Re: [RESEND PATCH 3/4] selftests/mm: split_huge_page_test: skip the test when thp is not available

Zi Yan
2026-03-13T15:27:49Z

On 13 Mar 2026, at 11:15, Mike Rapoport wrote:

> On Thu, Mar 12, 2026 at 10:11:12AM -0400, Zi Yan wrote:
>> On 12 Mar 2026, at 7:40, Chunyu Hu wrote:
>>
>>> When thp is not enabled on some kernel config such as realtime kernel, the
>>> test will report failure. Fix the false positive by skipping the test
>>> directly when thp is not enabled.
>>>
>>> There's a naming conflict on write_file() function, both thp_settings.h and
>>> split_huge_page_test.c define it. To make use of thp_is_enabled() helper in
>>> the thp_settings.h, rename this local write_file to safe_write_file to
>>> avoid the conflict. The reason to use 'safe_' is it does some error check.
>>
>> Both write_file() do safe checks. Actually the code of both functions looks
>> almost identical except that the thp_settings one does exit() instead of
>> ksft_exit_fail_msg().
>>
>> Can you rename the split_huge_page_test’s write_file() to write_file_local()
>> and add a comment above the function like
>> /* add _local to avoid a function conflict with thp_settings.h */?
>
> Looks like we can move the version that uses ksft_exit_fail_msg() to
> vm_util and drop the other one.

Could work.

tools/testing/selftests/mm/khugepaged.c uses the write_file() from
thp_settings.h in file_setup_area(), which is part of struct mem_ops.
I thought struct mem_ops was passed to some syscall, but it turns out
that it is used locally. The only downside is that file_setup_area() now
has this ksefltest friendly code. Someone might want to clean up
tools/testing/selftests/mm/khugepaged.c with kselftests APIs. :)

>
>> With that, feel free to add:
>>
>> Reviewed-by: Zi Yan <ziy@nvidia.com>
>>
>> Thanks.
>>
>>>
>>> Tested with thp disabled kernel:
>>> Before The fix:
>>> # --------------------------------------------------
>>> # running ./split_huge_page_test /tmp/xfs_dir_Ywup9p
>>> # --------------------------------------------------
>>> # TAP version 13
>>> # Bail out! Reading PMD pagesize failed
>>> # # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
>>> # [FAIL]
>>> not ok 61 split_huge_page_test /tmp/xfs_dir_Ywup9p # exit=1
>>>
>>> After the fix:
>>> # --------------------------------------------------
>>> # running ./split_huge_page_test /tmp/xfs_dir_YHPUPl
>>> # --------------------------------------------------
>>> # TAP version 13
>>> # 1..0 # SKIP Transparent Hugepages not available
>>> # [SKIP]
>>> ok 6 split_huge_page_test /tmp/xfs_dir_YHPUPl # SKIP
>>>
>>> CC: Li Wang <liwang@redhat.com>
>>> Signed-off-by: Chunyu Hu <chuhu@redhat.com>
>>> ---
>>> tools/testing/selftests/mm/split_huge_page_test.c | 9 +++++++--
>>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
>>> index e0167111bdd1..615b75ca62cc 100644
>>> --- a/tools/testing/selftests/mm/split_huge_page_test.c
>>> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
>>> @@ -21,6 +21,7 @@
>>> #include <time.h>
>>> #include "vm_util.h"
>>> #include "kselftest.h"
>>> +#include "thp_settings.h"
>>>
>>> uint64_t pagesize;
>>> unsigned int pageshift;
>>> @@ -255,7 +256,7 @@ static int check_after_split_folio_orders(char *vaddr_start, size_t len,
>>> return status;
>>> }
>>>
>>> -static void write_file(const char *path, const char *buf, size_t buflen)
>>> +static void safe_write_file(const char *path, const char *buf, size_t buflen)
>>> {
>>> int fd;
>>> ssize_t numwritten;
>>> @@ -283,7 +284,7 @@ static void write_debugfs(const char *fmt, ...)
>>> if (ret >= INPUT_MAX)
>>> ksft_exit_fail_msg("%s: Debugfs input is too long\n", __func__);
>>>
>>> - write_file(SPLIT_DEBUGFS, input, ret + 1);
>>> + safe_write_file(SPLIT_DEBUGFS, input, ret + 1);
>>> }
>>>
>>> static char *allocate_zero_filled_hugepage(size_t len)
>>> @@ -772,6 +773,10 @@ int main(int argc, char **argv)
>>> ksft_finished();
>>> }
>>>
>>> + if (!thp_is_enabled()) {
>>> + ksft_exit_skip("Transparent Hugepages not available\n");
>>> + }
>>> +
>>> if (argc > 1)
>>> optional_xfs_path = argv[1];
>>>
>>> --
>>> 2.53.0
>>
>>
>> Best Regards,
>> Yan, Zi
>
> --
> Sincerely yours,
> Mike.

Best Regards,
Yan, Zi