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Subject: Re: [PATCH 1/5 V2] Align stack boundaries based on personality
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Eric Munson <ebmunson@us.ibm.com>
In-Reply-To: <6061445882ce9574999bf343eeb333be02a1afa6.1216928613.git.ebmunson@us.ibm.com>
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	<6061445882ce9574999bf343eeb333be02a1afa6.1216928613.git.ebmunson@us.ibm.com>
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Date: Mon, 28 Jul 2008 13:09:53 -0700
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Cc: linux-mm@kvack.org, libhugetlbfs-devel@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org
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On Mon, 2008-07-28 at 12:17 -0700, Eric Munson wrote:
> 
> +static unsigned long personality_page_align(unsigned long addr)
> +{
> +       if (current->personality & HUGETLB_STACK)
> +#ifdef CONFIG_STACK_GROWSUP
> +               return HPAGE_ALIGN(addr);
> +#else
> +               return addr & HPAGE_MASK;
> +#endif
> +
> +       return PAGE_ALIGN(addr);
> +}
...
> -       stack_top = PAGE_ALIGN(stack_top);
> +       stack_top = personality_page_align(stack_top);

Just out of curiosity, why doesn't the existing small-page case seem to
care about the stack growing up/down?  Why do you need to care in the
large page case?

-- Dave