[review request] zfsboot/zfsloader: support accessing filesystems within a pool

[Andriy Gapon]

on 18/04/2012 17:40 Ian Lepore said the following:
> On Wed, 2012-04-18 at 17:36 +0300, Andriy Gapon wrote:
>> on 18/04/2012 17:22 Ian Lepore said the following:
>>> YES!  A size field (preferably as the first field in the struct) along
>>> with a flag to indicate that it's a new-style boot info struct that
>>> starts with a size field, will allow future changes without a lot of
>>> drama.  It can allow code that has to deal with the struct without
>>> interpretting it (such as trampoline code that has to copy it to a new
>>> stack or memory area as part of loading the kernel) to be immune to
>>> future changes.
>>
>> Yeah, placing the new field at front would immediately break compatibility and
>> even access to the flags field :-)
>>
> 
> Code would only assume the new field was at the front of the struct if
> the new flag is set, otherwise it would use the historical struct
> layout.

Right, but where the flag would reside?
And how the older code that is not aware of the new flag would cope with the new
layout?

-- 
Andriy Gapon