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