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dm-bufio.h
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1 /*
2  * Copyright (C) 2009-2011 Red Hat, Inc.
3  *
4  * Author: Mikulas Patocka <[email protected]>
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 *
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  */
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  */
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  */
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  */
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  */
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75  * pointer and dm_buffer pointer is no longer valid after this call.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  */
88 
89 /*
90  * Initiate writing of dirty buffers, without waiting for completion.
91  */
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  */
99 
100 /*
101  * Send an empty write barrier to the device to flush hardware disk cache.
102  */
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  */
110 
111 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c);
114 void *dm_bufio_get_block_data(struct dm_buffer *b);
115 void *dm_bufio_get_aux_data(struct dm_buffer *b);
117 
118 /*----------------------------------------------------------------*/
119 
120 #endif