289 lines
8.7 KiB
C
289 lines
8.7 KiB
C
|
/*
|
||
|
|
* 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 "qapi/qmp/qdict.h"
|
||
|
|
#include "block/copy-on-read.h"
|
||
|
|
|
||
|
|
|
||
|
|
typedef struct BDRVStateCOR {
|
||
|
|
BlockDriverState *bottom_bs;
|
||
|
|
bool chain_frozen;
|
||
|
|
} BDRVStateCOR;
|
||
|
|
|
||
|
|
|
||
|
|
static int cor_open(BlockDriverState *bs, QDict *options, int flags,
|
||
|
|
Error **errp)
|
||
|
|
{
|
||
|
|
BlockDriverState *bottom_bs = NULL;
|
||
|
|
BDRVStateCOR *state = bs->opaque;
|
||
|
|
/* Find a bottom node name, if any */
|
||
|
|
const char *bottom_node = qdict_get_try_str(options, "bottom");
|
||
|
|
|
||
|
|
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_read_flags = BDRV_REQ_PREFETCH;
|
||
|
|
|
||
|
|
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);
|
||
|
|
|
||
|
|
if (bottom_node) {
|
||
|
|
bottom_bs = bdrv_find_node(bottom_node);
|
||
|
|
if (!bottom_bs) {
|
||
|
|
error_setg(errp, "Bottom node '%s' not found", bottom_node);
|
||
|
|
qdict_del(options, "bottom");
|
||
|
|
return -EINVAL;
|
||
|
|
}
|
||
|
|
qdict_del(options, "bottom");
|
||
|
|
|
||
|
|
if (!bottom_bs->drv) {
|
||
|
|
error_setg(errp, "Bottom node '%s' not opened", bottom_node);
|
||
|
|
return -EINVAL;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (bottom_bs->drv->is_filter) {
|
||
|
|
error_setg(errp, "Bottom node '%s' is a filter", bottom_node);
|
||
|
|
return -EINVAL;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (bdrv_freeze_backing_chain(bs, bottom_bs, errp) < 0) {
|
||
|
|
return -EINVAL;
|
||
|
|
}
|
||
|
|
state->chain_frozen = true;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* We do freeze the chain, so it shouldn't be removed. Still, storing a
|
||
|
|
* pointer worth bdrv_ref().
|
||
|
|
*/
|
||
|
|
bdrv_ref(bottom_bs);
|
||
|
|
}
|
||
|
|
state->bottom_bs = bottom_bs;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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)
|
||
|
|
{
|
||
|
|
*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,
|
||
|
|
int64_t offset, int64_t bytes,
|
||
|
|
QEMUIOVector *qiov,
|
||
|
|
size_t qiov_offset,
|
||
|
|
BdrvRequestFlags flags)
|
||
|
|
{
|
||
|
|
int64_t n;
|
||
|
|
int local_flags;
|
||
|
|
int ret;
|
||
|
|
BDRVStateCOR *state = bs->opaque;
|
||
|
|
|
||
|
|
if (!state->bottom_bs) {
|
||
|
|
return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
|
||
|
|
flags | BDRV_REQ_COPY_ON_READ);
|
||
|
|
}
|
||
|
|
|
||
|
|
while (bytes) {
|
||
|
|
local_flags = flags;
|
||
|
|
|
||
|
|
/* In case of failure, try to copy-on-read anyway */
|
||
|
|
ret = bdrv_is_allocated(bs->file->bs, offset, bytes, &n);
|
||
|
|
if (ret <= 0) {
|
||
|
|
ret = bdrv_is_allocated_above(bdrv_backing_chain_next(bs->file->bs),
|
||
|
|
state->bottom_bs, true, offset,
|
||
|
|
n, &n);
|
||
|
|
if (ret > 0 || ret < 0) {
|
||
|
|
local_flags |= BDRV_REQ_COPY_ON_READ;
|
||
|
|
}
|
||
|
|
/* Finish earlier if the end of a backing file has been reached */
|
||
|
|
if (n == 0) {
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Skip if neither read nor write are needed */
|
||
|
|
if ((local_flags & (BDRV_REQ_PREFETCH | BDRV_REQ_COPY_ON_READ)) !=
|
||
|
|
BDRV_REQ_PREFETCH) {
|
||
|
|
ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset,
|
||
|
|
local_flags);
|
||
|
|
if (ret < 0) {
|
||
|
|
return ret;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
offset += n;
|
||
|
|
qiov_offset += n;
|
||
|
|
bytes -= n;
|
||
|
|
}
|
||
|
|
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
static int coroutine_fn cor_co_pwritev_part(BlockDriverState *bs,
|
||
|
|
int64_t offset,
|
||
|
|
int64_t bytes,
|
||
|
|
QEMUIOVector *qiov,
|
||
|
|
size_t qiov_offset,
|
||
|
|
BdrvRequestFlags 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, int64_t 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, int64_t bytes)
|
||
|
|
{
|
||
|
|
return bdrv_co_pdiscard(bs->file, offset, bytes);
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
static int coroutine_fn cor_co_pwritev_compressed(BlockDriverState *bs,
|
||
|
|
int64_t offset,
|
||
|
|
int64_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 void cor_close(BlockDriverState *bs)
|
||
|
|
{
|
||
|
|
BDRVStateCOR *s = bs->opaque;
|
||
|
|
|
||
|
|
if (s->chain_frozen) {
|
||
|
|
s->chain_frozen = false;
|
||
|
|
bdrv_unfreeze_backing_chain(bs, s->bottom_bs);
|
||
|
|
}
|
||
|
|
|
||
|
|
bdrv_unref(s->bottom_bs);
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
static BlockDriver bdrv_copy_on_read = {
|
||
|
|
.format_name = "copy-on-read",
|
||
|
|
.instance_size = sizeof(BDRVStateCOR),
|
||
|
|
|
||
|
|
.bdrv_open = cor_open,
|
||
|
|
.bdrv_close = cor_close,
|
||
|
|
.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)
|
||
|
|
{
|
||
|
|
BDRVStateCOR *s = cor_filter_bs->opaque;
|
||
|
|
|
||
|
|
/* unfreeze, as otherwise bdrv_replace_node() will fail */
|
||
|
|
if (s->chain_frozen) {
|
||
|
|
s->chain_frozen = false;
|
||
|
|
bdrv_unfreeze_backing_chain(cor_filter_bs, s->bottom_bs);
|
||
|
|
}
|
||
|
|
bdrv_drop_filter(cor_filter_bs, &error_abort);
|
||
|
|
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);
|