LXR linux/drivers/md/dm-bufio.h

   1/*
   2 * Copyright (C) 2009-2011 Red Hat, Inc.
   3 *
   4 * Author: Mikulas Patocka <mpatocka@redhat.com>
   5 *
   6 * This file is released under the GPL.
   7 */
   8
   9#ifndef DM_BUFIO_H
  10#define DM_BUFIO_H
  11
  12#include <linux/blkdev.h>
  13#include <linux/types.h>
  14
  15/*----------------------------------------------------------------*/
  16
  17struct dm_bufio_client;
  18struct dm_buffer;
  19
  20/*
  21 * Create a buffered IO cache on a given device
  22 */
  23struct dm_bufio_client *
  24dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
  25                       unsigned reserved_buffers, unsigned aux_size,
  26                       void (*alloc_callback)(struct dm_buffer *),
  27                       void (*write_callback)(struct dm_buffer *));
  28
  29/*
  30 * Release a buffered IO cache.
  31 */
  32void dm_bufio_client_destroy(struct dm_bufio_client *c);
  33
  34/*
  35 * WARNING: to avoid deadlocks, these conditions are observed:
  36 *
  37 * - At most one thread can hold at most "reserved_buffers" simultaneously.
  38 * - Each other threads can hold at most one buffer.
  39 * - Threads which call only dm_bufio_get can hold unlimited number of
  40 *   buffers.
  41 */
  42
  43/*
  44 * Read a given block from disk. Returns pointer to data.  Returns a
  45 * pointer to dm_buffer that can be used to release the buffer or to make
  46 * it dirty.
  47 */
  48void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
  49                    struct dm_buffer **bp);
  50
  51/*
  52 * Like dm_bufio_read, but return buffer from cache, don't read
  53 * it. If the buffer is not in the cache, return NULL.
  54 */
  55void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
  56                   struct dm_buffer **bp);
  57
  58/*
  59 * Like dm_bufio_read, but don't read anything from the disk.  It is
  60 * expected that the caller initializes the buffer and marks it dirty.
  61 */
  62void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
  63                   struct dm_buffer **bp);
  64
  65/*
  66 * Prefetch the specified blocks to the cache.
  67 * The function starts to read the blocks and returns without waiting for
  68 * I/O to finish.
  69 */
  70void dm_bufio_prefetch(struct dm_bufio_client *c,
  71                       sector_t block, unsigned n_blocks);
  72
  73/*
  74 * Release a reference obtained with dm_bufio_{read,get,new}. The data
  75 * pointer and dm_buffer pointer is no longer valid after this call.
  76 */
  77void dm_bufio_release(struct dm_buffer *b);
  78
  79/*
  80 * Mark a buffer dirty. It should be called after the buffer is modified.
  81 *
  82 * In case of memory pressure, the buffer may be written after
  83 * dm_bufio_mark_buffer_dirty, but before dm_bufio_write_dirty_buffers.  So
  84 * dm_bufio_write_dirty_buffers guarantees that the buffer is on-disk but
  85 * the actual writing may occur earlier.
  86 */
  87void dm_bufio_mark_buffer_dirty(struct dm_buffer *b);
  88
  89/*
  90 * Initiate writing of dirty buffers, without waiting for completion.
  91 */
  92void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c);
  93
  94/*
  95 * Write all dirty buffers. Guarantees that all dirty buffers created prior
  96 * to this call are on disk when this call exits.
  97 */
  98int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c);
  99
 100/*
 101 * Send an empty write barrier to the device to flush hardware disk cache.
 102 */
 103int dm_bufio_issue_flush(struct dm_bufio_client *c);
 104
 105/*
 106 * Like dm_bufio_release but also move the buffer to the new
 107 * block. dm_bufio_write_dirty_buffers is needed to commit the new block.
 108 */
 109void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block);
 110
 111unsigned dm_bufio_get_block_size(struct dm_bufio_client *c);
 112sector_t dm_bufio_get_device_size(struct dm_bufio_client *c);
 113sector_t dm_bufio_get_block_number(struct dm_buffer *b);
 114void *dm_bufio_get_block_data(struct dm_buffer *b);
 115void *dm_bufio_get_aux_data(struct dm_buffer *b);
 116struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b);
 117
 118/*----------------------------------------------------------------*/
 119
 120#endif
 121