Re: [PATCH 1/2] selftests/mm: handle EINVAL when configuring gigantic hugepages

[Usama Arif <usama.arif@linux.dev>]

On Thu, 25 Jun 2026 18:10:16 +0530 Sayali Patil <sayalip@linux.ibm.com> wrote:

> Some MM selftests attempt to configure the amount of
> HugeTLB pages of different sizes by writing to nr_hugepages.
> 
> PowerPC hash MMU pSeries systems advertise gigantic hugepage sizes 
> but do not support runtime allocation of such pages, writes
> to the corresponding nr_hugepages file fail with -EINVAL.
> This causes the test to bail out even though the failure is due
> to a platform limitation rather than the
> functionality being tested.
> 
> Treat -EINVAL from the sysfs write as a skipped configuration request
> and continue running the test instead of failing.
> 
> Before patch:
>    -------------------------
>    running ./hugetlb-madvise
>    -------------------------
>    TAP version 13
>    1..1
>      [INFO] detected hugetlb page size: 16777216 KiB
>      [INFO] detected hugetlb page size: 16384 KiB
>     ok 1 MADV_DONTNEED and MADV_REMOVE on hugetlb
>     Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
>     Bail out! /sys/kernel/mm/hugepages/hugepages-16777216kB/nr_hugepages
>     write(0) failed: Invalid argument
>     Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
>     [FAIL]
> 
> After patch:
>    -------------------------
>    running ./hugetlb-madvise
>    -------------------------
>    TAP version 13
>    1..1
>     [INFO] detected hugetlb page size: 16777216 KiB
>     [INFO] detected hugetlb page size: 16384 KiB
>    ok 1 MADV_DONTNEED and MADV_REMOVE on hugetlb
>    Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
>    /sys/kernel/mm/hugepages/hugepages-16777216kB/nr_hugepages
>    write(0) failed: Invalid argument
>    [PASS]
> 
> Fixes: 9d07250ea1eb ("selftests/mm: hugepage_settings: add APIs to get and set nr_hugepages")
> Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
> ---
>  tools/testing/selftests/mm/vm_util.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
> index 311fc5b4513e..a8f16eef5c7c 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -735,6 +735,13 @@ void write_file(const char *path, const char *buf, size_t buflen)
>  	saved_errno = errno;
>  	close(fd);
>  	errno = saved_errno;
> +
> +	if (numwritten < 0 && errno == EINVAL) {
> +		ksft_print_msg("%s write(%.*s) failed: %s\n", path,
> +			       (int)(buflen - 1), buf, strerror(errno));
> +		return;
> +	}
> +
This makes write_file() silently succeed for every EINVAL, not just the
gigantic-hugetlb setup case. Several callers use this helper for writes where
EINVAL is a real test failure, for example drop_caches or split huge page
setup. Those tests can now continue after a failed setup and report misleading
results.

Please keep the common helper strict and ignore EINVAL only in the hugetlb
path that is probing unsupported gigantic page runtime allocation.


>  	if (numwritten < 0)
>  		ksft_exit_fail_msg("%s write(%.*s) failed: %s\n", path, (int)(buflen - 1),
>  				buf, strerror(errno));
> -- 
> 2.52.0
> 
>