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/*
* Copy-on-read filter block driver
*
* Copyright (c) 2018 Red Hat, Inc.
*
* Author:
* Max Reitz <mreitz@redhat.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 or
* (at your option) version 3 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include "qemu/osdep.h"
#include "block/block_int.h"
#include "qemu/module.h"
static int cor_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file, false,
errp);
if (!bs->file) {
return -EINVAL;
}
bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
(BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
bs->file->bs->supported_zero_flags);
return 0;
}
#define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \
| BLK_PERM_WRITE \
| BLK_PERM_RESIZE)
#define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH)
static void cor_child_perm(BlockDriverState *bs, BdrvChild *c,
const BdrvChildClass *child_class,
BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
*nperm = perm & PERM_PASSTHROUGH;
*nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
/* We must not request write permissions for an inactive node, the child
* cannot provide it. */
if (!(bs->open_flags & BDRV_O_INACTIVE)) {
*nperm |= BLK_PERM_WRITE_UNCHANGED;
}
}
static int64_t cor_getlength(BlockDriverState *bs)
{
return bdrv_getlength(bs->file->bs);
}
static int coroutine_fn cor_co_preadv(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
return bdrv_co_preadv(bs->file, offset, bytes, qiov,
flags | BDRV_REQ_COPY_ON_READ);
}
static int coroutine_fn cor_co_pwritev(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
}
static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int bytes,
BdrvRequestFlags flags)
{
return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
}
static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs,
int64_t offset, int bytes)
{
return bdrv_co_pdiscard(bs->file, offset, bytes);
}
static void cor_eject(BlockDriverState *bs, bool eject_flag)
{
bdrv_eject(bs->file->bs, eject_flag);
}
static void cor_lock_medium(BlockDriverState *bs, bool locked)
{
bdrv_lock_medium(bs->file->bs, locked);
}
static BlockDriver bdrv_copy_on_read = {
.format_name = "copy-on-read",
.bdrv_open = cor_open,
.bdrv_child_perm = cor_child_perm,
.bdrv_getlength = cor_getlength,
.bdrv_co_preadv = cor_co_preadv,
.bdrv_co_pwritev = cor_co_pwritev,
.bdrv_co_pwrite_zeroes = cor_co_pwrite_zeroes,
.bdrv_co_pdiscard = cor_co_pdiscard,
.bdrv_eject = cor_eject,
.bdrv_lock_medium = cor_lock_medium,
.bdrv_co_block_status = bdrv_co_block_status_from_file,
.has_variable_length = true,
.is_filter = true,
};
static void bdrv_copy_on_read_init(void)
{
bdrv_register(&bdrv_copy_on_read);
}
block_init(bdrv_copy_on_read_init);
|
