/*
   * Copyright (C) 2003 Sistina Software
   * Copyright (C) 2004 - 2008 Red Hat, Inc. All rights reserved.
   *
   * Device-Mapper low-level I/O.
   *
   * This file is released under the GPL.
   */
  
  #ifndef _LINUX_DM_IO_H
  #define _LINUX_DM_IO_H
  
  #ifdef __KERNEL__
  
  #include <linux/types.h>
  
  struct dm_io_region {
  	struct block_device *bdev;
  	sector_t sector;
  	sector_t count;		/* If this is zero the region is ignored. */
  };
  
  struct page_list {
  	struct page_list *next;
  	struct page *page;
  };
  
  typedef void (*io_notify_fn)(unsigned long error, void *context);
  
  enum dm_io_mem_type {
  	DM_IO_PAGE_LIST,/* Page list */
  	DM_IO_BIO,	/* Bio vector */
  	DM_IO_VMA,	/* Virtual memory area */
  	DM_IO_KMEM,	/* Kernel memory */
  };
  
  struct dm_io_memory {
  	enum dm_io_mem_type type;
  
  	unsigned offset;
  
  	union {
  		struct page_list *pl;
  		struct bio *bio;
  		void *vma;
  		void *addr;
  	} ptr;
  };
  
  struct dm_io_notify {
  	io_notify_fn fn;	/* Callback for asynchronous requests */
  	void *context;		/* Passed to callback */
  };
  
  /*
   * IO request structure
   */
  struct dm_io_client;
  struct dm_io_request {
  	int bi_rw;			/* READ|WRITE - not READA */
  	struct dm_io_memory mem;	/* Memory to use for io */
  	struct dm_io_notify notify;	/* Synchronous if notify.fn is NULL */
  	struct dm_io_client *client;	/* Client memory handler */
  };
  
  /*
   * For async io calls, users can alternatively use the dm_io() function below
   * and dm_io_client_create() to create private mempools for the client.
   *
   * Create/destroy may block.
   */
  struct dm_io_client *dm_io_client_create(void);
  void dm_io_client_destroy(struct dm_io_client *client);
  
  /*
   * IO interface using private per-client pools.
   * Each bit in the optional 'sync_error_bits' bitset indicates whether an
   * error occurred doing io to the corresponding region.
   */
  int dm_io(struct dm_io_request *io_req, unsigned num_regions,
  	  struct dm_io_region *region, unsigned long *sync_error_bits);
  
  #endif	/* __KERNEL__ */
  #endif	/* _LINUX_DM_IO_H */