
 static inline enum req_op req_op(const struct request *req)
 {
     return req->cmd_flags & REQ_OP_MASK;
 }
 
 static inline bool blk_rq_is_passthrough(struct request *rq)
 {
     return blk_op_is_passthrough(req_op(rq));
 }
 
 static inline unsigned short req_get_ioprio(struct request *req)
 {
     return req->ioprio;
 }
 
 #define rq_data_dir(rq)     (op_is_write(req_op(rq)) ? WRITE : READ)
 
 #define rq_dma_dir(rq) \
     (op_is_write(req_op(rq)) ? DMA_TO_DEVICE : DMA_FROM_DEVICE)
 
 #define rq_list_add(listptr, rq)    do {        \
     (rq)->rq_next = *(listptr);         \
     *(listptr) = rq;                \
 } while (0)
 
 #define rq_list_pop(listptr)                \
 ({                          \
     struct request *__req = NULL;           \
     if ((listptr) && *(listptr))    {       \
         __req = *(listptr);         \
         *(listptr) = __req->rq_next;        \
     }                       \
     __req;                      \
 })
 
 #define rq_list_peek(listptr)               \
 ({                          \
     struct request *__req = NULL;           \
     if ((listptr) && *(listptr))            \
         __req = *(listptr);         \
     __req;                      \
 })
 
 #define rq_list_for_each(listptr, pos)          \
     for (pos = rq_list_peek((listptr)); pos; pos = rq_list_next(pos))
 
 #define rq_list_for_each_safe(listptr, pos, nxt)            \
     for (pos = rq_list_peek((listptr)), nxt = rq_list_next(pos);    \
         pos; pos = nxt, nxt = pos ? rq_list_next(pos) : NULL)
 
 #define rq_list_next(rq)    (rq)->rq_next
 #define rq_list_empty(list) ((list) == (struct request *) NULL)
 
 /**
  * rq_list_move() - move a struct request from one list to another
  * @src: The source list @rq is currently in
  * @dst: The destination list that @rq will be appended to
  * @rq: The request to move
  * @prev: The request preceding @rq in @src (NULL if @rq is the head)
  */
 static inline void rq_list_move(struct request **src, struct request **dst,
                 struct request *rq, struct request *prev)
 {
     if (prev)
         prev->rq_next = rq->rq_next;
     else
         *src = rq->rq_next;
     rq_list_add(dst, rq);
 }
 
 enum blk_eh_timer_return {
     BLK_EH_DONE,        /* drivers has completed the command */
     BLK_EH_RESET_TIMER, /* reset timer and try again */
 };
 
 #define BLK_TAG_ALLOC_FIFO 0 /* allocate starting from 0 */
 #define BLK_TAG_ALLOC_RR 1 /* allocate starting from last allocated tag */
 
 /**
  * struct blk_mq_hw_ctx - State for a hardware queue facing the hardware
  * block device
  */
 struct blk_mq_hw_ctx {
     struct {
         /** @lock: Protects the dispatch list. */
         spinlock_t      lock;
         /**
          * @dispatch: Used for requests that are ready to be
          * dispatched to the hardware but for some reason (e.g. lack of
          * resources) could not be sent to the hardware. As soon as the
          * driver can send new requests, requests at this list will
          * be sent first for a fairer dispatch.
          */
         struct list_head    dispatch;
          /**
           * @state: BLK_MQ_S_* flags. Defines the state of the hw
           * queue (active, scheduled to restart, stopped).
           */
         unsigned long       state;
     } ____cacheline_aligned_in_smp;
 
     /**
      * @run_work: Used for scheduling a hardware queue run at a later time.
      */
     struct delayed_work run_work;
     /** @cpumask: Map of available CPUs where this hctx can run. */
     cpumask_var_t       cpumask;
     /**
      * @next_cpu: Used by blk_mq_hctx_next_cpu() for round-robin CPU
      * selection from @cpumask.
      */
     int         next_cpu;
     /**
      * @next_cpu_batch: Counter of how many works left in the batch before
      * changing to the next CPU.
      */
     int         next_cpu_batch;
 
     /** @flags: BLK_MQ_F_* flags. Defines the behaviour of the queue. */
     unsigned long       flags;
 
     /**
      * @sched_data: Pointer owned by the IO scheduler attached to a request
      * queue. It's up to the IO scheduler how to use this pointer.
      */
     void            *sched_data;
     /**
      * @queue: Pointer to the request queue that owns this hardware context.
      */
     struct request_queue    *queue;
     /** @fq: Queue of requests that need to perform a flush operation. */
     struct blk_flush_queue  *fq;
 
     /**
      * @driver_data: Pointer to data owned by the block driver that created
      * this hctx
      */
     void            *driver_data;
 
     /**
      * @ctx_map: Bitmap for each software queue. If bit is on, there is a
      * pending request in that software queue.
      */
     struct sbitmap      ctx_map;
 
     /**
      * @dispatch_from: Software queue to be used when no scheduler was
      * selected.
      */
     struct blk_mq_ctx   *dispatch_from;
     /**
      * @dispatch_busy: Number used by blk_mq_update_dispatch_busy() to
      * decide if the hw_queue is busy using Exponential Weighted Moving
      * Average algorithm.
      */
     unsigned int        dispatch_busy;
 
     /** @type: HCTX_TYPE_* flags. Type of hardware queue. */
     unsigned short      type;
     /** @nr_ctx: Number of software queues. */
     unsigned short      nr_ctx;
     /** @ctxs: Array of software queues. */
     struct blk_mq_ctx   **ctxs;
 
     /** @dispatch_wait_lock: Lock for dispatch_wait queue. */
     spinlock_t      dispatch_wait_lock;
     /**
      * @dispatch_wait: Waitqueue to put requests when there is no tag
      * available at the moment, to wait for another try in the future.
      */
     wait_queue_entry_t  dispatch_wait;
 
     /**
      * @wait_index: Index of next available dispatch_wait queue to insert
      * requests.
      */
     atomic_t        wait_index;
 
     /**
      * @tags: Tags owned by the block driver. A tag at this set is only
      * assigned when a request is dispatched from a hardware queue.
      */
     struct blk_mq_tags  *tags;
     /**
      * @sched_tags: Tags owned by I/O scheduler. If there is an I/O
      * scheduler associated with a request queue, a tag is assigned when
      * that request is allocated. Else, this member is not used.
      */
     struct blk_mq_tags  *sched_tags;
 
     /** @queued: Number of queued requests. */
     unsigned long       queued;
     /** @run: Number of dispatched requests. */
     unsigned long       run;
 
     /** @numa_node: NUMA node the storage adapter has been connected to. */
     unsigned int        numa_node;
     /** @queue_num: Index of this hardware queue. */
     unsigned int        queue_num;
 
     /**
      * @nr_active: Number of active requests. Only used when a tag set is
      * shared across request queues.
      */
     atomic_t        nr_active;
 
     /** @cpuhp_online: List to store request if CPU is going to die */
     struct hlist_node   cpuhp_online;
     /** @cpuhp_dead: List to store request if some CPU die. */
     struct hlist_node   cpuhp_dead;
     /** @kobj: Kernel object for sysfs. */
     struct kobject      kobj;
 
 #ifdef CONFIG_BLK_DEBUG_FS
     /**
      * @debugfs_dir: debugfs directory for this hardware queue. Named
      * as cpu<cpu_number>.
      */
     struct dentry       *debugfs_dir;
     /** @sched_debugfs_dir: debugfs directory for the scheduler. */
     struct dentry       *sched_debugfs_dir;
 #endif
 
     /**
      * @hctx_list: if this hctx is not in use, this is an entry in
      * q->unused_hctx_list.
      */
     struct list_head    hctx_list;
 };
 
 /**
  * struct blk_mq_queue_map - Map software queues to hardware queues
  * @mq_map:       CPU ID to hardware queue index map. This is an array
  *  with nr_cpu_ids elements. Each element has a value in the range
  *  [@queue_offset, @queue_offset + @nr_queues).
  * @nr_queues:    Number of hardware queues to map CPU IDs onto.
  * @queue_offset: First hardware queue to map onto. Used by the PCIe NVMe
  *  driver to map each hardware queue type (enum hctx_type) onto a distinct
  *  set of hardware queues.
  */
 struct blk_mq_queue_map {
     unsigned int *mq_map;
     unsigned int nr_queues;
     unsigned int queue_offset;
 };
 
 /**
  * enum hctx_type - Type of hardware queue
  * @HCTX_TYPE_DEFAULT:  All I/O not otherwise accounted for.
  * @HCTX_TYPE_READ: Just for READ I/O.
  * @HCTX_TYPE_POLL: Polled I/O of any kind.
  * @HCTX_MAX_TYPES: Number of types of hctx.
  */
 enum hctx_type {
     HCTX_TYPE_DEFAULT,
     HCTX_TYPE_READ,
     HCTX_TYPE_POLL,
 
     HCTX_MAX_TYPES,
 };
 
 /**
  * struct blk_mq_tag_set - tag set that can be shared between request queues
  * @map:       One or more ctx -> hctx mappings. One map exists for each
  *         hardware queue type (enum hctx_type) that the driver wishes
  *         to support. There are no restrictions on maps being of the
  *         same size, and it's perfectly legal to share maps between
  *         types.
  * @nr_maps:       Number of elements in the @map array. A number in the range
  *         [1, HCTX_MAX_TYPES].
  * @ops:       Pointers to functions that implement block driver behavior.
  * @nr_hw_queues:  Number of hardware queues supported by the block driver that
  *         owns this data structure.
  * @queue_depth:   Number of tags per hardware queue, reserved tags included.
  * @reserved_tags: Number of tags to set aside for BLK_MQ_REQ_RESERVED tag
  *         allocations.
  * @cmd_size:      Number of additional bytes to allocate per request. The block
  *         driver owns these additional bytes.
  * @numa_node:     NUMA node the storage adapter has been connected to.
  * @timeout:       Request processing timeout in jiffies.
  * @flags:     Zero or more BLK_MQ_F_* flags.
  * @driver_data:   Pointer to data owned by the block driver that created this
  *         tag set.
  * @tags:      Tag sets. One tag set per hardware queue. Has @nr_hw_queues
  *         elements.
  * @shared_tags:
  *         Shared set of tags. Has @nr_hw_queues elements. If set,
  *         shared by all @tags.
  * @tag_list_lock: Serializes tag_list accesses.
  * @tag_list:      List of the request queues that use this tag set. See also
  *         request_queue.tag_set_list.
  */
 struct blk_mq_tag_set {
     struct blk_mq_queue_map map[HCTX_MAX_TYPES];
     unsigned int        nr_maps;
     const struct blk_mq_ops *ops;
     unsigned int        nr_hw_queues;
     unsigned int        queue_depth;
     unsigned int        reserved_tags;
     unsigned int        cmd_size;
     int         numa_node;
     unsigned int        timeout;
     unsigned int        flags;
     void            *driver_data;
 
     struct blk_mq_tags  **tags;
 
     struct blk_mq_tags  *shared_tags;
 
     struct mutex        tag_list_lock;
     struct list_head    tag_list;
 };
 
 /**
  * struct blk_mq_queue_data - Data about a request inserted in a queue
  *
  * @rq:   Request pointer.
  * @last: If it is the last request in the queue.
  */
 struct blk_mq_queue_data {
     struct request *rq;
     bool last;
 };
 
 typedef bool (busy_tag_iter_fn)(struct request *, void *);
 
 /**
  * struct blk_mq_ops - Callback functions that implements block driver
  * behaviour.
  */
 struct blk_mq_ops {
     /**
      * @queue_rq: Queue a new request from block IO.
      */
     blk_status_t (*queue_rq)(struct blk_mq_hw_ctx *,
                  const struct blk_mq_queue_data *);
 
     /**
      * @commit_rqs: If a driver uses bd->last to judge when to submit
      * requests to hardware, it must define this function. In case of errors
      * that make us stop issuing further requests, this hook serves the
      * purpose of kicking the hardware (which the last request otherwise
      * would have done).
      */
     void (*commit_rqs)(struct blk_mq_hw_ctx *);
 
     /**
      * @queue_rqs: Queue a list of new requests. Driver is guaranteed
      * that each request belongs to the same queue. If the driver doesn't
      * empty the @rqlist completely, then the rest will be queued
      * individually by the block layer upon return.
      */
     void (*queue_rqs)(struct request **rqlist);
 
     /**
      * @get_budget: Reserve budget before queue request, once .queue_rq is
      * run, it is driver's responsibility to release the
      * reserved budget. Also we have to handle failure case
      * of .get_budget for avoiding I/O deadlock.
      */
     int (*get_budget)(struct request_queue *);
 
     /**
      * @put_budget: Release the reserved budget.
      */
     void (*put_budget)(struct request_queue *, int);
 
     /**
      * @set_rq_budget_token: store rq's budget token
      */
     void (*set_rq_budget_token)(struct request *, int);
     /**
      * @get_rq_budget_token: retrieve rq's budget token
      */
     int (*get_rq_budget_token)(struct request *);
 
     /**
      * @timeout: Called on request timeout.
      */
     enum blk_eh_timer_return (*timeout)(struct request *);
 
     /**
      * @poll: Called to poll for completion of a specific tag.
      */
     int (*poll)(struct blk_mq_hw_ctx *, struct io_comp_batch *);
 
     /**
      * @complete: Mark the request as complete.
      */
     void (*complete)(struct request *);
 
     /**
      * @init_hctx: Called when the block layer side of a hardware queue has
      * been set up, allowing the driver to allocate/init matching
      * structures.
      */
     int (*init_hctx)(struct blk_mq_hw_ctx *, void *, unsigned int);
     /**
      * @exit_hctx: Ditto for exit/teardown.
      */
     void (*exit_hctx)(struct blk_mq_hw_ctx *, unsigned int);
 
     /**
      * @init_request: Called for every command allocated by the block layer
      * to allow the driver to set up driver specific data.
      *
      * Tag greater than or equal to queue_depth is for setting up
      * flush request.
      */
     int (*init_request)(struct blk_mq_tag_set *set, struct request *,
                 unsigned int, unsigned int);
     /**
      * @exit_request: Ditto for exit/teardown.
      */
     void (*exit_request)(struct blk_mq_tag_set *set, struct request *,
                  unsigned int);
 
     /**
      * @cleanup_rq: Called before freeing one request which isn't completed
      * yet, and usually for freeing the driver private data.
      */
     void (*cleanup_rq)(struct request *);
 
     /**
      * @busy: If set, returns whether or not this queue currently is busy.
      */
     bool (*busy)(struct request_queue *);
 
     /**
      * @map_queues: This allows drivers specify their own queue mapping by
      * overriding the setup-time function that builds the mq_map.
      */
     int (*map_queues)(struct blk_mq_tag_set *set);
 
 #ifdef CONFIG_BLK_DEBUG_FS
     /**
      * @show_rq: Used by the debugfs implementation to show driver-specific
      * information about a request.
      */
     void (*show_rq)(struct seq_file *m, struct request *rq);
 #endif
 };
 
 enum {
     BLK_MQ_F_SHOULD_MERGE   = 1 << 0,
     BLK_MQ_F_TAG_QUEUE_SHARED = 1 << 1,
     /*
      * Set when this device requires underlying blk-mq device for
      * completing IO:
      */
     BLK_MQ_F_STACKING   = 1 << 2,
     BLK_MQ_F_TAG_HCTX_SHARED = 1 << 3,
     BLK_MQ_F_BLOCKING   = 1 << 5,
     /* Do not allow an I/O scheduler to be configured. */
     BLK_MQ_F_NO_SCHED   = 1 << 6,
     /*
      * Select 'none' during queue registration in case of a single hwq
      * or shared hwqs instead of 'mq-deadline'.
      */
     BLK_MQ_F_NO_SCHED_BY_DEFAULT    = 1 << 7,
     BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,
     BLK_MQ_F_ALLOC_POLICY_BITS = 1,
 
     BLK_MQ_S_STOPPED    = 0,
     BLK_MQ_S_TAG_ACTIVE = 1,
     BLK_MQ_S_SCHED_RESTART  = 2,
 
     /* hw queue is inactive after all its CPUs become offline */
     BLK_MQ_S_INACTIVE   = 3,
 
     BLK_MQ_MAX_DEPTH    = 10240,
 
     BLK_MQ_CPU_WORK_BATCH   = 8,
 };
 #define BLK_MQ_FLAG_TO_ALLOC_POLICY(flags) \
     ((flags >> BLK_MQ_F_ALLOC_POLICY_START_BIT) & \
         ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1))
 #define BLK_ALLOC_POLICY_TO_MQ_FLAG(policy) \
     ((policy & ((1 << BLK_MQ_F_ALLOC_POLICY_BITS) - 1)) \
         << BLK_MQ_F_ALLOC_POLICY_START_BIT)
 
 #define BLK_MQ_NO_HCTX_IDX  (-1U)
 
 struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
         struct lock_class_key *lkclass);
 #define blk_mq_alloc_disk(set, queuedata)               \
 ({                                  \
     static struct lock_class_key __key;             \
                                     \
     __blk_mq_alloc_disk(set, queuedata, &__key);            \
 })
 struct gendisk *blk_mq_alloc_disk_for_queue(struct request_queue *q,
         struct lock_class_key *lkclass);
 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
 int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
         struct request_queue *q);
 void blk_mq_destroy_queue(struct request_queue *);
 
 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set);
 int blk_mq_alloc_sq_tag_set(struct blk_mq_tag_set *set,
         const struct blk_mq_ops *ops, unsigned int queue_depth,
         unsigned int set_flags);
 void blk_mq_free_tag_set(struct blk_mq_tag_set *set);
 
 void blk_mq_free_request(struct request *rq);
 
 bool blk_mq_queue_inflight(struct request_queue *q);
 
 enum {
     /* return when out of requests */
     BLK_MQ_REQ_NOWAIT   = (__force blk_mq_req_flags_t)(1 << 0),
     /* allocate from reserved pool */
     BLK_MQ_REQ_RESERVED = (__force blk_mq_req_flags_t)(1 << 1),
     /* set RQF_PM */
     BLK_MQ_REQ_PM       = (__force blk_mq_req_flags_t)(1 << 2),
 };
 
 struct request *blk_mq_alloc_request(struct request_queue *q, blk_opf_t opf,
         blk_mq_req_flags_t flags);
 struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
         blk_opf_t opf, blk_mq_req_flags_t flags,
         unsigned int hctx_idx);
 
 /*
  * Tag address space map.
  */
 struct blk_mq_tags {
     unsigned int nr_tags;
     unsigned int nr_reserved_tags;
 
     atomic_t active_queues;
 
     struct sbitmap_queue bitmap_tags;
     struct sbitmap_queue breserved_tags;
 
     struct request **rqs;
     struct request **static_rqs;
     struct list_head page_list;
 
     /*
      * used to clear request reference in rqs[] before freeing one
      * request pool
      */
     spinlock_t lock;
 };
 
 static inline struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags,
                            unsigned int tag)
 {
     if (tag < tags->nr_tags) {
         prefetch(tags->rqs[tag]);
         return tags->rqs[tag];
     }
 
     return NULL;
 }
 
 enum {
     BLK_MQ_UNIQUE_TAG_BITS = 16,
     BLK_MQ_UNIQUE_TAG_MASK = (1 << BLK_MQ_UNIQUE_TAG_BITS) - 1,
 };
 
 u32 blk_mq_unique_tag(struct request *rq);
 
 static inline u16 blk_mq_unique_tag_to_hwq(u32 unique_tag)
 {
     return unique_tag >> BLK_MQ_UNIQUE_TAG_BITS;
 }
 
 static inline u16 blk_mq_unique_tag_to_tag(u32 unique_tag)
 {
     return unique_tag & BLK_MQ_UNIQUE_TAG_MASK;
 }
 
 /**
  * blk_mq_rq_state() - read the current MQ_RQ_* state of a request
  * @rq: target request.
  */
 static inline enum mq_rq_state blk_mq_rq_state(struct request *rq)
 {
     return READ_ONCE(rq->state);
 }
 
 static inline int blk_mq_request_started(struct request *rq)
 {
     return blk_mq_rq_state(rq) != MQ_RQ_IDLE;
 }
 
 static inline int blk_mq_request_completed(struct request *rq)
 {
     return blk_mq_rq_state(rq) == MQ_RQ_COMPLETE;
 }
 
 /*
  * 
  * Set the state to complete when completing a request from inside ->queue_rq.
  * This is used by drivers that want to ensure special complete actions that
  * need access to the request are called on failure, e.g. by nvme for
  * multipathing.
  */
 static inline void blk_mq_set_request_complete(struct request *rq)
 {
     WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
 }
 
 /*
  * Complete the request directly instead of deferring it to softirq or
  * completing it another CPU. Useful in preemptible instead of an interrupt.
  */
 static inline void blk_mq_complete_request_direct(struct request *rq,
            void (*complete)(struct request *rq))
 {
     WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
     complete(rq);
 }
 
 void blk_mq_start_request(struct request *rq);
 void blk_mq_end_request(struct request *rq, blk_status_t error);
 void __blk_mq_end_request(struct request *rq, blk_status_t error);
 void blk_mq_end_request_batch(struct io_comp_batch *ib);
 
 /*
  * Only need start/end time stamping if we have iostat or
  * blk stats enabled, or using an IO scheduler.
  */
 static inline bool blk_mq_need_time_stamp(struct request *rq)
 {
     return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS | RQF_ELV));
 }
 
 static inline bool blk_mq_is_reserved_rq(struct request *rq)
 {
     return rq->rq_flags & RQF_RESV;
 }
 
 /*
  * Batched completions only work when there is no I/O error and no special
  * ->end_io handler.
  */
 static inline bool blk_mq_add_to_batch(struct request *req,
                        struct io_comp_batch *iob, int ioerror,
                        void (*complete)(struct io_comp_batch *))
 {
     if (!iob || (req->rq_flags & RQF_ELV) || req->end_io || ioerror)
         return false;
     if (!iob->complete)
         iob->complete = complete;
     else if (iob->complete != complete)
         return false;
     iob->need_ts |= blk_mq_need_time_stamp(req);
     rq_list_add(&iob->req_list, req);
     return true;
 }
 
 void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list);
 void blk_mq_kick_requeue_list(struct request_queue *q);
 void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs);
 void blk_mq_complete_request(struct request *rq);
 bool blk_mq_complete_request_remote(struct request *rq);
 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx);
 void blk_mq_stop_hw_queues(struct request_queue *q);
 void blk_mq_start_hw_queues(struct request_queue *q);
 void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async);
 void blk_mq_quiesce_queue(struct request_queue *q);
 void blk_mq_wait_quiesce_done(struct request_queue *q);
 void blk_mq_unquiesce_queue(struct request_queue *q);
 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs);
 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
 void blk_mq_run_hw_queues(struct request_queue *q, bool async);
 void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs);
 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
         busy_tag_iter_fn *fn, void *priv);
 void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset);
 void blk_mq_freeze_queue(struct request_queue *q);
 void blk_mq_unfreeze_queue(struct request_queue *q);
 void blk_freeze_queue_start(struct request_queue *q);
 void blk_mq_freeze_queue_wait(struct request_queue *q);
 int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
                      unsigned long timeout);
 
 int blk_mq_map_queues(struct blk_mq_queue_map *qmap);
 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues);
 
 void blk_mq_quiesce_queue_nowait(struct request_queue *q);
 
 unsigned int blk_mq_rq_cpu(struct request *rq);
 
 bool __blk_should_fake_timeout(struct request_queue *q);
 static inline bool blk_should_fake_timeout(struct request_queue *q)
 {
     if (IS_ENABLED(CONFIG_FAIL_IO_TIMEOUT) &&
         test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
         return __blk_should_fake_timeout(q);
     return false;
 }
 
 /**
  * blk_mq_rq_from_pdu - cast a PDU to a request
  * @pdu: the PDU (Protocol Data Unit) to be casted
  *
  * Return: request
  *
  * Driver command data is immediately after the request. So subtract request
  * size to get back to the original request.
  */
 static inline struct request *blk_mq_rq_from_pdu(void *pdu)
 {
     return pdu - sizeof(struct request);
 }
 
 /**
  * blk_mq_rq_to_pdu - cast a request to a PDU
  * @rq: the request to be casted
  *
  * Return: pointer to the PDU
  *
  * Driver command data is immediately after the request. So add request to get
  * the PDU.
  */
 static inline void *blk_mq_rq_to_pdu(struct request *rq)
 {
     return rq + 1;
 }
 
 #define queue_for_each_hw_ctx(q, hctx, i)               \
     xa_for_each(&(q)->hctx_table, (i), (hctx))
 
 #define hctx_for_each_ctx(hctx, ctx, i)                 \
     for ((i) = 0; (i) < (hctx)->nr_ctx &&               \
          ({ ctx = (hctx)->ctxs[(i)]; 1; }); (i)++)
 
 static inline void blk_mq_cleanup_rq(struct request *rq)
 {
     if (rq->q->mq_ops->cleanup_rq)
         rq->q->mq_ops->cleanup_rq(rq);
 }
 
 static inline void blk_rq_bio_prep(struct request *rq, struct bio *bio,
         unsigned int nr_segs)
 {
     rq->nr_phys_segments = nr_segs;
     rq->__data_len = bio->bi_iter.bi_size;
     rq->bio = rq->biotail = bio;
     rq->ioprio = bio_prio(bio);
 }
 
 void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx,
         struct lock_class_key *key);
 
 static inline bool rq_is_sync(struct request *rq)
 {
     return op_is_sync(rq->cmd_flags);
 }
 
 void blk_rq_init(struct request_queue *q, struct request *rq);
 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
         struct bio_set *bs, gfp_t gfp_mask,
         int (*bio_ctr)(struct bio *, struct bio *, void *), void *data);
 void blk_rq_unprep_clone(struct request *rq);
 blk_status_t blk_insert_cloned_request(struct request *rq);
 
 struct rq_map_data {
     struct page **pages;
     int page_order;
     int nr_entries;
     unsigned long offset;
     int null_mapped;
     int from_user;
 };
 
 int blk_rq_map_user(struct request_queue *, struct request *,
         struct rq_map_data *, void __user *, unsigned long, gfp_t);
 int blk_rq_map_user_iov(struct request_queue *, struct request *,
         struct rq_map_data *, const struct iov_iter *, gfp_t);
 int blk_rq_unmap_user(struct bio *);
 int blk_rq_map_kern(struct request_queue *, struct request *, void *,
         unsigned int, gfp_t);
 int blk_rq_append_bio(struct request *rq, struct bio *bio);
 void blk_execute_rq_nowait(struct request *rq, bool at_head);
 blk_status_t blk_execute_rq(struct request *rq, bool at_head);
 
 struct req_iterator {
     struct bvec_iter iter;
     struct bio *bio;
 };
 
 #define __rq_for_each_bio(_bio, rq) \
     if ((rq->bio))          \
         for (_bio = (rq)->bio; _bio; _bio = _bio->bi_next)
 
 #define rq_for_each_segment(bvl, _rq, _iter)            \
     __rq_for_each_bio(_iter.bio, _rq)           \
         bio_for_each_segment(bvl, _iter.bio, _iter.iter)
 
 #define rq_for_each_bvec(bvl, _rq, _iter)           \
     __rq_for_each_bio(_iter.bio, _rq)           \
         bio_for_each_bvec(bvl, _iter.bio, _iter.iter)
 
 #define rq_iter_last(bvec, _iter)               \
         (_iter.bio->bi_next == NULL &&          \
          bio_iter_last(bvec, _iter.iter))
 
 /*
  * blk_rq_pos()         : the current sector
  * blk_rq_bytes()       : bytes left in the entire request
  * blk_rq_cur_bytes()       : bytes left in the current segment
  * blk_rq_sectors()     : sectors left in the entire request
  * blk_rq_cur_sectors()     : sectors left in the current segment
  * blk_rq_stats_sectors()   : sectors of the entire request used for stats
  */
 static inline sector_t blk_rq_pos(const struct request *rq)
 {
     return rq->__sector;
 }
 
 static inline unsigned int blk_rq_bytes(const struct request *rq)
 {
     return rq->__data_len;
 }
 
 static inline int blk_rq_cur_bytes(const struct request *rq)
 {
     if (!rq->bio)
         return 0;
     if (!bio_has_data(rq->bio)) /* dataless requests such as discard */
         return rq->bio->bi_iter.bi_size;
     return bio_iovec(rq->bio).bv_len;
 }
 
 static inline unsigned int blk_rq_sectors(const struct request *rq)
 {
     return blk_rq_bytes(rq) >> SECTOR_SHIFT;
 }
 
 static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
 {
     return blk_rq_cur_bytes(rq) >> SECTOR_SHIFT;
 }
 
 static inline unsigned int blk_rq_stats_sectors(const struct request *rq)
 {
     return rq->stats_sectors;
 }
 
 /*
  * Some commands like WRITE SAME have a payload or data transfer size which
  * is different from the size of the request.  Any driver that supports such
  * commands using the RQF_SPECIAL_PAYLOAD flag needs to use this helper to
  * calculate the data transfer size.
  */
 static inline unsigned int blk_rq_payload_bytes(struct request *rq)
 {
     if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
         return rq->special_vec.bv_len;
     return blk_rq_bytes(rq);
 }
 
 /*
  * Return the first full biovec in the request.  The caller needs to check that
  * there are any bvecs before calling this helper.
  */
 static inline struct bio_vec req_bvec(struct request *rq)
 {
     if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
         return rq->special_vec;
     return mp_bvec_iter_bvec(rq->bio->bi_io_vec, rq->bio->bi_iter);
 }
 
 static inline unsigned int blk_rq_count_bios(struct request *rq)
 {
     unsigned int nr_bios = 0;
     struct bio *bio;
 
     __rq_for_each_bio(bio, rq)
         nr_bios++;
 
     return nr_bios;
 }
 
 void blk_steal_bios(struct bio_list *list, struct request *rq);
 
 /*
  * Request completion related functions.
  *
  * blk_update_request() completes given number of bytes and updates
  * the request without completing it.
  */
 bool blk_update_request(struct request *rq, blk_status_t error,
                    unsigned int nr_bytes);
 void blk_abort_request(struct request *);
 
 /*
  * Number of physical segments as sent to the device.
  *
  * Normally this is the number of discontiguous data segments sent by the
  * submitter.  But for data-less command like discard we might have no
  * actual data segments submitted, but the driver might have to add it's
  * own special payload.  In that case we still return 1 here so that this
  * special payload will be mapped.
  */
 static inline unsigned short blk_rq_nr_phys_segments(struct request *rq)
 {
     if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
         return 1;
     return rq->nr_phys_segments;
 }
 
 /*
  * Number of discard segments (or ranges) the driver needs to fill in.
  * Each discard bio merged into a request is counted as one segment.
  */
 static inline unsigned short blk_rq_nr_discard_segments(struct request *rq)
 {
     return max_t(unsigned short, rq->nr_phys_segments, 1);
 }
 
 int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
         struct scatterlist *sglist, struct scatterlist **last_sg);
 static inline int blk_rq_map_sg(struct request_queue *q, struct request *rq,
         struct scatterlist *sglist)
 {
     struct scatterlist *last_sg = NULL;
 
     return __blk_rq_map_sg(q, rq, sglist, &last_sg);
 }
 void blk_dump_rq_flags(struct request *, char *);
 
 #ifdef CONFIG_BLK_DEV_ZONED
 static inline unsigned int blk_rq_zone_no(struct request *rq)
 {
     return disk_zone_no(rq->q->disk, blk_rq_pos(rq));
 }
 
 static inline unsigned int blk_rq_zone_is_seq(struct request *rq)
 {
     return disk_zone_is_seq(rq->q->disk, blk_rq_pos(rq));
 }
 
 bool blk_req_needs_zone_write_lock(struct request *rq);
 bool blk_req_zone_write_trylock(struct request *rq);
 void __blk_req_zone_write_lock(struct request *rq);
 void __blk_req_zone_write_unlock(struct request *rq);
 
 static inline void blk_req_zone_write_lock(struct request *rq)
 {
     if (blk_req_needs_zone_write_lock(rq))
         __blk_req_zone_write_lock(rq);
 }
 
 static inline void blk_req_zone_write_unlock(struct request *rq)
 {
     if (rq->rq_flags & RQF_ZONE_WRITE_LOCKED)
         __blk_req_zone_write_unlock(rq);
 }
 
 static inline bool blk_req_zone_is_write_locked(struct request *rq)
 {
     return rq->q->disk->seq_zones_wlock &&
         test_bit(blk_rq_zone_no(rq), rq->q->disk->seq_zones_wlock);
 }
 
 static inline bool blk_req_can_dispatch_to_zone(struct request *rq)
 {
     if (!blk_req_needs_zone_write_lock(rq))
         return true;
     return !blk_req_zone_is_write_locked(rq);
 }
 #else /* CONFIG_BLK_DEV_ZONED */
 static inline bool blk_req_needs_zone_write_lock(struct request *rq)
 {
     return false;
 }
 
 static inline void blk_req_zone_write_lock(struct request *rq)
 {
 }
 
 static inline void blk_req_zone_write_unlock(struct request *rq)
 {
 }
 static inline bool blk_req_zone_is_write_locked(struct request *rq)
 {
     return false;
 }
 
 static inline bool blk_req_can_dispatch_to_zone(struct request *rq)
 {
     return true;
 }
 #endif /* CONFIG_BLK_DEV_ZONED */
 
 #endif /* BLK_MQ_H */

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