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  */
19 typedef uint64_t dm_block_t;
20 struct dm_block;
21 
22 dm_block_t dm_block_location(struct dm_block *b);
23 void *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  */
34 struct dm_block_manager;
35 struct dm_block_manager *dm_block_manager_create(
36 	struct block_device *bdev, unsigned int block_size,
37 	unsigned int max_held_per_thread);
38 void dm_block_manager_destroy(struct dm_block_manager *bm);
39 void dm_block_manager_reset(struct dm_block_manager *bm);
40 
41 unsigned int dm_bm_block_size(struct dm_block_manager *bm);
42 dm_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  */
52 struct dm_block_validator {
53 	const char *name;
54 	void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
55 
56 	/*
57 	 * Return 0 if the checksum is valid or < 0 on error.
58 	 */
59 	int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
60 };
61 
62 /*----------------------------------------------------------------*/
63 
64 /*
65  * You can have multiple concurrent readers or a single writer holding a
66  * block lock.
67  */
68 
69 /*
70  * dm_bm_lock() locks a block and returns through @result a pointer to
71  * memory that holds a copy of that block.  If you have write-locked the
72  * block then any changes you make to memory pointed to by @result will be
73  * written back to the disk sometime after dm_bm_unlock is called.
74  */
75 int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
76 		    struct dm_block_validator *v,
77 		    struct dm_block **result);
78 
79 int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b,
80 		     struct dm_block_validator *v,
81 		     struct dm_block **result);
82 
83 /*
84  * The *_try_lock variants return -EWOULDBLOCK if the block isn't
85  * available immediately.
86  */
87 int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b,
88 			struct dm_block_validator *v,
89 			struct dm_block **result);
90 
91 /*
92  * Use dm_bm_write_lock_zero() when you know you're going to
93  * overwrite the block completely.  It saves a disk read.
94  */
95 int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b,
96 			  struct dm_block_validator *v,
97 			  struct dm_block **result);
98 
99 void dm_bm_unlock(struct dm_block *b);
100 
101 /*
102  * It's a common idiom to have a superblock that should be committed last.
103  *
104  * @superblock should be write-locked on entry. It will be unlocked during
105  * this function.  All dirty blocks are guaranteed to be written and flushed
106  * before the superblock.
107  *
108  * This method always blocks.
109  */
110 int dm_bm_flush(struct dm_block_manager *bm);
111 
112 /*
113  * Request data is prefetched into the cache.
114  */
115 void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b);
116 
117 /*
118  * Switches the bm to a read only mode.  Once read-only mode
119  * has been entered the following functions will return -EPERM.
120  *
121  *   dm_bm_write_lock
122  *   dm_bm_write_lock_zero
123  *   dm_bm_flush_and_unlock
124  *
125  * Additionally you should not use dm_bm_unlock_move, however no error will
126  * be returned if you do.
127  */
128 bool dm_bm_is_read_only(struct dm_block_manager *bm);
129 void dm_bm_set_read_only(struct dm_block_manager *bm);
130 void dm_bm_set_read_write(struct dm_block_manager *bm);
131 
132 u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor);
133 
134 /*----------------------------------------------------------------*/
135 
136 #endif	/* _LINUX_DM_BLOCK_MANAGER_H */
137