[rhinstaller/blivet/pulls/265 master] Add more class methods for better use of metadata

vpodzime installerbot-noreply at redhat.com
Mon Nov 2 14:02:48 UTC 2015


> @@ -179,12 +179,64 @@ def freeSpaceEstimate(cls, device_size):
>              with size ``device_size``.
>              This is more guess then precise number.
>  
> +            .. note::
> +
> +                This is more guess then precise number. To get precise
> +                space taken the FS must provide this number to us.
> +
>              :param device_size: original device size
> -            :type device_size: ``Size`` object
> +            :type device_size: :class:`~.size.Size` object
>              :return: estimated free size after format
> +            :rtype: :class:`~.size.Size`
>          """
>          return device_size * cls._MetadataSizeFactor
>  
> +    @classmethod
> +    def deviceSizeWithUsableSpace(cls, usable_size):
> +        """ Get device size we need to get ``usable_size`` on the device.
> +            This calculation will add metadata to usable device on the FS.
> +
> +            .. note::
> +
> +                This is more guess then precise number. To get precise
> +                space taken the FS must provide this number to us.
> +
> +            :param usable_size: how much usable size we want on newly created device
> +            :type usable_size: :class:`~.size.Size` object
> +            :return: estimated size of the device which will have given amount of
> +                ``usable_size``
> +            :rtype: :class:`~.size.Size`
> +        """
> +        # to get usable size without metadata we will use
> +        # usable_size = device_size * _MetadataSizeFactor
> +        # we can change this to get device size with required usable_size
> +        # device_size = usable_size / _MetadataSizeFactor
> +        return Size(Decimal(usable_size) / Decimal(cls._MetadataSizeFactor))

I see everybody has the same first wrong idea about the computation. :) I must say I don't see too much sense in returning the metadata size as it's not really useful for anything else than adding it to the requested size and getting the required size. 

-- 
To view this pull request on github, visit https://github.com/rhinstaller/blivet/pull/265#discussion_r43630389


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