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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 #include "dm-snap.h"
10 
11 #include <linux/mm.h>
12 #include <linux/pagemap.h>
13 #include <linux/vmalloc.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 
transient_destroy(struct dm_exception_store * store)26 static void transient_destroy(struct dm_exception_store *store)
27 {
28 	kfree(store->context);
29 }
30 
transient_read_metadata(struct dm_exception_store * store,int (* callback)(void * callback_context,chunk_t old,chunk_t new),void * callback_context)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 
transient_prepare_exception(struct dm_exception_store * store,struct dm_snap_exception * e)39 static int transient_prepare_exception(struct dm_exception_store *store,
40 				       struct dm_snap_exception *e)
41 {
42 	struct transient_c *tc = (struct transient_c *) store->context;
43 	sector_t size = get_dev_size(store->snap->cow->bdev);
44 
45 	if (size < (tc->next_free + store->snap->chunk_size))
46 		return -1;
47 
48 	e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
49 	tc->next_free += store->snap->chunk_size;
50 
51 	return 0;
52 }
53 
transient_commit_exception(struct dm_exception_store * store,struct dm_snap_exception * e,void (* callback)(void *,int success),void * callback_context)54 static void transient_commit_exception(struct dm_exception_store *store,
55 				       struct dm_snap_exception *e,
56 				       void (*callback) (void *, int success),
57 				       void *callback_context)
58 {
59 	/* Just succeed */
60 	callback(callback_context, 1);
61 }
62 
transient_fraction_full(struct dm_exception_store * store,sector_t * numerator,sector_t * denominator)63 static void transient_fraction_full(struct dm_exception_store *store,
64 				    sector_t *numerator, sector_t *denominator)
65 {
66 	*numerator = ((struct transient_c *) store->context)->next_free;
67 	*denominator = get_dev_size(store->snap->cow->bdev);
68 }
69 
dm_create_transient(struct dm_exception_store * store)70 int dm_create_transient(struct dm_exception_store *store)
71 {
72 	struct transient_c *tc;
73 
74 	store->destroy = transient_destroy;
75 	store->read_metadata = transient_read_metadata;
76 	store->prepare_exception = transient_prepare_exception;
77 	store->commit_exception = transient_commit_exception;
78 	store->drop_snapshot = NULL;
79 	store->fraction_full = transient_fraction_full;
80 
81 	tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
82 	if (!tc)
83 		return -ENOMEM;
84 
85 	tc->next_free = 0;
86 	store->context = tc;
87 
88 	return 0;
89 }
90 
dm_transient_snapshot_init(void)91 int dm_transient_snapshot_init(void)
92 {
93 	return 0;
94 }
95 
dm_transient_snapshot_exit(void)96 void dm_transient_snapshot_exit(void)
97 {
98 }
99