Re: [aarcange@redhat.com: [PATCH] fork vs gup(-fast) fix]

[Nick Piggin <nickpiggin@yahoo.com.au>]

On Saturday 14 March 2009 15:46:30 Nick Piggin wrote:

> Index: linux-2.6/arch/x86/mm/gup.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/mm/gup.c	2009-03-14 02:48:06.000000000 +1100
> +++ linux-2.6/arch/x86/mm/gup.c	2009-03-14 02:48:12.000000000 +1100
> @@ -83,11 +83,14 @@ static noinline int gup_pte_range(pmd_t
>  		struct page *page;
>
>  		if ((pte_flags(pte) & (mask | _PAGE_SPECIAL)) != mask) {
> +failed:
>  			pte_unmap(ptep);
>  			return 0;
>  		}
>  		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
>  		page = pte_page(pte);
> +		if (unlikely(!PageDontCOW(page)))
> +			goto failed;
>  		get_page(page);
>  		pages[*nr] = page;
>  		(*nr)++;

Ah, that's stupid, the test should be confined just to PageAnon 
&& !PageDontCOW pages, of course.


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