block: fixup rq_init() a bit

[linux-2.6/x86.git] / include / linux / blkdev.h

#ifndef _LINUX_BLKDEV_H
#define _LINUX_BLKDEV_H

#ifdef CONFIG_BLOCK

#include <linux/sched.h>
#include <linux/major.h>
#include <linux/genhd.h>
#include <linux/list.h>
#include <linux/timer.h>
#include <linux/workqueue.h>
#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/wait.h>
#include <linux/mempool.h>
#include <linux/bio.h>
#include <linux/module.h>
#include <linux/stringify.h>
#include <linux/bsg.h>

#include <asm/scatterlist.h>

struct scsi_ioctl_command;

struct request_queue;
typedef struct request_queue request_queue_t __deprecated;
struct elevator_queue;
typedef struct elevator_queue elevator_t;
struct request_pm_state;
struct blk_trace;
struct request;
struct sg_io_hdr;

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

int put_io_context(struct io_context *ioc);
void exit_io_context(void);
struct io_context *get_io_context(gfp_t gfp_flags, int node);
struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
void copy_io_context(struct io_context **pdst, struct io_context **psrc);

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

struct request_list {
        int count[2];
        int starved[2];
        int elvpriv;
        mempool_t *rq_pool;
        wait_queue_head_t wait[2];
};

/*
 * request command types
 */
enum rq_cmd_type_bits {
        REQ_TYPE_FS             = 1,    /* fs request */
        REQ_TYPE_BLOCK_PC,              /* scsi command */
        REQ_TYPE_SENSE,                 /* sense request */
        REQ_TYPE_PM_SUSPEND,            /* suspend request */
        REQ_TYPE_PM_RESUME,             /* resume request */
        REQ_TYPE_PM_SHUTDOWN,           /* shutdown request */
        REQ_TYPE_FLUSH,                 /* flush request */
        REQ_TYPE_SPECIAL,               /* driver defined type */
        REQ_TYPE_LINUX_BLOCK,           /* generic block layer message */
        /*
         * for ATA/ATAPI devices. this really doesn't belong here, ide should
         * use REQ_TYPE_SPECIAL and use rq->cmd[0] with the range of driver
         * private REQ_LB opcodes to differentiate what type of request this is
         */
        REQ_TYPE_ATA_TASKFILE,
        REQ_TYPE_ATA_PC,
};

/*
 * For request of type REQ_TYPE_LINUX_BLOCK, rq->cmd[0] is the opcode being
 * sent down (similar to how REQ_TYPE_BLOCK_PC means that ->cmd[] holds a
 * SCSI cdb.
 *
 * 0x00 -> 0x3f are driver private, to be used for whatever purpose they need,
 * typically to differentiate REQ_TYPE_SPECIAL requests.
 *
 */
enum {
        /*
         * just examples for now
         */
        REQ_LB_OP_EJECT = 0x40,         /* eject request */
        REQ_LB_OP_FLUSH = 0x41,         /* flush device */
};

/*
 * request type modified bits. first three bits match BIO_RW* bits, important
 */
enum rq_flag_bits {
        __REQ_RW,               /* not set, read. set, write */
        __REQ_FAILFAST,         /* no low level driver retries */
        __REQ_SORTED,           /* elevator knows about this request */
        __REQ_SOFTBARRIER,      /* may not be passed by ioscheduler */
        __REQ_HARDBARRIER,      /* may not be passed by drive either */
        __REQ_FUA,              /* forced unit access */
        __REQ_NOMERGE,          /* don't touch this for merging */
        __REQ_STARTED,          /* drive already may have started this one */
        __REQ_DONTPREP,         /* don't call prep for this one */
        __REQ_QUEUED,           /* uses queueing */
        __REQ_ELVPRIV,          /* elevator private data attached */
        __REQ_FAILED,           /* set if the request failed */
        __REQ_QUIET,            /* don't worry about errors */
        __REQ_PREEMPT,          /* set for "ide_preempt" requests */
        __REQ_ORDERED_COLOR,    /* is before or after barrier */
        __REQ_RW_SYNC,          /* request is sync (O_DIRECT) */
        __REQ_ALLOCED,          /* request came from our alloc pool */
        __REQ_RW_META,          /* metadata io request */
        __REQ_NR_BITS,          /* stops here */
};

#define REQ_RW          (1 << __REQ_RW)
#define REQ_FAILFAST    (1 << __REQ_FAILFAST)
#define REQ_SORTED      (1 << __REQ_SORTED)
#define REQ_SOFTBARRIER (1 << __REQ_SOFTBARRIER)
#define REQ_HARDBARRIER (1 << __REQ_HARDBARRIER)
#define REQ_FUA         (1 << __REQ_FUA)
#define REQ_NOMERGE     (1 << __REQ_NOMERGE)
#define REQ_STARTED     (1 << __REQ_STARTED)
#define REQ_DONTPREP    (1 << __REQ_DONTPREP)
#define REQ_QUEUED      (1 << __REQ_QUEUED)
#define REQ_ELVPRIV     (1 << __REQ_ELVPRIV)
#define REQ_FAILED      (1 << __REQ_FAILED)
#define REQ_QUIET       (1 << __REQ_QUIET)
#define REQ_PREEMPT     (1 << __REQ_PREEMPT)
#define REQ_ORDERED_COLOR       (1 << __REQ_ORDERED_COLOR)
#define REQ_RW_SYNC     (1 << __REQ_RW_SYNC)
#define REQ_ALLOCED     (1 << __REQ_ALLOCED)
#define REQ_RW_META     (1 << __REQ_RW_META)

#define BLK_MAX_CDB     16

/*
 * try to put the fields that are referenced together in the same cacheline.
 * if you modify this structure, be sure to check block/blk-core.c:rq_init()
 * as well!
 */
struct request {
        struct list_head queuelist;
        struct list_head donelist;

        struct request_queue *q;

        unsigned int cmd_flags;
        enum rq_cmd_type_bits cmd_type;

        /* Maintain bio traversal state for part by part I/O submission.
         * hard_* are block layer internals, no driver should touch them!
         */

        sector_t sector;                /* next sector to submit */
        sector_t hard_sector;           /* next sector to complete */
        unsigned long nr_sectors;       /* no. of sectors left to submit */
        unsigned long hard_nr_sectors;  /* no. of sectors left to complete */
        /* no. of sectors left to submit in the current segment */
        unsigned int current_nr_sectors;

        /* no. of sectors left to complete in the current segment */
        unsigned int hard_cur_sectors;

        struct bio *bio;
        struct bio *biotail;

        struct hlist_node hash; /* merge hash */
        /*
         * 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;
        };

        /*
         * two pointers are available for the IO schedulers, if they need
         * more they have to dynamically allocate it.
         */
        void *elevator_private;
        void *elevator_private2;

        struct gendisk *rq_disk;
        unsigned long start_time;

        /* Number of scatter-gather DMA addr+len pairs after
         * physical address coalescing is performed.
         */
        unsigned short nr_phys_segments;

        /* Number of scatter-gather addr+len pairs after
         * physical and DMA remapping hardware coalescing is performed.
         * This is the number of scatter-gather entries the driver
         * will actually have to deal with after DMA mapping is done.
         */
        unsigned short nr_hw_segments;

        unsigned short ioprio;

        void *special;
        char *buffer;

        int tag;
        int errors;

        int ref_count;

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

        unsigned int data_len;
        unsigned int sense_len;
        void *data;
        void *sense;

        unsigned int timeout;
        int retries;

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

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

/*
 * State information carried for REQ_TYPE_PM_SUSPEND and REQ_TYPE_PM_RESUME
 * requests. Some step values could eventually be made generic.
 */
struct request_pm_state
{
        /* PM state machine step value, currently driver specific */
        int     pm_step;
        /* requested PM state value (S1, S2, S3, S4, ...) */
        u32     pm_state;
        void*   data;           /* for driver use */
};

#include <linux/elevator.h>

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

struct bio_vec;
typedef int (merge_bvec_fn) (struct request_queue *, struct bio *, struct bio_vec *);
typedef void (prepare_flush_fn) (struct request_queue *, struct request *);
typedef void (softirq_done_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 */
};

struct request_queue
{
        /*
         * Together with queue_head for cacheline sharing
         */
        struct list_head        queue_head;
        struct request          *last_merge;
        elevator_t              *elevator;

        /*
         * the queue request freelist, one for reads and one for writes
         */
        struct request_list     rq;

        request_fn_proc         *request_fn;
        make_request_fn         *make_request_fn;
        prep_rq_fn              *prep_rq_fn;
        unplug_fn               *unplug_fn;
        merge_bvec_fn           *merge_bvec_fn;
        prepare_flush_fn        *prepare_flush_fn;
        softirq_done_fn         *softirq_done_fn;

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

        /*
         * Auto-unplugging state
         */
        struct timer_list       unplug_timer;
        int                     unplug_thresh;  /* After this many requests */
        unsigned long           unplug_delay;   /* After this many jiffies */
        struct work_struct      unplug_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;

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

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

        /*
         * 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;

        /*
         * 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            max_sectors;
        unsigned int            max_hw_sectors;
        unsigned short          max_phys_segments;
        unsigned short          max_hw_segments;
        unsigned short          hardsect_size;
        unsigned int            max_segment_size;

        unsigned long           seg_boundary_mask;
        void                    *dma_drain_buffer;
        unsigned int            dma_drain_size;
        unsigned int            dma_alignment;

        struct blk_queue_tag    *queue_tags;
        struct list_head        tag_busy_list;

        unsigned int            nr_sorted;
        unsigned int            in_flight;

        /*
         * 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
        /*
         * reserved for flush operations
         */
        unsigned int            ordered, next_ordered, ordseq;
        int                     orderr, ordcolor;
        struct request          pre_flush_rq, bar_rq, post_flush_rq;
        struct request          *orig_bar_rq;

        struct mutex            sysfs_lock;

#if defined(CONFIG_BLK_DEV_BSG)
        struct bsg_class_device bsg_dev;
#endif
};

#define QUEUE_FLAG_CLUSTER      0       /* cluster several segments into 1 */
#define QUEUE_FLAG_QUEUED       1       /* uses generic tag queueing */
#define QUEUE_FLAG_STOPPED      2       /* queue is stopped */
#define QUEUE_FLAG_READFULL     3       /* read queue has been filled */
#define QUEUE_FLAG_WRITEFULL    4       /* write queue has been filled */
#define QUEUE_FLAG_DEAD         5       /* queue being torn down */
#define QUEUE_FLAG_REENTER      6       /* Re-entrancy avoidance */
#define QUEUE_FLAG_PLUGGED      7       /* queue is plugged */
#define QUEUE_FLAG_ELVSWITCH    8       /* don't use elevator, just do FIFO */
#define QUEUE_FLAG_BIDI         9       /* queue supports bidi requests */

enum {
        /*
         * Hardbarrier is supported with one of the following methods.
         *
         * NONE         : hardbarrier unsupported
         * DRAIN        : ordering by draining is enough
         * DRAIN_FLUSH  : ordering by draining w/ pre and post flushes
         * DRAIN_FUA    : ordering by draining w/ pre flush and FUA write
         * TAG          : ordering by tag is enough
         * TAG_FLUSH    : ordering by tag w/ pre and post flushes
         * TAG_FUA      : ordering by tag w/ pre flush and FUA write
         */
        QUEUE_ORDERED_NONE      = 0x00,
        QUEUE_ORDERED_DRAIN     = 0x01,
        QUEUE_ORDERED_TAG       = 0x02,

        QUEUE_ORDERED_PREFLUSH  = 0x10,
        QUEUE_ORDERED_POSTFLUSH = 0x20,
        QUEUE_ORDERED_FUA       = 0x40,

        QUEUE_ORDERED_DRAIN_FLUSH = QUEUE_ORDERED_DRAIN |
                        QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH,
        QUEUE_ORDERED_DRAIN_FUA = QUEUE_ORDERED_DRAIN |
                        QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_FUA,
        QUEUE_ORDERED_TAG_FLUSH = QUEUE_ORDERED_TAG |
                        QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH,
        QUEUE_ORDERED_TAG_FUA   = QUEUE_ORDERED_TAG |
                        QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_FUA,

        /*
         * Ordered operation sequence
         */
        QUEUE_ORDSEQ_STARTED    = 0x01, /* flushing in progress */
        QUEUE_ORDSEQ_DRAIN      = 0x02, /* waiting for the queue to be drained */
        QUEUE_ORDSEQ_PREFLUSH   = 0x04, /* pre-flushing in progress */
        QUEUE_ORDSEQ_BAR        = 0x08, /* original barrier req in progress */
        QUEUE_ORDSEQ_POSTFLUSH  = 0x10, /* post-flushing in progress */
        QUEUE_ORDSEQ_DONE       = 0x20,
};

#define blk_queue_plugged(q)    test_bit(QUEUE_FLAG_PLUGGED, &(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_flushing(q)   ((q)->ordseq)

#define blk_fs_request(rq)      ((rq)->cmd_type == REQ_TYPE_FS)
#define blk_pc_request(rq)      ((rq)->cmd_type == REQ_TYPE_BLOCK_PC)
#define blk_special_request(rq) ((rq)->cmd_type == REQ_TYPE_SPECIAL)
#define blk_sense_request(rq)   ((rq)->cmd_type == REQ_TYPE_SENSE)

#define blk_noretry_request(rq) ((rq)->cmd_flags & REQ_FAILFAST)
#define blk_rq_started(rq)      ((rq)->cmd_flags & REQ_STARTED)

#define blk_account_rq(rq)      (blk_rq_started(rq) && blk_fs_request(rq))

#define blk_pm_suspend_request(rq)      ((rq)->cmd_type == REQ_TYPE_PM_SUSPEND)
#define blk_pm_resume_request(rq)       ((rq)->cmd_type == REQ_TYPE_PM_RESUME)
#define blk_pm_request(rq)      \
        (blk_pm_suspend_request(rq) || blk_pm_resume_request(rq))

#define blk_sorted_rq(rq)       ((rq)->cmd_flags & REQ_SORTED)
#define blk_barrier_rq(rq)      ((rq)->cmd_flags & REQ_HARDBARRIER)
#define blk_fua_rq(rq)          ((rq)->cmd_flags & REQ_FUA)
#define blk_bidi_rq(rq)         ((rq)->next_rq != NULL)
#define blk_empty_barrier(rq)   (blk_barrier_rq(rq) && blk_fs_request(rq) && !(rq)->hard_nr_sectors)
/* 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)         ((rq)->cmd_flags & 1)

/*
 * We regard a request as sync, if it's a READ or a SYNC write.
 */
#define rq_is_sync(rq)          (rq_data_dir((rq)) == READ || (rq)->cmd_flags & REQ_RW_SYNC)
#define rq_is_meta(rq)          ((rq)->cmd_flags & REQ_RW_META)

static inline int blk_queue_full(struct request_queue *q, int rw)
{
        if (rw == READ)
                return test_bit(QUEUE_FLAG_READFULL, &q->queue_flags);
        return test_bit(QUEUE_FLAG_WRITEFULL, &q->queue_flags);
}

static inline void blk_set_queue_full(struct request_queue *q, int rw)
{
        if (rw == READ)
                set_bit(QUEUE_FLAG_READFULL, &q->queue_flags);
        else
                set_bit(QUEUE_FLAG_WRITEFULL, &q->queue_flags);
}

static inline void blk_clear_queue_full(struct request_queue *q, int rw)
{
        if (rw == READ)
                clear_bit(QUEUE_FLAG_READFULL, &q->queue_flags);
        else
                clear_bit(QUEUE_FLAG_WRITEFULL, &q->queue_flags);
}


/*
 * mergeable request must not have _NOMERGE or _BARRIER bit set, nor may
 * it already be started by driver.
 */
#define RQ_NOMERGE_FLAGS        \
        (REQ_NOMERGE | REQ_STARTED | REQ_HARDBARRIER | REQ_SOFTBARRIER)
#define rq_mergeable(rq)        \
        (!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && blk_fs_request((rq)))

/*
 * q->prep_rq_fn return values
 */
#define BLKPREP_OK              0       /* serve it */
#define BLKPREP_KILL            1       /* fatal error, kill */
#define BLKPREP_DEFER           2       /* leave on queue */

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
 */
#define BLK_BOUNCE_HIGH         ((u64)blk_max_low_pfn << PAGE_SHIFT)
#define BLK_BOUNCE_ANY          ((u64)blk_max_pfn << PAGE_SHIFT)
#define BLK_BOUNCE_ISA          (ISA_DMA_THRESHOLD)

/*
 * default timeout for SG_IO if none specified
 */
#define BLK_DEFAULT_SG_TIMEOUT  (60 * 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 req_iterator {
        int i;
        struct bio *bio;
};

/* This should not be used directly - use rq_for_each_segment */
#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.i)

#define rq_iter_last(rq, _iter)                                 \
                (_iter.bio->bi_next == NULL && _iter.i == _iter.bio->bi_vcnt-1)

extern int blk_register_queue(struct gendisk *disk);
extern void blk_unregister_queue(struct gendisk *disk);
extern void register_disk(struct gendisk *dev);
extern void generic_make_request(struct bio *bio);
extern void blk_put_request(struct request *);
extern void __blk_put_request(struct request_queue *, struct request *);
extern void blk_end_sync_rq(struct request *rq, int error);
extern struct request *blk_get_request(struct request_queue *, int, gfp_t);
extern void blk_insert_request(struct request_queue *, struct request *, int, void *);
extern void blk_requeue_request(struct request_queue *, struct request *);
extern void blk_plug_device(struct request_queue *);
extern int blk_remove_plug(struct request_queue *);
extern void blk_recount_segments(struct request_queue *, struct bio *);
extern int scsi_cmd_ioctl(struct file *, struct request_queue *,
                          struct gendisk *, unsigned int, void __user *);
extern int sg_scsi_ioctl(struct file *, struct request_queue *,
                struct gendisk *, struct scsi_ioctl_command __user *);

/*
 * Temporary export, until SCSI gets fixed up.
 */
extern int blk_rq_append_bio(struct request_queue *q, struct request *rq,
                             struct bio *bio);

/*
 * A queue has just exitted congestion.  Note this in the global counter of
 * congested queues, and wake up anyone who was waiting for requests to be
 * put back.
 */
static inline void blk_clear_queue_congested(struct request_queue *q, int rw)
{
        clear_bdi_congested(&q->backing_dev_info, rw);
}

/*
 * A queue has just entered congestion.  Flag that in the queue's VM-visible
 * state flags and increment the global gounter of congested queues.
 */
static inline void blk_set_queue_congested(struct request_queue *q, int rw)
{
        set_bdi_congested(&q->backing_dev_info, rw);
}

extern void blk_start_queue(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 *);
extern void blk_start_queueing(struct request_queue *);
extern int blk_rq_map_user(struct request_queue *, struct request *, void __user *, unsigned long);
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 sg_iovec *, int, unsigned int);
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 *);
extern int blk_verify_command(unsigned char *, int);
extern void blk_unplug(struct request_queue *q);

static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
{
        return bdev->bd_disk->queue;
}

static inline void blk_run_backing_dev(struct backing_dev_info *bdi,
                                       struct page *page)
{
        if (bdi && bdi->unplug_io_fn)
                bdi->unplug_io_fn(bdi, page);
}

static inline void blk_run_address_space(struct address_space *mapping)
{
        if (mapping)
                blk_run_backing_dev(mapping->backing_dev_info, NULL);
}

/*
 * blk_end_request() and friends.
 * __blk_end_request() and 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 int blk_end_request(struct request *rq, int error,
                                unsigned int nr_bytes);
extern int __blk_end_request(struct request *rq, int error,
                                unsigned int nr_bytes);
extern int blk_end_bidi_request(struct request *rq, int error,
                                unsigned int nr_bytes, unsigned int bidi_bytes);
extern void end_request(struct request *, int);
extern void end_queued_request(struct request *, int);
extern void end_dequeued_request(struct request *, int);
extern int blk_end_request_callback(struct request *rq, int error,
                                unsigned int nr_bytes,
                                int (drv_callback)(struct request *));
extern void blk_complete_request(struct request *);

/*
 * blk_end_request() takes bytes instead of sectors as a complete size.
 * blk_rq_bytes() returns bytes left to complete in the entire request.
 * blk_rq_cur_bytes() returns bytes left to complete in the current segment.
 */
extern unsigned int blk_rq_bytes(struct request *rq);
extern unsigned int blk_rq_cur_bytes(struct request *rq);

static inline void blkdev_dequeue_request(struct request *req)
{
        elv_dequeue_request(req->q, req);
}

/*
 * 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 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_sectors(struct request_queue *, unsigned int);
extern void blk_queue_max_phys_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_hw_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_hardsect_size(struct request_queue *, unsigned short);
extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);
extern int blk_queue_dma_drain(struct request_queue *q, void *buf,
                               unsigned int size);
extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
extern void blk_queue_merge_bvec(struct request_queue *, merge_bvec_fn *);
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 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
extern int blk_queue_ordered(struct request_queue *, unsigned, prepare_flush_fn *);
extern int blk_do_ordered(struct request_queue *, struct request **);
extern unsigned blk_ordered_cur_seq(struct request_queue *);
extern unsigned blk_ordered_req_seq(struct request *);
extern void blk_ordered_complete_seq(struct request_queue *, unsigned, int);

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

int 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 *);

/*
 * tag stuff
 */
#define blk_queue_tag_depth(q)          ((q)->queue_tags->busy)
#define blk_queue_tag_queue(q)          ((q)->queue_tags->busy < (q)->queue_tags->max_depth)
#define blk_rq_tagged(rq)               ((rq)->cmd_flags & REQ_QUEUED)
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 *);
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);
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];
}

extern int blkdev_issue_flush(struct block_device *, sector_t *);

#define MAX_PHYS_SEGMENTS 128
#define MAX_HW_SEGMENTS 128
#define SAFE_MAX_SECTORS 255
#define BLK_DEF_MAX_SECTORS 1024

#define MAX_SEGMENT_SIZE        65536

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

static inline int queue_hardsect_size(struct request_queue *q)
{
        int retval = 512;

        if (q && q->hardsect_size)
                retval = q->hardsect_size;

        return retval;
}

static inline int bdev_hardsect_size(struct block_device *bdev)
{
        return queue_hardsect_size(bdev_get_queue(bdev));
}

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

/* 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;
}

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)
{
        page_cache_release(p.v);
}

struct work_struct;
int kblockd_schedule_work(struct work_struct *work);
void kblockd_flush_work(struct work_struct *work);

#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) "-*")


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

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

static inline void exit_io_context(void)
{
}

struct io_context;
static inline int put_io_context(struct io_context *ioc)
{
        return 1;
}


#endif /* CONFIG_BLOCK */

#endif