1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
4  * Copyright (C) 2006-2008 Red Hat GmbH
5  *
6  * This file is released under the GPL.
7  */
8 
9 #include "dm-exception-store.h"
10 
11 #include <linux/mm.h>
12 #include <linux/pagemap.h>
13 #include <linux/vmalloc.h>
14 #include <linux/export.h>
15 #include <linux/slab.h>
16 #include <linux/dm-io.h>
17 
18 #define DM_MSG_PREFIX "transient snapshot"
19 
20 /*
21  *---------------------------------------------------------------
22  * Implementation of the store for non-persistent snapshots.
23  *---------------------------------------------------------------
24  */
25 struct transient_c {
26 	sector_t next_free;
27 };
28 
29 static void transient_dtr(struct dm_exception_store *store)
30 {
31 	kfree(store->context);
32 }
33 
34 static int transient_read_metadata(struct dm_exception_store *store,
35 				   int (*callback)(void *callback_context,
36 						   chunk_t old, chunk_t new),
37 				   void *callback_context)
38 {
39 	return 0;
40 }
41 
42 static int transient_prepare_exception(struct dm_exception_store *store,
43 				       struct dm_exception *e)
44 {
45 	struct transient_c *tc = store->context;
46 	sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
47 
48 	if (size < (tc->next_free + store->chunk_size))
49 		return -1;
50 
51 	e->new_chunk = sector_to_chunk(store, tc->next_free);
52 	tc->next_free += store->chunk_size;
53 
54 	return 0;
55 }
56 
57 static void transient_commit_exception(struct dm_exception_store *store,
58 				       struct dm_exception *e, int valid,
59 				       void (*callback)(void *, int success),
60 				       void *callback_context)
61 {
62 	/* Just succeed */
63 	callback(callback_context, valid);
64 }
65 
66 static void transient_usage(struct dm_exception_store *store,
67 			    sector_t *total_sectors,
68 			    sector_t *sectors_allocated,
69 			    sector_t *metadata_sectors)
70 {
71 	*sectors_allocated = ((struct transient_c *) store->context)->next_free;
72 	*total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
73 	*metadata_sectors = 0;
74 }
75 
76 static int transient_ctr(struct dm_exception_store *store, char *options)
77 {
78 	struct transient_c *tc;
79 
80 	tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
81 	if (!tc)
82 		return -ENOMEM;
83 
84 	tc->next_free = 0;
85 	store->context = tc;
86 
87 	return 0;
88 }
89 
90 static unsigned int transient_status(struct dm_exception_store *store,
91 				 status_type_t status, char *result,
92 				 unsigned int maxlen)
93 {
94 	unsigned int sz = 0;
95 
96 	switch (status) {
97 	case STATUSTYPE_INFO:
98 		break;
99 	case STATUSTYPE_TABLE:
100 		DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
101 		break;
102 	case STATUSTYPE_IMA:
103 		*result = '\0';
104 		break;
105 	}
106 
107 	return sz;
108 }
109 
110 static struct dm_exception_store_type _transient_type = {
111 	.name = "transient",
112 	.module = THIS_MODULE,
113 	.ctr = transient_ctr,
114 	.dtr = transient_dtr,
115 	.read_metadata = transient_read_metadata,
116 	.prepare_exception = transient_prepare_exception,
117 	.commit_exception = transient_commit_exception,
118 	.usage = transient_usage,
119 	.status = transient_status,
120 };
121 
122 static struct dm_exception_store_type _transient_compat_type = {
123 	.name = "N",
124 	.module = THIS_MODULE,
125 	.ctr = transient_ctr,
126 	.dtr = transient_dtr,
127 	.read_metadata = transient_read_metadata,
128 	.prepare_exception = transient_prepare_exception,
129 	.commit_exception = transient_commit_exception,
130 	.usage = transient_usage,
131 	.status = transient_status,
132 };
133 
134 int dm_transient_snapshot_init(void)
135 {
136 	int r;
137 
138 	r = dm_exception_store_type_register(&_transient_type);
139 	if (r) {
140 		DMWARN("Unable to register transient exception store type");
141 		return r;
142 	}
143 
144 	r = dm_exception_store_type_register(&_transient_compat_type);
145 	if (r) {
146 		DMWARN("Unable to register old-style transient exception store type");
147 		dm_exception_store_type_unregister(&_transient_type);
148 		return r;
149 	}
150 
151 	return r;
152 }
153 
154 void dm_transient_snapshot_exit(void)
155 {
156 	dm_exception_store_type_unregister(&_transient_type);
157 	dm_exception_store_type_unregister(&_transient_compat_type);
158 }
159