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 int coroutine_fn GRAPH_RDLOCK
snapshot_access_co_preadv_part(BlockDriverState * bs,int64_t offset,int64_t bytes,QEMUIOVector * qiov,size_t qiov_offset,BdrvRequestFlags flags)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 GRAPH_RDLOCK
snapshot_access_co_block_status(BlockDriverState * bs,bool want_zero,int64_t offset,int64_t bytes,int64_t * pnum,int64_t * map,BlockDriverState ** file)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 GRAPH_RDLOCK
snapshot_access_co_pdiscard(BlockDriverState * bs,int64_t offset,int64_t bytes)53 snapshot_access_co_pdiscard(BlockDriverState *bs, 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
snapshot_access_co_pwrite_zeroes(BlockDriverState * bs,int64_t offset,int64_t bytes,BdrvRequestFlags flags)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
snapshot_access_co_pwritev_part(BlockDriverState * bs,int64_t offset,int64_t bytes,QEMUIOVector * qiov,size_t qiov_offset,BdrvRequestFlags flags)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
snapshot_access_refresh_filename(BlockDriverState * bs)76 static void GRAPH_RDLOCK snapshot_access_refresh_filename(BlockDriverState *bs)
77 {
78 pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
79 bs->file->bs->filename);
80 }
81
snapshot_access_open(BlockDriverState * bs,QDict * options,int flags,Error ** errp)82 static int snapshot_access_open(BlockDriverState *bs, QDict *options, int flags,
83 Error **errp)
84 {
85 bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
86 BDRV_CHILD_DATA | BDRV_CHILD_PRIMARY,
87 false, errp);
88
89 GRAPH_RDLOCK_GUARD_MAINLOOP();
90
91 if (!bs->file) {
92 return -EINVAL;
93 }
94
95 bs->total_sectors = bs->file->bs->total_sectors;
96
97 return 0;
98 }
99
snapshot_access_child_perm(BlockDriverState * bs,BdrvChild * c,BdrvChildRole role,BlockReopenQueue * reopen_queue,uint64_t perm,uint64_t shared,uint64_t * nperm,uint64_t * nshared)100 static void snapshot_access_child_perm(BlockDriverState *bs, BdrvChild *c,
101 BdrvChildRole role,
102 BlockReopenQueue *reopen_queue,
103 uint64_t perm, uint64_t shared,
104 uint64_t *nperm, uint64_t *nshared)
105 {
106 /*
107 * Currently, we don't need any permissions. If bs->file provides
108 * snapshot-access API, we can use it.
109 */
110 *nperm = 0;
111 *nshared = BLK_PERM_ALL;
112 }
113
114 static BlockDriver bdrv_snapshot_access_drv = {
115 .format_name = "snapshot-access",
116
117 .bdrv_open = snapshot_access_open,
118
119 .bdrv_co_preadv_part = snapshot_access_co_preadv_part,
120 .bdrv_co_pwritev_part = snapshot_access_co_pwritev_part,
121 .bdrv_co_pwrite_zeroes = snapshot_access_co_pwrite_zeroes,
122 .bdrv_co_pdiscard = snapshot_access_co_pdiscard,
123 .bdrv_co_block_status = snapshot_access_co_block_status,
124
125 .bdrv_refresh_filename = snapshot_access_refresh_filename,
126
127 .bdrv_child_perm = snapshot_access_child_perm,
128 };
129
snapshot_access_init(void)130 static void snapshot_access_init(void)
131 {
132 bdrv_register(&bdrv_snapshot_access_drv);
133 }
134
135 block_init(snapshot_access_init);
136