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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);
39
40unsigned int dm_bm_block_size(struct dm_block_manager *bm);
41dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm);
42
43/*----------------------------------------------------------------*/
44
45/*
46 * The validator allows the caller to verify newly-read data and modify
47 * the data just before writing, e.g. to calculate checksums. It's
48 * important to be consistent with your use of validators. The only time
49 * you can change validators is if you call dm_bm_write_lock_zero.
50 */
51struct dm_block_validator {
52 const char *name;
53 void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
54
55 /*
56 * Return 0 if the checksum is valid or < 0 on error.
57 */
58 int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
59};
60
61/*----------------------------------------------------------------*/
62
63/*
64 * You can have multiple concurrent readers or a single writer holding a
65 * block lock.
66 */
67
68/*
69 * dm_bm_lock() locks a block and returns through @result a pointer to
70 * memory that holds a copy of that block. If you have write-locked the
71 * block then any changes you make to memory pointed to by @result will be
72 * written back to the disk sometime after dm_bm_unlock is called.
73 */
74int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
75 struct dm_block_validator *v,
76 struct dm_block **result);
77
78int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b,
79 struct dm_block_validator *v,
80 struct dm_block **result);
81
82/*
83 * The *_try_lock variants return -EWOULDBLOCK if the block isn't
84 * available immediately.
85 */
86int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b,
87 struct dm_block_validator *v,
88 struct dm_block **result);
89
90/*
91 * Use dm_bm_write_lock_zero() when you know you're going to
92 * overwrite the block completely. It saves a disk read.
93 */
94int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b,
95 struct dm_block_validator *v,
96 struct dm_block **result);
97
98void dm_bm_unlock(struct dm_block *b);
99
100/*
101 * It's a common idiom to have a superblock that should be committed last.
102 *
103 * @superblock should be write-locked on entry. It will be unlocked during
104 * this function. All dirty blocks are guaranteed to be written and flushed
105 * before the superblock.
106 *
107 * This method always blocks.
108 */
109int dm_bm_flush(struct dm_block_manager *bm);
110
111/*
112 * Request data is prefetched into the cache.
113 */
114void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b);
115
116/*
117 * Switches the bm to a read only mode. Once read-only mode
118 * has been entered the following functions will return -EPERM.
119 *
120 * dm_bm_write_lock
121 * dm_bm_write_lock_zero
122 * dm_bm_flush_and_unlock
123 *
124 * Additionally you should not use dm_bm_unlock_move, however no error will
125 * be returned if you do.
126 */
127bool dm_bm_is_read_only(struct dm_block_manager *bm);
128void dm_bm_set_read_only(struct dm_block_manager *bm);
129void dm_bm_set_read_write(struct dm_block_manager *bm);
130
131u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor);
132
133/*----------------------------------------------------------------*/
134
135#endif /* _LINUX_DM_BLOCK_MANAGER_H */