Linux v2.6.13-rc3

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

#ifndef _LINUX_BLKDEV_H
#define _LINUX_BLKDEV_H

#include <linux/config.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 <asm/scatterlist.h>

struct request_queue;
typedef struct request_queue request_queue_t;
struct elevator_queue;
typedef struct elevator_queue elevator_t;
struct request_pm_state;

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

/*
 * This is the per-process anticipatory I/O scheduler state.
 */
struct as_io_context {
        spinlock_t lock;

        void (*dtor)(struct as_io_context *aic); /* destructor */
        void (*exit)(struct as_io_context *aic); /* called on task exit */

        unsigned long state;
        atomic_t nr_queued; /* queued reads & sync writes */
        atomic_t nr_dispatched; /* number of requests gone to the drivers */

        /* IO History tracking */
        /* Thinktime */
        unsigned long last_end_request;
        unsigned long ttime_total;
        unsigned long ttime_samples;
        unsigned long ttime_mean;
        /* Layout pattern */
        unsigned int seek_samples;
        sector_t last_request_pos;
        u64 seek_total;
        sector_t seek_mean;
};

struct cfq_queue;
struct cfq_io_context {
        /*
         * circular list of cfq_io_contexts belonging to a process io context
         */
        struct list_head list;
        struct cfq_queue *cfqq;
        void *key;

        struct io_context *ioc;

        unsigned long last_end_request;
        unsigned long last_queue;
        unsigned long ttime_total;
        unsigned long ttime_samples;
        unsigned long ttime_mean;

        void (*dtor)(struct cfq_io_context *);
        void (*exit)(struct cfq_io_context *);
};

/*
 * This is the per-process I/O subsystem state.  It is refcounted and
 * kmalloc'ed. Currently all fields are modified in process io context
 * (apart from the atomic refcount), so require no locking.
 */
struct io_context {
        atomic_t refcount;
        struct task_struct *task;

        int (*set_ioprio)(struct io_context *, unsigned int);

        /*
         * For request batching
         */
        unsigned long last_waited; /* Time last woken after wait for request */
        int nr_batch_requests;     /* Number of requests left in the batch */

        struct as_io_context *aic;
        struct cfq_io_context *cic;
};

void put_io_context(struct io_context *ioc);
void exit_io_context(void);
struct io_context *current_io_context(int gfp_flags);
struct io_context *get_io_context(int gfp_flags);
void copy_io_context(struct io_context **pdst, struct io_context **psrc);
void swap_io_context(struct io_context **ioc1, struct io_context **ioc2);

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

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

#define BLK_MAX_CDB     16

/*
 * try to put the fields that are referenced together in the same cacheline
 */
struct request {
        struct list_head queuelist; /* looking for ->queue? you must _not_
                                     * access it directly, use
                                     * blkdev_dequeue_request! */
        unsigned long flags;            /* see REQ_ bits below */

        /* 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 */
        unsigned long nr_sectors;       /* no. of sectors left to submit */
        /* no. of sectors left to submit in the current segment */
        unsigned int current_nr_sectors;

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

        struct bio *bio;
        struct bio *biotail;

        void *elevator_private;

        unsigned short ioprio;

        int rq_status;  /* should split this into a few status bits */
        struct gendisk *rq_disk;
        int errors;
        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;

        int tag;
        char *buffer;

        int ref_count;
        request_queue_t *q;
        struct request_list *rl;

        struct completion *waiting;
        void *special;

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

        unsigned int data_len;
        void *data;

        unsigned int sense_len;
        void *sense;

        unsigned int timeout;

        /*
         * For Power Management requests
         */
        struct request_pm_state *pm;

        /*
         * completion callback. end_io_data should be folded in with waiting
         */
        rq_end_io_fn *end_io;
        void *end_io_data;
};

/*
 * 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_SOFTBARRIER,      /* may not be passed by ioscheduler */
        __REQ_HARDBARRIER,      /* may not be passed by drive either */
        __REQ_CMD,              /* is a regular fs rw request */
        __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 */
        /*
         * for ATA/ATAPI devices
         */
        __REQ_PC,               /* packet command (special) */
        __REQ_BLOCK_PC,         /* queued down pc from block layer */
        __REQ_SENSE,            /* sense retrival */

        __REQ_FAILED,           /* set if the request failed */
        __REQ_QUIET,            /* don't worry about errors */
        __REQ_SPECIAL,          /* driver suplied command */
        __REQ_DRIVE_CMD,
        __REQ_DRIVE_TASK,
        __REQ_DRIVE_TASKFILE,
        __REQ_PREEMPT,          /* set for "ide_preempt" requests */
        __REQ_PM_SUSPEND,       /* suspend request */
        __REQ_PM_RESUME,        /* resume request */
        __REQ_PM_SHUTDOWN,      /* shutdown request */
        __REQ_BAR_PREFLUSH,     /* barrier pre-flush done */
        __REQ_BAR_POSTFLUSH,    /* barrier post-flush */
        __REQ_BAR_FLUSH,        /* rq is the flush request */
        __REQ_NR_BITS,          /* stops here */
};

#define REQ_RW          (1 << __REQ_RW)
#define REQ_FAILFAST    (1 << __REQ_FAILFAST)
#define REQ_SOFTBARRIER (1 << __REQ_SOFTBARRIER)
#define REQ_HARDBARRIER (1 << __REQ_HARDBARRIER)
#define REQ_CMD         (1 << __REQ_CMD)
#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_PC          (1 << __REQ_PC)
#define REQ_BLOCK_PC    (1 << __REQ_BLOCK_PC)
#define REQ_SENSE       (1 << __REQ_SENSE)
#define REQ_FAILED      (1 << __REQ_FAILED)
#define REQ_QUIET       (1 << __REQ_QUIET)
#define REQ_SPECIAL     (1 << __REQ_SPECIAL)
#define REQ_DRIVE_CMD   (1 << __REQ_DRIVE_CMD)
#define REQ_DRIVE_TASK  (1 << __REQ_DRIVE_TASK)
#define REQ_DRIVE_TASKFILE      (1 << __REQ_DRIVE_TASKFILE)
#define REQ_PREEMPT     (1 << __REQ_PREEMPT)
#define REQ_PM_SUSPEND  (1 << __REQ_PM_SUSPEND)
#define REQ_PM_RESUME   (1 << __REQ_PM_RESUME)
#define REQ_PM_SHUTDOWN (1 << __REQ_PM_SHUTDOWN)
#define REQ_BAR_PREFLUSH        (1 << __REQ_BAR_PREFLUSH)
#define REQ_BAR_POSTFLUSH       (1 << __REQ_BAR_POSTFLUSH)
#define REQ_BAR_FLUSH   (1 << __REQ_BAR_FLUSH)

/*
 * State information carried for REQ_PM_SUSPEND and REQ_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 int (merge_request_fn) (request_queue_t *, struct request *,
                                struct bio *);
typedef int (merge_requests_fn) (request_queue_t *, struct request *,
                                 struct request *);
typedef void (request_fn_proc) (request_queue_t *q);
typedef int (make_request_fn) (request_queue_t *q, struct bio *bio);
typedef int (prep_rq_fn) (request_queue_t *, struct request *);
typedef void (unplug_fn) (request_queue_t *);

struct bio_vec;
typedef int (merge_bvec_fn) (request_queue_t *, struct bio *, struct bio_vec *);
typedef void (activity_fn) (void *data, int rw);
typedef int (issue_flush_fn) (request_queue_t *, struct gendisk *, sector_t *);
typedef int (prepare_flush_fn) (request_queue_t *, struct request *);
typedef void (end_flush_fn) (request_queue_t *, 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 */
        struct list_head busy_list;     /* fifo list of busy tags */
        int busy;                       /* current depth */
        int max_depth;                  /* what we will send to device */
        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;
        merge_request_fn        *back_merge_fn;
        merge_request_fn        *front_merge_fn;
        merge_requests_fn       *merge_requests_fn;
        make_request_fn         *make_request_fn;
        prep_rq_fn              *prep_rq_fn;
        unplug_fn               *unplug_fn;
        merge_bvec_fn           *merge_bvec_fn;
        activity_fn             *activity_fn;
        issue_flush_fn          *issue_flush_fn;
        prepare_flush_fn        *prepare_flush_fn;
        end_flush_fn            *end_flush_fn;

        /*
         * 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;

        void                    *activity_data;

        /*
         * queue needs bounce pages for pages above this limit
         */
        unsigned long           bounce_pfn;
        unsigned int            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 short          max_sectors;
        unsigned short          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;
        unsigned int            dma_alignment;

        struct blk_queue_tag    *queue_tags;

        atomic_t                refcnt;

        unsigned int            in_flight;

        /*
         * sg stuff
         */
        unsigned int            sg_timeout;
        unsigned int            sg_reserved_size;
        int                     node;

        struct list_head        drain_list;

        /*
         * reserved for flush operations
         */
        struct request          *flush_rq;
        unsigned char           ordered;
};

enum {
        QUEUE_ORDERED_NONE,
        QUEUE_ORDERED_TAG,
        QUEUE_ORDERED_FLUSH,
};

#define RQ_INACTIVE             (-1)
#define RQ_ACTIVE               1
#define RQ_SCSI_BUSY            0xffff
#define RQ_SCSI_DONE            0xfffe
#define RQ_SCSI_DISCONNECTING   0xffe0

#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       /* write queue has been filled */
#define QUEUE_FLAG_WRITEFULL    4       /* read 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_DRAIN        8       /* draining queue for sched switch */
#define QUEUE_FLAG_FLUSH        9       /* doing barrier flush sequence */

#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)   test_bit(QUEUE_FLAG_FLUSH, &(q)->queue_flags)

#define blk_fs_request(rq)      ((rq)->flags & REQ_CMD)
#define blk_pc_request(rq)      ((rq)->flags & REQ_BLOCK_PC)
#define blk_noretry_request(rq) ((rq)->flags & REQ_FAILFAST)
#define blk_rq_started(rq)      ((rq)->flags & REQ_STARTED)

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

#define blk_pm_suspend_request(rq)      ((rq)->flags & REQ_PM_SUSPEND)
#define blk_pm_resume_request(rq)       ((rq)->flags & REQ_PM_RESUME)
#define blk_pm_request(rq)      \
        ((rq)->flags & (REQ_PM_SUSPEND | REQ_PM_RESUME))

#define blk_barrier_rq(rq)      ((rq)->flags & REQ_HARDBARRIER)
#define blk_barrier_preflush(rq)        ((rq)->flags & REQ_BAR_PREFLUSH)
#define blk_barrier_postflush(rq)       ((rq)->flags & REQ_BAR_POSTFLUSH)

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

#define rq_data_dir(rq)         ((rq)->flags & 1)

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)->flags & RQ_NOMERGE_FLAGS) && blk_fs_request((rq)))

/*
 * noop, requests are automagically marked as active/inactive by I/O
 * scheduler -- see elv_next_request
 */
#define blk_queue_headactive(q, head_active)

/*
 * 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)

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

#define rq_for_each_bio(_bio, rq)       \
        if ((rq->bio))                  \
                for (_bio = (rq)->bio; _bio; _bio = _bio->bi_next)

struct sec_size {
        unsigned block_size;
        unsigned block_size_bits;
};

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_end_sync_rq(struct request *rq);
extern void blk_attempt_remerge(request_queue_t *, struct request *);
extern struct request *blk_get_request(request_queue_t *, int, int);
extern void blk_insert_request(request_queue_t *, struct request *, int, void *);
extern void blk_requeue_request(request_queue_t *, struct request *);
extern void blk_plug_device(request_queue_t *);
extern int blk_remove_plug(request_queue_t *);
extern void blk_recount_segments(request_queue_t *, struct bio *);
extern int scsi_cmd_ioctl(struct file *, struct gendisk *, unsigned int, void __user *);
extern void blk_start_queue(request_queue_t *q);
extern void blk_stop_queue(request_queue_t *q);
extern void blk_sync_queue(struct request_queue *q);
extern void __blk_stop_queue(request_queue_t *q);
extern void blk_run_queue(request_queue_t *);
extern void blk_queue_activity_fn(request_queue_t *, activity_fn *, void *);
extern struct request *blk_rq_map_user(request_queue_t *, int, void __user *, unsigned int);
extern int blk_rq_unmap_user(struct request *, struct bio *, unsigned int);
extern int blk_execute_rq(request_queue_t *, struct gendisk *, struct request *);

static inline request_queue_t *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);
}

/*
 * end_request() and friends. Must be called with the request queue spinlock
 * acquired. All functions called within end_request() _must_be_ atomic.
 *
 * Several drivers define their own end_request and call
 * end_that_request_first() and end_that_request_last()
 * for parts of the original function. This prevents
 * code duplication in drivers.
 */
extern int end_that_request_first(struct request *, int, int);
extern int end_that_request_chunk(struct request *, int, int);
extern void end_that_request_last(struct request *);
extern void end_request(struct request *req, int uptodate);

/*
 * end_that_request_first/chunk() takes an uptodate argument. we account
 * any value <= as an io error. 0 means -EIO for compatability reasons,
 * any other < 0 value is the direct error type. An uptodate value of
 * 1 indicates successful io completion
 */
#define end_io_error(uptodate)  (unlikely((uptodate) <= 0))

static inline void blkdev_dequeue_request(struct request *req)
{
        BUG_ON(list_empty(&req->queuelist));

        list_del_init(&req->queuelist);

        if (req->rl)
                elv_remove_request(req->q, req);
}

/*
 * Access functions for manipulating queue properties
 */
extern request_queue_t *blk_init_queue_node(request_fn_proc *rfn,
                                        spinlock_t *lock, int node_id);
extern request_queue_t *blk_init_queue(request_fn_proc *, spinlock_t *);
extern void blk_cleanup_queue(request_queue_t *);
extern void blk_queue_make_request(request_queue_t *, make_request_fn *);
extern void blk_queue_bounce_limit(request_queue_t *, u64);
extern void blk_queue_max_sectors(request_queue_t *, unsigned short);
extern void blk_queue_max_phys_segments(request_queue_t *, unsigned short);
extern void blk_queue_max_hw_segments(request_queue_t *, unsigned short);
extern void blk_queue_max_segment_size(request_queue_t *, unsigned int);
extern void blk_queue_hardsect_size(request_queue_t *, unsigned short);
extern void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b);
extern void blk_queue_segment_boundary(request_queue_t *, unsigned long);
extern void blk_queue_prep_rq(request_queue_t *, prep_rq_fn *pfn);
extern void blk_queue_merge_bvec(request_queue_t *, merge_bvec_fn *);
extern void blk_queue_dma_alignment(request_queue_t *, int);
extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
extern void blk_queue_ordered(request_queue_t *, int);
extern void blk_queue_issue_flush_fn(request_queue_t *, issue_flush_fn *);
extern struct request *blk_start_pre_flush(request_queue_t *,struct request *);
extern int blk_complete_barrier_rq(request_queue_t *, struct request *, int);
extern int blk_complete_barrier_rq_locked(request_queue_t *, struct request *, int);

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

int blk_get_queue(request_queue_t *);
request_queue_t *blk_alloc_queue(int gfp_mask);
request_queue_t *blk_alloc_queue_node(int,int);
#define blk_put_queue(q) blk_cleanup_queue((q))

/*
 * 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)->flags & REQ_QUEUED)
extern int blk_queue_start_tag(request_queue_t *, struct request *);
extern struct request *blk_queue_find_tag(request_queue_t *, int);
extern void blk_queue_end_tag(request_queue_t *, struct request *);
extern int blk_queue_init_tags(request_queue_t *, int, struct blk_queue_tag *);
extern void blk_queue_free_tags(request_queue_t *);
extern int blk_queue_resize_tags(request_queue_t *, int);
extern void blk_queue_invalidate_tags(request_queue_t *);
extern long blk_congestion_wait(int rw, long timeout);

extern void blk_rq_bio_prep(request_queue_t *, struct request *, struct bio *);
extern int blkdev_issue_flush(struct block_device *, sector_t *);

#define MAX_PHYS_SEGMENTS 128
#define MAX_HW_SEGMENTS 128
#define MAX_SECTORS 255

#define MAX_SEGMENT_SIZE        65536

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

static inline int queue_hardsect_size(request_queue_t *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(request_queue_t *q)
{
        int retval = 511;

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

        return retval;
}

static inline int bdev_dma_aligment(struct block_device *bdev)
{
        return queue_dma_alignment(bdev_get_queue(bdev));
}

#define blk_finished_io(nsects) do { } while (0)
#define blk_started_io(nsects)  do { } while (0)

/* 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;
}

extern 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(void);

#ifdef CONFIG_LBD
# include <asm/div64.h>
# define sector_div(a, b) do_div(a, b)
#else
# define sector_div(n, b)( \
{ \
        int _res; \
        _res = (n) % (b); \
        (n) /= (b); \
        _res; \
} \
)
#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) "-*")


#endif