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3241b1d3 JT |
1 | /* |
2 | * Copyright (C) 2011 Red Hat, Inc. | |
3 | * | |
4 | * This file is released under the GPL. | |
5 | */ | |
6 | ||
7 | #ifndef _LINUX_DM_TRANSACTION_MANAGER_H | |
8 | #define _LINUX_DM_TRANSACTION_MANAGER_H | |
9 | ||
10 | #include "dm-block-manager.h" | |
11 | ||
12 | struct dm_transaction_manager; | |
13 | struct dm_space_map; | |
14 | ||
15 | /*----------------------------------------------------------------*/ | |
16 | ||
17 | /* | |
18 | * This manages the scope of a transaction. It also enforces immutability | |
19 | * of the on-disk data structures by limiting access to writeable blocks. | |
20 | * | |
21 | * Clients should not fiddle with the block manager directly. | |
22 | */ | |
23 | ||
24 | void dm_tm_destroy(struct dm_transaction_manager *tm); | |
25 | ||
26 | /* | |
27 | * The non-blocking version of a transaction manager is intended for use in | |
28 | * fast path code that needs to do lookups e.g. a dm mapping function. | |
29 | * You create the non-blocking variant from a normal tm. The interface is | |
30 | * the same, except that most functions will just return -EWOULDBLOCK. | |
31 | * Methods that return void yet may block should not be called on a clone | |
32 | * viz. dm_tm_inc, dm_tm_dec. Call dm_tm_destroy() as you would with a normal | |
33 | * tm when you've finished with it. You may not destroy the original prior | |
34 | * to clones. | |
35 | */ | |
36 | struct dm_transaction_manager *dm_tm_create_non_blocking_clone(struct dm_transaction_manager *real); | |
37 | ||
38 | /* | |
39 | * We use a 2-phase commit here. | |
40 | * | |
41 | * i) In the first phase the block manager is told to start flushing, and | |
42 | * the changes to the space map are written to disk. You should interrogate | |
43 | * your particular space map to get detail of its root node etc. to be | |
44 | * included in your superblock. | |
45 | * | |
46 | * ii) @root will be committed last. You shouldn't use more than the | |
47 | * first 512 bytes of @root if you wish the transaction to survive a power | |
48 | * failure. You *must* have a write lock held on @root for both stage (i) | |
49 | * and (ii). The commit will drop the write lock. | |
50 | */ | |
51 | int dm_tm_pre_commit(struct dm_transaction_manager *tm); | |
52 | int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *root); | |
53 | ||
54 | /* | |
55 | * These methods are the only way to get hold of a writeable block. | |
56 | */ | |
57 | ||
58 | /* | |
59 | * dm_tm_new_block() is pretty self-explanatory. Make sure you do actually | |
60 | * write to the whole of @data before you unlock, otherwise you could get | |
61 | * a data leak. (The other option is for tm_new_block() to zero new blocks | |
62 | * before handing them out, which will be redundant in most, if not all, | |
63 | * cases). | |
64 | * Zeroes the new block and returns with write lock held. | |
65 | */ | |
66 | int dm_tm_new_block(struct dm_transaction_manager *tm, | |
67 | struct dm_block_validator *v, | |
68 | struct dm_block **result); | |
69 | ||
70 | /* | |
71 | * dm_tm_shadow_block() allocates a new block and copies the data from @orig | |
72 | * to it. It then decrements the reference count on original block. Use | |
73 | * this to update the contents of a block in a data structure, don't | |
74 | * confuse this with a clone - you shouldn't access the orig block after | |
75 | * this operation. Because the tm knows the scope of the transaction it | |
76 | * can optimise requests for a shadow of a shadow to a no-op. Don't forget | |
77 | * to unlock when you've finished with the shadow. | |
78 | * | |
79 | * The @inc_children flag is used to tell the caller whether it needs to | |
80 | * adjust reference counts for children. (Data in the block may refer to | |
81 | * other blocks.) | |
82 | * | |
83 | * Shadowing implicitly drops a reference on @orig so you must not have | |
84 | * it locked when you call this. | |
85 | */ | |
86 | int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig, | |
87 | struct dm_block_validator *v, | |
88 | struct dm_block **result, int *inc_children); | |
89 | ||
90 | /* | |
91 | * Read access. You can lock any block you want. If there's a write lock | |
92 | * on it outstanding then it'll block. | |
93 | */ | |
94 | int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b, | |
95 | struct dm_block_validator *v, | |
96 | struct dm_block **result); | |
97 | ||
98 | int dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b); | |
99 | ||
100 | /* | |
101 | * Functions for altering the reference count of a block directly. | |
102 | */ | |
103 | void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b); | |
104 | ||
105 | void dm_tm_dec(struct dm_transaction_manager *tm, dm_block_t b); | |
106 | ||
107 | int dm_tm_ref(struct dm_transaction_manager *tm, dm_block_t b, | |
108 | uint32_t *result); | |
109 | ||
110 | struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm); | |
111 | ||
112 | /* | |
113 | * A little utility that ties the knot by producing a transaction manager | |
114 | * that has a space map managed by the transaction manager... | |
115 | * | |
116 | * Returns a tm that has an open transaction to write the new disk sm. | |
117 | * Caller should store the new sm root and commit. | |
384ef0e6 JT |
118 | * |
119 | * The superblock location is passed so the metadata space map knows it | |
120 | * shouldn't be used. | |
3241b1d3 JT |
121 | */ |
122 | int dm_tm_create_with_sm(struct dm_block_manager *bm, dm_block_t sb_location, | |
3241b1d3 | 123 | struct dm_transaction_manager **tm, |
384ef0e6 | 124 | struct dm_space_map **sm); |
3241b1d3 JT |
125 | |
126 | int dm_tm_open_with_sm(struct dm_block_manager *bm, dm_block_t sb_location, | |
384ef0e6 | 127 | void *sm_root, size_t root_len, |
3241b1d3 | 128 | struct dm_transaction_manager **tm, |
384ef0e6 | 129 | struct dm_space_map **sm); |
3241b1d3 JT |
130 | |
131 | #endif /* _LINUX_DM_TRANSACTION_MANAGER_H */ |