On Fri 03-08-12 15:32:35, Michal Hocko wrote:
> On Fri 03-08-12 20:56:45, Hillf Danton wrote:
> > The computation of page offset index is open coded, and incorrect, to
> > be used in scanning prio tree, as huge page offset is required, and is
> > fixed with the well defined routine.
>
> I guess that nobody reported this because if someone really wants to
> share he will use aligned address for mmap/shmat and so the index is 0.
> Anyway it is worth fixing. Thanks for pointing out!
I have looked at the code again and I don't think there is any problem
at all. vma_prio_tree_foreach understands page units so it will find
appropriate svmas.
Or am I missing something?
>
> >
> > Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
> > ---
> >
> > --- a/arch/x86/mm/hugetlbpage.c Fri Aug 3 20:34:58 2012
> > +++ b/arch/x86/mm/hugetlbpage.c Fri Aug 3 20:40:16 2012
> > @@ -72,12 +72,15 @@ static void huge_pmd_share(struct mm_str
> > if (!vma_shareable(vma, addr))
> > return;
> >
> > + idx = linear_page_index(vma, addr);
> > +
>
> You can use linear_hugepage_index directly and remove the idx
> initialization as well.
>
> > mutex_lock(&mapping->i_mmap_mutex);
> > vma_prio_tree_foreach(svma, &iter, &mapping->i_mmap, idx, idx) {
> > if (svma == vma)
> > continue;
> >
> > - saddr = page_table_shareable(svma, vma, addr, idx);
> > + saddr = page_table_shareable(svma, vma, addr,
> > + idx * (PMD_SIZE/PAGE_SIZE));
>
> Why not just fixing page_table_shareable as well rather than playing
> tricks like this?
>
> > if (saddr) {
> > spte = huge_pte_offset(svma->vm_mm, saddr);
> > if (spte) {
> > --
>
> --
> Michal Hocko
> SUSE Labs
--
Michal Hocko
SUSE Labs
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