Re: [RFC] shared page table for hugetlbpage memory causing leak.

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* Adam Litke <agl@us.ibm.com> [2008-01-16 12:54:28]:

> Since we know we are dealing with a hugetlb VMA, how about the
> following, simpler, _untested_ patch:
> 
> Signed-off-by: Adam Litke <agl@us.ibm.com>
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 6f97821..75b0e4f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -644,6 +644,11 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
>  		dst_pte = huge_pte_alloc(dst, addr);
>  		if (!dst_pte)
>  			goto nomem;
> +
> +		/* If page table is shared do not copy or take references */
> +		if (src_pte == dst_pte)
> +			continue;
> +

Shouldn't you be checking the PTE contents rather than the pointers?
Shouldn't the check be

                if (unlikely(pte_same(*src_pte, *dst_pte))
                        continue;


>  		spin_lock(&dst->page_table_lock);
>  		spin_lock(&src->page_table_lock);
>  		if (!pte_none(*src_pte)) {
> 

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL

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