qemu/block/backup-top.c
Vladimir Sementsov-Ogievskiy b75d64b329 block/backup-top: drop .active
We don't need this workaround anymore: bdrv_append is already smart
enough and we can use new bdrv_drop_filter().

This commit efficiently reverts also recent 705dde27c6, which
checked .active on io path. Still it said that the problem should be
theoretical. And the logic of filter removement is changed anyway.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210428151804.439460-25-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2021-04-30 12:27:48 +02:00

254 lines
7.5 KiB
C

/*
* backup-top filter driver
*
* The driver performs Copy-Before-Write (CBW) operation: it is injected above
* some node, and before each write it copies _old_ data to the target node.
*
* Copyright (c) 2018-2019 Virtuozzo International GmbH.
*
* Author:
* Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.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 of the License, or
* (at your option) any later version.
*
* 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 "sysemu/block-backend.h"
#include "qemu/cutils.h"
#include "qapi/error.h"
#include "block/block_int.h"
#include "block/qdict.h"
#include "block/block-copy.h"
#include "block/backup-top.h"
typedef struct BDRVBackupTopState {
BlockCopyState *bcs;
BdrvChild *target;
int64_t cluster_size;
} BDRVBackupTopState;
static coroutine_fn int backup_top_co_preadv(
BlockDriverState *bs, uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
}
static coroutine_fn int backup_top_cbw(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, BdrvRequestFlags flags)
{
BDRVBackupTopState *s = bs->opaque;
uint64_t off, end;
if (flags & BDRV_REQ_WRITE_UNCHANGED) {
return 0;
}
off = QEMU_ALIGN_DOWN(offset, s->cluster_size);
end = QEMU_ALIGN_UP(offset + bytes, s->cluster_size);
return block_copy(s->bcs, off, end - off, true);
}
static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs,
int64_t offset, int bytes)
{
int ret = backup_top_cbw(bs, offset, bytes, 0);
if (ret < 0) {
return ret;
}
return bdrv_co_pdiscard(bs->backing, offset, bytes);
}
static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int bytes, BdrvRequestFlags flags)
{
int ret = backup_top_cbw(bs, offset, bytes, flags);
if (ret < 0) {
return ret;
}
return bdrv_co_pwrite_zeroes(bs->backing, offset, bytes, flags);
}
static coroutine_fn int backup_top_co_pwritev(BlockDriverState *bs,
uint64_t offset,
uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
int ret = backup_top_cbw(bs, offset, bytes, flags);
if (ret < 0) {
return ret;
}
return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
}
static int coroutine_fn backup_top_co_flush(BlockDriverState *bs)
{
if (!bs->backing) {
return 0;
}
return bdrv_co_flush(bs->backing->bs);
}
static void backup_top_refresh_filename(BlockDriverState *bs)
{
if (bs->backing == NULL) {
/*
* we can be here after failed bdrv_attach_child in
* bdrv_set_backing_hd
*/
return;
}
pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
bs->backing->bs->filename);
}
static void backup_top_child_perm(BlockDriverState *bs, BdrvChild *c,
BdrvChildRole role,
BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
if (!(role & BDRV_CHILD_FILTERED)) {
/*
* Target child
*
* Share write to target (child_file), to not interfere
* with guest writes to its disk which may be in target backing chain.
* Can't resize during a backup block job because we check the size
* only upfront.
*/
*nshared = BLK_PERM_ALL & ~BLK_PERM_RESIZE;
*nperm = BLK_PERM_WRITE;
} else {
/* Source child */
bdrv_default_perms(bs, c, role, reopen_queue,
perm, shared, nperm, nshared);
if (perm & BLK_PERM_WRITE) {
*nperm = *nperm | BLK_PERM_CONSISTENT_READ;
}
*nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
}
}
BlockDriver bdrv_backup_top_filter = {
.format_name = "backup-top",
.instance_size = sizeof(BDRVBackupTopState),
.bdrv_co_preadv = backup_top_co_preadv,
.bdrv_co_pwritev = backup_top_co_pwritev,
.bdrv_co_pwrite_zeroes = backup_top_co_pwrite_zeroes,
.bdrv_co_pdiscard = backup_top_co_pdiscard,
.bdrv_co_flush = backup_top_co_flush,
.bdrv_refresh_filename = backup_top_refresh_filename,
.bdrv_child_perm = backup_top_child_perm,
.is_filter = true,
};
BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
uint64_t cluster_size,
BackupPerf *perf,
BdrvRequestFlags write_flags,
BlockCopyState **bcs,
Error **errp)
{
ERRP_GUARD();
int ret;
BDRVBackupTopState *state;
BlockDriverState *top;
bool appended = false;
assert(source->total_sectors == target->total_sectors);
top = bdrv_new_open_driver(&bdrv_backup_top_filter, filter_node_name,
BDRV_O_RDWR, errp);
if (!top) {
return NULL;
}
state = top->opaque;
top->total_sectors = source->total_sectors;
top->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
(BDRV_REQ_FUA & source->supported_write_flags);
top->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
source->supported_zero_flags);
bdrv_ref(target);
state->target = bdrv_attach_child(top, target, "target", &child_of_bds,
BDRV_CHILD_DATA, errp);
if (!state->target) {
bdrv_unref(target);
bdrv_unref(top);
return NULL;
}
bdrv_drained_begin(source);
ret = bdrv_append(top, source, errp);
if (ret < 0) {
error_prepend(errp, "Cannot append backup-top filter: ");
goto fail;
}
appended = true;
state->cluster_size = cluster_size;
state->bcs = block_copy_state_new(top->backing, state->target,
cluster_size, perf->use_copy_range,
write_flags, errp);
if (!state->bcs) {
error_prepend(errp, "Cannot create block-copy-state: ");
goto fail;
}
*bcs = state->bcs;
bdrv_drained_end(source);
return top;
fail:
if (appended) {
bdrv_backup_top_drop(top);
} else {
bdrv_unref(top);
}
bdrv_drained_end(source);
return NULL;
}
void bdrv_backup_top_drop(BlockDriverState *bs)
{
BDRVBackupTopState *s = bs->opaque;
bdrv_drop_filter(bs, &error_abort);
block_copy_state_free(s->bcs);
bdrv_unref(bs);
}