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/blk_types.h>
  #include <linux/mm.h>
  #include <linux/types.h>
  #include <linux/mm_types.h>
  #include <linux/blkdev.h>
  
  struct address_space;
  struct fiemap_extent_info;
  struct inode;
  struct iomap_dio;
  struct iomap_writepage_ctx;
  struct iov_iter;
  struct kiocb;
  struct page;
  struct vm_area_struct;
  struct vm_fault;
  
  /*
   * Types of block ranges for iomap mappings:
   */
  #define IOMAP_HOLE	0	/* no blocks allocated, need allocation */
  #define IOMAP_DELALLOC	1	/* delayed allocation blocks */
  #define IOMAP_MAPPED	2	/* blocks allocated at @addr */
  #define IOMAP_UNWRITTEN	3	/* blocks allocated at @addr in unwritten state */
  #define IOMAP_INLINE	4	/* data inline in the inode */
  
  /*
   * Flags reported by the file system from iomap_begin:
   *
   * IOMAP_F_NEW indicates that the blocks have been newly allocated and need
   * zeroing for areas that no data is copied to.
   *
   * IOMAP_F_DIRTY indicates the inode has uncommitted metadata needed to access
   * written data and requires fdatasync to commit them to persistent storage.
   * This needs to take into account metadata changes that *may* be made at IO
   * completion, such as file size updates from direct IO.
   *
   * IOMAP_F_SHARED indicates that the blocks are shared, and will need to be
   * unshared as part a write.
   *
   * IOMAP_F_MERGED indicates that the iomap contains the merge of multiple block
   * mappings.
   *
   * IOMAP_F_BUFFER_HEAD indicates that the file system requires the use of
   * buffer heads for this mapping.
   */
  #define IOMAP_F_NEW		0x01
  #define IOMAP_F_DIRTY		0x02
  #define IOMAP_F_SHARED		0x04
  #define IOMAP_F_MERGED		0x08
  #define IOMAP_F_BUFFER_HEAD	0x10
  #define IOMAP_F_ZONE_APPEND	0x20
  
  /*
   * Flags set by the core iomap code during operations:
   *
   * IOMAP_F_SIZE_CHANGED indicates to the iomap_end method that the file size
   * has changed as the result of this write operation.
   */
  #define IOMAP_F_SIZE_CHANGED	0x100
  
  /*
   * 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_page_ops;
  
  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 */
  	const struct iomap_page_ops *page_ops;
  };
  
  static inline sector_t iomap_sector(const struct iomap *iomap, loff_t pos)
  {
  	return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT;
  }
  
  /*
   * Returns the inline data pointer for logical offset @pos.
   */
  static inline void *iomap_inline_data(const struct iomap *iomap, loff_t pos)
  {
  	return iomap->inline_data + pos - iomap->offset;
  }
  
  /*
   * Check if the mapping's length is within the valid range for inline data.
   * This is used to guard against accessing data beyond the page inline_data
   * points at.
   */
  static inline bool iomap_inline_data_valid(const struct iomap *iomap)
  {
  	return iomap->length <= PAGE_SIZE - offset_in_page(iomap->inline_data);
  }
  
  /*
   * When a filesystem sets page_ops in an iomap mapping it returns, page_prepare
   * and page_done will be called for each page written to.  This only applies to
   * buffered writes as unbuffered writes will not typically have pages
   * associated with them.
   *
   * When page_prepare succeeds, page_done will always be called to do any
   * cleanup work necessary.  In that page_done call, @page will be NULL if the
   * associated page could not be obtained.
   */
  struct iomap_page_ops {
  	int (*page_prepare)(struct inode *inode, loff_t pos, unsigned len);
  	void (*page_done)(struct inode *inode, loff_t pos, unsigned copied,
  			struct page *page);
  };
  
  /*
   * 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 */
  #define IOMAP_OVERWRITE_ONLY	(1 << 6) /* only pure overwrites allowed */
  #define IOMAP_UNSHARE		(1 << 7) /* unshare_file_range */
  #ifdef CONFIG_FS_DAX
  #define IOMAP_DAX		(1 << 8) /* DAX mapping */
  #else
  #define IOMAP_DAX		0
  #endif /* CONFIG_FS_DAX */
  
  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,
  			struct iomap *srcmap);
  
  	/*
  	 * 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);
  };
  
  /**
   * struct iomap_iter - Iterate through a range of a file
   * @inode: Set at the start of the iteration and should not change.
   * @pos: The current file position we are operating on.  It is updated by
   *	calls to iomap_iter().  Treat as read-only in the body.
   * @len: The remaining length of the file segment we're operating on.
   *	It is updated at the same time as @pos.
   * @processed: The number of bytes processed by the body in the most recent
   *	iteration, or a negative errno. 0 causes the iteration to stop.
   * @flags: Zero or more of the iomap_begin flags above.
   * @iomap: Map describing the I/O iteration
   * @srcmap: Source map for COW operations
   */
  struct iomap_iter {
  	struct inode *inode;
  	loff_t pos;
  	u64 len;
  	s64 processed;
  	unsigned flags;
  	struct iomap iomap;
  	struct iomap srcmap;
  };
  
  int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops);
  
  /**
   * iomap_length - length of the current iomap iteration
   * @iter: iteration structure
   *
   * Returns the length that the operation applies to for the current iteration.
   */
  static inline u64 iomap_length(const struct iomap_iter *iter)
  {
  	u64 end = iter->iomap.offset + iter->iomap.length;
  
  	if (iter->srcmap.type != IOMAP_HOLE)
  		end = min(end, iter->srcmap.offset + iter->srcmap.length);
  	return min(iter->len, end - iter->pos);
  }
  
  /**
   * iomap_iter_srcmap - return the source map for the current iomap iteration
   * @i: iteration structure
   *
   * Write operations on file systems with reflink support might require a
   * source and a destination map.  This function retourns the source map
   * for a given operation, which may or may no be identical to the destination
   * map in &i->iomap.
   */
  static inline const struct iomap *iomap_iter_srcmap(const struct iomap_iter *i)
  {
  	if (i->srcmap.type != IOMAP_HOLE)
  		return &i->srcmap;
  	return &i->iomap;
  }
  
  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);
  void iomap_readahead(struct readahead_control *, const struct iomap_ops *ops);
  bool iomap_is_partially_uptodate(struct folio *, size_t from, size_t count);
  int iomap_releasepage(struct page *page, gfp_t gfp_mask);
  void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t 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_unshare(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);
  vm_fault_t iomap_page_mkwrite(struct vm_fault *vmf,
  			const struct iomap_ops *ops);
  int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  		u64 start, u64 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);
  
  /*
   * Structure for writeback I/O completions.
   */
  struct iomap_ioend {
  	struct list_head	io_list;	/* next ioend in chain */
  	u16			io_type;
  	u16			io_flags;	/* IOMAP_F_* */
  	u32			io_folios;	/* folios added to ioend */
  	struct inode		*io_inode;	/* file being written to */
  	size_t			io_size;	/* size of the extent */
  	loff_t			io_offset;	/* offset in the file */
  	sector_t		io_sector;	/* start sector of ioend */
  	struct bio		*io_bio;	/* bio being built */
  	struct bio		io_inline_bio;	/* MUST BE LAST! */
  };
  
  struct iomap_writeback_ops {
  	/*
  	 * Required, maps the blocks so that writeback can be performed on
  	 * the range starting at offset.
  	 */
  	int (*map_blocks)(struct iomap_writepage_ctx *wpc, struct inode *inode,
  				loff_t offset);
  
  	/*
  	 * Optional, allows the file systems to perform actions just before
  	 * submitting the bio and/or override the bio end_io handler for complex
  	 * operations like copy on write extent manipulation or unwritten extent
  	 * conversions.
  	 */
  	int (*prepare_ioend)(struct iomap_ioend *ioend, int status);
  
  	/*
  	 * Optional, allows the file system to discard state on a page where
  	 * we failed to submit any I/O.
  	 */
  	void (*discard_folio)(struct folio *folio, loff_t pos);
  };
  
  struct iomap_writepage_ctx {
  	struct iomap		iomap;
  	struct iomap_ioend	*ioend;
  	const struct iomap_writeback_ops *ops;
  };
  
  void iomap_finish_ioends(struct iomap_ioend *ioend, int error);
  void iomap_ioend_try_merge(struct iomap_ioend *ioend,
  		struct list_head *more_ioends);
  void iomap_sort_ioends(struct list_head *ioend_list);
  int iomap_writepage(struct page *page, struct writeback_control *wbc,
  		struct iomap_writepage_ctx *wpc,
  		const struct iomap_writeback_ops *ops);
  int iomap_writepages(struct address_space *mapping,
  		struct writeback_control *wbc, struct iomap_writepage_ctx *wpc,
  		const struct iomap_writeback_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) */
  
  struct iomap_dio_ops {
  	int (*end_io)(struct kiocb *iocb, ssize_t size, int error,
  		      unsigned flags);
  	void (*submit_io)(const struct iomap_iter *iter, struct bio *bio,
  		          loff_t file_offset);
  };
  
  /*
   * Wait for the I/O to complete in iomap_dio_rw even if the kiocb is not
   * synchronous.
   */
  #define IOMAP_DIO_FORCE_WAIT	(1 << 0)
  
  /*
   * Do not allocate blocks or zero partial blocks, but instead fall back to
   * the caller by returning -EAGAIN.  Used to optimize direct I/O writes that
   * are not aligned to the file system block size.
    */
  #define IOMAP_DIO_OVERWRITE_ONLY	(1 << 1)
  
  /*
   * When a page fault occurs, return a partial synchronous result and allow
   * the caller to retry the rest of the operation after dealing with the page
   * fault.
   */
  #define IOMAP_DIO_PARTIAL		(1 << 2)
  
  ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
  		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
  		unsigned int dio_flags, size_t done_before);
  struct iomap_dio *__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
  		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
  		unsigned int dio_flags, size_t done_before);
  ssize_t iomap_dio_complete(struct iomap_dio *dio);
  
  #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 */
  