#ifndef LINUX_IOMAP_H
  #define LINUX_IOMAP_H 1
  
  #include <linux/types.h>

  struct fiemap_extent_info;

  struct inode;
  struct iov_iter;
  struct kiocb;
  struct vm_area_struct;
  struct vm_fault;
  
  /*
   * Types of block ranges for iomap mappings:
   */

  #define IOMAP_HOLE	0x01	/* no blocks allocated, need allocation */
  #define IOMAP_DELALLOC	0x02	/* delayed allocation blocks */
  #define IOMAP_MAPPED	0x03	/* blocks allocated @blkno */
  #define IOMAP_UNWRITTEN	0x04	/* blocks allocated @blkno in unwritten state */

  /*

   * Flags for all iomap mappings:

   */

  #define IOMAP_F_NEW	0x01	/* blocks have been newly allocated */
  
  /*
   * Flags that only need to be reported for IOMAP_REPORT requests:
   */
  #define IOMAP_F_MERGED	0x10	/* contains multiple blocks/extents */
  #define IOMAP_F_SHARED	0x20	/* block shared with another file */

  
  /*

   * Magic value for blkno:
   */

  #define IOMAP_NULL_BLOCK -1LL	/* blkno is not valid */
  
  struct iomap {

  	sector_t		blkno;	/* 1st sector of mapping, 512b units */
  	loff_t			offset;	/* file offset of mapping, bytes */
  	u64			length;	/* length of mapping, bytes */

  	u16			type;	/* type of mapping */
  	u16			flags;	/* flags for mapping */

  	struct block_device	*bdev;	/* block device for I/O */
  };
  
  /*
   * Flags for iomap_begin / iomap_end.  No flag implies a read.
   */

  #define IOMAP_WRITE		(1 << 0) /* writing, must allocate blocks */
  #define IOMAP_ZERO		(1 << 1) /* zeroing operation, may skip holes */
  #define IOMAP_REPORT		(1 << 2) /* report extent status, e.g. FIEMAP */

  
  struct iomap_ops {
  	/*
  	 * Return the existing mapping at pos, or reserve space starting at
  	 * pos for up to length, as long as we can do it as a single mapping.
  	 * The actual length is returned in iomap->length.
  	 */
  	int (*iomap_begin)(struct inode *inode, loff_t pos, loff_t length,
  			unsigned flags, struct iomap *iomap);
  
  	/*
  	 * Commit and/or unreserve space previous allocated using iomap_begin.
  	 * Written indicates the length of the successful write operation which
  	 * needs to be commited, while the rest needs to be unreserved.
  	 * Written might be zero if no data was written.
  	 */
  	int (*iomap_end)(struct inode *inode, loff_t pos, loff_t length,
  			ssize_t written, unsigned flags, struct iomap *iomap);

  };

  ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
  		struct iomap_ops *ops);

  int iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
  		struct iomap_ops *ops);

  int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
  		bool *did_zero, struct iomap_ops *ops);
  int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
  		struct iomap_ops *ops);
  int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
  		struct iomap_ops *ops);

  int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  		loff_t start, loff_t len, struct iomap_ops *ops);

  #endif /* LINUX_IOMAP_H */