Resizing root file-system vs wedges

[Jared McNeill <jmcneill%invisible.ca@localhost>]

Hi folks --

I'm trying to add support for auto-detecting the boot device to the armv7 
and arm64 images. Seemed like the easiest way was to use GPT, wedges, and 
mount by name.

I've hit a few issues:

 - I need a reliable way to find the backing device for a given wedge so I
   can "gpt resizedisk" and "gpt resize" from an rc script. It looks like
   I can get this today with 'dkctl dk1 getwedgeinfo' but it doesn't look
   like the output is meant to be parsed.

 - Inconsistent / nonexistent support for mount by name in the system. The
   kernel wants "wedge:name", fstab wants "NAME=name", and none of the
   tools (gpt, dkctl, resize_ffs) I am using seem to accept a label at
   all.

 - DIOCMWEDGES fails if one of the partitions is opened. In this case it
   is the root partition, which is mounted read-only. It looks like the
   changes actually do get applied, but since the kernel doesn't see the
   changes, "resize_ffs -c" doesn't work until after I reboot.

Any suggestions?

Thanks,
Jared