text: /*
   * Block data types and constants.  Directly include this file only to
   * break include dependency loop.
   */
  #ifndef __LINUX_BLK_TYPES_H
  #define __LINUX_BLK_TYPES_H
  
  #include <linux/types.h>
  
  struct bio_set;
  struct bio;
  struct bio_integrity_payload;
  struct page;
  struct block_device;
  struct io_context;
  struct cgroup_subsys_state;
  typedef void (bio_end_io_t) (struct bio *, int);
  typedef void (bio_destructor_t) (struct bio *);
  
  /*
   * was unsigned short, but we might as well be ready for > 64kB I/O pages
   */
  struct bio_vec {
  	struct page	*bv_page;
  	unsigned int	bv_len;
  	unsigned int	bv_offset;
  };
  
  #ifdef CONFIG_BLOCK
  
  struct bvec_iter {
  	sector_t		bi_sector;	/* device address in 512 byte
  						   sectors */
  	unsigned int		bi_size;	/* residual I/O count */
  
  	unsigned int		bi_idx;		/* current index into bvl_vec */
  
  	unsigned int            bi_bvec_done;	/* number of bytes completed in
  						   current bvec */
  };
  
  /*
   * main unit of I/O for the block layer and lower layers (ie drivers and
   * stacking drivers)
   */
  struct bio {
  	struct bio		*bi_next;	/* request queue link */
  	struct block_device	*bi_bdev;
  	unsigned long		bi_flags;	/* status, command, etc */
  	unsigned long		bi_rw;		/* bottom bits READ/WRITE,
  						 * top bits priority
  						 */
  
  	struct bvec_iter	bi_iter;
  
  	/* Number of segments in this BIO after
  	 * physical address coalescing is performed.
  	 */
  	unsigned int		bi_phys_segments;
  
  	/*
  	 * To keep track of the max segment size, we account for the
  	 * sizes of the first and last mergeable segments in this bio.
  	 */
  	unsigned int		bi_seg_front_size;
  	unsigned int		bi_seg_back_size;
  
  	atomic_t		bi_remaining;
  
  	bio_end_io_t		*bi_end_io;
  
  	void			*bi_private;
  #ifdef CONFIG_BLK_CGROUP
  	/*
  	 * Optional ioc and css associated with this bio.  Put on bio
  	 * release.  Read comment on top of bio_associate_current().
  	 */
  	struct io_context	*bi_ioc;
  	struct cgroup_subsys_state *bi_css;
  #endif
  #if defined(CONFIG_BLK_DEV_INTEGRITY)
  	struct bio_integrity_payload *bi_integrity;  /* data integrity */
  #endif
  
  	unsigned short		bi_vcnt;	/* how many bio_vec's */
  
  	/*
  	 * Everything starting with bi_max_vecs will be preserved by bio_reset()
  	 */
  
  	unsigned short		bi_max_vecs;	/* max bvl_vecs we can hold */
  
  	atomic_t		bi_cnt;		/* pin count */
  
  	struct bio_vec		*bi_io_vec;	/* the actual vec list */
  
  	struct bio_set		*bi_pool;
  
  	/*
  	 * We can inline a number of vecs at the end of the bio, to avoid
  	 * double allocations for a small number of bio_vecs. This member
  	 * MUST obviously be kept at the very end of the bio.
  	 */
  	struct bio_vec		bi_inline_vecs[0];
  };
  
  #define BIO_RESET_BYTES		offsetof(struct bio, bi_max_vecs)
  
  /*
   * bio flags
   */
  #define BIO_UPTODATE	0	/* ok after I/O completion */
  #define BIO_RW_BLOCK	1	/* RW_AHEAD set, and read/write would block */
  #define BIO_EOF		2	/* out-out-bounds error */
  #define BIO_SEG_VALID	3	/* bi_phys_segments valid */
  #define BIO_CLONED	4	/* doesn't own data */
  #define BIO_BOUNCED	5	/* bio is a bounce bio */
  #define BIO_USER_MAPPED 6	/* contains user pages */
  #define BIO_EOPNOTSUPP	7	/* not supported */
  #define BIO_NULL_MAPPED 8	/* contains invalid user pages */
  #define BIO_FS_INTEGRITY 9	/* fs owns integrity data, not block layer */
  #define BIO_QUIET	10	/* Make BIO Quiet */
  #define BIO_MAPPED_INTEGRITY 11/* integrity metadata has been remapped */
  #define BIO_SNAP_STABLE	12	/* bio data must be snapshotted during write */
  
  /*
   * Flags starting here get preserved by bio_reset() - this includes
   * BIO_POOL_IDX()
   */
  #define BIO_RESET_BITS	13
  #define BIO_OWNS_VEC	13	/* bio_free() should free bvec */
  
  #define bio_flagged(bio, flag)	((bio)->bi_flags & (1 << (flag)))
  
  /*
   * top 4 bits of bio flags indicate the pool this bio came from
   */
  #define BIO_POOL_BITS		(4)
  #define BIO_POOL_NONE		((1UL << BIO_POOL_BITS) - 1)
  #define BIO_POOL_OFFSET		(BITS_PER_LONG - BIO_POOL_BITS)
  #define BIO_POOL_MASK		(1UL << BIO_POOL_OFFSET)
  #define BIO_POOL_IDX(bio)	((bio)->bi_flags >> BIO_POOL_OFFSET)
  
  #endif /* CONFIG_BLOCK */
  
  /*
   * Request flags.  For use in the cmd_flags field of struct request, and in
   * bi_rw of struct bio.  Note that some flags are only valid in either one.
   */
  enum rq_flag_bits {
  	/* common flags */
  	__REQ_WRITE,		/* not set, read. set, write */
  	__REQ_FAILFAST_DEV,	/* no driver retries of device errors */
  	__REQ_FAILFAST_TRANSPORT, /* no driver retries of transport errors */
  	__REQ_FAILFAST_DRIVER,	/* no driver retries of driver errors */
  
  	__REQ_SYNC,		/* request is sync (sync write or read) */
  	__REQ_META,		/* metadata io request */
  	__REQ_PRIO,		/* boost priority in cfq */
  	__REQ_DISCARD,		/* request to discard sectors */
  	__REQ_SECURE,		/* secure discard (used with __REQ_DISCARD) */
  	__REQ_WRITE_SAME,	/* write same block many times */
  
  	__REQ_NOIDLE,		/* don't anticipate more IO after this one */
  	__REQ_FUA,		/* forced unit access */
  	__REQ_FLUSH,		/* request for cache flush */
  
  	/* bio only flags */
  	__REQ_RAHEAD,		/* read ahead, can fail anytime */
  	__REQ_THROTTLED,	/* This bio has already been subjected to
  				 * throttling rules. Don't do it again. */
  
  	/* request only flags */
  	__REQ_SORTED,		/* elevator knows about this request */
  	__REQ_SOFTBARRIER,	/* may not be passed by ioscheduler */
  	__REQ_NOMERGE,		/* don't touch this for merging */
  	__REQ_STARTED,		/* drive already may have started this one */
  	__REQ_DONTPREP,		/* don't call prep for this one */
  	__REQ_QUEUED,		/* uses queueing */
  	__REQ_ELVPRIV,		/* elevator private data attached */
  	__REQ_FAILED,		/* set if the request failed */
  	__REQ_QUIET,		/* don't worry about errors */
  	__REQ_PREEMPT,		/* set for "ide_preempt" requests */
  	__REQ_ALLOCED,		/* request came from our alloc pool */
  	__REQ_COPY_USER,	/* contains copies of user pages */
  	__REQ_FLUSH_SEQ,	/* request for flush sequence */
  	__REQ_IO_STAT,		/* account I/O stat */
  	__REQ_MIXED_MERGE,	/* merge of different types, fail separately */
  	__REQ_KERNEL, 		/* direct IO to kernel pages */
  	__REQ_PM,		/* runtime pm request */
  	__REQ_END,		/* last of chain of requests */
  	__REQ_HASHED,		/* on IO scheduler merge hash */
  	__REQ_MQ_INFLIGHT,	/* track inflight for MQ */
  	__REQ_NR_BITS,		/* stops here */
  };
  
  #define REQ_WRITE		(1ULL << __REQ_WRITE)
  #define REQ_FAILFAST_DEV	(1ULL << __REQ_FAILFAST_DEV)
  #define REQ_FAILFAST_TRANSPORT	(1ULL << __REQ_FAILFAST_TRANSPORT)
  #define REQ_FAILFAST_DRIVER	(1ULL << __REQ_FAILFAST_DRIVER)
  #define REQ_SYNC		(1ULL << __REQ_SYNC)
  #define REQ_META		(1ULL << __REQ_META)
  #define REQ_PRIO		(1ULL << __REQ_PRIO)
  #define REQ_DISCARD		(1ULL << __REQ_DISCARD)
  #define REQ_WRITE_SAME		(1ULL << __REQ_WRITE_SAME)
  #define REQ_NOIDLE		(1ULL << __REQ_NOIDLE)
  
  #define REQ_FAILFAST_MASK \
  	(REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)
  #define REQ_COMMON_MASK \
  	(REQ_WRITE | REQ_FAILFAST_MASK | REQ_SYNC | REQ_META | REQ_PRIO | \
  	 REQ_DISCARD | REQ_WRITE_SAME | REQ_NOIDLE | REQ_FLUSH | REQ_FUA | \
  	 REQ_SECURE)
  #define REQ_CLONE_MASK		REQ_COMMON_MASK
  
  #define BIO_NO_ADVANCE_ITER_MASK	(REQ_DISCARD|REQ_WRITE_SAME)
  
  /* This mask is used for both bio and request merge checking */
  #define REQ_NOMERGE_FLAGS \
  	(REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA)
  
  #define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)
  #define REQ_THROTTLED		(1ULL << __REQ_THROTTLED)
  
  #define REQ_SORTED		(1ULL << __REQ_SORTED)
  #define REQ_SOFTBARRIER		(1ULL << __REQ_SOFTBARRIER)
  #define REQ_FUA			(1ULL << __REQ_FUA)
  #define REQ_NOMERGE		(1ULL << __REQ_NOMERGE)
  #define REQ_STARTED		(1ULL << __REQ_STARTED)
  #define REQ_DONTPREP		(1ULL << __REQ_DONTPREP)
  #define REQ_QUEUED		(1ULL << __REQ_QUEUED)
  #define REQ_ELVPRIV		(1ULL << __REQ_ELVPRIV)
  #define REQ_FAILED		(1ULL << __REQ_FAILED)
  #define REQ_QUIET		(1ULL << __REQ_QUIET)
  #define REQ_PREEMPT		(1ULL << __REQ_PREEMPT)
  #define REQ_ALLOCED		(1ULL << __REQ_ALLOCED)
  #define REQ_COPY_USER		(1ULL << __REQ_COPY_USER)
  #define REQ_FLUSH		(1ULL << __REQ_FLUSH)
  #define REQ_FLUSH_SEQ		(1ULL << __REQ_FLUSH_SEQ)
  #define REQ_IO_STAT		(1ULL << __REQ_IO_STAT)
  #define REQ_MIXED_MERGE		(1ULL << __REQ_MIXED_MERGE)
  #define REQ_SECURE		(1ULL << __REQ_SECURE)
  #define REQ_KERNEL		(1ULL << __REQ_KERNEL)
  #define REQ_PM			(1ULL << __REQ_PM)
  #define REQ_END			(1ULL << __REQ_END)
  #define REQ_HASHED		(1ULL << __REQ_HASHED)
  #define REQ_MQ_INFLIGHT		(1ULL << __REQ_MQ_INFLIGHT)
  
  #endif /* __LINUX_BLK_TYPES_H */
  