Re: [PATCH 3/4] thp: fix MADV_DONTNEED vs. MADV_FREE race

[Kirill A. Shutemov]

On Fri, Mar 03, 2017 at 01:35:11PM +0800, Hillf Danton wrote:
> 
> On March 02, 2017 11:11 PM Kirill A. Shutemov wrote: 
> > 
> > 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);
> > 
> $ grep -n set_pmd_at  linux-4.10/arch/powerpc/mm/pgtable-book3s64.c
> 
> /*
>  * set a new huge pmd. We should not be called for updating
>  * an existing pmd entry. That should go via pmd_hugepage_update.
>  */
> void set_pmd_at(struct mm_struct *mm, unsigned long addr,

+Aneesh.

Urgh... Power is special again.

I think this should work fine.