block: introduce backup-top filter driver

Backup-top filter caches write operations and does copy-before-write
operations.

The driver will be used in backup instead of write-notifiers.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20191001131409.14202-5-vsementsov@virtuozzo.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2019-10-01 16:14:08 +03:00 committed by Max Reitz
parent 0f4b02b73e
commit 7df7868b96
3 changed files with 323 additions and 0 deletions

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@ -42,6 +42,7 @@ block-obj-y += block-copy.o
block-obj-y += crypto.o
block-obj-y += aio_task.o
block-obj-y += backup-top.o
common-obj-y += stream.o

281
block/backup-top.c Normal file
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@ -0,0 +1,281 @@
/*
* 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;
bool active;
} 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)
{
/*
* Here we'd like to use block_copy(), but block-copy need to be moved to
* use BdrvChildren to correctly use it in backup-top filter. It's a TODO.
*/
abort();
}
static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs,
int64_t offset, int bytes)
{
int ret = backup_top_cbw(bs, offset, bytes);
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);
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)
{
if (!(flags & BDRV_REQ_WRITE_UNCHANGED)) {
int ret = backup_top_cbw(bs, offset, bytes);
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,
const BdrvChildRole *role,
BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
BDRVBackupTopState *s = bs->opaque;
if (!s->active) {
/*
* The filter node may be in process of bdrv_append(), which firstly do
* bdrv_set_backing_hd() and then bdrv_replace_node(). This means that
* we can't unshare BLK_PERM_WRITE during bdrv_append() operation. So,
* let's require nothing during bdrv_append() and refresh permissions
* after it (see bdrv_backup_top_append()).
*/
*nperm = 0;
*nshared = BLK_PERM_ALL;
return;
}
if (role == &child_file) {
/*
* Target child
*
* Share write to target (child_file), to not interfere
* with guest writes to its disk which may be in target backing chain.
*/
*nshared = BLK_PERM_ALL;
*nperm = BLK_PERM_WRITE;
} else {
/* Source child */
bdrv_filter_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;
}
}
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_co_block_status = bdrv_co_block_status_from_backing,
.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,
BdrvRequestFlags write_flags,
BlockCopyState **bcs,
Error **errp)
{
Error *local_err = NULL;
BDRVBackupTopState *state;
BlockDriverState *top = bdrv_new_open_driver(&bdrv_backup_top_filter,
filter_node_name,
BDRV_O_RDWR, errp);
if (!top) {
return NULL;
}
top->total_sectors = source->total_sectors;
top->opaque = state = g_new0(BDRVBackupTopState, 1);
bdrv_ref(target);
state->target = bdrv_attach_child(top, target, "target", &child_file, errp);
if (!state->target) {
bdrv_unref(target);
bdrv_unref(top);
return NULL;
}
bdrv_drained_begin(source);
bdrv_ref(top);
bdrv_append(top, source, &local_err);
if (local_err) {
error_prepend(&local_err, "Cannot append backup-top filter: ");
goto append_failed;
}
/*
* bdrv_append() finished successfully, now we can require permissions
* we want.
*/
state->active = true;
bdrv_child_refresh_perms(top, top->backing, &local_err);
if (local_err) {
error_prepend(&local_err,
"Cannot set permissions for backup-top filter: ");
goto failed_after_append;
}
/*
* TODO: Create block-copy-state here (which will utilize @cluster_size and
* @write_flags parameters which are unused now). For this, block-copy
* should be refactored to use BdrvChildren.
*/
state->bcs = NULL;
if (!state->bcs) {
error_setg(&local_err, "Cannot create block-copy-state");
goto failed_after_append;
}
*bcs = state->bcs;
bdrv_drained_end(source);
return top;
failed_after_append:
state->active = false;
bdrv_backup_top_drop(top);
append_failed:
bdrv_drained_end(source);
bdrv_unref_child(top, state->target);
bdrv_unref(top);
error_propagate(errp, local_err);
return NULL;
}
void bdrv_backup_top_drop(BlockDriverState *bs)
{
BDRVBackupTopState *s = bs->opaque;
AioContext *aio_context = bdrv_get_aio_context(bs);
block_copy_state_free(s->bcs);
aio_context_acquire(aio_context);
bdrv_drained_begin(bs);
s->active = false;
bdrv_child_refresh_perms(bs, bs->backing, &error_abort);
bdrv_replace_node(bs, backing_bs(bs), &error_abort);
bdrv_set_backing_hd(bs, NULL, &error_abort);
bdrv_drained_end(bs);
bdrv_unref(bs);
aio_context_release(aio_context);
}

41
block/backup-top.h Normal file
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@ -0,0 +1,41 @@
/*
* 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/>.
*/
#ifndef BACKUP_TOP_H
#define BACKUP_TOP_H
#include "block/block_int.h"
#include "block/block-copy.h"
BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
uint64_t cluster_size,
BdrvRequestFlags write_flags,
BlockCopyState **bcs,
Error **errp);
void bdrv_backup_top_drop(BlockDriverState *bs);
#endif /* BACKUP_TOP_H */