Re: [CFC/CFT] large changes in the loader(8) code

On Jun 27, 2012, at 1:48 PM, Andrey V. Elsukov wrote:

> On 28.06.2012 00:14, Marcel Moolenaar wrote:
>>> Our loader detects that primary GPT header is damaged. It tries to read
>>> backup GPT header from the last LBA and it detects that there is
>>> "GEOM::" signature. It tries to read one previous sector and there is
>>> *valid* GPT header.
>> 
>> How do you know it's valid? It's in a location that is not valid
>> to begin with. Validity is based on rules and you're violating the
>> the rules without defining exactly what we call valid given the
>> new rules. This may seem nitpicking, but having went through the
>> hassle of dealing with the broken way we created the dangerously
>> dedicated disk, I appreciate the importance of being anal when it
>> comes to something that lives on non-volatile storage and gets to
>> be exposed to a world much larger than FreeBSD.
> 
> So why do you not prevent to attach GEOM_PART_GPT to any providers that
> are not the disk drive? This will be the right solution to all our
> problems. Just don't create invalid GPT.

It's not even the right solution, as it prevents legit nesting
of gpart GEOMs *and* is fundamentally based on a flawed assumption
that any non-disk GEOM underneath gpart yields an invalid GPT.
Think gnop.

-- 
Marcel Moolenaar
marcel_at_xcllnt.net