LXR qemu/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
  27static 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 &
  38                                    bs->file->bs->supported_write_flags);
  39
  40    bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
  41                               ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP) &
  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
  53static 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    if (c == NULL) {
  60        *nperm = (perm & PERM_PASSTHROUGH) | BLK_PERM_WRITE_UNCHANGED;
  61        *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
  62        return;
  63    }
  64
  65    *nperm = (perm & PERM_PASSTHROUGH) |
  66             (c->perm & PERM_UNCHANGED);
  67    *nshared = (shared & PERM_PASSTHROUGH) |
  68               (c->shared_perm & PERM_UNCHANGED);
  69}
  70
  71
  72static int64_t cor_getlength(BlockDriverState *bs)
  73{
  74    return bdrv_getlength(bs->file->bs);
  75}
  76
  77
  78static int coroutine_fn cor_co_truncate(BlockDriverState *bs, int64_t offset,
  79                                        PreallocMode prealloc, Error **errp)
  80{
  81    return bdrv_co_truncate(bs->file, offset, prealloc, errp);
  82}
  83
  84
  85static int coroutine_fn cor_co_preadv(BlockDriverState *bs,
  86                                      uint64_t offset, uint64_t bytes,
  87                                      QEMUIOVector *qiov, int flags)
  88{
  89    return bdrv_co_preadv(bs->file, offset, bytes, qiov,
  90                          flags | BDRV_REQ_COPY_ON_READ);
  91}
  92
  93
  94static int coroutine_fn cor_co_pwritev(BlockDriverState *bs,
  95                                       uint64_t offset, uint64_t bytes,
  96                                       QEMUIOVector *qiov, int flags)
  97{
  98
  99    return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
 100}
 101
 102
 103static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs,
 104                                             int64_t offset, int bytes,
 105                                             BdrvRequestFlags flags)
 106{
 107    return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
 108}
 109
 110
 111static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs,
 112                                        int64_t offset, int bytes)
 113{
 114    return bdrv_co_pdiscard(bs->file, offset, bytes);
 115}
 116
 117
 118static void cor_eject(BlockDriverState *bs, bool eject_flag)
 119{
 120    bdrv_eject(bs->file->bs, eject_flag);
 121}
 122
 123
 124static void cor_lock_medium(BlockDriverState *bs, bool locked)
 125{
 126    bdrv_lock_medium(bs->file->bs, locked);
 127}
 128
 129
 130static bool cor_recurse_is_first_non_filter(BlockDriverState *bs,
 131                                            BlockDriverState *candidate)
 132{
 133    return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate);
 134}
 135
 136
 137BlockDriver bdrv_copy_on_read = {
 138    .format_name                        = "copy-on-read",
 139
 140    .bdrv_open                          = cor_open,
 141    .bdrv_child_perm                    = cor_child_perm,
 142
 143    .bdrv_getlength                     = cor_getlength,
 144    .bdrv_co_truncate                   = cor_co_truncate,
 145
 146    .bdrv_co_preadv                     = cor_co_preadv,
 147    .bdrv_co_pwritev                    = cor_co_pwritev,
 148    .bdrv_co_pwrite_zeroes              = cor_co_pwrite_zeroes,
 149    .bdrv_co_pdiscard                   = cor_co_pdiscard,
 150
 151    .bdrv_eject                         = cor_eject,
 152    .bdrv_lock_medium                   = cor_lock_medium,
 153
 154    .bdrv_co_block_status               = bdrv_co_block_status_from_file,
 155
 156    .bdrv_recurse_is_first_non_filter   = cor_recurse_is_first_non_filter,
 157
 158    .has_variable_length                = true,
 159    .is_filter                          = true,
 160};
 161
 162static void bdrv_copy_on_read_init(void)
 163{
 164    bdrv_register(&bdrv_copy_on_read);
 165}
 166
 167block_init(bdrv_copy_on_read_init);
 168