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
12struct dm_transaction_manager;
13struct 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
24void 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 */
36struct 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) Make all changes for the transaction *except* for the superblock.
42 * Then call dm_tm_pre_commit() to flush them to disk.
43 *
44 * ii) Lock your superblock.  Update.  Then call dm_tm_commit() which will
45 * unlock the superblock and flush it.  No other blocks should be updated
46 * during this period.  Care should be taken to never unlock a partially
47 * updated superblock; perform any operations that could fail *before* you
48 * take the superblock lock.
49 */
50int dm_tm_pre_commit(struct dm_transaction_manager *tm);
51int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *superblock);
52
53/*
54 * These methods are the only way to get hold of a writeable block.
55 */
56
57/*
58 * dm_tm_new_block() is pretty self-explanatory.  Make sure you do actually
59 * write to the whole of @data before you unlock, otherwise you could get
60 * a data leak.  (The other option is for tm_new_block() to zero new blocks
61 * before handing them out, which will be redundant in most, if not all,
62 * cases).
63 * Zeroes the new block and returns with write lock held.
64 */
65int dm_tm_new_block(struct dm_transaction_manager *tm,
66		    struct dm_block_validator *v,
67		    struct dm_block **result);
68
69/*
70 * dm_tm_shadow_block() allocates a new block and copies the data from @orig
71 * to it.  It then decrements the reference count on original block.  Use
72 * this to update the contents of a block in a data structure, don't
73 * confuse this with a clone - you shouldn't access the orig block after
74 * this operation.  Because the tm knows the scope of the transaction it
75 * can optimise requests for a shadow of a shadow to a no-op.  Don't forget
76 * to unlock when you've finished with the shadow.
77 *
78 * The @inc_children flag is used to tell the caller whether it needs to
79 * adjust reference counts for children.  (Data in the block may refer to
80 * other blocks.)
81 *
82 * Shadowing implicitly drops a reference on @orig so you must not have
83 * it locked when you call this.
84 */
85int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
86		       struct dm_block_validator *v,
87		       struct dm_block **result, int *inc_children);
88
89/*
90 * Read access.  You can lock any block you want.  If there's a write lock
91 * on it outstanding then it'll block.
92 */
93int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
94		    struct dm_block_validator *v,
95		    struct dm_block **result);
96
97int dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b);
98
99/*
100 * Functions for altering the reference count of a block directly.
101 */
102void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b);
103
104void dm_tm_dec(struct dm_transaction_manager *tm, dm_block_t b);
105
106int dm_tm_ref(struct dm_transaction_manager *tm, dm_block_t b,
107	      uint32_t *result);
108
109struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm);
110
111/*
112 * A little utility that ties the knot by producing a transaction manager
113 * that has a space map managed by the transaction manager...
114 *
115 * Returns a tm that has an open transaction to write the new disk sm.
116 * Caller should store the new sm root and commit.
117 *
118 * The superblock location is passed so the metadata space map knows it
119 * shouldn't be used.
120 */
121int dm_tm_create_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
122			 struct dm_transaction_manager **tm,
123			 struct dm_space_map **sm);
124
125int dm_tm_open_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
126		       void *sm_root, size_t root_len,
127		       struct dm_transaction_manager **tm,
128		       struct dm_space_map **sm);
129
130#endif	/* _LINUX_DM_TRANSACTION_MANAGER_H */
131