linux-kernel - Re: [PATCH v4 07/19] selftests/resctrl: Refactor remount_resctrl(bool mum_resctrlfs) to mount

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Date:   Thu, 13 Jul 2023 15:57:05 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        <linux-kselftest@...r.kernel.org>, Shuah Khan <shuah@...nel.org>,
        "Shaopeng Tan" <tan.shaopeng@...fujitsu.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 07/19] selftests/resctrl: Refactor remount_resctrl(bool
 mum_resctrlfs) to mount_resctrl()

Hi Ilpo,

On 7/13/2023 6:19 AM, Ilpo Järvinen wrote:
> Mount/umount of the resctrl FS is now paired nicely per test.
> 
> Rename remount_resctrl(bool mum_resctrlfs) to mount_resctrl(). Make
> it unconditionally try to mount the resctrl FS and return error if
> resctrl FS was mounted already.
> 
> While at it, group the mount/umount prototypes in the header.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---
>  tools/testing/selftests/resctrl/resctrl.h     |  2 +-
>  .../testing/selftests/resctrl/resctrl_tests.c |  8 ++++----
>  tools/testing/selftests/resctrl/resctrlfs.c   | 20 +++++--------------
>  3 files changed, 10 insertions(+), 20 deletions(-)
> 
> diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
> index f455f0b7e314..23af3fb73cb4 100644
> --- a/tools/testing/selftests/resctrl/resctrl.h
> +++ b/tools/testing/selftests/resctrl/resctrl.h
> @@ -85,8 +85,8 @@ extern char llc_occup_path[1024];
>  int get_vendor(void);
>  bool check_resctrlfs_support(void);
>  int filter_dmesg(void);
> -int remount_resctrlfs(bool mum_resctrlfs);
>  int get_resource_id(int cpu_no, int *resource_id);
> +int mount_resctrlfs(void);
>  int umount_resctrlfs(void);
>  int validate_bw_report_request(char *bw_report);
>  bool validate_resctrl_feature_request(const char *resctrl_val);
> diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
> index a421d045de08..3f26d2279f75 100644
> --- a/tools/testing/selftests/resctrl/resctrl_tests.c
> +++ b/tools/testing/selftests/resctrl/resctrl_tests.c
> @@ -77,7 +77,7 @@ static void run_mbm_test(bool has_ben, char **benchmark_cmd, int span,
>  
>  	ksft_print_msg("Starting MBM BW change ...\n");
>  
> -	res = remount_resctrlfs(true);
> +	res = mount_resctrlfs();
>  	if (res) {
>  		ksft_exit_fail_msg("Failed to mount resctrl FS\n");
>  		return;
> @@ -106,7 +106,7 @@ static void run_mba_test(bool has_ben, char **benchmark_cmd, int span,
>  
>  	ksft_print_msg("Starting MBA Schemata change ...\n");
>  
> -	res = remount_resctrlfs(true);
> +	res = mount_resctrlfs();
>  	if (res) {
>  		ksft_exit_fail_msg("Failed to mount resctrl FS\n");
>  		return;
> @@ -132,7 +132,7 @@ static void run_cmt_test(bool has_ben, char **benchmark_cmd, int cpu_no)
>  
>  	ksft_print_msg("Starting CMT test ...\n");
>  
> -	res = remount_resctrlfs(true);
> +	res = mount_resctrlfs();
>  	if (res) {
>  		ksft_exit_fail_msg("Failed to mount resctrl FS\n");
>  		return;
> @@ -160,7 +160,7 @@ static void run_cat_test(int cpu_no, int no_of_bits)
>  
>  	ksft_print_msg("Starting CAT test ...\n");
>  
> -	res = remount_resctrlfs(true);
> +	res = mount_resctrlfs();
>  	if (res) {
>  		ksft_exit_fail_msg("Failed to mount resctrl FS\n");
>  		return;
> diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
> index b3a05488d360..f622245adafe 100644
> --- a/tools/testing/selftests/resctrl/resctrlfs.c
> +++ b/tools/testing/selftests/resctrl/resctrlfs.c
> @@ -48,29 +48,19 @@ static int find_resctrl_mount(char *buffer)
>  }
>  
>  /*
> - * remount_resctrlfs - Remount resctrl FS at /sys/fs/resctrl
> - * @mum_resctrlfs:	Should the resctrl FS be remounted?
> + * mount_resctrlfs - Mount resctrl FS at /sys/fs/resctrl
>   *
>   * If not mounted, mount it.
> - * If mounted and mum_resctrlfs then remount resctrl FS.
> - * If mounted and !mum_resctrlfs then noop
>   *
>   * Return: 0 on success, non-zero on failure
>   */

Since it is not obviously a "failure" I do think it will help to
add to the comments that resctrl already being mounted is treated as
a failure.

> -int remount_resctrlfs(bool mum_resctrlfs)
> +int mount_resctrlfs(void)
>  {
> -	char mountpoint[256];
>  	int ret;
>  
> -	ret = find_resctrl_mount(mountpoint);
> -	if (ret)
> -		strcpy(mountpoint, RESCTRL_PATH);
> -
> -	if (!ret && mum_resctrlfs && umount(mountpoint))
> -		ksft_print_msg("Fail: unmounting \"%s\"\n", mountpoint);
> -
> -	if (!ret && !mum_resctrlfs)
> -		return 0;
> +	ret = find_resctrl_mount(NULL);
> +	if (!ret)
> +		return -1;

This treats "ret == 0" as a failure. What about -ENXIO? It seems to
me that only "ret == -ENOENT" is "success".

>  
>  	ksft_print_msg("Mounting resctrl to \"%s\"\n", RESCTRL_PATH);
>  	ret = mount("resctrl", RESCTRL_PATH, "resctrl", 0, NULL);


Reinette