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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (C) 2011 Red Hat, Inc.
4 *
5 * This file is released under the GPL.
6 */
7
8#ifndef _LINUX_DM_BLOCK_MANAGER_H
9#define _LINUX_DM_BLOCK_MANAGER_H
10
11#include <linux/types.h>
12#include <linux/blkdev.h>
13
14/*----------------------------------------------------------------*/
15
16/*
17 * Block number.
18 */
19typedef uint64_t dm_block_t;
20struct dm_block;
21
22dm_block_t dm_block_location(struct dm_block *b);
23void *dm_block_data(struct dm_block *b);
24
25/*----------------------------------------------------------------*/
26
27/*
28 * @name should be a unique identifier for the block manager, no longer
29 * than 32 chars.
30 *
31 * @max_held_per_thread should be the maximum number of locks, read or
32 * write, that an individual thread holds at any one time.
33 */
34struct dm_block_manager;
35struct dm_block_manager *dm_block_manager_create(
36 struct block_device *bdev, unsigned int block_size,
37 unsigned int max_held_per_thread);
38void dm_block_manager_destroy(struct dm_block_manager *bm);
39void dm_block_manager_reset(struct dm_block_manager *bm);
40
41unsigned int dm_bm_block_size(struct dm_block_manager *bm);
42dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm);
43
44/*----------------------------------------------------------------*/
45
46/*
47 * The validator allows the caller to verify newly-read data and modify
48 * the data just before writing, e.g. to calculate checksums. It's
49 * important to be consistent with your use of validators. The only time
50 * you can change validators is if you call dm_bm_write_lock_zero.
51 */
52struct dm_block_validator {
53 const char *name;
54 void (*prepare_for_write)(const struct dm_block_validator *v,
55 struct dm_block *b, size_t block_size);
56
57 /*
58 * Return 0 if the checksum is valid or < 0 on error.
59 */
60 int (*check)(const struct dm_block_validator *v,
61 struct dm_block *b, size_t block_size);
62};
63
64/*----------------------------------------------------------------*/
65
66/*
67 * You can have multiple concurrent readers or a single writer holding a
68 * block lock.
69 */
70
71/*
72 * dm_bm_lock() locks a block and returns through @result a pointer to
73 * memory that holds a copy of that block. If you have write-locked the
74 * block then any changes you make to memory pointed to by @result will be
75 * written back to the disk sometime after dm_bm_unlock is called.
76 */
77int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
78 const struct dm_block_validator *v,
79 struct dm_block **result);
80
81int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b,
82 const struct dm_block_validator *v,
83 struct dm_block **result);
84
85/*
86 * The *_try_lock variants return -EWOULDBLOCK if the block isn't
87 * available immediately.
88 */
89int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b,
90 const struct dm_block_validator *v,
91 struct dm_block **result);
92
93/*
94 * Use dm_bm_write_lock_zero() when you know you're going to
95 * overwrite the block completely. It saves a disk read.
96 */
97int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b,
98 const struct dm_block_validator *v,
99 struct dm_block **result);
100
101void dm_bm_unlock(struct dm_block *b);
102
103/*
104 * It's a common idiom to have a superblock that should be committed last.
105 *
106 * @superblock should be write-locked on entry. It will be unlocked during
107 * this function. All dirty blocks are guaranteed to be written and flushed
108 * before the superblock.
109 *
110 * This method always blocks.
111 */
112int dm_bm_flush(struct dm_block_manager *bm);
113
114/*
115 * Request data is prefetched into the cache.
116 */
117void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b);
118
119/*
120 * Switches the bm to a read only mode. Once read-only mode
121 * has been entered the following functions will return -EPERM.
122 *
123 * dm_bm_write_lock
124 * dm_bm_write_lock_zero
125 * dm_bm_flush_and_unlock
126 *
127 * Additionally you should not use dm_bm_unlock_move, however no error will
128 * be returned if you do.
129 */
130bool dm_bm_is_read_only(struct dm_block_manager *bm);
131void dm_bm_set_read_only(struct dm_block_manager *bm);
132void dm_bm_set_read_write(struct dm_block_manager *bm);
133
134u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor);
135
136/*----------------------------------------------------------------*/
137
138#endif /* _LINUX_DM_BLOCK_MANAGER_H */