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 #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 if (c == NULL) { 60 *nperm = (perm & PERM_PASSTHROUGH) | BLK_PERM_WRITE_UNCHANGED; 61 *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED; 62 return; 63 } 64 65 *nperm = (perm & PERM_PASSTHROUGH) | 66 (c->perm & PERM_UNCHANGED); 67 *nshared = (shared & PERM_PASSTHROUGH) | 68 (c->shared_perm & PERM_UNCHANGED); 69 } 70 71 72 static int64_t cor_getlength(BlockDriverState *bs) 73 { 74 return bdrv_getlength(bs->file->bs); 75 } 76 77 78 static int coroutine_fn cor_co_truncate(BlockDriverState *bs, int64_t offset, 79 PreallocMode prealloc, Error **errp) 80 { 81 return bdrv_co_truncate(bs->file, offset, prealloc, errp); 82 } 83 84 85 static int coroutine_fn cor_co_preadv(BlockDriverState *bs, 86 uint64_t offset, uint64_t bytes, 87 QEMUIOVector *qiov, int flags) 88 { 89 return bdrv_co_preadv(bs->file, offset, bytes, qiov, 90 flags | BDRV_REQ_COPY_ON_READ); 91 } 92 93 94 static int coroutine_fn cor_co_pwritev(BlockDriverState *bs, 95 uint64_t offset, uint64_t bytes, 96 QEMUIOVector *qiov, int flags) 97 { 98 99 return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags); 100 } 101 102 103 static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs, 104 int64_t offset, int bytes, 105 BdrvRequestFlags flags) 106 { 107 return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags); 108 } 109 110 111 static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs, 112 int64_t offset, int bytes) 113 { 114 return bdrv_co_pdiscard(bs->file, offset, bytes); 115 } 116 117 118 static void cor_eject(BlockDriverState *bs, bool eject_flag) 119 { 120 bdrv_eject(bs->file->bs, eject_flag); 121 } 122 123 124 static void cor_lock_medium(BlockDriverState *bs, bool locked) 125 { 126 bdrv_lock_medium(bs->file->bs, locked); 127 } 128 129 130 static bool cor_recurse_is_first_non_filter(BlockDriverState *bs, 131 BlockDriverState *candidate) 132 { 133 return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate); 134 } 135 136 137 BlockDriver bdrv_copy_on_read = { 138 .format_name = "copy-on-read", 139 140 .bdrv_open = cor_open, 141 .bdrv_child_perm = cor_child_perm, 142 143 .bdrv_getlength = cor_getlength, 144 .bdrv_co_truncate = cor_co_truncate, 145 146 .bdrv_co_preadv = cor_co_preadv, 147 .bdrv_co_pwritev = cor_co_pwritev, 148 .bdrv_co_pwrite_zeroes = cor_co_pwrite_zeroes, 149 .bdrv_co_pdiscard = cor_co_pdiscard, 150 151 .bdrv_eject = cor_eject, 152 .bdrv_lock_medium = cor_lock_medium, 153 154 .bdrv_co_block_status = bdrv_co_block_status_from_file, 155 156 .bdrv_recurse_is_first_non_filter = cor_recurse_is_first_non_filter, 157 158 .has_variable_length = true, 159 .is_filter = true, 160 }; 161 162 static void bdrv_copy_on_read_init(void) 163 { 164 bdrv_register(&bdrv_copy_on_read); 165 } 166 167 block_init(bdrv_copy_on_read_init); 168