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

[Larry Woodman <lwoodman@redhat.com>]

On Thu, 2008-01-17 at 15:49 +0530, Balbir Singh wrote:
> * 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?
No, this is chacking for shared page tables not shared pages.
> 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)) {
> > 
> 

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