Jonathan Brassow | aea53d9 | 2009-01-06 03:05:15 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2001-2002 Sistina Software (UK) Limited. |
| 3 | * Copyright (C) 2008 Red Hat, Inc. All rights reserved. |
| 4 | * |
| 5 | * Device-mapper snapshot exception store. |
| 6 | * |
| 7 | * This file is released under the GPL. |
| 8 | */ |
| 9 | |
| 10 | #ifndef _LINUX_DM_EXCEPTION_STORE |
| 11 | #define _LINUX_DM_EXCEPTION_STORE |
| 12 | |
| 13 | #include <linux/blkdev.h> |
| 14 | |
| 15 | /* |
| 16 | * The snapshot code deals with largish chunks of the disk at a |
| 17 | * time. Typically 32k - 512k. |
| 18 | */ |
| 19 | typedef sector_t chunk_t; |
| 20 | |
| 21 | /* |
| 22 | * An exception is used where an old chunk of data has been |
| 23 | * replaced by a new one. |
| 24 | * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number |
| 25 | * of chunks that follow contiguously. Remaining bits hold the number of the |
| 26 | * chunk within the device. |
| 27 | */ |
| 28 | struct dm_snap_exception { |
| 29 | struct list_head hash_list; |
| 30 | |
| 31 | chunk_t old_chunk; |
| 32 | chunk_t new_chunk; |
| 33 | }; |
| 34 | |
| 35 | /* |
| 36 | * Abstraction to handle the meta/layout of exception stores (the |
| 37 | * COW device). |
| 38 | */ |
| 39 | struct exception_store { |
| 40 | /* |
| 41 | * Destroys this object when you've finished with it. |
| 42 | */ |
| 43 | void (*destroy) (struct exception_store *store); |
| 44 | |
| 45 | /* |
| 46 | * The target shouldn't read the COW device until this is |
| 47 | * called. |
| 48 | */ |
| 49 | int (*read_metadata) (struct exception_store *store); |
| 50 | |
| 51 | /* |
| 52 | * Find somewhere to store the next exception. |
| 53 | */ |
| 54 | int (*prepare_exception) (struct exception_store *store, |
| 55 | struct dm_snap_exception *e); |
| 56 | |
| 57 | /* |
| 58 | * Update the metadata with this exception. |
| 59 | */ |
| 60 | void (*commit_exception) (struct exception_store *store, |
| 61 | struct dm_snap_exception *e, |
| 62 | void (*callback) (void *, int success), |
| 63 | void *callback_context); |
| 64 | |
| 65 | /* |
| 66 | * The snapshot is invalid, note this in the metadata. |
| 67 | */ |
| 68 | void (*drop_snapshot) (struct exception_store *store); |
| 69 | |
| 70 | /* |
| 71 | * Return how full the snapshot is. |
| 72 | */ |
| 73 | void (*fraction_full) (struct exception_store *store, |
| 74 | sector_t *numerator, |
| 75 | sector_t *denominator); |
| 76 | |
| 77 | struct dm_snapshot *snap; |
| 78 | void *context; |
| 79 | }; |
| 80 | |
| 81 | /* |
| 82 | * Funtions to manipulate consecutive chunks |
| 83 | */ |
| 84 | # if defined(CONFIG_LBD) || (BITS_PER_LONG == 64) |
| 85 | # define DM_CHUNK_CONSECUTIVE_BITS 8 |
| 86 | # define DM_CHUNK_NUMBER_BITS 56 |
| 87 | |
| 88 | static inline chunk_t dm_chunk_number(chunk_t chunk) |
| 89 | { |
| 90 | return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL); |
| 91 | } |
| 92 | |
| 93 | static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e) |
| 94 | { |
| 95 | return e->new_chunk >> DM_CHUNK_NUMBER_BITS; |
| 96 | } |
| 97 | |
| 98 | static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e) |
| 99 | { |
| 100 | e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS); |
| 101 | |
| 102 | BUG_ON(!dm_consecutive_chunk_count(e)); |
| 103 | } |
| 104 | |
| 105 | # else |
| 106 | # define DM_CHUNK_CONSECUTIVE_BITS 0 |
| 107 | |
| 108 | static inline chunk_t dm_chunk_number(chunk_t chunk) |
| 109 | { |
| 110 | return chunk; |
| 111 | } |
| 112 | |
| 113 | static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e) |
| 114 | { |
| 115 | return 0; |
| 116 | } |
| 117 | |
| 118 | static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e) |
| 119 | { |
| 120 | } |
| 121 | |
| 122 | # endif |
| 123 | |
| 124 | /* |
| 125 | * Two exception store implementations. |
| 126 | */ |
| 127 | int dm_create_persistent(struct exception_store *store); |
| 128 | |
| 129 | int dm_create_transient(struct exception_store *store); |
| 130 | |
| 131 | #endif /* _LINUX_DM_EXCEPTION_STORE */ |