290 lines
8.6 KiB
C
290 lines
8.6 KiB
C
/*
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* backup-top filter driver
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*
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* The driver performs Copy-Before-Write (CBW) operation: it is injected above
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* some node, and before each write it copies _old_ data to the target node.
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*
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* Copyright (c) 2018-2019 Virtuozzo International GmbH.
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*
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* Author:
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* Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "qemu/osdep.h"
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#include "sysemu/block-backend.h"
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#include "qemu/cutils.h"
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#include "qapi/error.h"
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#include "block/block_int.h"
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#include "block/qdict.h"
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#include "block/block-copy.h"
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#include "block/backup-top.h"
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typedef struct BDRVBackupTopState {
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BlockCopyState *bcs;
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BdrvChild *target;
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bool active;
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int64_t cluster_size;
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} BDRVBackupTopState;
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static coroutine_fn int backup_top_co_preadv(
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BlockDriverState *bs, uint64_t offset, uint64_t bytes,
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QEMUIOVector *qiov, int flags)
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{
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return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
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}
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static coroutine_fn int backup_top_cbw(BlockDriverState *bs, uint64_t offset,
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uint64_t bytes, BdrvRequestFlags flags)
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{
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BDRVBackupTopState *s = bs->opaque;
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uint64_t off, end;
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if (flags & BDRV_REQ_WRITE_UNCHANGED) {
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return 0;
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}
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off = QEMU_ALIGN_DOWN(offset, s->cluster_size);
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end = QEMU_ALIGN_UP(offset + bytes, s->cluster_size);
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return block_copy(s->bcs, off, end - off, NULL);
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}
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static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs,
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int64_t offset, int bytes)
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{
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int ret = backup_top_cbw(bs, offset, bytes, 0);
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if (ret < 0) {
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return ret;
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}
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return bdrv_co_pdiscard(bs->backing, offset, bytes);
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}
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static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs,
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int64_t offset, int bytes, BdrvRequestFlags flags)
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{
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int ret = backup_top_cbw(bs, offset, bytes, flags);
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if (ret < 0) {
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return ret;
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}
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return bdrv_co_pwrite_zeroes(bs->backing, offset, bytes, flags);
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}
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static coroutine_fn int backup_top_co_pwritev(BlockDriverState *bs,
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uint64_t offset,
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uint64_t bytes,
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QEMUIOVector *qiov, int flags)
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{
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int ret = backup_top_cbw(bs, offset, bytes, flags);
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if (ret < 0) {
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return ret;
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}
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return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
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}
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static int coroutine_fn backup_top_co_flush(BlockDriverState *bs)
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{
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if (!bs->backing) {
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return 0;
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}
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return bdrv_co_flush(bs->backing->bs);
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}
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static void backup_top_refresh_filename(BlockDriverState *bs)
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{
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if (bs->backing == NULL) {
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/*
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* we can be here after failed bdrv_attach_child in
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* bdrv_set_backing_hd
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*/
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return;
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}
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pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
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bs->backing->bs->filename);
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}
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static void backup_top_child_perm(BlockDriverState *bs, BdrvChild *c,
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BdrvChildRole role,
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BlockReopenQueue *reopen_queue,
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uint64_t perm, uint64_t shared,
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uint64_t *nperm, uint64_t *nshared)
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{
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BDRVBackupTopState *s = bs->opaque;
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if (!s->active) {
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/*
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* The filter node may be in process of bdrv_append(), which firstly do
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* bdrv_set_backing_hd() and then bdrv_replace_node(). This means that
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* we can't unshare BLK_PERM_WRITE during bdrv_append() operation. So,
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* let's require nothing during bdrv_append() and refresh permissions
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* after it (see bdrv_backup_top_append()).
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*/
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*nperm = 0;
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*nshared = BLK_PERM_ALL;
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return;
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}
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if (!(role & BDRV_CHILD_FILTERED)) {
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/*
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* Target child
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*
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* Share write to target (child_file), to not interfere
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* with guest writes to its disk which may be in target backing chain.
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* Can't resize during a backup block job because we check the size
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* only upfront.
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*/
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*nshared = BLK_PERM_ALL & ~BLK_PERM_RESIZE;
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*nperm = BLK_PERM_WRITE;
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} else {
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/* Source child */
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bdrv_default_perms(bs, c, role, reopen_queue,
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perm, shared, nperm, nshared);
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if (perm & BLK_PERM_WRITE) {
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*nperm = *nperm | BLK_PERM_CONSISTENT_READ;
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}
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*nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
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}
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}
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BlockDriver bdrv_backup_top_filter = {
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.format_name = "backup-top",
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.instance_size = sizeof(BDRVBackupTopState),
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.bdrv_co_preadv = backup_top_co_preadv,
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.bdrv_co_pwritev = backup_top_co_pwritev,
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.bdrv_co_pwrite_zeroes = backup_top_co_pwrite_zeroes,
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.bdrv_co_pdiscard = backup_top_co_pdiscard,
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.bdrv_co_flush = backup_top_co_flush,
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.bdrv_co_block_status = bdrv_co_block_status_from_backing,
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.bdrv_refresh_filename = backup_top_refresh_filename,
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.bdrv_child_perm = backup_top_child_perm,
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.is_filter = true,
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};
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BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
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BlockDriverState *target,
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const char *filter_node_name,
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uint64_t cluster_size,
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BdrvRequestFlags write_flags,
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BlockCopyState **bcs,
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Error **errp)
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{
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Error *local_err = NULL;
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BDRVBackupTopState *state;
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BlockDriverState *top;
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bool appended = false;
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assert(source->total_sectors == target->total_sectors);
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top = bdrv_new_open_driver(&bdrv_backup_top_filter, filter_node_name,
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BDRV_O_RDWR, errp);
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if (!top) {
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return NULL;
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}
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state = top->opaque;
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top->total_sectors = source->total_sectors;
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top->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
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(BDRV_REQ_FUA & source->supported_write_flags);
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top->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
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((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
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source->supported_zero_flags);
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bdrv_ref(target);
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state->target = bdrv_attach_child(top, target, "target", &child_of_bds,
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BDRV_CHILD_DATA, errp);
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if (!state->target) {
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bdrv_unref(target);
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bdrv_unref(top);
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return NULL;
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}
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bdrv_drained_begin(source);
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bdrv_ref(top);
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bdrv_append(top, source, &local_err);
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if (local_err) {
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error_prepend(&local_err, "Cannot append backup-top filter: ");
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goto fail;
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}
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appended = true;
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/*
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* bdrv_append() finished successfully, now we can require permissions
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* we want.
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*/
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state->active = true;
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bdrv_child_refresh_perms(top, top->backing, &local_err);
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if (local_err) {
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error_prepend(&local_err,
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"Cannot set permissions for backup-top filter: ");
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goto fail;
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}
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state->cluster_size = cluster_size;
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state->bcs = block_copy_state_new(top->backing, state->target,
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cluster_size, write_flags, &local_err);
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if (local_err) {
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error_prepend(&local_err, "Cannot create block-copy-state: ");
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goto fail;
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}
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*bcs = state->bcs;
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bdrv_drained_end(source);
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return top;
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fail:
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if (appended) {
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state->active = false;
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bdrv_backup_top_drop(top);
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} else {
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bdrv_unref(top);
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}
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bdrv_drained_end(source);
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error_propagate(errp, local_err);
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return NULL;
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}
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void bdrv_backup_top_drop(BlockDriverState *bs)
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{
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BDRVBackupTopState *s = bs->opaque;
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bdrv_drained_begin(bs);
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block_copy_state_free(s->bcs);
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s->active = false;
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bdrv_child_refresh_perms(bs, bs->backing, &error_abort);
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bdrv_replace_node(bs, backing_bs(bs), &error_abort);
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bdrv_set_backing_hd(bs, NULL, &error_abort);
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bdrv_drained_end(bs);
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bdrv_unref(bs);
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}
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