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#include "qemu/module.h"
  26
  27
  28static 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
  54static 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
  71static int64_t cor_getlength(BlockDriverState *bs)
  72{
  73    return bdrv_getlength(bs->file->bs);
  74}
  75
  76
  77static 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
  86static 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
  95static 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
 103static 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
 110static void cor_eject(BlockDriverState *bs, bool eject_flag)
 111{
 112    bdrv_eject(bs->file->bs, eject_flag);
 113}
 114
 115
 116static void cor_lock_medium(BlockDriverState *bs, bool locked)
 117{
 118    bdrv_lock_medium(bs->file->bs, locked);
 119}
 120
 121
 122static BlockDriver bdrv_copy_on_read = {
 123    .format_name                        = "copy-on-read",
 124
 125    .bdrv_open                          = cor_open,
 126    .bdrv_child_perm                    = cor_child_perm,
 127
 128    .bdrv_getlength                     = cor_getlength,
 129
 130    .bdrv_co_preadv                     = cor_co_preadv,
 131    .bdrv_co_pwritev                    = cor_co_pwritev,
 132    .bdrv_co_pwrite_zeroes              = cor_co_pwrite_zeroes,
 133    .bdrv_co_pdiscard                   = cor_co_pdiscard,
 134
 135    .bdrv_eject                         = cor_eject,
 136    .bdrv_lock_medium                   = cor_lock_medium,
 137
 138    .bdrv_co_block_status               = bdrv_co_block_status_from_file,
 139
 140    .has_variable_length                = true,
 141    .is_filter                          = true,
 142};
 143
 144static void bdrv_copy_on_read_init(void)
 145{
 146    bdrv_register(&bdrv_copy_on_read);
 147}
 148
 149block_init(bdrv_copy_on_read_init);
 150