Re: [RFC PATCH] Sector 2 of non-embedded core.img: write early or patch later?

["Vesa Jääskeläinen" <chaac@nic.fi>]

Pavel Roskin wrote:
> Hello!
> 
> We have a serious problem with installing onto partitions (e.g.
> grub-install /dev/sda1) and drives with geometry that doesn't leave
> enough space for core.img to be embedded before the first partition.
> While it's not a desirable configuration, it should work, but it
> doesn't.
> 
> Either we should write sector 2 before the core.img is checked for
> readability or we should delay patching sector 2 in memory until the
> verification is done.  Otherwise, the verification will fail.
> 
> Delayed patching changes nothing in terms of I/O but needs a longer
> patch and won't scale well if we want to put more information into
> sector 2, as we'll need to cache more data.

Why not make a structure that holds every modification information that 
needs to be done ("configuration block"). And then you provide core.img 
and variable filled with configuration information to patch function 
that modifies core.img properly. This way you only need to write this once.

With this you can either modify compare or patch two copies of the 
images with same configuration information.