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