text: /* SPDX-License-Identifier: GPL-2.0 */
  #ifndef LINUX_IOMAP_H
  #define LINUX_IOMAP_H 1
  
  #include <linux/atomic.h>
  #include <linux/bitmap.h>
  #include <linux/mm.h>
  #include <linux/types.h>
  
  struct address_space;
  struct fiemap_extent_info;
  struct inode;
  struct iov_iter;
  struct kiocb;
  struct page;
  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 at @addr */
  #define IOMAP_UNWRITTEN	0x04	/* blocks allocated at @addr in unwritten state */
  #define IOMAP_INLINE	0x05	/* data inline in the inode */
  
  /*
   * Flags for all iomap mappings:
   *
   * IOMAP_F_DIRTY indicates the inode has uncommitted metadata needed to access
   * written data and requires fdatasync to commit them to persistent storage.
   */
  #define IOMAP_F_NEW		0x01	/* blocks have been newly allocated */
  #define IOMAP_F_DIRTY		0x02	/* uncommitted metadata */
  #define IOMAP_F_BUFFER_HEAD	0x04	/* file system requires buffer heads */
  
  /*
   * 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 */
  
  /*
   * Flags from 0x1000 up are for file system specific usage:
   */
  #define IOMAP_F_PRIVATE		0x1000
  
  
  /*
   * Magic value for addr:
   */
  #define IOMAP_NULL_ADDR -1ULL	/* addr is not valid */
  
  struct iomap {
  	u64			addr; /* disk offset of mapping, bytes */
  	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 */
  	struct dax_device	*dax_dev; /* dax_dev for dax operations */
  	void			*inline_data;
  	void			*private; /* filesystem private */
  
  	/*
  	 * Called when finished processing a page in the mapping returned in
  	 * this iomap.  At least for now this is only supported in the buffered
  	 * write path.
  	 */
  	void (*page_done)(struct inode *inode, loff_t pos, unsigned copied,
  			struct page *page, struct iomap *iomap);
  };
  
  /*
   * 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 */
  #define IOMAP_FAULT		(1 << 3) /* mapping for page fault */
  #define IOMAP_DIRECT		(1 << 4) /* direct I/O */
  #define IOMAP_NOWAIT		(1 << 5) /* do not block */
  
  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);
  };
  
  /*
   * Structure allocate for each page when block size < PAGE_SIZE to track
   * sub-page uptodate status and I/O completions.
   */
  struct iomap_page {
  	atomic_t		read_count;
  	atomic_t		write_count;
  	DECLARE_BITMAP(uptodate, PAGE_SIZE / 512);
  };
  
  static inline struct iomap_page *to_iomap_page(struct page *page)
  {
  	if (page_has_private(page))
  		return (struct iomap_page *)page_private(page);
  	return NULL;
  }
  
  ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
  		const struct iomap_ops *ops);
  int iomap_readpage(struct page *page, const struct iomap_ops *ops);
  int iomap_readpages(struct address_space *mapping, struct list_head *pages,
  		unsigned nr_pages, const struct iomap_ops *ops);
  int iomap_set_page_dirty(struct page *page);
  int iomap_is_partially_uptodate(struct page *page, unsigned long from,
  		unsigned long count);
  int iomap_releasepage(struct page *page, gfp_t gfp_mask);
  void iomap_invalidatepage(struct page *page, unsigned int offset,
  		unsigned int len);
  #ifdef CONFIG_MIGRATION
  int iomap_migrate_page(struct address_space *mapping, struct page *newpage,
  		struct page *page, enum migrate_mode mode);
  #else
  #define iomap_migrate_page NULL
  #endif
  int iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
  		const struct iomap_ops *ops);
  int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
  		bool *did_zero, const struct iomap_ops *ops);
  int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
  		const struct iomap_ops *ops);
  int iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops);
  int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  		loff_t start, loff_t len, const struct iomap_ops *ops);
  loff_t iomap_seek_hole(struct inode *inode, loff_t offset,
  		const struct iomap_ops *ops);
  loff_t iomap_seek_data(struct inode *inode, loff_t offset,
  		const struct iomap_ops *ops);
  sector_t iomap_bmap(struct address_space *mapping, sector_t bno,
  		const struct iomap_ops *ops);
  
  /*
   * Flags for direct I/O ->end_io:
   */
  #define IOMAP_DIO_UNWRITTEN	(1 << 0)	/* covers unwritten extent(s) */
  #define IOMAP_DIO_COW		(1 << 1)	/* covers COW extent(s) */
  typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t ret,
  		unsigned flags);
  ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
  		const struct iomap_ops *ops, iomap_dio_end_io_t end_io);
  
  #ifdef CONFIG_SWAP
  struct file;
  struct swap_info_struct;
  
  int iomap_swapfile_activate(struct swap_info_struct *sis,
  		struct file *swap_file, sector_t *pagespan,
  		const struct iomap_ops *ops);
  #else
  # define iomap_swapfile_activate(sis, swapfile, pagespan, ops)	(-EIO)
  #endif /* CONFIG_SWAP */
  
  #endif /* LINUX_IOMAP_H */
  