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  * Release a reference obtained with dm_bufio_{read,get,new}. The data
67  * pointer and dm_buffer pointer is no longer valid after this call.
68  */
69 void dm_bufio_release(struct dm_buffer *b);
70 
71 /*
72  * Mark a buffer dirty. It should be called after the buffer is modified.
73  *
74  * In case of memory pressure, the buffer may be written after
75  * dm_bufio_mark_buffer_dirty, but before dm_bufio_write_dirty_buffers.  So
76  * dm_bufio_write_dirty_buffers guarantees that the buffer is on-disk but
77  * the actual writing may occur earlier.
78  */
79 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b);
80 
81 /*
82  * Initiate writing of dirty buffers, without waiting for completion.
83  */
84 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c);
85 
86 /*
87  * Write all dirty buffers. Guarantees that all dirty buffers created prior
88  * to this call are on disk when this call exits.
89  */
90 int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c);
91 
92 /*
93  * Send an empty write barrier to the device to flush hardware disk cache.
94  */
95 int dm_bufio_issue_flush(struct dm_bufio_client *c);
96 
97 /*
98  * Like dm_bufio_release but also move the buffer to the new
99  * block. dm_bufio_write_dirty_buffers is needed to commit the new block.
100  */
101 void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block);
102 
103 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c);
104 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c);
105 sector_t dm_bufio_get_block_number(struct dm_buffer *b);
106 void *dm_bufio_get_block_data(struct dm_buffer *b);
107 void *dm_bufio_get_aux_data(struct dm_buffer *b);
108 struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b);
109 
110 /*----------------------------------------------------------------*/
111 
112 #endif
113