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  *---------------------------------------------------------------*/
22 struct transient_c {
23 	sector_t next_free;
24 };
25 
26 static void transient_dtr(struct dm_exception_store *store)
27 {
28 	kfree(store->context);
29 }
30 
31 static 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 
39 static 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 
54 static 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 
63 static 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 
73 static 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 
88 static 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 
104 static 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 
116 static 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 
128 int 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 
149 void 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