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

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Message-ID: <213adda0-1db2-46e7-9342-cc97fbd58d96@collabora.com>
Date: Fri, 20 Jun 2025 19:46:05 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: 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>
Cc: 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 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)).

> +			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);