On Mon, Mar 06, 2017 at 08:19:03AM +0530, Aneesh Kumar K.V wrote:
> "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> writes:
>
> > Basically the same race as with numa balancing in change_huge_pmd(), but
> > a bit simpler to mitigate: we don't need to preserve dirty/young flags
> > here due to MADV_FREE functionality.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > Cc: Minchan Kim <minchan@xxxxxxxxxx>
> > ---
> > mm/huge_memory.c | 2 --
> > 1 file changed, 2 deletions(-)
> >
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index bb2b3646bd78..324217c31ec9 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -1566,8 +1566,6 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
> > deactivate_page(page);
> >
> > if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
> > - orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
> > - tlb->fullmm);
> > orig_pmd = pmd_mkold(orig_pmd);
> > orig_pmd = pmd_mkclean(orig_pmd);
> >
>
> Instead can we do a new interface that does something like
>
> pmdp_huge_update(tlb->mm, addr, pmd, new_pmd);
>
> We do have a variant already in ptep_set_access_flags. What we need is
> something that can be used to update THP pmd, without converting it to
> pmd_none and one which doens't loose reference and change bit ?
Sounds like a good idea. Would you volunteer to implement it?
I don't have time for this right now.
--
Kirill A. Shutemov
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