#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/stringify.h>

  #include <linux/gfp.h>

  #include <linux/bsg.h>

  #include <linux/smp.h>

  
  #include <asm/scatterlist.h>

  struct module;

  struct scsi_ioctl_command;

  struct request_queue;

  struct elevator_queue;

  struct request_pm_state;

  struct blk_trace;

  struct request;
  struct sg_io_hdr;

  struct bsg_job;

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

  struct request;

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

  
  struct request_list {

  	/*
  	 * count[], starved[], and wait[] are indexed by
  	 * BLK_RW_SYNC/BLK_RW_ASYNC
  	 */

  	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_SPECIAL,		/* driver defined type */

  	/*
  	 * 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,

  };

  #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:blk_rq_init()

   * as well!

   */
  struct request {

  	struct list_head queuelist;

  	struct call_single_data csd;

  	struct request_queue *q;

  	unsigned int cmd_flags;
  	enum rq_cmd_type_bits cmd_type;

  	unsigned long atomic_flags;

  	int cpu;

  	/* 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;

  	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;

  	};

  	/*

  	 * 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
  	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;

  	int ref_count;

  	void *special;		/* opaque pointer available for LLD use */
  	char *buffer;		/* kaddr of the current segment if available */

  	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;

  };

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

  /*

   * 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 void (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;

  struct bvec_merge_data {
  	struct block_device *bi_bdev;
  	sector_t bi_sector;
  	unsigned bi_size;
  	unsigned long bi_rw;
  };
  typedef int (merge_bvec_fn) (struct request_queue *, struct bvec_merge_data *,
  			     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 */
  };

  #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 int		max_hw_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		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;

  };

  struct request_queue {

  	/*
  	 * Together with queue_head for cacheline sharing
  	 */
  	struct list_head	queue_head;
  	struct request		*last_merge;

  	struct elevator_queue	*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;

  	unprep_rq_fn		*unprep_rq_fn;

  	merge_bvec_fn		*merge_bvec_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;

  
  	/*

  	 * 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;
  
  	/*
  	 * 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];

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

  	struct list_head	icq_list;

  	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

  	 */

  	unsigned int		flush_flags;

  	unsigned int		flush_not_queueable:1;

  	unsigned int		flush_queue_delayed:1;

  	unsigned int		flush_pending_idx:1;
  	unsigned int		flush_running_idx:1;
  	unsigned long		flush_pending_since;
  	struct list_head	flush_queue[2];
  	struct list_head	flush_data_in_flight;

  	struct request		flush_rq;

  
  	struct mutex		sysfs_lock;

  
  #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

  #ifdef CONFIG_LOCKDEP
  	int			ioc_release_depth;
  #endif

  };

  #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_DEAD		5	/* queue being torn down */

  #define QUEUE_FLAG_ELVSWITCH	6	/* don't use elevator, just do FIFO */
  #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_SECDISCARD  17	/* supports SECDISCARD */

  #define QUEUE_FLAG_SAME_FORCE  18	/* force complete on same CPU */

  
  #define QUEUE_FLAG_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\

  				 (1 << QUEUE_FLAG_STACKABLE)	|	\

  				 (1 << QUEUE_FLAG_SAME_COMP)	|	\
  				 (1 << QUEUE_FLAG_ADD_RANDOM))

  static inline int queue_is_locked(struct request_queue *q)
  {

  #ifdef CONFIG_SMP

  	spinlock_t *lock = q->queue_lock;
  	return lock && spin_is_locked(lock);

  #else
  	return 1;
  #endif

  }

  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)
  {
  	WARN_ON_ONCE(!queue_is_locked(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)
  {
  	WARN_ON_ONCE(!queue_is_locked(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)
  {

  	WARN_ON_ONCE(!queue_is_locked(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)
  {

  	WARN_ON_ONCE(!queue_is_locked(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_dead(q)	test_bit(QUEUE_FLAG_DEAD, &(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_secdiscard(q)	(blk_queue_discard(q) && \
  	test_bit(QUEUE_FLAG_SECDISCARD, &(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 || \
  	  ((rq)->cmd_flags & REQ_DISCARD)))

  #define blk_pm_request(rq)	\

  	((rq)->cmd_type == REQ_TYPE_PM_SUSPEND || \
  	 (rq)->cmd_type == REQ_TYPE_PM_RESUME)

  #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)		((rq)->cmd_flags & 1)

  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(unsigned int rw_flags)
  {

  	return !(rw_flags & REQ_WRITE) || (rw_flags & REQ_SYNC);

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

  static inline int blk_queue_full(struct request_queue *q, int sync)

  {

  	if (sync)
  		return test_bit(QUEUE_FLAG_SYNCFULL, &q->queue_flags);
  	return test_bit(QUEUE_FLAG_ASYNCFULL, &q->queue_flags);

  }

  static inline void blk_set_queue_full(struct request_queue *q, int sync)

  {

  	if (sync)
  		queue_flag_set(QUEUE_FLAG_SYNCFULL, q);

  	else

  		queue_flag_set(QUEUE_FLAG_ASYNCFULL, q);

  }

  static inline void blk_clear_queue_full(struct request_queue *q, int sync)

  {

  	if (sync)
  		queue_flag_clear(QUEUE_FLAG_SYNCFULL, q);

  	else

  		queue_flag_clear(QUEUE_FLAG_ASYNCFULL, q);

  }
  
  
  /*
   * 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_SOFTBARRIER | REQ_FLUSH | REQ_FUA)

  #define rq_mergeable(rq)	\

  	(!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \

  	 (((rq)->cmd_flags & REQ_DISCARD) || \
  	  (rq)->cmd_type == REQ_TYPE_FS))

  
  /*

   * 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
   */

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

  #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

  extern int blk_register_queue(struct gendisk *disk);
  extern void blk_unregister_queue(struct gendisk *disk);

  extern void 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 struct request *blk_make_request(struct request_queue *, struct bio *,
  					gfp_t);

  extern void blk_requeue_request(struct request_queue *, struct request *);

  extern void blk_add_request_payload(struct request *rq, struct page *page,
  		unsigned int len);

  extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);

  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 void blk_delay_queue(struct request_queue *, unsigned long);

  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 void blk_queue_bio(struct request_queue *q, 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 sync)

  {

  	clear_bdi_congested(&q->backing_dev_info, sync);

  }
  
  /*
   * 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 sync)

  {

  	set_bdi_congested(&q->backing_dev_info, sync);

  }

  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 *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 *, struct sg_iovec *, int,
  			       unsigned int, 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 *);

  static inline struct request_queue *bdev_get_queue(struct block_device *bdev)

  {
  	return bdev->bd_disk->queue;
  }

  /*

   * 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;

  }

  /*

   * 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 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_abort_queue(struct request_queue *);

  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_limits_max_hw_sectors(struct queue_limits *, unsigned int);

  extern void blk_queue_max_hw_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_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_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_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 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(struct request_queue *q, unsigned int flush);

  extern void blk_queue_flush_queueable(struct request_queue *q, bool queueable);

  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 *);

  /*

   * 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 {

  	unsigned long magic; /* detect uninitialized use-cases */
  	struct list_head list; /* requests */
  	struct list_head cb_list; /* md requires an unplug callback */
  	unsigned int should_sort; /* list to be sorted before flushing? */

  };

  #define BLK_MAX_REQUEST_COUNT 16

  struct blk_plug_cb {
  	struct list_head list;
  	void (*callback)(struct blk_plug_cb *);
  };

  
  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->cb_list));

  }

  /*
   * tag stuff
   */

  #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];
  }

  
  #define BLKDEV_DISCARD_SECURE  0x01    /* secure discard */
  
  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_zeroout(struct block_device *bdev, sector_t sector,

  			sector_t nr_sects, gfp_t gfp_mask);

  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);

  }

  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	= 1024,
  	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 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 << 9) & (granularity - 1);

  	return (granularity + lim->alignment_offset - alignment)
  		& (granularity - 1);

  }

  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 = (sector << 9) & (lim->discard_granularity - 1);

  	if (!lim->max_discard_sectors)
  		return 0;

  	return (lim->discard_granularity + lim->discard_alignment - alignment)
  		& (lim->discard_granularity - 1);

  }

  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 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 !q->flush_not_queueable;
  }

  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 request_queue *q, struct work_struct *work);

  #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)

  #define INTEGRITY_FLAG_READ	2	/* verify data integrity on read */
  #define INTEGRITY_FLAG_WRITE	4	/* generate data integrity on write */

  
  struct blk_integrity_exchg {
  	void			*prot_buf;
  	void			*data_buf;
  	sector_t		sector;
  	unsigned int		data_size;
  	unsigned short		sector_size;
  	const char		*disk_name;
  };
  
  typedef void (integrity_gen_fn) (struct blk_integrity_exchg *);
  typedef int (integrity_vrfy_fn) (struct blk_integrity_exchg *);
  typedef void (integrity_set_tag_fn) (void *, void *, unsigned int);
  typedef void (integrity_get_tag_fn) (void *, void *, unsigned int);
  
  struct blk_integrity {
  	integrity_gen_fn	*generate_fn;
  	integrity_vrfy_fn	*verify_fn;
  	integrity_set_tag_fn	*set_tag_fn;
  	integrity_get_tag_fn	*get_tag_fn;
  
  	unsigned short		flags;
  	unsigned short		tuple_size;
  	unsigned short		sector_size;
  	unsigned short		tag_size;
  
  	const char		*name;
  
  	struct kobject		kobj;
  };

  extern bool blk_integrity_is_initialized(struct gendisk *);

  extern int 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 int blk_integrity_merge_rq(struct request_queue *, struct request *,
  				  struct request *);
  extern int blk_integrity_merge_bio(struct request_queue *, struct request *,
  				   struct bio *);

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

  static inline struct blk_integrity *blk_get_integrity(struct gendisk *disk)
  {
  	return disk->integrity;
  }

  static inline int blk_integrity_rq(struct request *rq)
  {

  	if (rq->bio == NULL)
  		return 0;

  	return bio_integrity(rq->bio);
  }

  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;
  }

  #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 0;
  }
  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 int blk_integrity_register(struct gendisk *d,
  					 struct blk_integrity *b)
  {
  	return 0;
  }
  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 int blk_integrity_merge_rq(struct request_queue *rq,
  					 struct request *r1,
  					 struct request *r2)
  {
  	return 0;
  }
  static inline int blk_integrity_merge_bio(struct request_queue *rq,
  					  struct request *r,
  					  struct bio *b)
  {
  	return 0;
  }
  static inline bool blk_integrity_is_initialized(struct gendisk *g)
  {
  	return 0;
  }

  
  #endif /* CONFIG_BLK_DEV_INTEGRITY */

  struct block_device_operations {

  	int (*open) (struct block_device *, fmode_t);
  	int (*release) (struct gendisk *, fmode_t);

  	int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
  	int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);

  	int (*direct_access) (struct block_device *, sector_t,
  						void **, unsigned 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;
  };

  extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
  				 unsigned long);

  #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;
  }

  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;
  }

  #endif /* CONFIG_BLOCK */

  #endif