Re: [BUG] mm/hugetlb: possible temporary resv underflow

[Breno Leitao <leitao@debian.org>]

On Tue, Jul 14, 2026 at 12:48:16PM +0200, Guillaume Morin wrote:
> > > I am not sure what the best fix is but checking folio_mapcount() == 0 
> > > in __unmap_hugepage_range() seems to do the trick
> > > 
> > >                 adjust_reservation = false;
> > >  
> > >                 spin_lock_irq(&hugetlb_lock);
> > >                 if (!h->surplus_huge_pages && __vma_private_lock(vma) &&
> > > -                   folio_test_anon(folio)) {
> > > +                   folio_test_anon(folio) &&
> > > +                   folio_mapcount(folio) == 0) {
> > >                         folio_set_hugetlb_restore_reserve(page_folio(page));
> > >                         /* Reservation to be adjusted after the spin lock */
> > >                         adjust_reservation = true;
> > 
> > The fix looks correct to me.
> 
> Excellent! Will you be submitting a patch or do you need me to do
> something there?

Up to you. You can either send it, or, I  can do it myself.