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
  17 struct dm_bufio_client;
  18 struct dm_buffer;
  19
  20 /*
  21  * Create a buffered IO cache on a given device
  22  */
  23 struct dm_bufio_client *
  24 dm_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  */
  32 void 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  */
  48 void *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  */
  55 void *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  */
  62 void *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  */
  70 void 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  */
  77 void 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  */
  87 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b);
  88
  89 /*
  90  * Initiate writing of dirty buffers, without waiting for completion.
  91  */
  92 void 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  */
  98 int 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  */
 103 int 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  */
 109 void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block);
 110
 111 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c);
 112 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c);
 113 sector_t dm_bufio_get_block_number(struct dm_buffer *b);
 114 void *dm_bufio_get_block_data(struct dm_buffer *b);
 115 void *dm_bufio_get_aux_data(struct dm_buffer *b);
 116 struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b);
 117
 118 /*----------------------------------------------------------------*/
 119
 120 #endif