> > > On 9/21/26 6:35 PM, Yeoreum Yun wrote: > > There are intermittent failures in collapse_max_ptes_swap() and > > collapse_max_ptes_shared() when using the khugepaged_context: > > > > // while running ./khugepaged -s 2 > > > > # Run test: collapse_max_ptes_shared (khugepaged:anon) > > # Allocate huge page... OK > > # Share huge page over fork()... OK > > # Trigger CoW on page 1023 of 2048... OK > > # Maybe collapse with max_ptes_shared exceeded.... OK > > # Trigger CoW on page 1024 of 2048... Fail > > Bail out! Unexpected huge page > > # Planned tests != run tests (26 != 23) > > # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 > > > > # Run test: collapse_max_ptes_swap (khugepaged:anon) > > # Swapout 257 of 2048 pages... OK > > # Maybe collapse with max_ptes_swap exceeded.... OK > > # Swapout 256 of 2048 pages... OK > > Bail out! Unexpected huge page > > # Planned tests != run tests (26 != 17) > > # Totals: pass:17 fail:0 xfail:0 xpass:0 skip:0 error:0 > > > > This happens because khugepaged may collapse the pages before > > wait_for_scan() > > is called, causing a sanity check that expects uncollapsed pages to fail. > > > > For example, in collapse_max_ptes_swap(), after faulting the pages back in > > and paging out up to max_ptes_swap pages, khugepaged may collapse them again > > before c->collapse() is called. > > > > To prevent this, mark the VMA with MADV_NOHUGEPAGE after it has been > > collapsed by wait_for_scan() for anon. This prevents khugepaged from > > collapsing it again before c->collapse() is called. > > > > This failure was observed on NVIDIA Spark with 16KB page. > > > > Signed-off-by: Yeoreum Yun <[email protected]> > > --- > > tools/testing/selftests/mm/khugepaged.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/tools/testing/selftests/mm/khugepaged.c > > b/tools/testing/selftests/mm/khugepaged.c > > index c32244b565658..1aad4bb427ece 100644 > > --- a/tools/testing/selftests/mm/khugepaged.c > > +++ b/tools/testing/selftests/mm/khugepaged.c > > @@ -578,6 +578,9 @@ static bool wait_for_scan(const char *msg, char *p, > > size_t len, > > usleep(TICK); > > } > > + if (!strncmp(ops->name, "anon", 4)) > > We usually use the 'if (ops == &__anon_ops)' check in this file to identify > anonymous test cases. > > With that, LGTM. > Reviewed-by: Baolin Wang <[email protected]> > Tested-by: Baolin Wang <[email protected]>
I think this is merged at mm/mm-unstable already So, I'll send another patch to change it with is_anon(). Thanks! -- Sincerely, Yeoreum Yun
