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