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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"
#include "qapi/error.h"
#include "block/copy-on-read.h"
typedef struct BDRVStateCOR {
bool active;
} BDRVStateCOR;
static int cor_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
BDRVStateCOR *state = bs->opaque;
bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
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);
state->active = true;
/*
* We don't need to call bdrv_child_refresh_perms() now as the permissions
* will be updated later when the filter node gets its parent.
*/
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,
BdrvChildRole role,
BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
BDRVStateCOR *s = bs->opaque;
if (!s->active) {
/*
* While the filter is being removed
*/
*nperm = 0;
*nshared = BLK_PERM_ALL;
return;
}
*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_part(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov,
size_t qiov_offset,
int flags)
{
return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
flags | BDRV_REQ_COPY_ON_READ);
}
static int coroutine_fn cor_co_pwritev_part(BlockDriverState *bs,
uint64_t offset,
uint64_t bytes,
QEMUIOVector *qiov,
size_t qiov_offset, int flags)
{
return bdrv_co_pwritev_part(bs->file, offset, bytes, qiov, qiov_offset,
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 int coroutine_fn cor_co_pwritev_compressed(BlockDriverState *bs,
uint64_t offset,
uint64_t bytes,
QEMUIOVector *qiov)
{
return bdrv_co_pwritev(bs->file, offset, bytes, qiov,
BDRV_REQ_WRITE_COMPRESSED);
}
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",
.instance_size = sizeof(BDRVStateCOR),
.bdrv_open = cor_open,
.bdrv_child_perm = cor_child_perm,
.bdrv_getlength = cor_getlength,
.bdrv_co_preadv_part = cor_co_preadv_part,
.bdrv_co_pwritev_part = cor_co_pwritev_part,
.bdrv_co_pwrite_zeroes = cor_co_pwrite_zeroes,
.bdrv_co_pdiscard = cor_co_pdiscard,
.bdrv_co_pwritev_compressed = cor_co_pwritev_compressed,
.bdrv_eject = cor_eject,
.bdrv_lock_medium = cor_lock_medium,
.has_variable_length = true,
.is_filter = true,
};
void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs)
{
BdrvChild *child;
BlockDriverState *bs;
BDRVStateCOR *s = cor_filter_bs->opaque;
child = bdrv_filter_child(cor_filter_bs);
if (!child) {
return;
}
bs = child->bs;
/* Retain the BDS until we complete the graph change. */
bdrv_ref(bs);
/* Hold a guest back from writing while permissions are being reset. */
bdrv_drained_begin(bs);
/* Drop permissions before the graph change. */
s->active = false;
bdrv_child_refresh_perms(cor_filter_bs, child, &error_abort);
bdrv_replace_node(cor_filter_bs, bs, &error_abort);
bdrv_drained_end(bs);
bdrv_unref(bs);
bdrv_unref(cor_filter_bs);
}
static void bdrv_copy_on_read_init(void)
{
bdrv_register(&bdrv_copy_on_read);
}
block_init(bdrv_copy_on_read_init);
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