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 26 27 static int cor_open(BlockDriverState *bs, QDict *options, int flags, 28 Error **errp) 29 { 30 bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file, false, 31 errp); 32 if (!bs->file) { 33 return -EINVAL; 34 } 35 36 bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED | 37 (BDRV_REQ_FUA & 38 bs->file->bs->supported_write_flags); 39 40 bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED | 41 ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP) & 42 bs->file->bs->supported_zero_flags); 43 44 return 0; 45 } 46 47 48 static void cor_close(BlockDriverState *bs) 49 { 50 } 51 52 53 #define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \ 54 | BLK_PERM_WRITE \ 55 | BLK_PERM_RESIZE) 56 #define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH) 57 58 static void cor_child_perm(BlockDriverState *bs, BdrvChild *c, 59 const BdrvChildRole *role, 60 BlockReopenQueue *reopen_queue, 61 uint64_t perm, uint64_t shared, 62 uint64_t *nperm, uint64_t *nshared) 63 { 64 if (c == NULL) { 65 *nperm = (perm & PERM_PASSTHROUGH) | BLK_PERM_WRITE_UNCHANGED; 66 *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED; 67 return; 68 } 69 70 *nperm = (perm & PERM_PASSTHROUGH) | 71 (c->perm & PERM_UNCHANGED); 72 *nshared = (shared & PERM_PASSTHROUGH) | 73 (c->shared_perm & PERM_UNCHANGED); 74 } 75 76 77 static int64_t cor_getlength(BlockDriverState *bs) 78 { 79 return bdrv_getlength(bs->file->bs); 80 } 81 82 83 static int coroutine_fn cor_co_truncate(BlockDriverState *bs, int64_t offset, 84 PreallocMode prealloc, Error **errp) 85 { 86 return bdrv_co_truncate(bs->file, offset, prealloc, errp); 87 } 88 89 90 static int coroutine_fn cor_co_preadv(BlockDriverState *bs, 91 uint64_t offset, uint64_t bytes, 92 QEMUIOVector *qiov, int flags) 93 { 94 return bdrv_co_preadv(bs->file, offset, bytes, qiov, 95 flags | BDRV_REQ_COPY_ON_READ); 96 } 97 98 99 static int coroutine_fn cor_co_pwritev(BlockDriverState *bs, 100 uint64_t offset, uint64_t bytes, 101 QEMUIOVector *qiov, int flags) 102 { 103 104 return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags); 105 } 106 107 108 static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs, 109 int64_t offset, int bytes, 110 BdrvRequestFlags flags) 111 { 112 return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags); 113 } 114 115 116 static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs, 117 int64_t offset, int bytes) 118 { 119 return bdrv_co_pdiscard(bs->file, offset, bytes); 120 } 121 122 123 static void cor_eject(BlockDriverState *bs, bool eject_flag) 124 { 125 bdrv_eject(bs->file->bs, eject_flag); 126 } 127 128 129 static void cor_lock_medium(BlockDriverState *bs, bool locked) 130 { 131 bdrv_lock_medium(bs->file->bs, locked); 132 } 133 134 135 static bool cor_recurse_is_first_non_filter(BlockDriverState *bs, 136 BlockDriverState *candidate) 137 { 138 return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate); 139 } 140 141 142 BlockDriver bdrv_copy_on_read = { 143 .format_name = "copy-on-read", 144 145 .bdrv_open = cor_open, 146 .bdrv_close = cor_close, 147 .bdrv_child_perm = cor_child_perm, 148 149 .bdrv_getlength = cor_getlength, 150 .bdrv_co_truncate = cor_co_truncate, 151 152 .bdrv_co_preadv = cor_co_preadv, 153 .bdrv_co_pwritev = cor_co_pwritev, 154 .bdrv_co_pwrite_zeroes = cor_co_pwrite_zeroes, 155 .bdrv_co_pdiscard = cor_co_pdiscard, 156 157 .bdrv_eject = cor_eject, 158 .bdrv_lock_medium = cor_lock_medium, 159 160 .bdrv_co_block_status = bdrv_co_block_status_from_file, 161 162 .bdrv_recurse_is_first_non_filter = cor_recurse_is_first_non_filter, 163 164 .has_variable_length = true, 165 .is_filter = true, 166 }; 167 168 static void bdrv_copy_on_read_init(void) 169 { 170 bdrv_register(&bdrv_copy_on_read); 171 } 172 173 block_init(bdrv_copy_on_read_init); 174