Merge tag 'libnvdimm-for-4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm...

[deliverable/linux.git] / include / linux / blkdev.h

#ifndef _LINUX_BLKDEV_H
#define _LINUX_BLKDEV_H

#include <linux/sched.h>

#ifdef CONFIG_BLOCK

#include <linux/major.h>
#include <linux/genhd.h>
#include <linux/list.h>
#include <linux/llist.h>
#include <linux/timer.h>
#include <linux/workqueue.h>
#include <linux/pagemap.h>
#include <linux/backing-dev-defs.h>
#include <linux/wait.h>
#include <linux/mempool.h>
#include <linux/pfn.h>
#include <linux/bio.h>
#include <linux/stringify.h>
#include <linux/gfp.h>
#include <linux/bsg.h>
#include <linux/smp.h>
#include <linux/rcupdate.h>
#include <linux/percpu-refcount.h>
#include <linux/scatterlist.h>

struct module;
struct scsi_ioctl_command;

struct request_queue;
struct elevator_queue;
struct blk_trace;
struct request;
struct sg_io_hdr;
struct bsg_job;
struct blkcg_gq;
struct blk_flush_queue;
struct pr_ops;

#define BLKDEV_MIN_RQ   4
#define BLKDEV_MAX_RQ   128     /* Default maximum */

/*
 * Maximum number of blkcg policies allowed to be registered concurrently.
 * Defined here to simplify include dependency.
 */
#define BLKCG_MAX_POLS          2

struct request;
typedef void (rq_end_io_fn)(struct request *, int);

#define BLK_RL_SYNCFULL         (1U << 0)
#define BLK_RL_ASYNCFULL        (1U << 1)

struct request_list {
        struct request_queue    *q;     /* the queue this rl belongs to */
#ifdef CONFIG_BLK_CGROUP
        struct blkcg_gq         *blkg;  /* blkg this request pool belongs to */
#endif
        /*
         * count[], starved[], and wait[] are indexed by
         * BLK_RW_SYNC/BLK_RW_ASYNC
         */
        int                     count[2];
        int                     starved[2];
        mempool_t               *rq_pool;
        wait_queue_head_t       wait[2];
        unsigned int            flags;
};

/*
 * request command types
 */
enum rq_cmd_type_bits {
        REQ_TYPE_FS             = 1,    /* fs request */
        REQ_TYPE_BLOCK_PC,              /* scsi command */
        REQ_TYPE_DRV_PRIV,              /* driver defined types from here */
};

#define BLK_MAX_CDB     16

/*
 * 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 list_head queuelist;
        union {
                struct call_single_data csd;
                u64 fifo_time;
        };

        struct request_queue *q;
        struct blk_mq_ctx *mq_ctx;

        int cpu;
        unsigned cmd_type;
        u64 cmd_flags;
        unsigned long atomic_flags;

        /* 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;

        /*
         * 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 list_head 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 */
                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;
        };

        struct gendisk *rq_disk;
        struct hd_struct *part;
        unsigned long start_time;
#ifdef CONFIG_BLK_CGROUP
        struct request_list *rl;                /* rl this rq is alloced from */
        unsigned long long start_time_ns;
        unsigned long long io_start_time_ns;    /* when passed to hardware */
#endif
        /* Number of scatter-gather DMA addr+len pairs after
         * physical address coalescing is performed.
         */
        unsigned short nr_phys_segments;
#if defined(CONFIG_BLK_DEV_INTEGRITY)
        unsigned short nr_integrity_segments;
#endif

        unsigned short ioprio;

        void *special;          /* opaque pointer available for LLD use */

        int tag;
        int errors;

        /*
         * when request is used as a packet command carrier
         */
        unsigned char __cmd[BLK_MAX_CDB];
        unsigned char *cmd;
        unsigned short cmd_len;

        unsigned int extra_len; /* length of alignment and padding */
        unsigned int sense_len;
        unsigned int resid_len; /* residual count */
        void *sense;

        unsigned long deadline;
        struct list_head timeout_list;
        unsigned int timeout;
        int retries;

        /*
         * completion callback.
         */
        rq_end_io_fn *end_io;
        void *end_io_data;

        /* for bidi */
        struct request *next_rq;
};

#define REQ_OP_SHIFT (8 * sizeof(u64) - REQ_OP_BITS)
#define req_op(req)  ((req)->cmd_flags >> REQ_OP_SHIFT)

#define req_set_op(req, op) do {                                \
        WARN_ON(op >= (1 << REQ_OP_BITS));                      \
        (req)->cmd_flags &= ((1ULL << REQ_OP_SHIFT) - 1);       \
        (req)->cmd_flags |= ((u64) (op) << REQ_OP_SHIFT);       \
} while (0)

#define req_set_op_attrs(req, op, flags) do {   \
        req_set_op(req, op);                    \
        (req)->cmd_flags |= flags;              \
} while (0)

static inline unsigned short req_get_ioprio(struct request *req)
{
        return req->ioprio;
}

#include <linux/elevator.h>

struct blk_queue_ctx;

typedef void (request_fn_proc) (struct request_queue *q);
typedef blk_qc_t (make_request_fn) (struct request_queue *q, struct bio *bio);
typedef int (prep_rq_fn) (struct request_queue *, struct request *);
typedef void (unprep_rq_fn) (struct request_queue *, struct request *);

struct bio_vec;
typedef void (softirq_done_fn)(struct request *);
typedef int (dma_drain_needed_fn)(struct request *);
typedef int (lld_busy_fn) (struct request_queue *q);
typedef int (bsg_job_fn) (struct bsg_job *);

enum blk_eh_timer_return {
        BLK_EH_NOT_HANDLED,
        BLK_EH_HANDLED,
        BLK_EH_RESET_TIMER,
};

typedef enum blk_eh_timer_return (rq_timed_out_fn)(struct request *);

enum blk_queue_state {
        Queue_down,
        Queue_up,
};

struct blk_queue_tag {
        struct request **tag_index;     /* map of busy tags */
        unsigned long *tag_map;         /* bit map of free/busy tags */
        int busy;                       /* current depth */
        int max_depth;                  /* what we will send to device */
        int real_max_depth;             /* what the array can hold */
        atomic_t refcnt;                /* map can be shared */
        int alloc_policy;               /* tag allocation policy */
        int next_tag;                   /* next tag */
};
#define BLK_TAG_ALLOC_FIFO 0 /* allocate starting from 0 */
#define BLK_TAG_ALLOC_RR 1 /* allocate starting from last allocated tag */

#define BLK_SCSI_MAX_CMDS       (256)
#define BLK_SCSI_CMD_PER_LONG   (BLK_SCSI_MAX_CMDS / (sizeof(long) * 8))

struct queue_limits {
        unsigned long           bounce_pfn;
        unsigned long           seg_boundary_mask;
        unsigned long           virt_boundary_mask;

        unsigned int            max_hw_sectors;
        unsigned int            max_dev_sectors;
        unsigned int            chunk_sectors;
        unsigned int            max_sectors;
        unsigned int            max_segment_size;
        unsigned int            physical_block_size;
        unsigned int            alignment_offset;
        unsigned int            io_min;
        unsigned int            io_opt;
        unsigned int            max_discard_sectors;
        unsigned int            max_hw_discard_sectors;
        unsigned int            max_write_same_sectors;
        unsigned int            discard_granularity;
        unsigned int            discard_alignment;

        unsigned short          logical_block_size;
        unsigned short          max_segments;
        unsigned short          max_integrity_segments;

        unsigned char           misaligned;
        unsigned char           discard_misaligned;
        unsigned char           cluster;
        unsigned char           discard_zeroes_data;
        unsigned char           raid_partial_stripes_expensive;
};

struct request_queue {
        /*
         * Together with queue_head for cacheline sharing
         */
        struct list_head        queue_head;
        struct request          *last_merge;
        struct elevator_queue   *elevator;
        int                     nr_rqs[2];      /* # allocated [a]sync rqs */
        int                     nr_rqs_elvpriv; /* # allocated rqs w/ elvpriv */

        /*
         * If blkcg is not used, @q->root_rl serves all requests.  If blkcg
         * is used, root blkg allocates from @q->root_rl and all other
         * blkgs from their own blkg->rl.  Which one to use should be
         * determined using bio_request_list().
         */
        struct request_list     root_rl;

        request_fn_proc         *request_fn;
        make_request_fn         *make_request_fn;
        prep_rq_fn              *prep_rq_fn;
        unprep_rq_fn            *unprep_rq_fn;
        softirq_done_fn         *softirq_done_fn;
        rq_timed_out_fn         *rq_timed_out_fn;
        dma_drain_needed_fn     *dma_drain_needed;
        lld_busy_fn             *lld_busy_fn;

        struct blk_mq_ops       *mq_ops;

        unsigned int            *mq_map;

        /* sw queues */
        struct blk_mq_ctx __percpu      *queue_ctx;
        unsigned int            nr_queues;

        /* hw dispatch queues */
        struct blk_mq_hw_ctx    **queue_hw_ctx;
        unsigned int            nr_hw_queues;

        /*
         * Dispatch queue sorting
         */
        sector_t                end_sector;
        struct request          *boundary_rq;

        /*
         * Delayed queue handling
         */
        struct delayed_work     delay_work;

        struct backing_dev_info backing_dev_info;

        /*
         * The queue owner gets to use this for whatever they like.
         * ll_rw_blk doesn't touch it.
         */
        void                    *queuedata;

        /*
         * various queue flags, see QUEUE_* below
         */
        unsigned long           queue_flags;

        /*
         * ida allocated id for this queue.  Used to index queues from
         * ioctx.
         */
        int                     id;

        /*
         * queue needs bounce pages for pages above this limit
         */
        gfp_t                   bounce_gfp;

        /*
         * protects queue structures from reentrancy. ->__queue_lock should
         * _never_ be used directly, it is queue private. always use
         * ->queue_lock.
         */
        spinlock_t              __queue_lock;
        spinlock_t              *queue_lock;

        /*
         * queue kobject
         */
        struct kobject kobj;

        /*
         * mq queue kobject
         */
        struct kobject mq_kobj;

#ifdef  CONFIG_BLK_DEV_INTEGRITY
        struct blk_integrity integrity;
#endif  /* CONFIG_BLK_DEV_INTEGRITY */

#ifdef CONFIG_PM
        struct device           *dev;
        int                     rpm_status;
        unsigned int            nr_pending;
#endif

        /*
         * queue settings
         */
        unsigned long           nr_requests;    /* Max # of requests */
        unsigned int            nr_congestion_on;
        unsigned int            nr_congestion_off;
        unsigned int            nr_batching;

        unsigned int            dma_drain_size;
        void                    *dma_drain_buffer;
        unsigned int            dma_pad_mask;
        unsigned int            dma_alignment;

        struct blk_queue_tag    *queue_tags;
        struct list_head        tag_busy_list;

        unsigned int            nr_sorted;
        unsigned int            in_flight[2];
        /*
         * Number of active block driver functions for which blk_drain_queue()
         * must wait. Must be incremented around functions that unlock the
         * queue_lock internally, e.g. scsi_request_fn().
         */
        unsigned int            request_fn_active;

        unsigned int            rq_timeout;
        struct timer_list       timeout;
        struct work_struct      timeout_work;
        struct list_head        timeout_list;

        struct list_head        icq_list;
#ifdef CONFIG_BLK_CGROUP
        DECLARE_BITMAP          (blkcg_pols, BLKCG_MAX_POLS);
        struct blkcg_gq         *root_blkg;
        struct list_head        blkg_list;
#endif

        struct queue_limits     limits;

        /*
         * sg stuff
         */
        unsigned int            sg_timeout;
        unsigned int            sg_reserved_size;
        int                     node;
#ifdef CONFIG_BLK_DEV_IO_TRACE
        struct blk_trace        *blk_trace;
#endif
        /*
         * for flush operations
         */
        struct blk_flush_queue  *fq;

        struct list_head        requeue_list;
        spinlock_t              requeue_lock;
        struct work_struct      requeue_work;

        struct mutex            sysfs_lock;

        int                     bypass_depth;
        atomic_t                mq_freeze_depth;

#if defined(CONFIG_BLK_DEV_BSG)
        bsg_job_fn              *bsg_job_fn;
        int                     bsg_job_size;
        struct bsg_class_device bsg_dev;
#endif

#ifdef CONFIG_BLK_DEV_THROTTLING
        /* Throttle data */
        struct throtl_data *td;
#endif
        struct rcu_head         rcu_head;
        wait_queue_head_t       mq_freeze_wq;
        struct percpu_ref       q_usage_counter;
        struct list_head        all_q_node;

        struct blk_mq_tag_set   *tag_set;
        struct list_head        tag_set_list;
        struct bio_set          *bio_split;

        bool                    mq_sysfs_init_done;
};

#define QUEUE_FLAG_QUEUED       1       /* uses generic tag queueing */
#define QUEUE_FLAG_STOPPED      2       /* queue is stopped */
#define QUEUE_FLAG_SYNCFULL     3       /* read queue has been filled */
#define QUEUE_FLAG_ASYNCFULL    4       /* write queue has been filled */
#define QUEUE_FLAG_DYING        5       /* queue being torn down */
#define QUEUE_FLAG_BYPASS       6       /* act as dumb FIFO queue */
#define QUEUE_FLAG_BIDI         7       /* queue supports bidi requests */
#define QUEUE_FLAG_NOMERGES     8       /* disable merge attempts */
#define QUEUE_FLAG_SAME_COMP    9       /* complete on same CPU-group */
#define QUEUE_FLAG_FAIL_IO     10       /* fake timeout */
#define QUEUE_FLAG_STACKABLE   11       /* supports request stacking */
#define QUEUE_FLAG_NONROT      12       /* non-rotational device (SSD) */
#define QUEUE_FLAG_VIRT        QUEUE_FLAG_NONROT /* paravirt device */
#define QUEUE_FLAG_IO_STAT     13       /* do IO stats */
#define QUEUE_FLAG_DISCARD     14       /* supports DISCARD */
#define QUEUE_FLAG_NOXMERGES   15       /* No extended merges */
#define QUEUE_FLAG_ADD_RANDOM  16       /* Contributes to random pool */
#define QUEUE_FLAG_SECERASE    17       /* supports secure erase */
#define QUEUE_FLAG_SAME_FORCE  18       /* force complete on same CPU */
#define QUEUE_FLAG_DEAD        19       /* queue tear-down finished */
#define QUEUE_FLAG_INIT_DONE   20       /* queue is initialized */
#define QUEUE_FLAG_NO_SG_MERGE 21       /* don't attempt to merge SG segments*/
#define QUEUE_FLAG_POLL        22       /* IO polling enabled if set */
#define QUEUE_FLAG_WC          23       /* Write back caching */
#define QUEUE_FLAG_FUA         24       /* device supports FUA writes */
#define QUEUE_FLAG_FLUSH_NQ    25       /* flush not queueuable */
#define QUEUE_FLAG_DAX         26       /* device supports DAX */

#define QUEUE_FLAG_DEFAULT      ((1 << QUEUE_FLAG_IO_STAT) |            \
                                 (1 << QUEUE_FLAG_STACKABLE)    |       \
                                 (1 << QUEUE_FLAG_SAME_COMP)    |       \
                                 (1 << QUEUE_FLAG_ADD_RANDOM))

#define QUEUE_FLAG_MQ_DEFAULT   ((1 << QUEUE_FLAG_IO_STAT) |            \
                                 (1 << QUEUE_FLAG_STACKABLE)    |       \
                                 (1 << QUEUE_FLAG_SAME_COMP)    |       \
                                 (1 << QUEUE_FLAG_POLL))

static inline void queue_lockdep_assert_held(struct request_queue *q)
{
        if (q->queue_lock)
                lockdep_assert_held(q->queue_lock);
}

static inline void queue_flag_set_unlocked(unsigned int flag,
                                           struct request_queue *q)
{
        __set_bit(flag, &q->queue_flags);
}

static inline int queue_flag_test_and_clear(unsigned int flag,
                                            struct request_queue *q)
{
        queue_lockdep_assert_held(q);

        if (test_bit(flag, &q->queue_flags)) {
                __clear_bit(flag, &q->queue_flags);
                return 1;
        }

        return 0;
}

static inline int queue_flag_test_and_set(unsigned int flag,
                                          struct request_queue *q)
{
        queue_lockdep_assert_held(q);

        if (!test_bit(flag, &q->queue_flags)) {
                __set_bit(flag, &q->queue_flags);
                return 0;
        }

        return 1;
}

static inline void queue_flag_set(unsigned int flag, struct request_queue *q)
{
        queue_lockdep_assert_held(q);
        __set_bit(flag, &q->queue_flags);
}

static inline void queue_flag_clear_unlocked(unsigned int flag,
                                             struct request_queue *q)
{
        __clear_bit(flag, &q->queue_flags);
}

static inline int queue_in_flight(struct request_queue *q)
{
        return q->in_flight[0] + q->in_flight[1];
}

static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
{
        queue_lockdep_assert_held(q);
        __clear_bit(flag, &q->queue_flags);
}

#define blk_queue_tagged(q)     test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
#define blk_queue_stopped(q)    test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
#define blk_queue_dying(q)      test_bit(QUEUE_FLAG_DYING, &(q)->queue_flags)
#define blk_queue_dead(q)       test_bit(QUEUE_FLAG_DEAD, &(q)->queue_flags)
#define blk_queue_bypass(q)     test_bit(QUEUE_FLAG_BYPASS, &(q)->queue_flags)
#define blk_queue_init_done(q)  test_bit(QUEUE_FLAG_INIT_DONE, &(q)->queue_flags)
#define blk_queue_nomerges(q)   test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
#define blk_queue_noxmerges(q)  \
        test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags)
#define blk_queue_nonrot(q)     test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)
#define blk_queue_io_stat(q)    test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
#define blk_queue_add_random(q) test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)
#define blk_queue_stackable(q)  \
        test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags)
#define blk_queue_discard(q)    test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
#define blk_queue_secure_erase(q) \
        (test_bit(QUEUE_FLAG_SECERASE, &(q)->queue_flags))
#define blk_queue_dax(q)        test_bit(QUEUE_FLAG_DAX, &(q)->queue_flags)

#define blk_noretry_request(rq) \
        ((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \
                             REQ_FAILFAST_DRIVER))

#define blk_account_rq(rq) \
        (((rq)->cmd_flags & REQ_STARTED) && \
         ((rq)->cmd_type == REQ_TYPE_FS))

#define blk_rq_cpu_valid(rq)    ((rq)->cpu != -1)
#define blk_bidi_rq(rq)         ((rq)->next_rq != NULL)
/* rq->queuelist of dequeued request must be list_empty() */
#define blk_queued_rq(rq)       (!list_empty(&(rq)->queuelist))

#define list_entry_rq(ptr)      list_entry((ptr), struct request, queuelist)

#define rq_data_dir(rq)         (op_is_write(req_op(rq)) ? WRITE : READ)

/*
 * Driver can handle struct request, if it either has an old style
 * request_fn defined, or is blk-mq based.
 */
static inline bool queue_is_rq_based(struct request_queue *q)
{
        return q->request_fn || q->mq_ops;
}

static inline unsigned int blk_queue_cluster(struct request_queue *q)
{
        return q->limits.cluster;
}

/*
 * We regard a request as sync, if either a read or a sync write
 */
static inline bool rw_is_sync(int op, unsigned int rw_flags)
{
        return op == REQ_OP_READ || (rw_flags & REQ_SYNC);
}

static inline bool rq_is_sync(struct request *rq)
{
        return rw_is_sync(req_op(rq), rq->cmd_flags);
}

static inline bool blk_rl_full(struct request_list *rl, bool sync)
{
        unsigned int flag = sync ? BLK_RL_SYNCFULL : BLK_RL_ASYNCFULL;

        return rl->flags & flag;
}

static inline void blk_set_rl_full(struct request_list *rl, bool sync)
{
        unsigned int flag = sync ? BLK_RL_SYNCFULL : BLK_RL_ASYNCFULL;

        rl->flags |= flag;
}

static inline void blk_clear_rl_full(struct request_list *rl, bool sync)
{
        unsigned int flag = sync ? BLK_RL_SYNCFULL : BLK_RL_ASYNCFULL;

        rl->flags &= ~flag;
}

static inline bool rq_mergeable(struct request *rq)
{
        if (rq->cmd_type != REQ_TYPE_FS)
                return false;

        if (req_op(rq) == REQ_OP_FLUSH)
                return false;

        if (rq->cmd_flags & REQ_NOMERGE_FLAGS)
                return false;

        return true;
}

static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
{
        if (bio_data(a) == bio_data(b))
                return true;

        return false;
}

/*
 * q->prep_rq_fn return values
 */
enum {
        BLKPREP_OK,             /* serve it */
        BLKPREP_KILL,           /* fatal error, kill, return -EIO */
        BLKPREP_DEFER,          /* leave on queue */
        BLKPREP_INVALID,        /* invalid command, kill, return -EREMOTEIO */
};

extern unsigned long blk_max_low_pfn, blk_max_pfn;

/*
 * standard bounce addresses:
 *
 * BLK_BOUNCE_HIGH      : bounce all highmem pages
 * BLK_BOUNCE_ANY       : don't bounce anything
 * BLK_BOUNCE_ISA       : bounce pages above ISA DMA boundary
 */

#if BITS_PER_LONG == 32
#define BLK_BOUNCE_HIGH         ((u64)blk_max_low_pfn << PAGE_SHIFT)
#else
#define BLK_BOUNCE_HIGH         -1ULL
#endif
#define BLK_BOUNCE_ANY          (-1ULL)
#define BLK_BOUNCE_ISA          (DMA_BIT_MASK(24))

/*
 * default timeout for SG_IO if none specified
 */
#define BLK_DEFAULT_SG_TIMEOUT  (60 * HZ)
#define BLK_MIN_SG_TIMEOUT      (7 * HZ)

#ifdef CONFIG_BOUNCE
extern int init_emergency_isa_pool(void);
extern void blk_queue_bounce(struct request_queue *q, struct bio **bio);
#else
static inline int init_emergency_isa_pool(void)
{
        return 0;
}
static inline void blk_queue_bounce(struct request_queue *q, struct bio **bio)
{
}
#endif /* CONFIG_MMU */

struct rq_map_data {
        struct page **pages;
        int page_order;
        int nr_entries;
        unsigned long offset;
        int null_mapped;
        int from_user;
};

struct req_iterator {
        struct bvec_iter iter;
        struct bio *bio;
};

/* This should not be used directly - use rq_for_each_segment */
#define for_each_bio(_bio)              \
        for (; _bio; _bio = _bio->bi_next)
#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_iter_last(bvec, _iter)                               \
                (_iter.bio->bi_next == NULL &&                  \
                 bio_iter_last(bvec, _iter.iter))

#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
extern void rq_flush_dcache_pages(struct request *rq);
#else
static inline void rq_flush_dcache_pages(struct request *rq)
{
}
#endif

#ifdef CONFIG_PRINTK
#define vfs_msg(sb, level, fmt, ...)                            \
        __vfs_msg(sb, level, fmt, ##__VA_ARGS__)
#else
#define vfs_msg(sb, level, fmt, ...)                            \
do {                                                            \
        no_printk(fmt, ##__VA_ARGS__);                          \
        __vfs_msg(sb, "", " ");                                 \
} while (0)
#endif

extern int blk_register_queue(struct gendisk *disk);
extern void blk_unregister_queue(struct gendisk *disk);
extern blk_qc_t generic_make_request(struct bio *bio);
extern void blk_rq_init(struct request_queue *q, struct request *rq);
extern void blk_put_request(struct request *);
extern void __blk_put_request(struct request_queue *, struct request *);
extern struct request *blk_get_request(struct request_queue *, int, gfp_t);
extern void blk_rq_set_block_pc(struct request *);
extern void blk_requeue_request(struct request_queue *, struct request *);
extern void blk_add_request_payload(struct request *rq, struct page *page,
                int offset, unsigned int len);
extern int blk_lld_busy(struct request_queue *q);
extern 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);
extern void blk_rq_unprep_clone(struct request *rq);
extern int blk_insert_cloned_request(struct request_queue *q,
                                     struct request *rq);
extern int blk_rq_append_bio(struct request *rq, struct bio *bio);
extern void blk_delay_queue(struct request_queue *, unsigned long);
extern void blk_queue_split(struct request_queue *, struct bio **,
                            struct bio_set *);
extern void blk_recount_segments(struct request_queue *, struct bio *);
extern int scsi_verify_blk_ioctl(struct block_device *, unsigned int);
extern int scsi_cmd_blk_ioctl(struct block_device *, fmode_t,
                              unsigned int, void __user *);
extern int scsi_cmd_ioctl(struct request_queue *, struct gendisk *, fmode_t,
                          unsigned int, void __user *);
extern int sg_scsi_ioctl(struct request_queue *, struct gendisk *, fmode_t,
                         struct scsi_ioctl_command __user *);

extern int blk_queue_enter(struct request_queue *q, bool nowait);
extern void blk_queue_exit(struct request_queue *q);
extern void blk_start_queue(struct request_queue *q);
extern void blk_start_queue_async(struct request_queue *q);
extern void blk_stop_queue(struct request_queue *q);
extern void blk_sync_queue(struct request_queue *q);
extern void __blk_stop_queue(struct request_queue *q);
extern void __blk_run_queue(struct request_queue *q);
extern void __blk_run_queue_uncond(struct request_queue *q);
extern void blk_run_queue(struct request_queue *);
extern void blk_run_queue_async(struct request_queue *q);
extern int blk_rq_map_user(struct request_queue *, struct request *,
                           struct rq_map_data *, void __user *, unsigned long,
                           gfp_t);
extern int blk_rq_unmap_user(struct bio *);
extern int blk_rq_map_kern(struct request_queue *, struct request *, void *, unsigned int, gfp_t);
extern int blk_rq_map_user_iov(struct request_queue *, struct request *,
                               struct rq_map_data *, const struct iov_iter *,
                               gfp_t);
extern int blk_execute_rq(struct request_queue *, struct gendisk *,
                          struct request *, int);
extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,
                                  struct request *, int, rq_end_io_fn *);

bool blk_poll(struct request_queue *q, blk_qc_t cookie);

static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
{
        return bdev->bd_disk->queue;    /* this is never NULL */
}

/*
 * 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
 */
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)
{
        return rq->bio ? bio_cur_bytes(rq->bio) : 0;
}

extern 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) >> 9;
}

static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
{
        return blk_rq_cur_bytes(rq) >> 9;
}

static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
                                                     int op)
{
        if (unlikely(op == REQ_OP_DISCARD))
                return min(q->limits.max_discard_sectors, UINT_MAX >> 9);

        if (unlikely(op == REQ_OP_WRITE_SAME))
                return q->limits.max_write_same_sectors;

        return q->limits.max_sectors;
}

/*
 * Return maximum size of a request at given offset. Only valid for
 * file system requests.
 */
static inline unsigned int blk_max_size_offset(struct request_queue *q,
                                               sector_t offset)
{
        if (!q->limits.chunk_sectors)
                return q->limits.max_sectors;

        return q->limits.chunk_sectors -
                        (offset & (q->limits.chunk_sectors - 1));
}

static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
                                                  sector_t offset)
{
        struct request_queue *q = rq->q;

        if (unlikely(rq->cmd_type != REQ_TYPE_FS))
                return q->limits.max_hw_sectors;

        if (!q->limits.chunk_sectors || (req_op(rq) == REQ_OP_DISCARD))
                return blk_queue_get_max_sectors(q, req_op(rq));

        return min(blk_max_size_offset(q, offset),
                        blk_queue_get_max_sectors(q, req_op(rq)));
}

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;
}

/*
 * Request issue related functions.
 */
extern struct request *blk_peek_request(struct request_queue *q);
extern void blk_start_request(struct request *rq);
extern struct request *blk_fetch_request(struct request_queue *q);

/*
 * Request completion related functions.
 *
 * blk_update_request() completes given number of bytes and updates
 * the request without completing it.
 *
 * blk_end_request() and friends.  __blk_end_request() must be called
 * with the request queue spinlock acquired.
 *
 * Several drivers define their own end_request and call
 * blk_end_request() for parts of the original function.
 * This prevents code duplication in drivers.
 */
extern bool blk_update_request(struct request *rq, int error,
                               unsigned int nr_bytes);
extern void blk_finish_request(struct request *rq, int error);
extern bool blk_end_request(struct request *rq, int error,
                            unsigned int nr_bytes);
extern void blk_end_request_all(struct request *rq, int error);
extern bool blk_end_request_cur(struct request *rq, int error);
extern bool blk_end_request_err(struct request *rq, int error);
extern bool __blk_end_request(struct request *rq, int error,
                              unsigned int nr_bytes);
extern void __blk_end_request_all(struct request *rq, int error);
extern bool __blk_end_request_cur(struct request *rq, int error);
extern bool __blk_end_request_err(struct request *rq, int error);

extern void blk_complete_request(struct request *);
extern void __blk_complete_request(struct request *);
extern void blk_abort_request(struct request *);
extern void blk_unprep_request(struct request *);

/*
 * Access functions for manipulating queue properties
 */
extern struct request_queue *blk_init_queue_node(request_fn_proc *rfn,
                                        spinlock_t *lock, int node_id);
extern struct request_queue *blk_init_queue(request_fn_proc *, spinlock_t *);
extern struct request_queue *blk_init_allocated_queue(struct request_queue *,
                                                      request_fn_proc *, spinlock_t *);
extern void blk_cleanup_queue(struct request_queue *);
extern void blk_queue_make_request(struct request_queue *, make_request_fn *);
extern void blk_queue_bounce_limit(struct request_queue *, u64);
extern void blk_queue_max_hw_sectors(struct request_queue *, unsigned int);
extern void blk_queue_chunk_sectors(struct request_queue *, unsigned int);
extern void blk_queue_max_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_max_discard_sectors(struct request_queue *q,
                unsigned int max_discard_sectors);
extern void blk_queue_max_write_same_sectors(struct request_queue *q,
                unsigned int max_write_same_sectors);
extern void blk_queue_logical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_physical_block_size(struct request_queue *, unsigned int);
extern void blk_queue_alignment_offset(struct request_queue *q,
                                       unsigned int alignment);
extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);
extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
extern void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt);
extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);
extern void blk_set_default_limits(struct queue_limits *lim);
extern void blk_set_stacking_limits(struct queue_limits *lim);
extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                            sector_t offset);
extern int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
                            sector_t offset);
extern void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
                              sector_t offset);
extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);
extern void blk_queue_dma_pad(struct request_queue *, unsigned int);
extern void blk_queue_update_dma_pad(struct request_queue *, unsigned int);
extern int blk_queue_dma_drain(struct request_queue *q,
                               dma_drain_needed_fn *dma_drain_needed,
                               void *buf, unsigned int size);
extern void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn);
extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
extern void blk_queue_virt_boundary(struct request_queue *, unsigned long);
extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
extern void blk_queue_unprep_rq(struct request_queue *, unprep_rq_fn *ufn);
extern void blk_queue_dma_alignment(struct request_queue *, int);
extern void blk_queue_update_dma_alignment(struct request_queue *, int);
extern void blk_queue_softirq_done(struct request_queue *, softirq_done_fn *);
extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
extern void blk_queue_flush_queueable(struct request_queue *q, bool queueable);
extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fua);
extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);

extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);
extern void blk_dump_rq_flags(struct request *, char *);
extern long nr_blockdev_pages(void);

bool __must_check blk_get_queue(struct request_queue *);
struct request_queue *blk_alloc_queue(gfp_t);
struct request_queue *blk_alloc_queue_node(gfp_t, int);
extern void blk_put_queue(struct request_queue *);
extern void blk_set_queue_dying(struct request_queue *);

/*
 * block layer runtime pm functions
 */
#ifdef CONFIG_PM
extern void blk_pm_runtime_init(struct request_queue *q, struct device *dev);
extern int blk_pre_runtime_suspend(struct request_queue *q);
extern void blk_post_runtime_suspend(struct request_queue *q, int err);
extern void blk_pre_runtime_resume(struct request_queue *q);
extern void blk_post_runtime_resume(struct request_queue *q, int err);
extern void blk_set_runtime_active(struct request_queue *q);
#else
static inline void blk_pm_runtime_init(struct request_queue *q,
        struct device *dev) {}
static inline int blk_pre_runtime_suspend(struct request_queue *q)
{
        return -ENOSYS;
}
static inline void blk_post_runtime_suspend(struct request_queue *q, int err) {}
static inline void blk_pre_runtime_resume(struct request_queue *q) {}
static inline void blk_post_runtime_resume(struct request_queue *q, int err) {}
extern inline void blk_set_runtime_active(struct request_queue *q) {}
#endif

/*
 * blk_plug permits building a queue of related requests by holding the I/O
 * fragments for a short period. This allows merging of sequential requests
 * into single larger request. As the requests are moved from a per-task list to
 * the device's request_queue in a batch, this results in improved scalability
 * as the lock contention for request_queue lock is reduced.
 *
 * It is ok not to disable preemption when adding the request to the plug list
 * or when attempting a merge, because blk_schedule_flush_list() will only flush
 * the plug list when the task sleeps by itself. For details, please see
 * schedule() where blk_schedule_flush_plug() is called.
 */
struct blk_plug {
        struct list_head list; /* requests */
        struct list_head mq_list; /* blk-mq requests */
        struct list_head cb_list; /* md requires an unplug callback */
};
#define BLK_MAX_REQUEST_COUNT 16

struct blk_plug_cb;
typedef void (*blk_plug_cb_fn)(struct blk_plug_cb *, bool);
struct blk_plug_cb {
        struct list_head list;
        blk_plug_cb_fn callback;
        void *data;
};
extern struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug,
                                             void *data, int size);
extern void blk_start_plug(struct blk_plug *);
extern void blk_finish_plug(struct blk_plug *);
extern void blk_flush_plug_list(struct blk_plug *, bool);

static inline void blk_flush_plug(struct task_struct *tsk)
{
        struct blk_plug *plug = tsk->plug;

        if (plug)
                blk_flush_plug_list(plug, false);
}

static inline void blk_schedule_flush_plug(struct task_struct *tsk)
{
        struct blk_plug *plug = tsk->plug;

        if (plug)
                blk_flush_plug_list(plug, true);
}

static inline bool blk_needs_flush_plug(struct task_struct *tsk)
{
        struct blk_plug *plug = tsk->plug;

        return plug &&
                (!list_empty(&plug->list) ||
                 !list_empty(&plug->mq_list) ||
                 !list_empty(&plug->cb_list));
}

/*
 * tag stuff
 */
extern int blk_queue_start_tag(struct request_queue *, struct request *);
extern struct request *blk_queue_find_tag(struct request_queue *, int);
extern void blk_queue_end_tag(struct request_queue *, struct request *);
extern int blk_queue_init_tags(struct request_queue *, int, struct blk_queue_tag *, int);
extern void blk_queue_free_tags(struct request_queue *);
extern int blk_queue_resize_tags(struct request_queue *, int);
extern void blk_queue_invalidate_tags(struct request_queue *);
extern struct blk_queue_tag *blk_init_tags(int, int);
extern void blk_free_tags(struct blk_queue_tag *);

static inline struct request *blk_map_queue_find_tag(struct blk_queue_tag *bqt,
                                                int tag)
{
        if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
                return NULL;
        return bqt->tag_index[tag];
}


#define BLKDEV_DISCARD_SECURE   (1 << 0)        /* issue a secure erase */
#define BLKDEV_DISCARD_ZERO     (1 << 1)        /* must reliably zero data */

extern int blkdev_issue_flush(struct block_device *, gfp_t, sector_t *);
extern int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, unsigned long flags);
extern int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, int flags,
                struct bio **biop);
extern int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, struct page *page);
extern int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
                sector_t nr_sects, gfp_t gfp_mask, bool discard);
static inline int sb_issue_discard(struct super_block *sb, sector_t block,
                sector_t nr_blocks, gfp_t gfp_mask, unsigned long flags)
{
        return blkdev_issue_discard(sb->s_bdev, block << (sb->s_blocksize_bits - 9),
                                    nr_blocks << (sb->s_blocksize_bits - 9),
                                    gfp_mask, flags);
}
static inline int sb_issue_zeroout(struct super_block *sb, sector_t block,
                sector_t nr_blocks, gfp_t gfp_mask)
{
        return blkdev_issue_zeroout(sb->s_bdev,
                                    block << (sb->s_blocksize_bits - 9),
                                    nr_blocks << (sb->s_blocksize_bits - 9),
                                    gfp_mask, true);
}

extern int blk_verify_command(unsigned char *cmd, fmode_t has_write_perm);

enum blk_default_limits {
        BLK_MAX_SEGMENTS        = 128,
        BLK_SAFE_MAX_SECTORS    = 255,
        BLK_DEF_MAX_SECTORS     = 2560,
        BLK_MAX_SEGMENT_SIZE    = 65536,
        BLK_SEG_BOUNDARY_MASK   = 0xFFFFFFFFUL,
};

#define blkdev_entry_to_request(entry) list_entry((entry), struct request, queuelist)

static inline unsigned long queue_bounce_pfn(struct request_queue *q)
{
        return q->limits.bounce_pfn;
}

static inline unsigned long queue_segment_boundary(struct request_queue *q)
{
        return q->limits.seg_boundary_mask;
}

static inline unsigned long queue_virt_boundary(struct request_queue *q)
{
        return q->limits.virt_boundary_mask;
}

static inline unsigned int queue_max_sectors(struct request_queue *q)
{
        return q->limits.max_sectors;
}

static inline unsigned int queue_max_hw_sectors(struct request_queue *q)
{
        return q->limits.max_hw_sectors;
}

static inline unsigned short queue_max_segments(struct request_queue *q)
{
        return q->limits.max_segments;
}

static inline unsigned int queue_max_segment_size(struct request_queue *q)
{
        return q->limits.max_segment_size;
}

static inline unsigned short queue_logical_block_size(struct request_queue *q)
{
        int retval = 512;

        if (q && q->limits.logical_block_size)
                retval = q->limits.logical_block_size;

        return retval;
}

static inline unsigned short bdev_logical_block_size(struct block_device *bdev)
{
        return queue_logical_block_size(bdev_get_queue(bdev));
}

static inline unsigned int queue_physical_block_size(struct request_queue *q)
{
        return q->limits.physical_block_size;
}

static inline unsigned int bdev_physical_block_size(struct block_device *bdev)
{
        return queue_physical_block_size(bdev_get_queue(bdev));
}

static inline unsigned int queue_io_min(struct request_queue *q)
{
        return q->limits.io_min;
}

static inline int bdev_io_min(struct block_device *bdev)
{
        return queue_io_min(bdev_get_queue(bdev));
}

static inline unsigned int queue_io_opt(struct request_queue *q)
{
        return q->limits.io_opt;
}

static inline int bdev_io_opt(struct block_device *bdev)
{
        return queue_io_opt(bdev_get_queue(bdev));
}

static inline int queue_alignment_offset(struct request_queue *q)
{
        if (q->limits.misaligned)
                return -1;

        return q->limits.alignment_offset;
}

static inline int queue_limit_alignment_offset(struct queue_limits *lim, sector_t sector)
{
        unsigned int granularity = max(lim->physical_block_size, lim->io_min);
        unsigned int alignment = sector_div(sector, granularity >> 9) << 9;

        return (granularity + lim->alignment_offset - alignment) % granularity;
}

static inline int bdev_alignment_offset(struct block_device *bdev)
{
        struct request_queue *q = bdev_get_queue(bdev);

        if (q->limits.misaligned)
                return -1;

        if (bdev != bdev->bd_contains)
                return bdev->bd_part->alignment_offset;

        return q->limits.alignment_offset;
}

static inline int queue_discard_alignment(struct request_queue *q)
{
        if (q->limits.discard_misaligned)
                return -1;

        return q->limits.discard_alignment;
}

static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector_t sector)
{
        unsigned int alignment, granularity, offset;

        if (!lim->max_discard_sectors)
                return 0;

        /* Why are these in bytes, not sectors? */
        alignment = lim->discard_alignment >> 9;
        granularity = lim->discard_granularity >> 9;
        if (!granularity)
                return 0;

        /* Offset of the partition start in 'granularity' sectors */
        offset = sector_div(sector, granularity);

        /* And why do we do this modulus *again* in blkdev_issue_discard()? */
        offset = (granularity + alignment - offset) % granularity;

        /* Turn it back into bytes, gaah */
        return offset << 9;
}

static inline int bdev_discard_alignment(struct block_device *bdev)
{
        struct request_queue *q = bdev_get_queue(bdev);

        if (bdev != bdev->bd_contains)
                return bdev->bd_part->discard_alignment;

        return q->limits.discard_alignment;
}

static inline unsigned int queue_discard_zeroes_data(struct request_queue *q)
{
        if (q->limits.max_discard_sectors && q->limits.discard_zeroes_data == 1)
                return 1;

        return 0;
}

static inline unsigned int bdev_discard_zeroes_data(struct block_device *bdev)
{
        return queue_discard_zeroes_data(bdev_get_queue(bdev));
}

static inline unsigned int bdev_write_same(struct block_device *bdev)
{
        struct request_queue *q = bdev_get_queue(bdev);

        if (q)
                return q->limits.max_write_same_sectors;

        return 0;
}

static inline int queue_dma_alignment(struct request_queue *q)
{
        return q ? q->dma_alignment : 511;
}

static inline int blk_rq_aligned(struct request_queue *q, unsigned long addr,
                                 unsigned int len)
{
        unsigned int alignment = queue_dma_alignment(q) | q->dma_pad_mask;
        return !(addr & alignment) && !(len & alignment);
}

/* assumes size > 256 */
static inline unsigned int blksize_bits(unsigned int size)
{
        unsigned int bits = 8;
        do {
                bits++;
                size >>= 1;
        } while (size > 256);
        return bits;
}

static inline unsigned int block_size(struct block_device *bdev)
{
        return bdev->bd_block_size;
}

static inline bool queue_flush_queueable(struct request_queue *q)
{
        return !test_bit(QUEUE_FLAG_FLUSH_NQ, &q->queue_flags);
}

typedef struct {struct page *v;} Sector;

unsigned char *read_dev_sector(struct block_device *, sector_t, Sector *);

static inline void put_dev_sector(Sector p)
{
        put_page(p.v);
}

static inline bool __bvec_gap_to_prev(struct request_queue *q,
                                struct bio_vec *bprv, unsigned int offset)
{
        return offset ||
                ((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
}

/*
 * Check if adding a bio_vec after bprv with offset would create a gap in
 * the SG list. Most drivers don't care about this, but some do.
 */
static inline bool bvec_gap_to_prev(struct request_queue *q,
                                struct bio_vec *bprv, unsigned int offset)
{
        if (!queue_virt_boundary(q))
                return false;
        return __bvec_gap_to_prev(q, bprv, offset);
}

static inline bool bio_will_gap(struct request_queue *q, struct bio *prev,
                         struct bio *next)
{
        if (bio_has_data(prev) && queue_virt_boundary(q)) {
                struct bio_vec pb, nb;

                bio_get_last_bvec(prev, &pb);
                bio_get_first_bvec(next, &nb);

                return __bvec_gap_to_prev(q, &pb, nb.bv_offset);
        }

        return false;
}

static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
{
        return bio_will_gap(req->q, req->biotail, bio);
}

static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
{
        return bio_will_gap(req->q, bio, req->bio);
}

struct work_struct;
int kblockd_schedule_work(struct work_struct *work);
int kblockd_schedule_delayed_work(struct delayed_work *dwork, unsigned long delay);
int kblockd_schedule_delayed_work_on(int cpu, struct delayed_work *dwork, unsigned long delay);

#ifdef CONFIG_BLK_CGROUP
/*
 * This should not be using sched_clock(). A real patch is in progress
 * to fix this up, until that is in place we need to disable preemption
 * around sched_clock() in this function and set_io_start_time_ns().
 */
static inline void set_start_time_ns(struct request *req)
{
        preempt_disable();
        req->start_time_ns = sched_clock();
        preempt_enable();
}

static inline void set_io_start_time_ns(struct request *req)
{
        preempt_disable();
        req->io_start_time_ns = sched_clock();
        preempt_enable();
}

static inline uint64_t rq_start_time_ns(struct request *req)
{
        return req->start_time_ns;
}

static inline uint64_t rq_io_start_time_ns(struct request *req)
{
        return req->io_start_time_ns;
}
#else
static inline void set_start_time_ns(struct request *req) {}
static inline void set_io_start_time_ns(struct request *req) {}
static inline uint64_t rq_start_time_ns(struct request *req)
{
        return 0;
}
static inline uint64_t rq_io_start_time_ns(struct request *req)
{
        return 0;
}
#endif

#define MODULE_ALIAS_BLOCKDEV(major,minor) \
        MODULE_ALIAS("block-major-" __stringify(major) "-" __stringify(minor))
#define MODULE_ALIAS_BLOCKDEV_MAJOR(major) \
        MODULE_ALIAS("block-major-" __stringify(major) "-*")

#if defined(CONFIG_BLK_DEV_INTEGRITY)

enum blk_integrity_flags {
        BLK_INTEGRITY_VERIFY            = 1 << 0,
        BLK_INTEGRITY_GENERATE          = 1 << 1,
        BLK_INTEGRITY_DEVICE_CAPABLE    = 1 << 2,
        BLK_INTEGRITY_IP_CHECKSUM       = 1 << 3,
};

struct blk_integrity_iter {
        void                    *prot_buf;
        void                    *data_buf;
        sector_t                seed;
        unsigned int            data_size;
        unsigned short          interval;
        const char              *disk_name;
};

typedef int (integrity_processing_fn) (struct blk_integrity_iter *);

struct blk_integrity_profile {
        integrity_processing_fn         *generate_fn;
        integrity_processing_fn         *verify_fn;
        const char                      *name;
};

extern void blk_integrity_register(struct gendisk *, struct blk_integrity *);
extern void blk_integrity_unregister(struct gendisk *);
extern int blk_integrity_compare(struct gendisk *, struct gendisk *);
extern int blk_rq_map_integrity_sg(struct request_queue *, struct bio *,
                                   struct scatterlist *);
extern int blk_rq_count_integrity_sg(struct request_queue *, struct bio *);
extern bool blk_integrity_merge_rq(struct request_queue *, struct request *,
                                   struct request *);
extern bool blk_integrity_merge_bio(struct request_queue *, struct request *,
                                    struct bio *);

static inline struct blk_integrity *blk_get_integrity(struct gendisk *disk)
{
        struct blk_integrity *bi = &disk->queue->integrity;

        if (!bi->profile)
                return NULL;

        return bi;
}

static inline
struct blk_integrity *bdev_get_integrity(struct block_device *bdev)
{
        return blk_get_integrity(bdev->bd_disk);
}

static inline bool blk_integrity_rq(struct request *rq)
{
        return rq->cmd_flags & REQ_INTEGRITY;
}

static inline void blk_queue_max_integrity_segments(struct request_queue *q,
                                                    unsigned int segs)
{
        q->limits.max_integrity_segments = segs;
}

static inline unsigned short
queue_max_integrity_segments(struct request_queue *q)
{
        return q->limits.max_integrity_segments;
}

static inline bool integrity_req_gap_back_merge(struct request *req,
                                                struct bio *next)
{
        struct bio_integrity_payload *bip = bio_integrity(req->bio);
        struct bio_integrity_payload *bip_next = bio_integrity(next);

        return bvec_gap_to_prev(req->q, &bip->bip_vec[bip->bip_vcnt - 1],
                                bip_next->bip_vec[0].bv_offset);
}

static inline bool integrity_req_gap_front_merge(struct request *req,
                                                 struct bio *bio)
{
        struct bio_integrity_payload *bip = bio_integrity(bio);
        struct bio_integrity_payload *bip_next = bio_integrity(req->bio);

        return bvec_gap_to_prev(req->q, &bip->bip_vec[bip->bip_vcnt - 1],
                                bip_next->bip_vec[0].bv_offset);
}

#else /* CONFIG_BLK_DEV_INTEGRITY */

struct bio;
struct block_device;
struct gendisk;
struct blk_integrity;

static inline int blk_integrity_rq(struct request *rq)
{
        return 0;
}
static inline int blk_rq_count_integrity_sg(struct request_queue *q,
                                            struct bio *b)
{
        return 0;
}
static inline int blk_rq_map_integrity_sg(struct request_queue *q,
                                          struct bio *b,
                                          struct scatterlist *s)
{
        return 0;
}
static inline struct blk_integrity *bdev_get_integrity(struct block_device *b)
{
        return NULL;
}
static inline struct blk_integrity *blk_get_integrity(struct gendisk *disk)
{
        return NULL;
}
static inline int blk_integrity_compare(struct gendisk *a, struct gendisk *b)
{
        return 0;
}
static inline void blk_integrity_register(struct gendisk *d,
                                         struct blk_integrity *b)
{
}
static inline void blk_integrity_unregister(struct gendisk *d)
{
}
static inline void blk_queue_max_integrity_segments(struct request_queue *q,
                                                    unsigned int segs)
{
}
static inline unsigned short queue_max_integrity_segments(struct request_queue *q)
{
        return 0;
}
static inline bool blk_integrity_merge_rq(struct request_queue *rq,
                                          struct request *r1,
                                          struct request *r2)
{
        return true;
}
static inline bool blk_integrity_merge_bio(struct request_queue *rq,
                                           struct request *r,
                                           struct bio *b)
{
        return true;
}

static inline bool integrity_req_gap_back_merge(struct request *req,
                                                struct bio *next)
{
        return false;
}
static inline bool integrity_req_gap_front_merge(struct request *req,
                                                 struct bio *bio)
{
        return false;
}

#endif /* CONFIG_BLK_DEV_INTEGRITY */

/**
 * struct blk_dax_ctl - control and output parameters for ->direct_access
 * @sector: (input) offset relative to a block_device
 * @addr: (output) kernel virtual address for @sector populated by driver
 * @pfn: (output) page frame number for @addr populated by driver
 * @size: (input) number of bytes requested
 */
struct blk_dax_ctl {
        sector_t sector;
        void *addr;
        long size;
        pfn_t pfn;
};

struct block_device_operations {
        int (*open) (struct block_device *, fmode_t);
        void (*release) (struct gendisk *, fmode_t);
        int (*rw_page)(struct block_device *, sector_t, struct page *, int rw);
        int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
        int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
        long (*direct_access)(struct block_device *, sector_t, void **, pfn_t *,
                        long);
        unsigned int (*check_events) (struct gendisk *disk,
                                      unsigned int clearing);
        /* ->media_changed() is DEPRECATED, use ->check_events() instead */
        int (*media_changed) (struct gendisk *);
        void (*unlock_native_capacity) (struct gendisk *);
        int (*revalidate_disk) (struct gendisk *);
        int (*getgeo)(struct block_device *, struct hd_geometry *);
        /* this callback is with swap_lock and sometimes page table lock held */
        void (*swap_slot_free_notify) (struct block_device *, unsigned long);
        struct module *owner;
        const struct pr_ops *pr_ops;
};

extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
                                 unsigned long);
extern int bdev_read_page(struct block_device *, sector_t, struct page *);
extern int bdev_write_page(struct block_device *, sector_t, struct page *,
                                                struct writeback_control *);
extern long bdev_direct_access(struct block_device *, struct blk_dax_ctl *);
extern int bdev_dax_supported(struct super_block *, int);
extern bool bdev_dax_capable(struct block_device *);
#else /* CONFIG_BLOCK */

struct block_device;

/*
 * stubs for when the block layer is configured out
 */
#define buffer_heads_over_limit 0

static inline long nr_blockdev_pages(void)
{
        return 0;
}

struct blk_plug {
};

static inline void blk_start_plug(struct blk_plug *plug)
{
}

static inline void blk_finish_plug(struct blk_plug *plug)
{
}

static inline void blk_flush_plug(struct task_struct *task)
{
}

static inline void blk_schedule_flush_plug(struct task_struct *task)
{
}


static inline bool blk_needs_flush_plug(struct task_struct *tsk)
{
        return false;
}

static inline int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
                                     sector_t *error_sector)
{
        return 0;
}

#endif /* CONFIG_BLOCK */

#endif