Re: [PATCH v4 3/5] selftests/mm: move write_file helper to vm_util

[Zi Yan <ziy@nvidia.com>]

On 19 Mar 2026, at 12:06, Chunyu Hu wrote:

> thp_settings provides write_file() helper for safely writing to a file and
> exit when write failure happens. It's a very low level helper and many sub
> tests need such a helper, not only thp tests.
>
> split_huge_page_test also defines a write_file locally. The two have minior
> differences in return type and used exit api. And there would be conflicts
> if split_huge_page_test wanted to include thp_settings.h because of
> different prototype, making it less convenient.
>
> It's possisble to merge the two, although some tests don't use the
> kselftest infrastrucutre for testing. It would also work when using the
> ksft_exit_msg() to exit in my test, as the counters are all zero. Output
> will be like:
>
>   TAP version 13
>   1..62
>   Bail out! /proc/sys/vm/drop_caches1 open failed: No such file or directory
>   # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> So here we just keep the version in split_huge_page_test, and move it into
> the vm_util. This makes it easy to maitain and user could just include one
> vm_util.h when they don't need thp setting helpers. Keep the prototype of
> void return as the function will exit on any error, return value is not
> necessary, and will simply the callers like write_num() and write_string().
>
> Suggested-by: Mike Rapoport <rppt@kernel.org>
> Signed-off-by: Chunyu Hu <chuhu@redhat.com>
> ---
> Changes in v3:
>   - make the write_file void return
> Changes in v2:
>   new patch from v2
> ---
>  .../selftests/mm/split_huge_page_test.c       | 15 --------
>  tools/testing/selftests/mm/thp_settings.c     | 35 ++-----------------
>  tools/testing/selftests/mm/thp_settings.h     |  1 -
>  tools/testing/selftests/mm/vm_util.c          | 15 ++++++++
>  tools/testing/selftests/mm/vm_util.h          |  2 ++
>  5 files changed, 20 insertions(+), 48 deletions(-)
>
LGTM.

Reviewed-by: Zi Yan <ziy@nvidia.com>

Best Regards,
Yan, Zi