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>

1 files changed, 41 insertions, 0 deletions

diff --git a/block/backup-top.h b/block/backup-top.h
new file mode 100644
index 0000000000..e5cabfa197
--- /dev/null
+++ b/block/backup-top.h
@@ -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 */