Root/drivers/md/dm-snap-transient.c

1/*
2 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
3 * Copyright (C) 2006-2008 Red Hat GmbH
4 *
5 * This file is released under the GPL.
6 */
7
8#include "dm-exception-store.h"
9
10#include <linux/mm.h>
11#include <linux/pagemap.h>
12#include <linux/vmalloc.h>
13#include <linux/export.h>
14#include <linux/slab.h>
15#include <linux/dm-io.h>
16
17#define DM_MSG_PREFIX "transient snapshot"
18
19/*-----------------------------------------------------------------
20 * Implementation of the store for non-persistent snapshots.
21 *---------------------------------------------------------------*/
22struct transient_c {
23    sector_t next_free;
24};
25
26static void transient_dtr(struct dm_exception_store *store)
27{
28    kfree(store->context);
29}
30
31static int transient_read_metadata(struct dm_exception_store *store,
32                   int (*callback)(void *callback_context,
33                           chunk_t old, chunk_t new),
34                   void *callback_context)
35{
36    return 0;
37}
38
39static int transient_prepare_exception(struct dm_exception_store *store,
40                       struct dm_exception *e)
41{
42    struct transient_c *tc = store->context;
43    sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
44
45    if (size < (tc->next_free + store->chunk_size))
46        return -1;
47
48    e->new_chunk = sector_to_chunk(store, tc->next_free);
49    tc->next_free += store->chunk_size;
50
51    return 0;
52}
53
54static void transient_commit_exception(struct dm_exception_store *store,
55                       struct dm_exception *e,
56                       void (*callback) (void *, int success),
57                       void *callback_context)
58{
59    /* Just succeed */
60    callback(callback_context, 1);
61}
62
63static void transient_usage(struct dm_exception_store *store,
64                sector_t *total_sectors,
65                sector_t *sectors_allocated,
66                sector_t *metadata_sectors)
67{
68    *sectors_allocated = ((struct transient_c *) store->context)->next_free;
69    *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
70    *metadata_sectors = 0;
71}
72
73static int transient_ctr(struct dm_exception_store *store,
74             unsigned argc, char **argv)
75{
76    struct transient_c *tc;
77
78    tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
79    if (!tc)
80        return -ENOMEM;
81
82    tc->next_free = 0;
83    store->context = tc;
84
85    return 0;
86}
87
88static unsigned transient_status(struct dm_exception_store *store,
89                 status_type_t status, char *result,
90                 unsigned maxlen)
91{
92    unsigned sz = 0;
93
94    switch (status) {
95    case STATUSTYPE_INFO:
96        break;
97    case STATUSTYPE_TABLE:
98        DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
99    }
100
101    return sz;
102}
103
104static struct dm_exception_store_type _transient_type = {
105    .name = "transient",
106    .module = THIS_MODULE,
107    .ctr = transient_ctr,
108    .dtr = transient_dtr,
109    .read_metadata = transient_read_metadata,
110    .prepare_exception = transient_prepare_exception,
111    .commit_exception = transient_commit_exception,
112    .usage = transient_usage,
113    .status = transient_status,
114};
115
116static struct dm_exception_store_type _transient_compat_type = {
117    .name = "N",
118    .module = THIS_MODULE,
119    .ctr = transient_ctr,
120    .dtr = transient_dtr,
121    .read_metadata = transient_read_metadata,
122    .prepare_exception = transient_prepare_exception,
123    .commit_exception = transient_commit_exception,
124    .usage = transient_usage,
125    .status = transient_status,
126};
127
128int dm_transient_snapshot_init(void)
129{
130    int r;
131
132    r = dm_exception_store_type_register(&_transient_type);
133    if (r) {
134        DMWARN("Unable to register transient exception store type");
135        return r;
136    }
137
138    r = dm_exception_store_type_register(&_transient_compat_type);
139    if (r) {
140        DMWARN("Unable to register old-style transient "
141               "exception store type");
142        dm_exception_store_type_unregister(&_transient_type);
143        return r;
144    }
145
146    return r;
147}
148
149void dm_transient_snapshot_exit(void)
150{
151    dm_exception_store_type_unregister(&_transient_type);
152    dm_exception_store_type_unregister(&_transient_compat_type);
153}
154

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