#ifndef _LINUX_BLKDEV_H
  #define _LINUX_BLKDEV_H

  #include <linux/sched.h>

  #ifdef CONFIG_BLOCK

  #include <linux/major.h>
  #include <linux/genhd.h>
  #include <linux/list.h>

  #include <linux/llist.h>

  #include <linux/timer.h>
  #include <linux/workqueue.h>
  #include <linux/pagemap.h>

  #include <linux/backing-dev-defs.h>

  #include <linux/wait.h>
  #include <linux/mempool.h>

  #include <linux/pfn.h>

  #include <linux/bio.h>

  #include <linux/stringify.h>

  #include <linux/gfp.h>

  #include <linux/bsg.h>

  #include <linux/smp.h>

  #include <linux/rcupdate.h>

  #include <linux/percpu-refcount.h>

  #include <linux/scatterlist.h>

  #include <linux/blkzoned.h>

  struct module;

  struct scsi_ioctl_command;

  struct request_queue;

  struct elevator_queue;

  struct blk_trace;

  struct request;
  struct sg_io_hdr;

  struct bsg_job;

  struct blkcg_gq;

  struct blk_flush_queue;

  struct pr_ops;

  struct rq_wb;

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

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

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

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

  struct request_list {

  	struct request_queue	*q;	/* the queue this rl belongs to */

  #ifdef CONFIG_BLK_CGROUP
  	struct blkcg_gq		*blkg;	/* blkg this request pool belongs to */
  #endif

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

  	int			count[2];
  	int			starved[2];
  	mempool_t		*rq_pool;
  	wait_queue_head_t	wait[2];

  	unsigned int		flags;

  };

  /*
   * request command types
   */
  enum rq_cmd_type_bits {
  	REQ_TYPE_FS		= 1,	/* fs request */
  	REQ_TYPE_BLOCK_PC,		/* scsi command */

  	REQ_TYPE_DRV_PRIV,		/* driver defined types from here */

  };

  /*
   * request flags */
  typedef __u32 __bitwise req_flags_t;
  
  /* elevator knows about this request */
  #define RQF_SORTED		((__force req_flags_t)(1 << 0))
  /* drive already may have started this one */
  #define RQF_STARTED		((__force req_flags_t)(1 << 1))
  /* uses tagged queueing */
  #define RQF_QUEUED		((__force req_flags_t)(1 << 2))
  /* may not be passed by ioscheduler */
  #define RQF_SOFTBARRIER		((__force req_flags_t)(1 << 3))
  /* request for flush sequence */
  #define RQF_FLUSH_SEQ		((__force req_flags_t)(1 << 4))
  /* merge of different types, fail separately */
  #define RQF_MIXED_MERGE		((__force req_flags_t)(1 << 5))
  /* track inflight for MQ */
  #define RQF_MQ_INFLIGHT		((__force req_flags_t)(1 << 6))
  /* don't call prep for this one */
  #define RQF_DONTPREP		((__force req_flags_t)(1 << 7))
  /* set for "ide_preempt" requests and also for requests for which the SCSI
     "quiesce" state must be ignored. */
  #define RQF_PREEMPT		((__force req_flags_t)(1 << 8))
  /* contains copies of user pages */
  #define RQF_COPY_USER		((__force req_flags_t)(1 << 9))
  /* vaguely specified driver internal error.  Ignored by the block layer */
  #define RQF_FAILED		((__force req_flags_t)(1 << 10))
  /* don't warn about errors */
  #define RQF_QUIET		((__force req_flags_t)(1 << 11))
  /* elevator private data attached */
  #define RQF_ELVPRIV		((__force req_flags_t)(1 << 12))
  /* account I/O stat */
  #define RQF_IO_STAT		((__force req_flags_t)(1 << 13))
  /* request came from our alloc pool */
  #define RQF_ALLOCED		((__force req_flags_t)(1 << 14))
  /* runtime pm request */
  #define RQF_PM			((__force req_flags_t)(1 << 15))
  /* on IO scheduler merge hash */
  #define RQF_HASHED		((__force req_flags_t)(1 << 16))

  /* IO stats tracking on */
  #define RQF_STATS		((__force req_flags_t)(1 << 17))

  /* Look at ->special_vec for the actual data payload instead of the
     bio chain. */
  #define RQF_SPECIAL_PAYLOAD	((__force req_flags_t)(1 << 18))

  
  /* flags that prevent us from merging requests: */
  #define RQF_NOMERGE_FLAGS \

  	(RQF_STARTED | RQF_SOFTBARRIER | RQF_FLUSH_SEQ | RQF_SPECIAL_PAYLOAD)

  #define BLK_MAX_CDB	16
  
  /*

   * Try to put the fields that are referenced together in the same cacheline.
   *
   * If you modify this structure, make sure to update blk_rq_init() and
   * especially blk_mq_rq_ctx_init() to take care of the added fields.

   */
  struct request {

  	struct list_head queuelist;

  	union {
  		struct call_single_data csd;

  		u64 fifo_time;

  	};

  	struct request_queue *q;

  	struct blk_mq_ctx *mq_ctx;

  	int cpu;

  	unsigned cmd_type;

  	unsigned int cmd_flags;		/* op and common flags */

  	req_flags_t rq_flags;

  	unsigned long atomic_flags;

  	/* the following two fields are internal, NEVER access directly */

  	unsigned int __data_len;	/* total data len */

  	sector_t __sector;		/* sector cursor */

  
  	struct bio *bio;
  	struct bio *biotail;

  	/*
  	 * The hash is used inside the scheduler, and killed once the
  	 * request reaches the dispatch list. The ipi_list is only used
  	 * to queue the request for softirq completion, which is long
  	 * after the request has been unhashed (and even removed from
  	 * the dispatch list).
  	 */
  	union {
  		struct hlist_node hash;	/* merge hash */
  		struct list_head ipi_list;
  	};

  	/*
  	 * The rb_node is only used inside the io scheduler, requests
  	 * are pruned when moved to the dispatch queue. So let the

  	 * completion_data share space with the rb_node.

  	 */
  	union {
  		struct rb_node rb_node;	/* sort/lookup */

  		struct bio_vec special_vec;

  		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;

  	struct blk_issue_stat issue_stat;

  #ifdef CONFIG_BLK_CGROUP

  	struct request_list *rl;		/* rl this rq is alloced from */

  	unsigned long long start_time_ns;
  	unsigned long long io_start_time_ns;    /* when passed to hardware */
  #endif

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

  #if defined(CONFIG_BLK_DEV_INTEGRITY)
  	unsigned short nr_integrity_segments;
  #endif

  	unsigned short ioprio;

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

  	int tag;
  	int errors;

  	/*
  	 * when request is used as a packet command carrier
  	 */

  	unsigned char __cmd[BLK_MAX_CDB];
  	unsigned char *cmd;

  	unsigned short cmd_len;

  	unsigned int extra_len;	/* length of alignment and padding */

  	unsigned int sense_len;

  	unsigned int resid_len;	/* residual count */

  	void *sense;

  	unsigned long deadline;
  	struct list_head timeout_list;

  	unsigned int timeout;

  	int retries;

  
  	/*

  	 * completion callback.

  	 */
  	rq_end_io_fn *end_io;
  	void *end_io_data;

  
  	/* for bidi */
  	struct request *next_rq;

  };

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

  #include <linux/elevator.h>

  struct blk_queue_ctx;

  typedef void (request_fn_proc) (struct request_queue *q);

  typedef blk_qc_t (make_request_fn) (struct request_queue *q, struct bio *bio);

  typedef int (prep_rq_fn) (struct request_queue *, struct request *);

  typedef void (unprep_rq_fn) (struct request_queue *, struct request *);

  
  struct bio_vec;

  typedef void (softirq_done_fn)(struct request *);

  typedef int (dma_drain_needed_fn)(struct request *);

  typedef int (lld_busy_fn) (struct request_queue *q);

  typedef int (bsg_job_fn) (struct bsg_job *);

  enum blk_eh_timer_return {
  	BLK_EH_NOT_HANDLED,
  	BLK_EH_HANDLED,
  	BLK_EH_RESET_TIMER,
  };
  
  typedef enum blk_eh_timer_return (rq_timed_out_fn)(struct request *);

  enum blk_queue_state {
  	Queue_down,
  	Queue_up,
  };

  struct blk_queue_tag {
  	struct request **tag_index;	/* map of busy tags */
  	unsigned long *tag_map;		/* bit map of free/busy tags */

  	int max_depth;			/* what we will send to device */

  	int real_max_depth;		/* what the array can hold */

  	atomic_t refcnt;		/* map can be shared */

  	int alloc_policy;		/* tag allocation policy */
  	int next_tag;			/* next tag */

  };

  #define BLK_TAG_ALLOC_FIFO 0 /* allocate starting from 0 */
  #define BLK_TAG_ALLOC_RR 1 /* allocate starting from last allocated tag */

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

  /*
   * Zoned block device models (zoned limit).
   */
  enum blk_zoned_model {
  	BLK_ZONED_NONE,	/* Regular block device */
  	BLK_ZONED_HA,	/* Host-aware zoned block device */
  	BLK_ZONED_HM,	/* Host-managed zoned block device */
  };

  struct queue_limits {
  	unsigned long		bounce_pfn;
  	unsigned long		seg_boundary_mask;

  	unsigned long		virt_boundary_mask;

  
  	unsigned int		max_hw_sectors;

  	unsigned int		max_dev_sectors;

  	unsigned int		chunk_sectors;

  	unsigned int		max_sectors;
  	unsigned int		max_segment_size;

  	unsigned int		physical_block_size;
  	unsigned int		alignment_offset;
  	unsigned int		io_min;
  	unsigned int		io_opt;

  	unsigned int		max_discard_sectors;

  	unsigned int		max_hw_discard_sectors;

  	unsigned int		max_write_same_sectors;

  	unsigned int		max_write_zeroes_sectors;

  	unsigned int		discard_granularity;
  	unsigned int		discard_alignment;

  
  	unsigned short		logical_block_size;

  	unsigned short		max_segments;

  	unsigned short		max_integrity_segments;

  	unsigned char		misaligned;

  	unsigned char		discard_misaligned;

  	unsigned char		cluster;

  	unsigned char		discard_zeroes_data;

  	unsigned char		raid_partial_stripes_expensive;

  	enum blk_zoned_model	zoned;

  };

  #ifdef CONFIG_BLK_DEV_ZONED
  
  struct blk_zone_report_hdr {
  	unsigned int	nr_zones;
  	u8		padding[60];
  };
  
  extern int blkdev_report_zones(struct block_device *bdev,
  			       sector_t sector, struct blk_zone *zones,
  			       unsigned int *nr_zones, gfp_t gfp_mask);
  extern int blkdev_reset_zones(struct block_device *bdev, sector_t sectors,
  			      sector_t nr_sectors, gfp_t gfp_mask);

  extern int blkdev_report_zones_ioctl(struct block_device *bdev, fmode_t mode,
  				     unsigned int cmd, unsigned long arg);
  extern int blkdev_reset_zones_ioctl(struct block_device *bdev, fmode_t mode,
  				    unsigned int cmd, unsigned long arg);
  
  #else /* CONFIG_BLK_DEV_ZONED */
  
  static inline int blkdev_report_zones_ioctl(struct block_device *bdev,
  					    fmode_t mode, unsigned int cmd,
  					    unsigned long arg)
  {
  	return -ENOTTY;
  }
  
  static inline int blkdev_reset_zones_ioctl(struct block_device *bdev,
  					   fmode_t mode, unsigned int cmd,
  					   unsigned long arg)
  {
  	return -ENOTTY;
  }

  #endif /* CONFIG_BLK_DEV_ZONED */

  struct request_queue {

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

  	struct elevator_queue	*elevator;

  	int			nr_rqs[2];	/* # allocated [a]sync rqs */
  	int			nr_rqs_elvpriv;	/* # allocated rqs w/ elvpriv */

  	struct rq_wb		*rq_wb;

  	/*

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

  	 */

  	struct request_list	root_rl;

  
  	request_fn_proc		*request_fn;

  	make_request_fn		*make_request_fn;
  	prep_rq_fn		*prep_rq_fn;

  	unprep_rq_fn		*unprep_rq_fn;

  	softirq_done_fn		*softirq_done_fn;

  	rq_timed_out_fn		*rq_timed_out_fn;

  	dma_drain_needed_fn	*dma_drain_needed;

  	lld_busy_fn		*lld_busy_fn;

  	struct blk_mq_ops	*mq_ops;
  
  	unsigned int		*mq_map;
  
  	/* sw queues */

  	struct blk_mq_ctx __percpu	*queue_ctx;

  	unsigned int		nr_queues;

  	unsigned int		queue_depth;

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

  	/*

  	 * Dispatch queue sorting
  	 */

  	sector_t		end_sector;

  	struct request		*boundary_rq;

  
  	/*

  	 * Delayed queue handling

  	 */

  	struct delayed_work	delay_work;

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

  	/*

  	 * various queue flags, see QUEUE_* below

  	 */

  	unsigned long		queue_flags;

  
  	/*

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

  	 * queue needs bounce pages for pages above this limit

  	 */

  	gfp_t			bounce_gfp;

  
  	/*

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

  	 */

  	spinlock_t		__queue_lock;

  	spinlock_t		*queue_lock;
  
  	/*
  	 * queue kobject
  	 */
  	struct kobject kobj;

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

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

  #ifdef CONFIG_PM

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

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

  	unsigned int		dma_drain_size;

  	void			*dma_drain_buffer;

  	unsigned int		dma_pad_mask;

  	unsigned int		dma_alignment;
  
  	struct blk_queue_tag	*queue_tags;

  	struct list_head	tag_busy_list;

  	unsigned int		nr_sorted;

  	unsigned int		in_flight[2];

  
  	struct blk_rq_stat	rq_stats[2];

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

  	unsigned int		rq_timeout;

  	int			poll_nsec;

  	struct timer_list	timeout;

  	struct work_struct	timeout_work;

  	struct list_head	timeout_list;

  	struct list_head	icq_list;

  #ifdef CONFIG_BLK_CGROUP

  	DECLARE_BITMAP		(blkcg_pols, BLKCG_MAX_POLS);

  	struct blkcg_gq		*root_blkg;

  	struct list_head	blkg_list;

  #endif

  	struct queue_limits	limits;

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

  	int			node;

  #ifdef CONFIG_BLK_DEV_IO_TRACE

  	struct blk_trace	*blk_trace;

  #endif

  	/*

  	 * for flush operations

  	 */

  	struct blk_flush_queue	*fq;

  	struct list_head	requeue_list;
  	spinlock_t		requeue_lock;

  	struct delayed_work	requeue_work;

  	struct mutex		sysfs_lock;

  	int			bypass_depth;

  	atomic_t		mq_freeze_depth;

  #if defined(CONFIG_BLK_DEV_BSG)

  	bsg_job_fn		*bsg_job_fn;
  	int			bsg_job_size;

  	struct bsg_class_device bsg_dev;
  #endif

  
  #ifdef CONFIG_BLK_DEV_THROTTLING
  	/* Throttle data */
  	struct throtl_data *td;
  #endif

  	struct rcu_head		rcu_head;

  	wait_queue_head_t	mq_freeze_wq;

  	struct percpu_ref	q_usage_counter;

  	struct list_head	all_q_node;

  
  	struct blk_mq_tag_set	*tag_set;
  	struct list_head	tag_set_list;

  	struct bio_set		*bio_split;

  
  	bool			mq_sysfs_init_done;

  };

  #define QUEUE_FLAG_QUEUED	1	/* uses generic tag queueing */
  #define QUEUE_FLAG_STOPPED	2	/* queue is stopped */

  #define	QUEUE_FLAG_SYNCFULL	3	/* read queue has been filled */
  #define QUEUE_FLAG_ASYNCFULL	4	/* write queue has been filled */

  #define QUEUE_FLAG_DYING	5	/* queue being torn down */

  #define QUEUE_FLAG_BYPASS	6	/* act as dumb FIFO queue */

  #define QUEUE_FLAG_BIDI		7	/* queue supports bidi requests */
  #define QUEUE_FLAG_NOMERGES     8	/* disable merge attempts */

  #define QUEUE_FLAG_SAME_COMP	9	/* complete on same CPU-group */

  #define QUEUE_FLAG_FAIL_IO     10	/* fake timeout */
  #define QUEUE_FLAG_STACKABLE   11	/* supports request stacking */
  #define QUEUE_FLAG_NONROT      12	/* non-rotational device (SSD) */

  #define QUEUE_FLAG_VIRT        QUEUE_FLAG_NONROT /* paravirt device */

  #define QUEUE_FLAG_IO_STAT     13	/* do IO stats */
  #define QUEUE_FLAG_DISCARD     14	/* supports DISCARD */
  #define QUEUE_FLAG_NOXMERGES   15	/* No extended merges */
  #define QUEUE_FLAG_ADD_RANDOM  16	/* Contributes to random pool */

  #define QUEUE_FLAG_SECERASE    17	/* supports secure erase */

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

  #define QUEUE_FLAG_DEAD        19	/* queue tear-down finished */

  #define QUEUE_FLAG_INIT_DONE   20	/* queue is initialized */

  #define QUEUE_FLAG_NO_SG_MERGE 21	/* don't attempt to merge SG segments*/

  #define QUEUE_FLAG_POLL	       22	/* IO polling enabled if set */

  #define QUEUE_FLAG_WC	       23	/* Write back caching */
  #define QUEUE_FLAG_FUA	       24	/* device supports FUA writes */

  #define QUEUE_FLAG_FLUSH_NQ    25	/* flush not queueuable */

  #define QUEUE_FLAG_DAX         26	/* device supports DAX */

  #define QUEUE_FLAG_STATS       27	/* track rq completion times */

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

  				 (1 << QUEUE_FLAG_STACKABLE)	|	\

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

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

  				 (1 << QUEUE_FLAG_STACKABLE)	|	\

  				 (1 << QUEUE_FLAG_SAME_COMP)	|	\
  				 (1 << QUEUE_FLAG_POLL))

  static inline void queue_lockdep_assert_held(struct request_queue *q)

  {

  	if (q->queue_lock)
  		lockdep_assert_held(q->queue_lock);

  }

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

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

  	queue_lockdep_assert_held(q);

  
  	if (test_bit(flag, &q->queue_flags)) {
  		__clear_bit(flag, &q->queue_flags);
  		return 1;
  	}
  
  	return 0;
  }
  
  static inline int queue_flag_test_and_set(unsigned int flag,
  					  struct request_queue *q)
  {

  	queue_lockdep_assert_held(q);

  
  	if (!test_bit(flag, &q->queue_flags)) {
  		__set_bit(flag, &q->queue_flags);
  		return 0;
  	}
  
  	return 1;
  }

  static inline void queue_flag_set(unsigned int flag, struct request_queue *q)
  {

  	queue_lockdep_assert_held(q);

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

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

  static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
  {

  	queue_lockdep_assert_held(q);

  	__clear_bit(flag, &q->queue_flags);
  }

  #define blk_queue_tagged(q)	test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
  #define blk_queue_stopped(q)	test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)

  #define blk_queue_dying(q)	test_bit(QUEUE_FLAG_DYING, &(q)->queue_flags)

  #define blk_queue_dead(q)	test_bit(QUEUE_FLAG_DEAD, &(q)->queue_flags)

  #define blk_queue_bypass(q)	test_bit(QUEUE_FLAG_BYPASS, &(q)->queue_flags)

  #define blk_queue_init_done(q)	test_bit(QUEUE_FLAG_INIT_DONE, &(q)->queue_flags)

  #define blk_queue_nomerges(q)	test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)

  #define blk_queue_noxmerges(q)	\
  	test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags)

  #define blk_queue_nonrot(q)	test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)

  #define blk_queue_io_stat(q)	test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)

  #define blk_queue_add_random(q)	test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)

  #define blk_queue_stackable(q)	\
  	test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags)

  #define blk_queue_discard(q)	test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)

  #define blk_queue_secure_erase(q) \
  	(test_bit(QUEUE_FLAG_SECERASE, &(q)->queue_flags))

  #define blk_queue_dax(q)	test_bit(QUEUE_FLAG_DAX, &(q)->queue_flags)

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

  	(((rq)->rq_flags & RQF_STARTED) && \

  	 ((rq)->cmd_type == REQ_TYPE_FS))

  #define blk_rq_cpu_valid(rq)	((rq)->cpu != -1)

  #define blk_bidi_rq(rq)		((rq)->next_rq != NULL)

  /* rq->queuelist of dequeued request must be list_empty() */
  #define blk_queued_rq(rq)	(!list_empty(&(rq)->queuelist))

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

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

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

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

  static inline enum blk_zoned_model
  blk_queue_zoned_model(struct request_queue *q)
  {
  	return q->limits.zoned;
  }
  
  static inline bool blk_queue_is_zoned(struct request_queue *q)
  {
  	switch (blk_queue_zoned_model(q)) {
  	case BLK_ZONED_HA:
  	case BLK_ZONED_HM:
  		return true;
  	default:
  		return false;
  	}
  }

  static inline unsigned int blk_queue_zone_size(struct request_queue *q)
  {
  	return blk_queue_is_zoned(q) ? q->limits.chunk_sectors : 0;
  }

  static inline bool rq_is_sync(struct request *rq)
  {

  	return op_is_sync(rq->cmd_flags);

  }

  static inline bool blk_rl_full(struct request_list *rl, bool sync)

  {

  	unsigned int flag = sync ? BLK_RL_SYNCFULL : BLK_RL_ASYNCFULL;
  
  	return rl->flags & flag;

  }

  static inline void blk_set_rl_full(struct request_list *rl, bool sync)

  {

  	unsigned int flag = sync ? BLK_RL_SYNCFULL : BLK_RL_ASYNCFULL;
  
  	rl->flags |= flag;

  }

  static inline void blk_clear_rl_full(struct request_list *rl, bool sync)

  {

  	unsigned int flag = sync ? BLK_RL_SYNCFULL : BLK_RL_ASYNCFULL;
  
  	rl->flags &= ~flag;

  }

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

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

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

  	if (rq->cmd_flags & REQ_NOMERGE_FLAGS)

  		return false;
  	if (rq->rq_flags & RQF_NOMERGE_FLAGS)

  		return false;
  
  	return true;
  }

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

  static inline unsigned int blk_queue_depth(struct request_queue *q)
  {
  	if (q->queue_depth)
  		return q->queue_depth;
  
  	return q->nr_requests;
  }

  /*

   * q->prep_rq_fn return values
   */

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

  
  extern unsigned long blk_max_low_pfn, blk_max_pfn;
  
  /*
   * standard bounce addresses:
   *
   * BLK_BOUNCE_HIGH	: bounce all highmem pages
   * BLK_BOUNCE_ANY	: don't bounce anything
   * BLK_BOUNCE_ISA	: bounce pages above ISA DMA boundary
   */

  
  #if BITS_PER_LONG == 32

  #define BLK_BOUNCE_HIGH		((u64)blk_max_low_pfn << PAGE_SHIFT)

  #else
  #define BLK_BOUNCE_HIGH		-1ULL
  #endif
  #define BLK_BOUNCE_ANY		(-1ULL)

  #define BLK_BOUNCE_ISA		(DMA_BIT_MASK(24))

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

  #define BLK_MIN_SG_TIMEOUT	(7 * HZ)

  #ifdef CONFIG_BOUNCE

  extern int init_emergency_isa_pool(void);

  extern void blk_queue_bounce(struct request_queue *q, struct bio **bio);

  #else
  static inline int init_emergency_isa_pool(void)
  {
  	return 0;
  }

  static inline void blk_queue_bounce(struct request_queue *q, struct bio **bio)

  {
  }
  #endif /* CONFIG_MMU */

  struct rq_map_data {
  	struct page **pages;
  	int page_order;
  	int nr_entries;

  	unsigned long offset;

  	int null_mapped;

  	int from_user;

  };

  struct req_iterator {

  	struct bvec_iter iter;

  	struct bio *bio;
  };
  
  /* This should not be used directly - use rq_for_each_segment */

  #define for_each_bio(_bio)		\
  	for (; _bio; _bio = _bio->bi_next)

  #define __rq_for_each_bio(_bio, rq)	\

  	if ((rq->bio))			\
  		for (_bio = (rq)->bio; _bio; _bio = _bio->bi_next)

  #define rq_for_each_segment(bvl, _rq, _iter)			\
  	__rq_for_each_bio(_iter.bio, _rq)			\

  		bio_for_each_segment(bvl, _iter.bio, _iter.iter)

  #define rq_iter_last(bvec, _iter)				\

  		(_iter.bio->bi_next == NULL &&			\

  		 bio_iter_last(bvec, _iter.iter))

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

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

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

  extern blk_qc_t generic_make_request(struct bio *bio);

  extern void blk_rq_init(struct request_queue *q, struct request *rq);

  extern void blk_put_request(struct request *);

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

  extern struct request *blk_get_request(struct request_queue *, int, gfp_t);

  extern void blk_rq_set_block_pc(struct request *);

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

  extern int blk_lld_busy(struct request_queue *q);

  extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
  			     struct bio_set *bs, gfp_t gfp_mask,
  			     int (*bio_ctr)(struct bio *, struct bio *, void *),
  			     void *data);
  extern void blk_rq_unprep_clone(struct request *rq);

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

  extern int blk_rq_append_bio(struct request *rq, struct bio *bio);

  extern void blk_delay_queue(struct request_queue *, unsigned long);

  extern void blk_queue_split(struct request_queue *, struct bio **,
  			    struct bio_set *);

  extern void blk_recount_segments(struct request_queue *, struct bio *);

  extern int scsi_verify_blk_ioctl(struct block_device *, unsigned int);

  extern int scsi_cmd_blk_ioctl(struct block_device *, fmode_t,
  			      unsigned int, void __user *);

  extern int scsi_cmd_ioctl(struct request_queue *, struct gendisk *, fmode_t,
  			  unsigned int, void __user *);

  extern int sg_scsi_ioctl(struct request_queue *, struct gendisk *, fmode_t,
  			 struct scsi_ioctl_command __user *);

  extern int blk_queue_enter(struct request_queue *q, bool nowait);

  extern void blk_queue_exit(struct request_queue *q);

  extern void blk_start_queue(struct request_queue *q);

  extern void blk_start_queue_async(struct request_queue *q);

  extern void blk_stop_queue(struct request_queue *q);

  extern void blk_sync_queue(struct request_queue *q);

  extern void __blk_stop_queue(struct request_queue *q);

  extern void __blk_run_queue(struct request_queue *q);

  extern void __blk_run_queue_uncond(struct request_queue *q);

  extern void blk_run_queue(struct request_queue *);

  extern void blk_run_queue_async(struct request_queue *q);

  extern void blk_mq_quiesce_queue(struct request_queue *q);

  extern int blk_rq_map_user(struct request_queue *, struct request *,

  			   struct rq_map_data *, void __user *, unsigned long,
  			   gfp_t);

  extern int blk_rq_unmap_user(struct bio *);

  extern int blk_rq_map_kern(struct request_queue *, struct request *, void *, unsigned int, gfp_t);
  extern int blk_rq_map_user_iov(struct request_queue *, struct request *,

  			       struct rq_map_data *, const struct iov_iter *,
  			       gfp_t);

  extern int blk_execute_rq(struct request_queue *, struct gendisk *,

  			  struct request *, int);

  extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,

  				  struct request *, int, rq_end_io_fn *);

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

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

  {

  	return bdev->bd_disk->queue;	/* this is never NULL */

  }

  /*

   * blk_rq_pos()			: the current sector
   * blk_rq_bytes()		: bytes left in the entire request
   * blk_rq_cur_bytes()		: bytes left in the current segment
   * blk_rq_err_bytes()		: bytes left till the next error boundary
   * blk_rq_sectors()		: sectors left in the entire request
   * blk_rq_cur_sectors()		: sectors left in the current segment

   */

  static inline sector_t blk_rq_pos(const struct request *rq)
  {

  	return rq->__sector;

  }
  
  static inline unsigned int blk_rq_bytes(const struct request *rq)
  {

  	return rq->__data_len;

  }

  static inline int blk_rq_cur_bytes(const struct request *rq)
  {
  	return rq->bio ? bio_cur_bytes(rq->bio) : 0;
  }

  extern unsigned int blk_rq_err_bytes(const struct request *rq);

  static inline unsigned int blk_rq_sectors(const struct request *rq)
  {

  	return blk_rq_bytes(rq) >> 9;

  }
  
  static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
  {

  	return blk_rq_cur_bytes(rq) >> 9;

  }

  static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,

  						     int op)

  {

  	if (unlikely(op == REQ_OP_DISCARD || op == REQ_OP_SECURE_ERASE))

  		return min(q->limits.max_discard_sectors, UINT_MAX >> 9);

  	if (unlikely(op == REQ_OP_WRITE_SAME))

  		return q->limits.max_write_same_sectors;

  	if (unlikely(op == REQ_OP_WRITE_ZEROES))
  		return q->limits.max_write_zeroes_sectors;

  	return q->limits.max_sectors;
  }

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

  		return q->limits.max_sectors;

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

  static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
  						  sector_t offset)

  {
  	struct request_queue *q = rq->q;

  	if (unlikely(rq->cmd_type != REQ_TYPE_FS))

  		return q->limits.max_hw_sectors;

  	if (!q->limits.chunk_sectors ||
  	    req_op(rq) == REQ_OP_DISCARD ||
  	    req_op(rq) == REQ_OP_SECURE_ERASE)

  		return blk_queue_get_max_sectors(q, req_op(rq));

  	return min(blk_max_size_offset(q, offset),

  			blk_queue_get_max_sectors(q, req_op(rq)));

  }

  static inline unsigned int blk_rq_count_bios(struct request *rq)
  {
  	unsigned int nr_bios = 0;
  	struct bio *bio;
  
  	__rq_for_each_bio(bio, rq)
  		nr_bios++;
  
  	return nr_bios;
  }

  /*

   * blk_rq_set_prio - associate a request with prio from ioc
   * @rq: request of interest
   * @ioc: target iocontext
   *
   * Assocate request prio with ioc prio so request based drivers
   * can leverage priority information.
   */
  static inline void blk_rq_set_prio(struct request *rq, struct io_context *ioc)
  {
  	if (ioc)
  		rq->ioprio = ioc->ioprio;
  }
  
  /*

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

   * Request completion related functions.
   *
   * blk_update_request() completes given number of bytes and updates
   * the request without completing it.
   *

   * blk_end_request() and friends.  __blk_end_request() must be called
   * with the request queue spinlock acquired.

   *
   * Several drivers define their own end_request and call

   * blk_end_request() for parts of the original function.
   * This prevents code duplication in drivers.

   */

  extern bool blk_update_request(struct request *rq, int error,
  			       unsigned int nr_bytes);

  extern void blk_finish_request(struct request *rq, int error);

  extern bool blk_end_request(struct request *rq, int error,
  			    unsigned int nr_bytes);
  extern void blk_end_request_all(struct request *rq, int error);
  extern bool blk_end_request_cur(struct request *rq, int error);

  extern bool blk_end_request_err(struct request *rq, int error);

  extern bool __blk_end_request(struct request *rq, int error,
  			      unsigned int nr_bytes);
  extern void __blk_end_request_all(struct request *rq, int error);
  extern bool __blk_end_request_cur(struct request *rq, int error);

  extern bool __blk_end_request_err(struct request *rq, int error);

  extern void blk_complete_request(struct request *);

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

  extern void blk_unprep_request(struct request *);

  /*

   * Access functions for manipulating queue properties
   */

  extern struct request_queue *blk_init_queue_node(request_fn_proc *rfn,

  					spinlock_t *lock, int node_id);

  extern struct request_queue *blk_init_queue(request_fn_proc *, spinlock_t *);

  extern struct request_queue *blk_init_allocated_queue(struct request_queue *,
  						      request_fn_proc *, spinlock_t *);

  extern void blk_cleanup_queue(struct request_queue *);
  extern void blk_queue_make_request(struct request_queue *, make_request_fn *);
  extern void blk_queue_bounce_limit(struct request_queue *, u64);

  extern void blk_queue_max_hw_sectors(struct request_queue *, unsigned int);

  extern void blk_queue_chunk_sectors(struct request_queue *, unsigned int);

  extern void blk_queue_max_segments(struct request_queue *, unsigned short);

  extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);

  extern void blk_queue_max_discard_sectors(struct request_queue *q,
  		unsigned int max_discard_sectors);

  extern void blk_queue_max_write_same_sectors(struct request_queue *q,
  		unsigned int max_write_same_sectors);

  extern void blk_queue_max_write_zeroes_sectors(struct request_queue *q,
  		unsigned int max_write_same_sectors);

  extern void blk_queue_logical_block_size(struct request_queue *, unsigned short);

  extern void blk_queue_physical_block_size(struct request_queue *, unsigned int);

  extern void blk_queue_alignment_offset(struct request_queue *q,
  				       unsigned int alignment);

  extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);

  extern void blk_queue_io_min(struct request_queue *q, unsigned int min);

  extern void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt);

  extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);

  extern void blk_set_queue_depth(struct request_queue *q, unsigned int depth);

  extern void blk_set_default_limits(struct queue_limits *lim);

  extern void blk_set_stacking_limits(struct queue_limits *lim);

  extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
  			    sector_t offset);

  extern int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
  			    sector_t offset);

  extern void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
  			      sector_t offset);

  extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);

  extern void blk_queue_dma_pad(struct request_queue *, unsigned int);

  extern void blk_queue_update_dma_pad(struct request_queue *, unsigned int);

  extern int blk_queue_dma_drain(struct request_queue *q,
  			       dma_drain_needed_fn *dma_drain_needed,
  			       void *buf, unsigned int size);

  extern void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn);

  extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);

  extern void blk_queue_virt_boundary(struct request_queue *, unsigned long);

  extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);

  extern void blk_queue_unprep_rq(struct request_queue *, unprep_rq_fn *ufn);

  extern void blk_queue_dma_alignment(struct request_queue *, int);

  extern void blk_queue_update_dma_alignment(struct request_queue *, int);

  extern void blk_queue_softirq_done(struct request_queue *, softirq_done_fn *);

  extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
  extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);

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

  extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fua);

  extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);

  static inline unsigned short blk_rq_nr_phys_segments(struct request *rq)
  {
  	if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
  		return 1;
  	return rq->nr_phys_segments;
  }

  extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);

  extern void blk_dump_rq_flags(struct request *, char *);

  extern long nr_blockdev_pages(void);

  bool __must_check blk_get_queue(struct request_queue *);

  struct request_queue *blk_alloc_queue(gfp_t);
  struct request_queue *blk_alloc_queue_node(gfp_t, int);
  extern void blk_put_queue(struct request_queue *);

  extern void blk_set_queue_dying(struct request_queue *);

  /*

   * block layer runtime pm functions
   */

  #ifdef CONFIG_PM

  extern void blk_pm_runtime_init(struct request_queue *q, struct device *dev);
  extern int blk_pre_runtime_suspend(struct request_queue *q);
  extern void blk_post_runtime_suspend(struct request_queue *q, int err);
  extern void blk_pre_runtime_resume(struct request_queue *q);
  extern void blk_post_runtime_resume(struct request_queue *q, int err);

  extern void blk_set_runtime_active(struct request_queue *q);

  #else
  static inline void blk_pm_runtime_init(struct request_queue *q,
  	struct device *dev) {}
  static inline int blk_pre_runtime_suspend(struct request_queue *q)
  {
  	return -ENOSYS;
  }
  static inline void blk_post_runtime_suspend(struct request_queue *q, int err) {}
  static inline void blk_pre_runtime_resume(struct request_queue *q) {}
  static inline void blk_post_runtime_resume(struct request_queue *q, int err) {}

  static inline void blk_set_runtime_active(struct request_queue *q) {}

  #endif
  
  /*

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

   */

  struct blk_plug {

  	struct list_head list; /* requests */

  	struct list_head mq_list; /* blk-mq requests */

  	struct list_head cb_list; /* md requires an unplug callback */

  };

  #define BLK_MAX_REQUEST_COUNT 16

  #define BLK_PLUG_FLUSH_SIZE (128 * 1024)

  struct blk_plug_cb;

  typedef void (*blk_plug_cb_fn)(struct blk_plug_cb *, bool);

  struct blk_plug_cb {
  	struct list_head list;

  	blk_plug_cb_fn callback;
  	void *data;

  };

  extern struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug,
  					     void *data, int size);

  extern void blk_start_plug(struct blk_plug *);
  extern void blk_finish_plug(struct blk_plug *);

  extern void blk_flush_plug_list(struct blk_plug *, bool);

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

  	if (plug)

  		blk_flush_plug_list(plug, false);
  }
  
  static inline void blk_schedule_flush_plug(struct task_struct *tsk)
  {
  	struct blk_plug *plug = tsk->plug;
  
  	if (plug)

  		blk_flush_plug_list(plug, true);

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

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

  }

  /*
   * tag stuff
   */

  extern int blk_queue_start_tag(struct request_queue *, struct request *);
  extern struct request *blk_queue_find_tag(struct request_queue *, int);
  extern void blk_queue_end_tag(struct request_queue *, struct request *);

  extern int blk_queue_init_tags(struct request_queue *, int, struct blk_queue_tag *, int);

  extern void blk_queue_free_tags(struct request_queue *);
  extern int blk_queue_resize_tags(struct request_queue *, int);
  extern void blk_queue_invalidate_tags(struct request_queue *);

  extern struct blk_queue_tag *blk_init_tags(int, int);

  extern void blk_free_tags(struct blk_queue_tag *);

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

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

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

  extern int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, unsigned long flags);

  extern int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,

  		sector_t nr_sects, gfp_t gfp_mask, int flags,

  		struct bio **biop);

  extern int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, struct page *page);

  extern int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
  		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop,
  		bool discard);

  extern int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,

  		sector_t nr_sects, gfp_t gfp_mask, bool discard);

  static inline int sb_issue_discard(struct super_block *sb, sector_t block,
  		sector_t nr_blocks, gfp_t gfp_mask, unsigned long flags)

  {

  	return blkdev_issue_discard(sb->s_bdev, block << (sb->s_blocksize_bits - 9),
  				    nr_blocks << (sb->s_blocksize_bits - 9),
  				    gfp_mask, flags);

  }

  static inline int sb_issue_zeroout(struct super_block *sb, sector_t block,

  		sector_t nr_blocks, gfp_t gfp_mask)

  {
  	return blkdev_issue_zeroout(sb->s_bdev,
  				    block << (sb->s_blocksize_bits - 9),
  				    nr_blocks << (sb->s_blocksize_bits - 9),

  				    gfp_mask, true);

  }

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

  enum blk_default_limits {
  	BLK_MAX_SEGMENTS	= 128,
  	BLK_SAFE_MAX_SECTORS	= 255,

  	BLK_DEF_MAX_SECTORS	= 2560,

  	BLK_MAX_SEGMENT_SIZE	= 65536,
  	BLK_SEG_BOUNDARY_MASK	= 0xFFFFFFFFUL,
  };

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

  static inline unsigned long queue_bounce_pfn(struct request_queue *q)
  {

  	return q->limits.bounce_pfn;

  }
  
  static inline unsigned long queue_segment_boundary(struct request_queue *q)
  {

  	return q->limits.seg_boundary_mask;

  }

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

  static inline unsigned int queue_max_sectors(struct request_queue *q)
  {

  	return q->limits.max_sectors;

  }
  
  static inline unsigned int queue_max_hw_sectors(struct request_queue *q)
  {

  	return q->limits.max_hw_sectors;

  }

  static inline unsigned short queue_max_segments(struct request_queue *q)

  {

  	return q->limits.max_segments;

  }
  
  static inline unsigned int queue_max_segment_size(struct request_queue *q)
  {

  	return q->limits.max_segment_size;

  }

  static inline unsigned short queue_logical_block_size(struct request_queue *q)

  {
  	int retval = 512;

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

  
  	return retval;
  }