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Date: Fri, 20 Jul 2007 10:03:04 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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Subject: Re: build fix for x86_64...
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To: "Luck, Tony" <tony.luck@intel.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>, Andi Kleen <ak@novell.com>, Arthur Jones <arthur.jones@qlogic.com>, Vasily Tarasov <vtaras@openvz.org>, linux-kernel@vger.kernel.org, Jan Kara <jack@ucw.cz>, linux-arch@vger.kernel.org
List-ID: <linux-arch.vger.kernel.org>

Luck, Tony wrote:
> 
> Which is better.  But if we unconditionally set this CONFIG variable, then the
> code in fs/quota.c will have to read:
> 
> #if defined(CONFIG_COMPAT) && defined(CONFIG_COMPAT_FOR_U64_ALIGNMENT)
> 
> We can keep it simpler if the Kconfig file does the conditional for us:
> 
> config COMPAT_FOR_U64_ALIGNMENT
> 	def_bool y
> 	depends on COMPAT
> 

No, that would be bad.  If compat_u64 is used to carry 32-bit ABIs
forward into 64-bit space without needing compatibility hacks, then this
would actually introduce ABI incompatibilities depending on CONFIG_COMPAT!

	-hpa