0fd05c8d80
Add a parameter that enables discard-after-copy. That is mostly useful in "push backup with fleecing" scheme, when source is snapshot-access format driver node, based on copy-before-write filter snapshot-access API: [guest] [snapshot-access] ~~ blockdev-backup ~~> [backup target] | | | root | file v v [copy-before-write] | | | file | target v v [active disk] [temp.img] In this case discard-after-copy does two things: - discard data in temp.img to save disk space - avoid further copy-before-write operation in discarded area Note that we have to declare WRITE permission on source in copy-before-write filter, for discard to work. Still we can't take it unconditionally, as it will break normal backup from RO source. So, we have to add a parameter and pass it thorough bdrv_open flags. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Reviewed-by: Fiona Ebner <f.ebner@proxmox.com> Tested-by: Fiona Ebner <f.ebner@proxmox.com> Acked-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20240313152822.626493-5-vsementsov@yandex-team.ru> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
48 lines
1.6 KiB
C
48 lines
1.6 KiB
C
/*
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* copy-before-write 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) 2018-2021 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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#ifndef COPY_BEFORE_WRITE_H
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#define COPY_BEFORE_WRITE_H
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#include "block/block_int.h"
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#include "block/block-copy.h"
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/*
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* Global state (GS) API. These functions run under the BQL.
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*
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* See include/block/block-global-state.h for more information about
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* the GS API.
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*/
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BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
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BlockDriverState *target,
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const char *filter_node_name,
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bool discard_source,
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BlockCopyState **bcs,
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Error **errp);
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void bdrv_cbw_drop(BlockDriverState *bs);
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#endif /* COPY_BEFORE_WRITE_H */
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