linux-kernel - Re: [PATCH v5 05/11] thp: change_huge_pmd(): keep huge zero page write-protected

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Date:	Wed, 14 Nov 2012 15:12:54 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: [PATCH v5 05/11] thp: change_huge_pmd(): keep huge zero page
 write-protected

On Wed, 7 Nov 2012, Kirill A. Shutemov wrote:

> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index d767a7c..05490b3 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1259,6 +1259,8 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
>  		pmd_t entry;
>  		entry = pmdp_get_and_clear(mm, addr, pmd);
>  		entry = pmd_modify(entry, newprot);
> +		if (is_huge_zero_pmd(entry))
> +			entry = pmd_wrprotect(entry);
>  		set_pmd_at(mm, addr, pmd, entry);
>  		spin_unlock(&vma->vm_mm->page_table_lock);
>  		ret = 1;

Nack, this should be handled in pmd_modify().
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