On 13.03.24 19:08, Markus Armbruster wrote:
Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru> writes:
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 <vsement...@yandex-team.ru>
Reviewed-by: Fiona Ebner <f.eb...@proxmox.com>
Tested-by: Fiona Ebner <f.eb...@proxmox.com>
[...]
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 1874f880a8..2ef52ae9a7 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1610,6 +1610,9 @@
# node specified by @drive. If this option is not given, a node
# name is autogenerated. (Since: 4.2)
#
+# @discard-source: Discard blocks on source which are already copied
"have been copied"?
Oh, right
+# to the target. (Since 9.1)
+#
# @x-perf: Performance options. (Since 6.0)
#
# Features:
@@ -1631,6 +1634,7 @@
'*on-target-error': 'BlockdevOnError',
'*auto-finalize': 'bool', '*auto-dismiss': 'bool',
'*filter-node-name': 'str',
+ '*discard-source': 'bool',
'*x-perf': { 'type': 'BackupPerf',
'features': [ 'unstable' ] } } }
QAPI schema
Acked-by: Markus Armbruster <arm...@redhat.com>
Thanks!
--
Best regards,
Vladimir
