linux-kernel - Re: [PATCH] I386: Deactivate the test for the dead CONFIG_DEBUG_PAGE

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Date:	Fri, 06 Jul 2007 12:54:54 -0700
From:	Zachary Amsden <zach@...are.com>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
CC:	"Robert P. J. Day" <rpjday@...dspring.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	Jeremy Fitzhardinge <jeremy@...source.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.osdl.org
Subject: Re: [PATCH] I386: Deactivate the test for the dead CONFIG_DEBUG_PAGE_TYPE
 variable.

Stefan Richter wrote:
> Robert P. J. Day wrote:
>   
>> Signed-off-by: Robert P. J. Day <rpjday@...dspring.com>
>>
>> ---
>>
>> diff --git a/arch/i386/kernel/vmi.c b/arch/i386/kernel/vmi.c
>>     
>
> Maintainers are apparently those under "PARAVIRT_OPS INTERFACE".
> CCs added.
>
>   
>> index c12720d..e3ce5c8 100644
>> --- a/arch/i386/kernel/vmi.c
>> +++ b/arch/i386/kernel/vmi.c
>> @@ -235,7 +235,7 @@ static void vmi_nop(void)
>>  {
>>  }
>>
>> -#ifdef CONFIG_DEBUG_PAGE_TYPE
>> +#if 0 /* debug page type */
>>
>>  #ifdef CONFIG_X86_PAE
>>  #define MAX_BOOT_PTS (2048+4+1)
>> @@ -336,7 +336,7 @@ static void vmi_check_page_type(u32 pfn, int type)
>>  #else
>>  #define vmi_set_page_type(p,t) do { } while (0)
>>  #define vmi_check_page_type(p,t) do { } while (0)
>> -#endif
>> +#endif /* debug page type */
>>
>>  #ifdef CONFIG_HIGHPTE
>>  static void *vmi_kmap_atomic_pte(struct page *page, enum km_type type)
>>     
>
> This misnamed CONFIG_DEBUG_PAGE_TYPE (it's not a Kconfig variable) has
> about 120 lines debug code dangling on it.  So, replacing it by #if 0
> will hopefully motivate a kind janitor to send a removal patch for that
> debug code eventually.  I don't do so just now because that code went in
> between 2.6.20 and 2.6.21-rc1, i.e. not so long ago.
>   

Nack.  This code was very tricky to get right and found some very 
obscure bugs.  I want to keep it around even in broken form for as long 
as possible.

Also, it is not misnamed.  I didn't add the rest of the code upstream 
because it steals bits from struct page.

Zach
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