The storage pool code now attempts to disable COW by default on btrfs,
but management applications may wish to override this behaviour. Thus we
introduce a concept of storage pool features:
<features>
<cow state='yes|no'/>
</features>
If the <cow> feature policy is set, it will be enforced. It will always
return an hard error if COW cannot be explicitly set or unset.
Reviewed-by: Neal Gompa <ngompa13@gmail.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
