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
  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);