On 9/23/26 12:54, Yeoreum Yun wrote: >> >> >> 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().
Unless it is in mm-stable we can reasonably squash stuff or resend. This shouldn't be an independent patch. -- Cheers, David
