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_of_bds, 32 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, 33 false, errp); 34 if (!bs->file) { 35 return -EINVAL; 36 } 37 38 bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED | 39 (BDRV_REQ_FUA & bs->file->bs->supported_write_flags); 40 41 bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED | 42 ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) & 43 bs->file->bs->supported_zero_flags); 44 45 return 0; 46 } 47 48 49 #define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \ 50 | BLK_PERM_WRITE \ 51 | BLK_PERM_RESIZE) 52 #define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH) 53 54 static void cor_child_perm(BlockDriverState *bs, BdrvChild *c, 55 BdrvChildRole role, 56 BlockReopenQueue *reopen_queue, 57 uint64_t perm, uint64_t shared, 58 uint64_t *nperm, uint64_t *nshared) 59 { 60 *nperm = perm & PERM_PASSTHROUGH; 61 *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED; 62 63 /* We must not request write permissions for an inactive node, the child 64 * cannot provide it. */ 65 if (!(bs->open_flags & BDRV_O_INACTIVE)) { 66 *nperm |= BLK_PERM_WRITE_UNCHANGED; 67 } 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_preadv(BlockDriverState *bs, 78 uint64_t offset, uint64_t bytes, 79 QEMUIOVector *qiov, int flags) 80 { 81 return bdrv_co_preadv(bs->file, offset, bytes, qiov, 82 flags | BDRV_REQ_COPY_ON_READ); 83 } 84 85 86 static int coroutine_fn cor_co_pwritev(BlockDriverState *bs, 87 uint64_t offset, uint64_t bytes, 88 QEMUIOVector *qiov, int flags) 89 { 90 91 return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags); 92 } 93 94 95 static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs, 96 int64_t offset, int bytes, 97 BdrvRequestFlags flags) 98 { 99 return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags); 100 } 101 102 103 static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs, 104 int64_t offset, int bytes) 105 { 106 return bdrv_co_pdiscard(bs->file, offset, bytes); 107 } 108 109 110 static int coroutine_fn cor_co_pwritev_compressed(BlockDriverState *bs, 111 uint64_t offset, 112 uint64_t bytes, 113 QEMUIOVector *qiov) 114 { 115 return bdrv_co_pwritev(bs->file, offset, bytes, qiov, 116 BDRV_REQ_WRITE_COMPRESSED); 117 } 118 119 120 static void cor_eject(BlockDriverState *bs, bool eject_flag) 121 { 122 bdrv_eject(bs->file->bs, eject_flag); 123 } 124 125 126 static void cor_lock_medium(BlockDriverState *bs, bool locked) 127 { 128 bdrv_lock_medium(bs->file->bs, locked); 129 } 130 131 132 static BlockDriver bdrv_copy_on_read = { 133 .format_name = "copy-on-read", 134 135 .bdrv_open = cor_open, 136 .bdrv_child_perm = cor_child_perm, 137 138 .bdrv_getlength = cor_getlength, 139 140 .bdrv_co_preadv = cor_co_preadv, 141 .bdrv_co_pwritev = cor_co_pwritev, 142 .bdrv_co_pwrite_zeroes = cor_co_pwrite_zeroes, 143 .bdrv_co_pdiscard = cor_co_pdiscard, 144 .bdrv_co_pwritev_compressed = cor_co_pwritev_compressed, 145 146 .bdrv_eject = cor_eject, 147 .bdrv_lock_medium = cor_lock_medium, 148 149 .has_variable_length = true, 150 .is_filter = true, 151 }; 152 153 static void bdrv_copy_on_read_init(void) 154 { 155 bdrv_register(&bdrv_copy_on_read); 156 } 157 158 block_init(bdrv_copy_on_read_init); 159