Re: [PATCH v7 1/6] selftests/mm: make file helpers return errors

[Usama Anjum <usama.anjum@arm.com>]

On 13/08/2026 7:12 pm, Sarthak Sharma wrote:
> Change read_file(), write_file(), read_num(), write_num() and
> write_num_ignore_einval() in vm_util.c to report failures to callers
> instead of exiting from the helper.
> 
> Make read_file() return a negative errno on failure and 0 on success, so
> callers can distinguish a successful read from an I/O error. Also make
> read_num() reject negative and malformed values.
> 
> Keep write_num_ignore_einval() silent for -EINVAL while returning other
> errors to its caller.
> 
> Update callers to print diagnostics and fail wherever required. Also add
> a helper print_file_access_error() in hugepage_settings.c to print
> TAP-compatible errors without a kselftest dependency. This prepares the
> helpers to be moved to tools/lib/mm without a kselftest dependency.
> 
> Signed-off-by: Sarthak Sharma <sarthak.sharma@arm.com>
> ---
>  .../testing/selftests/mm/hugepage_settings.c  |  98 +++++++++++---
>  tools/testing/selftests/mm/khugepaged.c       |  14 +-
>  .../selftests/mm/split_huge_page_test.c       |   5 +-
>  tools/testing/selftests/mm/vm_util.c          | 120 ++++++++++++------
>  tools/testing/selftests/mm/vm_util.h          |   8 +-
>  5 files changed, 178 insertions(+), 67 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/hugepage_settings.c b/tools/testing/selftests/mm/hugepage_settings.c
> index d7917dce3aba..5bcda01ac4f6 100644
> --- a/tools/testing/selftests/mm/hugepage_settings.c
> +++ b/tools/testing/selftests/mm/hugepage_settings.c
> @@ -8,6 +8,7 @@
>  #include <stdlib.h>
>  #include <string.h>
>  #include <unistd.h>
> +#include <errno.h>
>  
>  #include "vm_util.h"
>  #include "hugepage_settings.h"
> @@ -48,6 +49,11 @@ static const char * const shmem_enabled_strings[] = {
>  	NULL
>  };
>  
> +static void print_file_access_error(const char *path, int ret)
> +{
> +	printf("# %s: %s (%d)\n", path, strerror(-ret), -ret);
ksft_print_msg() is what you want here. It adds # by default.

...

Thanks,
Usama