linux-kernel - Re: PAT wc & vmap mapping count issue ?

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Date:	Thu, 30 Jul 2009 22:04:33 +0200
From:	Jerome Glisse <glisse@...edesktop.org>
To:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	suresh.b.siddha@...el.com
Subject: Re: PAT wc & vmap mapping count issue ?

On Thu, 2009-07-30 at 12:17 -0700, Pallipadi, Venkatesh wrote:
> This seems to be a regression from changeset
> 3869c4aa18835c8c61b44bd0f3ace36e9d3b5bd0
> 
> Below test patch should fix the problem. Can you please try it and let use know.
> We can then send a cleaner patch with changelog etc to upstream+stable kernels.
> 
> Thanks,
> Venki
> 
> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
> ---
>  arch/x86/mm/pageattr.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
> index 1b734d7..895d90e 100644
> --- a/arch/x86/mm/pageattr.c
> +++ b/arch/x86/mm/pageattr.c
> @@ -997,12 +997,15 @@ EXPORT_SYMBOL(set_memory_array_uc);
>  int _set_memory_wc(unsigned long addr, int numpages)
>  {
>  	int ret;
> +	unsigned long addr_copy = addr;
> +
>  	ret = change_page_attr_set(&addr, numpages,
>  				    __pgprot(_PAGE_CACHE_UC_MINUS), 0);
> -
>  	if (!ret) {
> -		ret = change_page_attr_set(&addr, numpages,
> -				    __pgprot(_PAGE_CACHE_WC), 0);
> +		ret = change_page_attr_set_clr(&addr_copy, numpages,
> +					       __pgprot(_PAGE_CACHE_WC),
> +					       __pgprot(_PAGE_CACHE_MASK),
> +					       0, 0, NULL);
>  	}
>  	return ret;
>  }

Yes it fixes the issue for me (at least it seems, so far after bunch of
minutes no corruption despite massive set_wc/set_wb/free_page calls).
Thanks a lot for tracking this down.

Cheers,
Jerome Glisse

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