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_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
  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    *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
  70static int64_t cor_getlength(BlockDriverState *bs)
  71{
  72    return bdrv_getlength(bs->file->bs);
  73}
  74
  75
  76static int coroutine_fn cor_co_preadv(BlockDriverState *bs,
  77                                      uint64_t offset, uint64_t bytes,
  78                                      QEMUIOVector *qiov, int flags)
  79{
  80    return bdrv_co_preadv(bs->file, offset, bytes, qiov,
  81                          flags | BDRV_REQ_COPY_ON_READ);
  82}
  83
  84
  85static int coroutine_fn cor_co_pwritev(BlockDriverState *bs,
  86                                       uint64_t offset, uint64_t bytes,
  87                                       QEMUIOVector *qiov, int flags)
  88{
  89
  90    return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
  91}
  92
  93
  94static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs,
  95                                             int64_t offset, int bytes,
  96                                             BdrvRequestFlags flags)
  97{
  98    return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
  99}
 100
 101
 102static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs,
 103                                        int64_t offset, int bytes)
 104{
 105    return bdrv_co_pdiscard(bs->file, offset, bytes);
 106}
 107
 108
 109static void cor_eject(BlockDriverState *bs, bool eject_flag)
 110{
 111    bdrv_eject(bs->file->bs, eject_flag);
 112}
 113
 114
 115static void cor_lock_medium(BlockDriverState *bs, bool locked)
 116{
 117    bdrv_lock_medium(bs->file->bs, locked);
 118}
 119
 120
 121static bool cor_recurse_is_first_non_filter(BlockDriverState *bs,
 122                                            BlockDriverState *candidate)
 123{
 124    return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate);
 125}
 126
 127
 128static BlockDriver bdrv_copy_on_read = {
 129    .format_name                        = "copy-on-read",
 130
 131    .bdrv_open                          = cor_open,
 132    .bdrv_child_perm                    = cor_child_perm,
 133
 134    .bdrv_getlength                     = cor_getlength,
 135
 136    .bdrv_co_preadv                     = cor_co_preadv,
 137    .bdrv_co_pwritev                    = cor_co_pwritev,
 138    .bdrv_co_pwrite_zeroes              = cor_co_pwrite_zeroes,
 139    .bdrv_co_pdiscard                   = cor_co_pdiscard,
 140
 141    .bdrv_eject                         = cor_eject,
 142    .bdrv_lock_medium                   = cor_lock_medium,
 143
 144    .bdrv_co_block_status               = bdrv_co_block_status_from_file,
 145
 146    .bdrv_recurse_is_first_non_filter   = cor_recurse_is_first_non_filter,
 147
 148    .has_variable_length                = true,
 149    .is_filter                          = true,
 150};
 151
 152static void bdrv_copy_on_read_init(void)
 153{
 154    bdrv_register(&bdrv_copy_on_read);
 155}
 156
 157block_init(bdrv_copy_on_read_init);
 158