linux-kernel - Re: pud_bad vs pud

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Message-ID: <498B35F9.601@goop.org>
Date:	Thu, 05 Feb 2009 10:54:49 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	William Lee Irwin III <wli@...omorphy.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: pud_bad vs pud_bad

Ingo Molnar wrote:
> * Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>
>   
>> I'm looking at unifying the 32 and 64-bit versions of pud_bad.
>>
>> 32-bits defines it as:
>>
>> static inline int pud_bad(pud_t pud)
>> {
>> 	return (pud_val(pud) & ~(PTE_PFN_MASK | _KERNPG_TABLE | _PAGE_USER)) != 0;
>> }
>>
>> and 64 as:
>>
>> static inline int pud_bad(pud_t pud)
>> {
>> 	return (pud_val(pud) & ~(PTE_PFN_MASK | _PAGE_USER)) != _KERNPG_TABLE;
>> }
>>
>>
>> I'm inclined to go with the 64-bit version, but I'm wondering if there's 
>> something subtle I'm missing here.
>>     
>
> Why go with the 64-bit version? The 32-bit check looks more compact and 
> should result in smaller code.
>   

Well, its stricter.  But I don't really understand what condition its 
actually testing for.

    J
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