7990d2c99c
In the block layer functions that determine options for a child block device, it's a common pattern to either copy options from the parent's options or to set a default string if the option isn't explicitly set yet for the child. Provide convenience functions so that it becomes a one-liner for each option. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>