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

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Message-ID: <f9b2deab-bdc4-4fd4-be1b-cb6617060086@collabora.com>
Date: Mon, 23 Jun 2025 09:22:31 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Chen Linxuan <chenlinxuan@...ontech.com>
Cc: 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 6/20/25 7:55 PM, Chen Linxuan wrote:
> 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.
ASSERT_* are macros. They can be used anywhere. Please give it a try.

> 
>>
>>> +                     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);
>>
>>
>>