linux-kernel - Re: [PATCH v2] selftests/filesystems/mount-notify: fix unused unused result warning

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Message-ID: <CAC1kPDMUUc3c7Ofyr7vXiW_Yt-kwrAOHK=9kQd5uCm2vv4h1gA@mail.gmail.com>
Date: Fri, 20 Jun 2025 22:55:55 +0800
From: Chen Linxuan <chenlinxuan@...ontech.com>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc: Chen Linxuan <chenlinxuan@...ontech.com>, Shuah Khan <shuah@...nel.org>, 
	Christian Brauner <brauner@...nel.org>, Amir Goldstein <amir73il@...il.com>, 
	John Hubbard <jhubbard@...dia.com>, Miklos Szeredi <mszeredi@...hat.com>, Jan Kara <jack@...e.cz>, 
	zhanjun@...ontech.com, niecheng1@...ontech.com, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] selftests/filesystems/mount-notify: fix unused unused
 result warning

On Fri, Jun 20, 2025 at 10:46 PM Muhammad Usama Anjum
<usama.anjum@...labora.com> wrote:
>
> On 6/20/25 8:50 AM, Chen Linxuan wrote:
> > When running `make kselftest`, the following compilation warning was encountered:
> >
> > mount-notify_test.c: In function ‘fanotify_rmdir’:
> > mount-notify_test.c:490:17: warning: ignoring return value of ‘chdir’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
> >   490 |                 chdir("/");
> >       |                 ^~~~~~~~~~
> >
> > Signed-off-by: Chen Linxuan <chenlinxuan@...ontech.com>
> > ---
> > Changes in v2:
> > - Apply changes suggested by Shuah Khan
> > - Link to v1: https://lore.kernel.org/all/20250610020758.2798787-2-chenlinxuan@uniontech.com/
> > ---
> >  .../filesystems/mount-notify/mount-notify_test.c  | 15 ++++++++++-----
> >  .../mount-notify/mount-notify_test_ns.c           | 15 ++++++++++-----
> >  2 files changed, 20 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c
> > index 5a3b0ace1a88c..f8e0c6b06e2d9 100644
> > --- a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c
> > +++ b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c
> > @@ -458,12 +458,17 @@ TEST_F(fanotify, rmdir)
> >       ASSERT_GE(ret, 0);
> >
> >       if (ret == 0) {
> > -             chdir("/");
> > -             unshare(CLONE_NEWNS);
> > -             mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL);
> > -             umount2("/a", MNT_DETACH);
> > +             if (chdir("/"))
> Please use the APIs provided by the kselftest_harness.h instead of checking
> return types manually. For example:
> use ASSERT_EQ(chdir("/", 0)).

Are you sure？We're in a forked sub process here.

>
> > +                     exit(-1);
> > +             if (unshare(CLONE_NEWNS))
> > +                     exit(-1);
> > +             if (mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL))
> > +                     exit(-1);
> > +             if (umount2("/a", MNT_DETACH))
> > +                     exit(-1);
> >               // This triggers a detach in the other namespace
> > -             rmdir("/a");
> > +             if (rmdir("/a"))
> > +                     exit(-1);
> >               exit(0);
> >       }
> >       wait(NULL);
> > diff --git a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
> > index d91946e69591a..d6a6a7ee87028 100644
> > --- a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
> > +++ b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
> > @@ -486,12 +486,17 @@ TEST_F(fanotify, rmdir)
> >       ASSERT_GE(ret, 0);
> >
> >       if (ret == 0) {
> > -             chdir("/");
> > -             unshare(CLONE_NEWNS);
> > -             mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL);
> > -             umount2("/a", MNT_DETACH);
> > +             if (chdir("/"))
> > +                     exit(-1);
> > +             if (unshare(CLONE_NEWNS))
> > +                     exit(-1);
> > +             if (mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL))
> > +                     exit(-1);
> > +             if (umount2("/a", MNT_DETACH))
> > +                     exit(-1);
> >               // This triggers a detach in the other namespace
> > -             rmdir("/a");
> > +             if (rmdir("/a"))
> > +                     exit(-1);
> >               exit(0);
> >       }
> >       wait(NULL);
>
>
>