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  */
58 struct 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 
63 void 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  */
70 int dm_cache_resize(struct dm_cache_metadata *cmd, dm_cblock_t new_cache_size);
71 dm_cblock_t dm_cache_size(struct dm_cache_metadata *cmd);
72 
73 int dm_cache_discard_bitset_resize(struct dm_cache_metadata *cmd,
74 				   sector_t discard_block_size,
75 				   dm_dblock_t new_nr_entries);
76 
77 typedef int (*load_discard_fn)(void *context, sector_t discard_block_size,
78 			       dm_dblock_t dblock, bool discarded);
79 int dm_cache_load_discards(struct dm_cache_metadata *cmd,
80 			   load_discard_fn fn, void *context);
81 
82 int dm_cache_set_discard(struct dm_cache_metadata *cmd, dm_dblock_t dblock, bool discard);
83 
84 int dm_cache_remove_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock);
85 int dm_cache_insert_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock, dm_oblock_t oblock);
86 int dm_cache_changed_this_transaction(struct dm_cache_metadata *cmd);
87 
88 typedef int (*load_mapping_fn)(void *context, dm_oblock_t oblock,
89 			       dm_cblock_t cblock, bool dirty,
90 			       uint32_t hint, bool hint_valid);
91 int dm_cache_load_mappings(struct dm_cache_metadata *cmd,
92 			   struct dm_cache_policy *policy,
93 			   load_mapping_fn fn,
94 			   void *context);
95 
96 int dm_cache_set_dirty(struct dm_cache_metadata *cmd, dm_cblock_t cblock, bool dirty);
97 
98 struct 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 
105 void dm_cache_metadata_get_stats(struct dm_cache_metadata *cmd,
106 				 struct dm_cache_statistics *stats);
107 void dm_cache_metadata_set_stats(struct dm_cache_metadata *cmd,
108 				 struct dm_cache_statistics *stats);
109 
110 int dm_cache_commit(struct dm_cache_metadata *cmd, bool clean_shutdown);
111 
112 int dm_cache_get_free_metadata_block_count(struct dm_cache_metadata *cmd,
113 					   dm_block_t *result);
114 
115 int dm_cache_get_metadata_dev_size(struct dm_cache_metadata *cmd,
116 				   dm_block_t *result);
117 
118 void 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 
132 int 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  */
137 int 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