linux-kernel - Re: [PATCH v5 08/11] thp: setup huge zero page on non-write page fault

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Message-ID: <alpine.DEB.2.00.1211141531110.22537@chino.kir.corp.google.com>
Date:	Wed, 14 Nov 2012 15:33:16 -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 08/11] thp: setup huge zero page on non-write page
 fault

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

> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index f36bc7d..41f05f1 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -726,6 +726,16 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  			return VM_FAULT_OOM;
>  		if (unlikely(khugepaged_enter(vma)))
>  			return VM_FAULT_OOM;
> +		if (!(flags & FAULT_FLAG_WRITE)) {
> +			pgtable_t pgtable;
> +			pgtable = pte_alloc_one(mm, haddr);
> +			if (unlikely(!pgtable))
> +				goto out;

No use in retrying, just return VM_FAULT_OOM.

> +			spin_lock(&mm->page_table_lock);
> +			set_huge_zero_page(pgtable, mm, vma, haddr, pmd);
> +			spin_unlock(&mm->page_table_lock);
> +			return 0;
> +		}
>  		page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
>  					  vma, haddr, numa_node_id(), 0);
>  		if (unlikely(!page)) {
--
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