/*
   * Copyright (C) 2009-2011 Red Hat, Inc.
   *
   * Author: Mikulas Patocka <mpatocka@redhat.com>
   *
   * This file is released under the GPL.
   */
  
  #ifndef DM_BUFIO_H
  #define DM_BUFIO_H
  
  #include <linux/blkdev.h>
  #include <linux/types.h>
  
  /*----------------------------------------------------------------*/
  
  struct dm_bufio_client;
  struct dm_buffer;
  
  /*
   * Create a buffered IO cache on a given device
   */
  struct dm_bufio_client *
  dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
  		       unsigned reserved_buffers, unsigned aux_size,
  		       void (*alloc_callback)(struct dm_buffer *),
  		       void (*write_callback)(struct dm_buffer *));
  
  /*
   * Release a buffered IO cache.
   */
  void dm_bufio_client_destroy(struct dm_bufio_client *c);
  
  /*
   * WARNING: to avoid deadlocks, these conditions are observed:
   *
   * - At most one thread can hold at most "reserved_buffers" simultaneously.
   * - Each other threads can hold at most one buffer.
   * - Threads which call only dm_bufio_get can hold unlimited number of
   *   buffers.
   */
  
  /*
   * Read a given block from disk. Returns pointer to data.  Returns a
   * pointer to dm_buffer that can be used to release the buffer or to make
   * it dirty.
   */
  void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
  		    struct dm_buffer **bp);
  
  /*
   * Like dm_bufio_read, but return buffer from cache, don't read
   * it. If the buffer is not in the cache, return NULL.
   */
  void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
  		   struct dm_buffer **bp);
  
  /*
   * Like dm_bufio_read, but don't read anything from the disk.  It is
   * expected that the caller initializes the buffer and marks it dirty.
   */
  void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
  		   struct dm_buffer **bp);
  
  /*
   * Prefetch the specified blocks to the cache.
   * The function starts to read the blocks and returns without waiting for
   * I/O to finish.
   */
  void dm_bufio_prefetch(struct dm_bufio_client *c,
  		       sector_t block, unsigned n_blocks);
  
  /*
   * Release a reference obtained with dm_bufio_{read,get,new}. The data
   * pointer and dm_buffer pointer is no longer valid after this call.
   */
  void dm_bufio_release(struct dm_buffer *b);
  
  /*
   * Mark a buffer dirty. It should be called after the buffer is modified.
   *
   * In case of memory pressure, the buffer may be written after
   * dm_bufio_mark_buffer_dirty, but before dm_bufio_write_dirty_buffers.  So
   * dm_bufio_write_dirty_buffers guarantees that the buffer is on-disk but
   * the actual writing may occur earlier.
   */
  void dm_bufio_mark_buffer_dirty(struct dm_buffer *b);
  
  /*
   * Initiate writing of dirty buffers, without waiting for completion.
   */
  void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c);
  
  /*
   * Write all dirty buffers. Guarantees that all dirty buffers created prior
   * to this call are on disk when this call exits.
   */
  int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c);
  
  /*
   * Send an empty write barrier to the device to flush hardware disk cache.
   */
  int dm_bufio_issue_flush(struct dm_bufio_client *c);
  
  /*
   * Like dm_bufio_release but also move the buffer to the new
   * block. dm_bufio_write_dirty_buffers is needed to commit the new block.
   */
  void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block);
  
  /*
   * Free the given buffer.
   * This is just a hint, if the buffer is in use or dirty, this function
   * does nothing.
   */
  void dm_bufio_forget(struct dm_bufio_client *c, sector_t block);
  
  /*
   * Set the minimum number of buffers before cleanup happens.
   */
  void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n);
  
  unsigned dm_bufio_get_block_size(struct dm_bufio_client *c);
  sector_t dm_bufio_get_device_size(struct dm_bufio_client *c);
  sector_t dm_bufio_get_block_number(struct dm_buffer *b);
  void *dm_bufio_get_block_data(struct dm_buffer *b);
  void *dm_bufio_get_aux_data(struct dm_buffer *b);
  struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b);
  
  /*----------------------------------------------------------------*/
  
  #endif