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 & 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
  52static 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
  71static int64_t cor_getlength(BlockDriverState *bs)
  72{
  73    return bdrv_getlength(bs->file->bs);
  74}
  75
  76
  77static 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
  84static 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
  93static 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
 102static 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
 110static 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
 117static void cor_eject(BlockDriverState *bs, bool eject_flag)
 118{
 119    bdrv_eject(bs->file->bs, eject_flag);
 120}
 121
 122
 123static void cor_lock_medium(BlockDriverState *bs, bool locked)
 124{
 125    bdrv_lock_medium(bs->file->bs, locked);
 126}
 127
 128
 129static 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
 136static 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
 161static void bdrv_copy_on_read_init(void)
 162{
 163    bdrv_register(&bdrv_copy_on_read);
 164}
 165
 166block_init(bdrv_copy_on_read_init);
 167