[OE-core] [PATCH 3/3] wic: apply --extra-space + --overhead to squashfs

[Ed Bartosh]

On Fri, Sep 08, 2017 at 07:33:03PM +0200, Enrico Scholz wrote:
> From: Enrico Scholz <enrico.scholz at ensc.de>
> 
> The --extra-space and --overhead option did not had an effect to squashfs
> partitions.  Although squashfs is read-only, it can be useful to allocate
> more space for the on-disk partition to avoid repartitioning of the whole
> disk when a new (and larger) squashfs image is written on later updates.
> 

Is it possible to just use --size or --fixed-size in .wks to allocate
partition of certain size?

> Patch calls get_rootfs_size() *after* creating the image and truncates
> it then.
> 
> Signed-off-by: Enrico Scholz <enrico.scholz at ensc.de>
> ---
>  scripts/lib/wic/partition.py | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/scripts/lib/wic/partition.py b/scripts/lib/wic/partition.py
> index b623bb9..da651f8 100644
> --- a/scripts/lib/wic/partition.py
> +++ b/scripts/lib/wic/partition.py
> @@ -195,6 +195,17 @@ class Partition():
>                             "larger (%d kB) than its allowed size %d kB" %
>                             (self.mountpoint, self.size, self.fixed_size))
>  
> +    def __extend_rootfs_image(self, rootfs):

Do we really need to mangle name of this method?
Please, consider reading this for further details:
http://python.net/~goodger/projects/pycon/2007/idiomatic/handout.html#naming

As this function is not going to be used anywhere I'd just use this code
in prepare_rootfs_squashfs. It would be less generic, but much more
readable and understandable.

> +        """Enlarges the rootfs so that it fulfills size/overhead-factor
> +        constraints"""
> +
> +        sz = (os.stat(rootfs).st_size + 1023) // 1024
> +        pad_sz = self.get_rootfs_size(sz)
> +
> +        if pad_sz > sz:
> +            with open(rootfs, 'a') as f:
> +                os.ftruncate(f.fileno(), pad_sz * 1024)
> +
>      def prepare_rootfs(self, cr_workdir, oe_builddir, rootfs_dir,
>                         native_sysroot):
>          """
> @@ -338,6 +349,8 @@ class Partition():
>                         (rootfs_dir, rootfs, extraopts)
>          exec_native_cmd(squashfs_cmd, native_sysroot, pseudo=pseudo)
>  
> +        self.__extend_rootfs_image(rootfs)
> +
>      def prepare_empty_partition_ext(self, rootfs, oe_builddir,
>                                      native_sysroot):
>          """

--
Regards,
Ed