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Date: Wed, 18 Apr 2012 17:36:55 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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To: Ian Lepore <freebsd@damnhippie.dyndns.org>
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Cc: freebsd-fs@FreeBSD.org, freebsd-hackers@FreeBSD.org,
	John Baldwin <jhb@FreeBSD.org>
Subject: Re: [review request] zfsboot/zfsloader: support accessing
 filesystems within a pool
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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 :-)

-- 
Andriy Gapon