Re: [PATCH] selftests/mm: khugepaged: skip swap tests when swap is unavailable

["David Hildenbrand (Arm)" <david@kernel.org>]

On 7/15/26 15:34, Jaeyeon Lee wrote:
> The collapse_swapin_single_pte and collapse_max_ptes_swap tests use
> MADV_PAGEOUT to swap out pages before verifying khugepaged collapse
> behavior. On systems without swap configured, MADV_PAGEOUT succeeds
> but the pages are not actually swapped out, so check_swap() returns
> false and the tests report a failure.
> 
> These tests cannot run meaningfully without swap, so a missing swap
> area is an environment limitation rather than a test failure. Detect
> the absence of swap via /proc/swaps and skip the affected tests
> instead of failing them.
> 
> Signed-off-by: Jaeyeon Lee <jaeyeon.lee.dev@gmail.com>
> ---
>  tools/testing/selftests/mm/khugepaged.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
> index 10e8dedcb087..f9b4ebe733ce 100644
> --- a/tools/testing/selftests/mm/khugepaged.c
> +++ b/tools/testing/selftests/mm/khugepaged.c
> @@ -100,6 +100,22 @@ static void skip(const char *msg)
>  	exit_status = KSFT_SKIP;
>  }
>  
> +static bool swap_available(void)
> +{
> +	char buf[256];
> +	bool ret;
> +	FILE *fp = fopen("/proc/swaps", "r");
> +
> +	if (!fp)
> +		return false;
> +
> +	fgets(buf, sizeof(buf), fp);
> +	ret = !!fgets(buf, sizeof(buf), fp);
> +
> +	fclose(fp);
> +	return ret;
> +}
> +

That doesn't mean that swapout will succeed.

Take a look at cow.c where we use pagemap_is_swapped() after MADV_PAGEOUT.

-- 
Cheers,

David