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 */
25struct transient_c {
26	sector_t next_free;
27};
28
29static void transient_dtr(struct dm_exception_store *store)
30{
31	kfree(store->context);
32}
33
34static 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
42static 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
57static 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
66static 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
76static 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
90static 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
110static 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
122static 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
134int 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
154void 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