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_exception *e)
40 {
41 	struct transient_c *tc = store->context;
42 	sector_t size = get_dev_size(dm_snap_cow(store->snap)->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_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_usage(struct dm_exception_store *store,
63 			    sector_t *total_sectors,
64 			    sector_t *sectors_allocated,
65 			    sector_t *metadata_sectors)
66 {
67 	*sectors_allocated = ((struct transient_c *) store->context)->next_free;
68 	*total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
69 	*metadata_sectors = 0;
70 }
71 
72 static int transient_ctr(struct dm_exception_store *store,
73 			 unsigned argc, char **argv)
74 {
75 	struct transient_c *tc;
76 
77 	tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
78 	if (!tc)
79 		return -ENOMEM;
80 
81 	tc->next_free = 0;
82 	store->context = tc;
83 
84 	return 0;
85 }
86 
87 static unsigned transient_status(struct dm_exception_store *store,
88 				 status_type_t status, char *result,
89 				 unsigned maxlen)
90 {
91 	unsigned sz = 0;
92 
93 	switch (status) {
94 	case STATUSTYPE_INFO:
95 		break;
96 	case STATUSTYPE_TABLE:
97 		DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
98 	}
99 
100 	return sz;
101 }
102 
103 static struct dm_exception_store_type _transient_type = {
104 	.name = "transient",
105 	.module = THIS_MODULE,
106 	.ctr = transient_ctr,
107 	.dtr = transient_dtr,
108 	.read_metadata = transient_read_metadata,
109 	.prepare_exception = transient_prepare_exception,
110 	.commit_exception = transient_commit_exception,
111 	.usage = transient_usage,
112 	.status = transient_status,
113 };
114 
115 static struct dm_exception_store_type _transient_compat_type = {
116 	.name = "N",
117 	.module = THIS_MODULE,
118 	.ctr = transient_ctr,
119 	.dtr = transient_dtr,
120 	.read_metadata = transient_read_metadata,
121 	.prepare_exception = transient_prepare_exception,
122 	.commit_exception = transient_commit_exception,
123 	.usage = transient_usage,
124 	.status = transient_status,
125 };
126 
127 int dm_transient_snapshot_init(void)
128 {
129 	int r;
130 
131 	r = dm_exception_store_type_register(&_transient_type);
132 	if (r) {
133 		DMWARN("Unable to register transient exception store type");
134 		return r;
135 	}
136 
137 	r = dm_exception_store_type_register(&_transient_compat_type);
138 	if (r) {
139 		DMWARN("Unable to register old-style transient "
140 		       "exception store type");
141 		dm_exception_store_type_unregister(&_transient_type);
142 		return r;
143 	}
144 
145 	return r;
146 }
147 
148 void dm_transient_snapshot_exit(void)
149 {
150 	dm_exception_store_type_unregister(&_transient_type);
151 	dm_exception_store_type_unregister(&_transient_compat_type);
152 }
153