> If the kernel, for any disk driver, keeps the label across last-close
> of all partitions on the disk, it's broken.

DIOCSDINFO is supposed to set the in-core label and *not* write it
out.  If the label is simply discarded, that entirely defeats the
point of DIOCSDINFO.  There are a number of cases where this behaviour
is desirable (e.g. using a disk that has a partition table for a
different system, and you don't want to modify it).

I submit that what you're arguing for goes direcly against historic
practice *and* the actual API.