On Mon, Feb 13, 2023 at 7:55 AM Alexandre Ghiti <alex@xxxxxxxx> wrote:
>
> Hi Matthew,
>
> On 2/13/23 16:50, Matthew Wilcox wrote:
> > On Mon, Feb 13, 2023 at 04:28:05PM +0100, Alexandre Ghiti wrote:
> >> The issue lies here: before using pteval in pfn_folio(), we should test it.
> >> The following patch fixes the issue for me:
> > Thanks for debugging it. I'd rather see this written as ...
> >
> > pte_t pteval = *_pte;
> > + unsigned long pfn;
> >
> > + if (pte_none(pteval))
> > + continue;
> > + pfn = pte_pfn(pteval);
> > + if (is_zero_pfn(pfn))
> > + continue;
> > + folio = pfn_folio(pfn);
> > + if (folio_test_large(folio))
> > + continue;
> > release_pte_folio(folio);
> >
> > makes sense?
>
>
> Sure, that's fine by me, I can send that or I'll add my tested-by on
> what you send, whatever suits you.
Thanks for debugging this! I'll send a fix patch using Matthew's
approach later today.
> Alex
>
>
> >
> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> >> index eb38bd1b1b2f..fef3414b481b 100644
> >> --- a/mm/khugepaged.c
> >> +++ b/mm/khugepaged.c
> >> @@ -514,10 +514,12 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte,
> >> while (--_pte >= pte) {
> >> pte_t pteval = *_pte;
> >>
> >> - folio = pfn_folio(pte_pfn(pteval));
> >> - if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) &&
> >> - !folio_test_large(folio))
> >> - release_pte_folio(folio);
> >> + if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) {
> >> + folio = pfn_folio(pte_pfn(pteval));
> >> +
> >> + if (!folio_test_large(folio))
> >> + release_pte_folio(folio);
> >> + }
> >> }
> >>
> >> list_for_each_entry_safe(folio, tmp, compound_pagelist, lru) {
> >>
> >>
> >> @Marek: could you give it a try?
> >>
> >> I can send a separate patch if needed, let me know.
> >>
> >> Thanks,
> >>
> >> Alex
> >>
> >>
> >>>> if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) &&
> >>>> - !PageCompound(page))
> >>>> - release_pte_page(page);
> >>>> + !folio_test_large(folio))
> >>>> + release_pte_folio(folio);
> >>>> }
> >>>> - list_for_each_entry_safe(page, tmp, compound_pagelist, lru) {
> >>>> - list_del(&page->lru);
> >>>> - release_pte_page(page);
> >>>> + list_for_each_entry_safe(folio, tmp, compound_pagelist, lru) {
> >>>> + list_del(&folio->lru);
> >>>> + release_pte_folio(folio);
> >>>> }
> >>>> }
> >>> Best regards
