Re: [PATCH v4 1/5] selftests/mm: make file helpers return errors

[Mike Rapoport]

On Wed, 27 May 2026 19:54:28 +0530, Sarthak Sharma <sarthak.sha...@arm.com> 
wrote:

Hi Sarthak,

>
> diff --git a/tools/testing/selftests/mm/hugepage_settings.c 
> b/tools/testing/selftests/mm/hugepage_settings.c
> index 2eab2110ac6a..c2f97fe97e58 100644
> --- a/tools/testing/selftests/mm/hugepage_settings.c
> +++ b/tools/testing/selftests/mm/hugepage_settings.c
> @@ -61,7 +62,9 @@ int thp_read_string(const char *name, const char * const 
> strings[])
>               exit(EXIT_FAILURE);
>       }
>  
> -     if (!read_file(path, buf, sizeof(buf))) {
> +     ret = read_file(path, buf, sizeof(buf));
> +     if (ret < 0) {
> +             errno = -ret;
>               perror(path);

Hmm, looks like those slipped ksft conversion :/

For kselftest compatibility this should be

        printf("# %s: %s (%d)\n", path, strerror(errno), errno);

> @@ -103,12 +106,18 @@ void thp_write_string(const char *name, const char *val)
>               printf("%s: Pathname is too long\n", __func__);
>               exit(EXIT_FAILURE);
>       }
> -     write_file(path, val, strlen(val) + 1);
> +     ret = write_file(path, val, strlen(val) + 1);
> +     if (ret < 0) {
> +             errno = -ret;
> +             perror(path);
> +             exit(EXIT_FAILURE);

These seem to repeat themself, how about we move prints to read/write
helpers?

Then it wouldn't matter for the callers what the exact error was, and no
need for errno games.

>
> diff --git a/tools/testing/selftests/mm/vm_util.c 
> b/tools/testing/selftests/mm/vm_util.c
> index 311fc5b4513e..290e5c29123e 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -703,62 +703,72 @@ int read_file(const char *path, char *buf, size_t 
> buflen)
>       int fd;
>       ssize_t numread;
>  
> +     if (buflen < 2)
> +             return -EINVAL;

heh, this feels overly protective :)

-- 
Sincerely yours,
Mike.