RE: [patch 3/8] x86 PAT: Add follow_pfnmp_pte routine to helptracking pfnmap pages

[Pallipadi, Venkatesh]

>-----Original Message-----
>From: Nick Piggin [mailto:npiggin@xxxxxxx] 
>Sent: Wednesday, November 12, 2008 3:27 PM
>To: Pallipadi, Venkatesh
>Cc: Ingo Molnar; Thomas Gleixner; H.Peter Anvin; Hugh Dickins; 
>Roland Dreier; Jesse Barnes; Jeremy Fitzhardinge; Arjan van de 
>Ven; linux-kernel@xxxxxxxxxxxxxxx; Siddha, Suresh B
>Subject: Re: [patch 3/8] x86 PAT: Add follow_pfnmp_pte routine 
>to help tracking pfnmap pages
>
>On Wed, Nov 12, 2008 at 01:26:50PM -0800, Venkatesh Pallipadi wrote:
>> 
>> Add a generic interface to follow pfn in a pfnmap vma range. 
>This is used by
>> one of the subsequent x86 PAT related patch to keep track of 
>memory types
>> for vma regions across vma copy and free.
>> 
>> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
>> Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
>> 
>> ---
>>  include/linux/mm.h |    3 +++
>>  mm/memory.c        |   43 
>+++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 46 insertions(+)
>> 
>> Index: tip/include/linux/mm.h
>> ===================================================================
>> --- tip.orig/include/linux/mm.h	2008-11-06 
>15:41:43.000000000 -0800
>> +++ tip/include/linux/mm.h	2008-11-10 09:44:45.000000000 -0800
>> @@ -1223,6 +1223,9 @@ struct page *follow_page(struct vm_area_
>>  #define FOLL_GET	0x04	/* do get_page on page */
>>  #define FOLL_ANON	0x08	/* give ZERO_PAGE if no pgtable */
>>  
>> +unsigned long follow_pfnmap_pte(struct vm_area_struct *vma,
>> +				unsigned long address, pte_t *ret_ptep);
>> +
>>  typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, 
>unsigned long addr,
>>  			void *data);
>>  extern int apply_to_page_range(struct mm_struct *mm, 
>unsigned long address,
>> Index: tip/mm/memory.c
>> ===================================================================
>> --- tip.orig/mm/memory.c	2008-11-06 15:41:43.000000000 -0800
>> +++ tip/mm/memory.c	2008-11-10 09:44:45.000000000 -0800
>> @@ -1111,6 +1111,49 @@ no_page_table:
>>  	return page;
>>  }
>>  
>> +unsigned long follow_pfnmap_pte(struct vm_area_struct *vma,
>> +			unsigned long address, pte_t *ret_ptep)
>> +{
>
>I think we'd typically return an int for functions like this. It
>probably wouldn't hurt to return more descriptive errors either.
>-EINVAL, perhaps, seems to fit best with what existing code there
>is doing.
>

Yes. Will change the return type to int with more appropriate
return values and update the patch.

Thanks,
Venki--
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