linux-kernel - Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as size

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Message-ID: <CAEemH2dZ3DxDPWuV1Uze213CqoFHec9kK+MeteigGANYTUzbqA@mail.gmail.com>
Date: Tue, 23 Dec 2025 10:41:22 +0800
From: Li Wang <liwang@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Laight <david.laight.linux@...il.com>, linux-kselftest@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	David Hildenbrand <david@...nel.org>, Mark Brown <broonie@...nel.org>, Shuah Khan <shuah@...nel.org>, 
	Waiman Long <longman@...hat.com>
Subject: Re: [PATCH v3 1/3] selftests/mm/write_to_hugetlbfs: parse -s as size_t

Andrew Morton <akpm@...ux-foundation.org> wrote:

> > > It is best to use strtoul() and check the 'end' character is '\0'.
> >
> > Hmm, that sounds like we need to go back to the patch V1 [1] method.
> > But I am not sure, @Andrew Morton, do you think so?
> >
> > --- a/tools/testing/selftests/mm/write_to_hugetlbfs.c
> > +++ b/tools/testing/selftests/mm/write_to_hugetlbfs.c
> > @@ -86,10 +86,17 @@ int main(int argc, char **argv)
> >         while ((c = getopt(argc, argv, "s:p:m:owlrn")) != -1) {
> >                 switch (c) {
> >                 case 's':
> > -                       if (sscanf(optarg, "%zu", &size) != 1) {
> > -                               perror("Invalid -s.");
> > +                       char *end = NULL;
> > +                       unsigned long tmp = strtoul(optarg, &end, 10);
> > +                       if (errno || end == optarg || *end != '\0') {
> > +                               perror("Invalid -s size");
> >                                 exit_usage();
> >                         }
> > +                       if (tmp == 0) {
> > +                               perror("size not found");
> > +                               exit_usage();
> > +                       }
> > +                       size = (size_t)tmp;
> >                         break;
> >                 case 'p':
>
> Geeze guys, it's just a selftest.
>
> hp2:/usr/src/linux-6.19-rc1> grep -r scanf tools/testing/selftests | wc -l
> 177
>
> if your command line breaks the selftest, fix your command line?

Yes, I am ok with sscanf() :-).

In fact, write_to hugetlbfs currently only accepts arguments from
charge_reserved_hugetlb.sh, and the way the '-s' is used is not
very diverse.

--
Regards,
Li Wang