1 | /* |
2 | * Copy-on-read filter block driver |
3 | * |
4 | * Copyright (c) 2018 Red Hat, Inc. |
5 | * |
6 | * Author: |
7 | * Max Reitz <mreitz@redhat.com> |
8 | * |
9 | * This program is free software; you can redistribute it and/or |
10 | * modify it under the terms of the GNU General Public License as |
11 | * published by the Free Software Foundation; either version 2 or |
12 | * (at your option) version 3 of the License. |
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 | #include "block/block_int.h" |
25 | #include "qemu/module.h" |
26 | |
27 | |
28 | static int cor_open(BlockDriverState *bs, QDict *options, int flags, |
29 | Error **errp) |
30 | { |
31 | bs->file = bdrv_open_child(NULL, options, "file" , bs, &child_file, false, |
32 | errp); |
33 | if (!bs->file) { |
34 | return -EINVAL; |
35 | } |
36 | |
37 | bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED | |
38 | (BDRV_REQ_FUA & bs->file->bs->supported_write_flags); |
39 | |
40 | bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED | |
41 | ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) & |
42 | bs->file->bs->supported_zero_flags); |
43 | |
44 | return 0; |
45 | } |
46 | |
47 | |
48 | #define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \ |
49 | | BLK_PERM_WRITE \ |
50 | | BLK_PERM_RESIZE) |
51 | #define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH) |
52 | |
53 | static void cor_child_perm(BlockDriverState *bs, BdrvChild *c, |
54 | const BdrvChildRole *role, |
55 | BlockReopenQueue *reopen_queue, |
56 | uint64_t perm, uint64_t shared, |
57 | uint64_t *nperm, uint64_t *nshared) |
58 | { |
59 | *nperm = perm & PERM_PASSTHROUGH; |
60 | *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED; |
61 | |
62 | /* We must not request write permissions for an inactive node, the child |
63 | * cannot provide it. */ |
64 | if (!(bs->open_flags & BDRV_O_INACTIVE)) { |
65 | *nperm |= BLK_PERM_WRITE_UNCHANGED; |
66 | } |
67 | } |
68 | |
69 | |
70 | static int64_t cor_getlength(BlockDriverState *bs) |
71 | { |
72 | return bdrv_getlength(bs->file->bs); |
73 | } |
74 | |
75 | |
76 | static int coroutine_fn cor_co_truncate(BlockDriverState *bs, int64_t offset, |
77 | PreallocMode prealloc, Error **errp) |
78 | { |
79 | return bdrv_co_truncate(bs->file, offset, prealloc, errp); |
80 | } |
81 | |
82 | |
83 | static int coroutine_fn cor_co_preadv(BlockDriverState *bs, |
84 | uint64_t offset, uint64_t bytes, |
85 | QEMUIOVector *qiov, int flags) |
86 | { |
87 | return bdrv_co_preadv(bs->file, offset, bytes, qiov, |
88 | flags | BDRV_REQ_COPY_ON_READ); |
89 | } |
90 | |
91 | |
92 | static int coroutine_fn cor_co_pwritev(BlockDriverState *bs, |
93 | uint64_t offset, uint64_t bytes, |
94 | QEMUIOVector *qiov, int flags) |
95 | { |
96 | |
97 | return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags); |
98 | } |
99 | |
100 | |
101 | static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs, |
102 | int64_t offset, int bytes, |
103 | BdrvRequestFlags flags) |
104 | { |
105 | return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags); |
106 | } |
107 | |
108 | |
109 | static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs, |
110 | int64_t offset, int bytes) |
111 | { |
112 | return bdrv_co_pdiscard(bs->file, offset, bytes); |
113 | } |
114 | |
115 | |
116 | static void cor_eject(BlockDriverState *bs, bool eject_flag) |
117 | { |
118 | bdrv_eject(bs->file->bs, eject_flag); |
119 | } |
120 | |
121 | |
122 | static void cor_lock_medium(BlockDriverState *bs, bool locked) |
123 | { |
124 | bdrv_lock_medium(bs->file->bs, locked); |
125 | } |
126 | |
127 | |
128 | static bool cor_recurse_is_first_non_filter(BlockDriverState *bs, |
129 | BlockDriverState *candidate) |
130 | { |
131 | return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate); |
132 | } |
133 | |
134 | |
135 | static BlockDriver bdrv_copy_on_read = { |
136 | .format_name = "copy-on-read" , |
137 | |
138 | .bdrv_open = cor_open, |
139 | .bdrv_child_perm = cor_child_perm, |
140 | |
141 | .bdrv_getlength = cor_getlength, |
142 | .bdrv_co_truncate = cor_co_truncate, |
143 | |
144 | .bdrv_co_preadv = cor_co_preadv, |
145 | .bdrv_co_pwritev = cor_co_pwritev, |
146 | .bdrv_co_pwrite_zeroes = cor_co_pwrite_zeroes, |
147 | .bdrv_co_pdiscard = cor_co_pdiscard, |
148 | |
149 | .bdrv_eject = cor_eject, |
150 | .bdrv_lock_medium = cor_lock_medium, |
151 | |
152 | .bdrv_co_block_status = bdrv_co_block_status_from_file, |
153 | |
154 | .bdrv_recurse_is_first_non_filter = cor_recurse_is_first_non_filter, |
155 | |
156 | .has_variable_length = true, |
157 | .is_filter = true, |
158 | }; |
159 | |
160 | static void bdrv_copy_on_read_init(void) |
161 | { |
162 | bdrv_register(&bdrv_copy_on_read); |
163 | } |
164 | |
165 | block_init(bdrv_copy_on_read_init); |
166 | |