[Libguestfs] qemu copyonread vs trimming?

[Richard W.M. Jones]

On Tue, Jul 27, 2021 at 05:55:57PM +0100, Richard W.M. Jones wrote:
>   -blockdev '{"driver":"nbd","server":{"type":"unix","path":"/tmp/nbdkit4IH9fV/socket"},"node-name":"libvirt-2-storage","cache":{"direct":false,"no-flush":true},"auto-read-only":true,"discard":"unmap"}' \
>   -blockdev '{"node-name":"libvirt-2-format","read-only":false,"discard":"unmap","cache":{"direct":false,"no-flush":true},"driver":"raw","file":"libvirt-2-storage"}' \
>   -blockdev '{"driver":"copy-on-read","node-name":"libvirt-CoR-sda","file":"libvirt-2-format"}' \

After discussion on IRC we believe the problem is a missing
discard:unmap attribute in this line.  There is a bug against libvirt
about this:

https://bugzilla.redhat.com/show_bug.cgi?id=1986509

Rich.

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