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Date: Wed, 9 May 2007 23:19:37 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Mark Fortescue <mark@mtfhpc.demon.co.uk>
Subject: Re: vm changes from linux-2.6.14 to linux-2.6.15
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	David Miller <davem@davemloft.net>
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On Wed, 2 May 2007 00:08:31 +0100 (BST) Mark Fortescue <mark@mtfhpc.demon.co.uk> wrote:

> On Wed, 2 May 2007, Benjamin Herrenschmidt wrote:
> 
> >
> >> I have attached a patch (so pine does not mangle it) for linux-2.6.20.9.
> >> Is this what you had in mind?
> >>
> >> For linux-2.6.21, more work will be needed as it has more code calling
> >> ptep_set_access_flags.
> >
> > I'm not 100% sure we need the 'update' argument... we can remove the
> > whole old_entry, pte_same, etc... and just have pte_set_access_flags()
> > read the old PTE and decide wether something needs to be changed or not.
> >
> > Ben.
> >
> >
> 
> The attached patch works on sun4c (with my simple ADA compile test) but 
> the change in functionality may break things other platforms.
> 
> The advantage of the previous patch is that the functionality is only 
> changed for sparc sun4c so less testing would be required.
> 
> Regards
>  	Mark Fortescue.
> 
> [Update-MMUCache-2.patch  TEXT/PLAIN (10.7KB)]
> diff -ruNpd linux-2.6.20.9/include/asm-generic/pgtable.h linux-test/include/asm-generic/pgtable.h
> --- linux-2.6.20.9/include/asm-generic/pgtable.h	2007-05-01 12:57:56.000000000 +0100
> +++ linux-test/include/asm-generic/pgtable.h	2007-05-01 23:13:23.000000000 +0100
> @@ -30,10 +30,17 @@ do {				  					\
>   * to optimize this.
>   */
>  #define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
> -do {				  					  \
> -	set_pte_at((__vma)->vm_mm, (__address), __ptep, __entry);	  \
> -	flush_tlb_page(__vma, __address);				  \
> -} while (0)
> +({									  \
> +	int __update = !pte_same(*(__ptep), __entry);			  \
> +									  \
> +	if (__update) {				  			  \
> +		set_pte_at((__vma)->vm_mm, (__address), __ptep, __entry); \
> +		flush_tlb_page(__vma, __address);			  \
> +	} else if (__dirty) {						  \
> +		flush_tlb_page(__vma, __address);			  \
> +	}								  \
> +	__update;							  \
> +})

We never seemed to reach completion here?