Root/drivers/md/dm-cache-metadata.h

1/*
2 * Copyright (C) 2012 Red Hat, Inc.
3 *
4 * This file is released under the GPL.
5 */
6
7#ifndef DM_CACHE_METADATA_H
8#define DM_CACHE_METADATA_H
9
10#include "dm-cache-block-types.h"
11#include "dm-cache-policy-internal.h"
12
13/*----------------------------------------------------------------*/
14
15#define DM_CACHE_METADATA_BLOCK_SIZE 4096
16
17/* FIXME: remove this restriction */
18/*
19 * The metadata device is currently limited in size.
20 *
21 * We have one block of index, which can hold 255 index entries. Each
22 * index entry contains allocation info about 16k metadata blocks.
23 */
24#define DM_CACHE_METADATA_MAX_SECTORS (255 * (1 << 14) * (DM_CACHE_METADATA_BLOCK_SIZE / (1 << SECTOR_SHIFT)))
25
26/*
27 * A metadata device larger than 16GB triggers a warning.
28 */
29#define DM_CACHE_METADATA_MAX_SECTORS_WARNING (16 * (1024 * 1024 * 1024 >> SECTOR_SHIFT))
30
31/*----------------------------------------------------------------*/
32
33/*
34 * Ext[234]-style compat feature flags.
35 *
36 * A new feature which old metadata will still be compatible with should
37 * define a DM_CACHE_FEATURE_COMPAT_* flag (rarely useful).
38 *
39 * A new feature that is not compatible with old code should define a
40 * DM_CACHE_FEATURE_INCOMPAT_* flag and guard the relevant code with
41 * that flag.
42 *
43 * A new feature that is not compatible with old code accessing the
44 * metadata RDWR should define a DM_CACHE_FEATURE_RO_COMPAT_* flag and
45 * guard the relevant code with that flag.
46 *
47 * As these various flags are defined they should be added to the
48 * following masks.
49 */
50#define DM_CACHE_FEATURE_COMPAT_SUPP 0UL
51#define DM_CACHE_FEATURE_COMPAT_RO_SUPP 0UL
52#define DM_CACHE_FEATURE_INCOMPAT_SUPP 0UL
53
54/*
55 * Reopens or creates a new, empty metadata volume.
56 * Returns an ERR_PTR on failure.
57 */
58struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
59                         sector_t data_block_size,
60                         bool may_format_device,
61                         size_t policy_hint_size);
62
63void dm_cache_metadata_close(struct dm_cache_metadata *cmd);
64
65/*
66 * The metadata needs to know how many cache blocks there are. We don't
67 * care about the origin, assuming the core target is giving us valid
68 * origin blocks to map to.
69 */
70int dm_cache_resize(struct dm_cache_metadata *cmd, dm_cblock_t new_cache_size);
71dm_cblock_t dm_cache_size(struct dm_cache_metadata *cmd);
72
73int dm_cache_discard_bitset_resize(struct dm_cache_metadata *cmd,
74                   sector_t discard_block_size,
75                   dm_dblock_t new_nr_entries);
76
77typedef int (*load_discard_fn)(void *context, sector_t discard_block_size,
78                   dm_dblock_t dblock, bool discarded);
79int dm_cache_load_discards(struct dm_cache_metadata *cmd,
80               load_discard_fn fn, void *context);
81
82int dm_cache_set_discard(struct dm_cache_metadata *cmd, dm_dblock_t dblock, bool discard);
83
84int dm_cache_remove_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock);
85int dm_cache_insert_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock, dm_oblock_t oblock);
86int dm_cache_changed_this_transaction(struct dm_cache_metadata *cmd);
87
88typedef int (*load_mapping_fn)(void *context, dm_oblock_t oblock,
89                   dm_cblock_t cblock, bool dirty,
90                   uint32_t hint, bool hint_valid);
91int dm_cache_load_mappings(struct dm_cache_metadata *cmd,
92               struct dm_cache_policy *policy,
93               load_mapping_fn fn,
94               void *context);
95
96int dm_cache_set_dirty(struct dm_cache_metadata *cmd, dm_cblock_t cblock, bool dirty);
97
98struct dm_cache_statistics {
99    uint32_t read_hits;
100    uint32_t read_misses;
101    uint32_t write_hits;
102    uint32_t write_misses;
103};
104
105void dm_cache_metadata_get_stats(struct dm_cache_metadata *cmd,
106                 struct dm_cache_statistics *stats);
107void dm_cache_metadata_set_stats(struct dm_cache_metadata *cmd,
108                 struct dm_cache_statistics *stats);
109
110int dm_cache_commit(struct dm_cache_metadata *cmd, bool clean_shutdown);
111
112int dm_cache_get_free_metadata_block_count(struct dm_cache_metadata *cmd,
113                       dm_block_t *result);
114
115int dm_cache_get_metadata_dev_size(struct dm_cache_metadata *cmd,
116                   dm_block_t *result);
117
118void dm_cache_dump(struct dm_cache_metadata *cmd);
119
120/*
121 * The policy is invited to save a 32bit hint value for every cblock (eg,
122 * for a hit count). These are stored against the policy name. If
123 * policies are changed, then hints will be lost. If the machine crashes,
124 * hints will be lost.
125 *
126 * The hints are indexed by the cblock, but many policies will not
127 * neccessarily have a fast way of accessing efficiently via cblock. So
128 * rather than querying the policy for each cblock, we let it walk its data
129 * structures and fill in the hints in whatever order it wishes.
130 */
131
132int dm_cache_begin_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *p);
133
134/*
135 * requests hints for every cblock and stores in the metadata device.
136 */
137int dm_cache_save_hint(struct dm_cache_metadata *cmd,
138               dm_cblock_t cblock, uint32_t hint);
139
140/*----------------------------------------------------------------*/
141
142#endif /* DM_CACHE_METADATA_H */
143

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