1 /*
2 * Copyright (C) 2011 Red Hat, Inc.
3 *
4 * This file is released under the GPL.
5 */
6
7 #ifndef _LINUX_DM_BLOCK_MANAGER_H
8 #define _LINUX_DM_BLOCK_MANAGER_H
9
10 #include <linux/types.h>
11 #include <linux/blkdev.h>
12
13 /*----------------------------------------------------------------*/
14
15 /*
16 * Block number.
17 */
18 typedef uint64_t dm_block_t;
19 struct dm_block;
20
21 dm_block_t dm_block_location(struct dm_block *b);
22 void *dm_block_data(struct dm_block *b);
23
24 /*----------------------------------------------------------------*/
25
26 /*
27 * @name should be a unique identifier for the block manager, no longer
28 * than 32 chars.
29 *
30 * @max_held_per_thread should be the maximum number of locks, read or
31 * write, that an individual thread holds at any one time.
32 */
33 struct dm_block_manager;
34 struct dm_block_manager *dm_block_manager_create(
35 struct block_device *bdev, unsigned block_size,
36 unsigned max_held_per_thread);
37 void dm_block_manager_destroy(struct dm_block_manager *bm);
38
39 unsigned dm_bm_block_size(struct dm_block_manager *bm);
40 dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm);
41
42 /*----------------------------------------------------------------*/
43
44 /*
45 * The validator allows the caller to verify newly-read data and modify
46 * the data just before writing, e.g. to calculate checksums. It's
47 * important to be consistent with your use of validators. The only time
48 * you can change validators is if you call dm_bm_write_lock_zero.
49 */
50 struct dm_block_validator {
51 const char *name;
52 void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
53
54 /*
55 * Return 0 if the checksum is valid or < 0 on error.
56 */
57 int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
58 };
59
60 /*----------------------------------------------------------------*/
61
62 /*
63 * You can have multiple concurrent readers or a single writer holding a
64 * block lock.
65 */
66
67 /*
68 * dm_bm_lock() locks a block and returns through @result a pointer to
69 * memory that holds a copy of that block. If you have write-locked the
70 * block then any changes you make to memory pointed to by @result will be
71 * written back to the disk sometime after dm_bm_unlock is called.
72 */
73 int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
74 struct dm_block_validator *v,
75 struct dm_block **result);
76
77 int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b,
78 struct dm_block_validator *v,
79 struct dm_block **result);
80
81 /*
82 * The *_try_lock variants return -EWOULDBLOCK if the block isn't
83 * available immediately.
84 */
85 int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b,
86 struct dm_block_validator *v,
87 struct dm_block **result);
88
89 /*
90 * Use dm_bm_write_lock_zero() when you know you're going to
91 * overwrite the block completely. It saves a disk read.
92 */
93 int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b,
94 struct dm_block_validator *v,
95 struct dm_block **result);
96
97 void dm_bm_unlock(struct dm_block *b);
98
99 /*
100 * It's a common idiom to have a superblock that should be committed last.
101 *
102 * @superblock should be write-locked on entry. It will be unlocked during
103 * this function. All dirty blocks are guaranteed to be written and flushed
104 * before the superblock.
105 *
106 * This method always blocks.
107 */
108 int dm_bm_flush(struct dm_block_manager *bm);
109
110 /*
111 * Request data is prefetched into the cache.
112 */
113 void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b);
114
115 /*
116 * Switches the bm to a read only mode. Once read-only mode
117 * has been entered the following functions will return -EPERM.
118 *
119 * dm_bm_write_lock
120 * dm_bm_write_lock_zero
121 * dm_bm_flush_and_unlock
122 *
123 * Additionally you should not use dm_bm_unlock_move, however no error will
124 * be returned if you do.
125 */
126 bool dm_bm_is_read_only(struct dm_block_manager *bm);
127 void dm_bm_set_read_only(struct dm_block_manager *bm);
128 void dm_bm_set_read_write(struct dm_block_manager *bm);
129
130 u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor);
131
132 /*----------------------------------------------------------------*/
133
134 #endif /* _LINUX_DM_BLOCK_MANAGER_H */