xref: /openbmc/qemu/block/snapshot-access.c (revision 0ba4e76b)
1 /*
2  * snapshot_access block driver
3  *
4  * Copyright (c) 2022 Virtuozzo International GmbH.
5  *
6  * Author:
7  *  Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17  * GNU General Public License for more details.
18  *
19  * You should have received a copy of the GNU General Public License
20  * along with this program. If not, see <http://www.gnu.org/licenses/>.
21  */
22 
23 #include "qemu/osdep.h"
24 
25 #include "sysemu/block-backend.h"
26 #include "qemu/cutils.h"
27 #include "block/block_int.h"
28 
29 static coroutine_fn int
30 snapshot_access_co_preadv_part(BlockDriverState *bs,
31                                int64_t offset, int64_t bytes,
32                                QEMUIOVector *qiov, size_t qiov_offset,
33                                BdrvRequestFlags flags)
34 {
35     if (flags) {
36         return -ENOTSUP;
37     }
38 
39     return bdrv_co_preadv_snapshot(bs->file, offset, bytes, qiov, qiov_offset);
40 }
41 
42 static int coroutine_fn
43 snapshot_access_co_block_status(BlockDriverState *bs,
44                                 bool want_zero, int64_t offset,
45                                 int64_t bytes, int64_t *pnum,
46                                 int64_t *map, BlockDriverState **file)
47 {
48     return bdrv_co_snapshot_block_status(bs->file->bs, want_zero, offset,
49                                          bytes, pnum, map, file);
50 }
51 
52 static int coroutine_fn snapshot_access_co_pdiscard(BlockDriverState *bs,
53                                              int64_t offset, int64_t bytes)
54 {
55     return bdrv_co_pdiscard_snapshot(bs->file->bs, offset, bytes);
56 }
57 
58 static int coroutine_fn
59 snapshot_access_co_pwrite_zeroes(BlockDriverState *bs,
60                                  int64_t offset, int64_t bytes,
61                                  BdrvRequestFlags flags)
62 {
63     return -ENOTSUP;
64 }
65 
66 static coroutine_fn int
67 snapshot_access_co_pwritev_part(BlockDriverState *bs,
68                                 int64_t offset, int64_t bytes,
69                                 QEMUIOVector *qiov, size_t qiov_offset,
70                                 BdrvRequestFlags flags)
71 {
72     return -ENOTSUP;
73 }
74 
75 
76 static void snapshot_access_refresh_filename(BlockDriverState *bs)
77 {
78     pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
79             bs->file->bs->filename);
80 }
81 
82 static int snapshot_access_open(BlockDriverState *bs, QDict *options, int flags,
83                                 Error **errp)
84 {
85     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
86                                BDRV_CHILD_DATA | BDRV_CHILD_PRIMARY,
87                                false, errp);
88     if (!bs->file) {
89         return -EINVAL;
90     }
91 
92     bs->total_sectors = bs->file->bs->total_sectors;
93 
94     return 0;
95 }
96 
97 static void snapshot_access_child_perm(BlockDriverState *bs, BdrvChild *c,
98                                 BdrvChildRole role,
99                                 BlockReopenQueue *reopen_queue,
100                                 uint64_t perm, uint64_t shared,
101                                 uint64_t *nperm, uint64_t *nshared)
102 {
103     /*
104      * Currently, we don't need any permissions. If bs->file provides
105      * snapshot-access API, we can use it.
106      */
107     *nperm = 0;
108     *nshared = BLK_PERM_ALL;
109 }
110 
111 BlockDriver bdrv_snapshot_access_drv = {
112     .format_name = "snapshot-access",
113 
114     .bdrv_open                  = snapshot_access_open,
115 
116     .bdrv_co_preadv_part        = snapshot_access_co_preadv_part,
117     .bdrv_co_pwritev_part       = snapshot_access_co_pwritev_part,
118     .bdrv_co_pwrite_zeroes      = snapshot_access_co_pwrite_zeroes,
119     .bdrv_co_pdiscard           = snapshot_access_co_pdiscard,
120     .bdrv_co_block_status       = snapshot_access_co_block_status,
121 
122     .bdrv_refresh_filename      = snapshot_access_refresh_filename,
123 
124     .bdrv_child_perm            = snapshot_access_child_perm,
125 };
126 
127 static void snapshot_access_init(void)
128 {
129     bdrv_register(&bdrv_snapshot_access_drv);
130 }
131 
132 block_init(snapshot_access_init);
133