linux-kernel - Re: [x86 PAT PATCH 1/2] x86, pat: remove the dependency on 'vm

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Date:	Tue, 03 Apr 2012 09:37:24 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	Konstantin Khlebnikov <koct9i@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pallipadi Venkatesh <venki@...gle.com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...nel.dk>
Subject: Re: [x86 PAT PATCH 1/2] x86, pat: remove the dependency on 'vm_pgoff'
 in track/untrack pfn vma routines

Suresh Siddha wrote:
> 'pfn' argument for track_pfn_vma_new() can be used for reserving the attribute
> for the pfn range. No need to depend on 'vm_pgoff'
>
> Similarly, untrack_pfn_vma() can depend on the 'pfn' argument if it
> is non-zero or can use follow_phys() to get the starting value of the pfn
> range.
>
> Also the non zero 'size' argument can be used instead of recomputing
> it from vma.
>
> This cleanup also prepares the ground for the track/untrack pfn vma routines
> to take over the ownership of setting PAT specific vm_flag in the 'vma'.
>
> Signed-off-by: Suresh Siddha<suresh.b.siddha@...el.com>
> Cc: Venkatesh Pallipadi<venki@...gle.com>
> Cc: Konstantin Khlebnikov<khlebnikov@...nvz.org>
> ---
>   arch/x86/mm/pat.c |   30 +++++++++++++++++-------------
>   1 files changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
> index f6ff57b..617f42b 100644
> --- a/arch/x86/mm/pat.c
> +++ b/arch/x86/mm/pat.c
> @@ -693,14 +693,10 @@ int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
>   			unsigned long pfn, unsigned long size)
>   {
>   	unsigned long flags;
> -	resource_size_t paddr;
> -	unsigned long vma_size = vma->vm_end - vma->vm_start;
>
> -	if (is_linear_pfn_mapping(vma)) {
> -		/* reserve the whole chunk starting from vm_pgoff */
> -		paddr = (resource_size_t)vma->vm_pgoff<<  PAGE_SHIFT;
> -		return reserve_pfn_range(paddr, vma_size, prot, 0);
> -	}
> +	/* reserve the whole chunk starting from pfn */
> +	if (is_linear_pfn_mapping(vma))
> +		return reserve_pfn_range(pfn, size, prot, 0);

you mix here pfn and paddr: old code passes paddr as first argument of reserve_pfn_range().

>
>   	if (!pat_enabled)
>   		return 0;
> @@ -716,20 +712,28 @@ int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
>   /*
>    * untrack_pfn_vma is called while unmapping a pfnmap for a region.
>    * untrack can be called for a specific region indicated by pfn and size or
> - * can be for the entire vma (in which case size can be zero).
> + * can be for the entire vma (in which case pfn, size are zero).
>    */
>   void untrack_pfn_vma(struct vm_area_struct *vma, unsigned long pfn,
>   			unsigned long size)
>   {
>   	resource_size_t paddr;
> -	unsigned long vma_size = vma->vm_end - vma->vm_start;
> +	unsigned long prot;
>
> -	if (is_linear_pfn_mapping(vma)) {
> -		/* free the whole chunk starting from vm_pgoff */
> -		paddr = (resource_size_t)vma->vm_pgoff<<  PAGE_SHIFT;
> -		free_pfn_range(paddr, vma_size);
> +	if (!is_linear_pfn_mapping(vma))
>   		return;
> +
> +	/* free the chunk starting from pfn or the whole chunk */
> +	paddr = (resource_size_t)pfn;
> +	if (!paddr&&  !size) {
> +		if (follow_phys(vma, vma->vm_start, 0,&prot,&paddr)) {
> +			WARN_ON_ONCE(1);
> +			return;
> +		}
> +
> +		size = vma->vm_end - vma->vm_start;
>   	}
> +	free_pfn_range(paddr, size);
>   }
>
>   pgprot_t pgprot_writecombine(pgprot_t prot)

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