block/copy-on-read.c

   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);