Re: [PATCHv5 08/28] khugepaged: ignore pmd tables with THP mapped with ptes

[Vlastimil Babka]

On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote:
> Prepare khugepaged to see compound pages mapped with pte. For now we
> won't collapse the pmd table with such pte.
>
> khugepaged is subject for future rework wrt new refcounting.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Tested-by: Sasha Levin <sasha.levin@xxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>   mm/huge_memory.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index fa3d4f78b716..ffc30e4462c1 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2653,6 +2653,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
>   		page = vm_normal_page(vma, _address, pteval);
>   		if (unlikely(!page))
>   			goto out_unmap;
> +
> +		/* TODO: teach khugepaged to collapse THP mapped with pte */
> +		if (PageCompound(page))
> +			goto out_unmap;
> +
>   		/*
>   		 * Record which node the original page is from and save this
>   		 * information to khugepaged_node_load[].
> @@ -2663,7 +2668,6 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
>   		if (khugepaged_scan_abort(node))
>   			goto out_unmap;
>   		khugepaged_node_load[node]++;
> -		VM_BUG_ON_PAGE(PageCompound(page), page);
>   		if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
>   			goto out_unmap;
>   		/*

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