Re: [PATCH v2 1/2] kselftest: mm: return fail when child test result is fail in khugepaged

[Baolin Wang]

On 9/21/26 6:35 PM, Yeoreum Yun wrote:
> Although the child process in collapse_fork*() or collapse_max_ptes_shared()
> reports `KSFT_FAIL`, the result is ignored because the test only checks
> whether the parent’s page was collapsed into a huge page.
>
> As a result, the test is considered successful whenever the parent’s page
> is a huge page, even if the child test fails, as shown below:
>
>    #
>    # 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  // child failed.
>    # Check if parent still has huge page... OK              // parent hpage success
>    ok 24 collapse_max_ptes_shared                           // considered as success
>    ...
>    # Totals: pass:26 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> To address this, propagate the child’s failure and skip the subsequent
> check in the parent.
>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>
> ---

Make sense to me.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>