[linux-block.git] / include / linux / blk-mq.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef BLK_MQ_H
#define BLK_MQ_H

#include <linux/blkdev.h>
#include <linux/sbitmap.h>
#include <linux/srcu.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))

/* 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;

        unsigned int 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 gendisk *rq_disk;
        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;
        refcount_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;
                int error_count; /* for legacy drivers, don't use */
        };


        /*
         * 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;
};

#define req_op(req) \
        ((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)

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;

        /**
         * @srcu: Sleepable RCU. Use as lock when type of the hardware queue is
         * blocking (BLK_MQ_F_BLOCKING). Must be the last member - see also
         * blk_mq_hw_ctx_size().
         */
        struct srcu_struct      srcu[];
};

/**
 * 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_iter_fn)(struct blk_mq_hw_ctx *, struct request *, void *,
                bool);
typedef bool (busy_tag_iter_fn)(struct request *, void *, bool);

/**
 * 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 *);

        /**
         * @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 *, bool);

        /**
         * @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);

        /**
         * @initialize_rq_fn: Called from inside blk_get_request().
         */
        void (*initialize_rq_fn)(struct request *rq);

        /**
         * @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 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_unregister_dev(struct device *, 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, unsigned int op,
                blk_mq_req_flags_t flags);
struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
                unsigned int op, 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);
}

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));
}

/*
 * 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);
bool blk_mq_queue_stopped(struct request_queue *q);
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_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)                               \
        for ((i) = 0; (i) < (q)->nr_hw_queues &&                        \
             ({ hctx = (q)->queue_hw_ctx[i]; 1; }); (i)++)

#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);

        if (bio->bi_bdev)
                rq->rq_disk = bio->bi_bdev->bd_disk;
}

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);
void blk_put_request(struct request *rq);
struct request *blk_get_request(struct request_queue *q, unsigned int op,
                blk_mq_req_flags_t flags);
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_queue *q,
                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 gendisk *, struct request *, int,
                rq_end_io_fn *);
blk_status_t blk_execute_rq(struct gendisk *bd_disk, struct request *rq,
                int 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_err_bytes()           : bytes left till the next error boundary
 * 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;
}

unsigned int blk_rq_err_bytes(const struct request *rq);

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 blk_queue_zone_no(rq->q, blk_rq_pos(rq));
}

static inline unsigned int blk_rq_zone_is_seq(struct request *rq)
{
        return blk_queue_zone_is_seq(rq->q, 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->seq_zones_wlock &&
                test_bit(blk_rq_zone_no(rq), rq->q->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 */

#ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
# error "You should define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE for your platform"
#endif
#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
void rq_flush_dcache_pages(struct request *rq);
#else
static inline void rq_flush_dcache_pages(struct request *rq)
{
}
#endif /* ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE */
#endif /* BLK_MQ_H */