Re: [PATCH v2 3/3] selftests/mm: restore enable_soft_offline in hugetlb-soft-offline

On 15/08/2026 9:07 am, Song Hu wrote:
> hugetlb-soft-offline toggles /proc/sys/vm/enable_soft_offline between 1
> and 0 (test_soft_offline_common(1) then (0)) and leaves it at 0 when it
> finishes, silently disabling soft offlining for the whole system after
> the run.
> 
> Save the original value before the test and restore it from an atexit()
> handler, so the sysctl is also restored when the test exits early via
> ksft_exit_fail_msg(), as hugepage_restore_settings_atexit() in
> hugepage_settings.c already does.  Use read_num()/write_num() from
> vm_util instead of the hand-rolled popen()/fopen() helpers.
> 
> Signed-off-by: Song Hu <[email protected]>
> ---
>  .../selftests/mm/hugetlb-soft-offline.c       | 35 +++++++------------
>  1 file changed, 12 insertions(+), 23 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/hugetlb-soft-offline.c b/tools/testing/selftests/mm/hugetlb-soft-offline.c
> index bc202e4ed2bd..86259921d54c 100644
> --- a/tools/testing/selftests/mm/hugetlb-soft-offline.c
> +++ b/tools/testing/selftests/mm/hugetlb-soft-offline.c
> @@ -23,6 +23,7 @@
>  #include <sys/types.h>
>  
>  #include "kselftest.h"
> +#include "vm_util.h"
>  #include "hugepage_settings.h"
>  
>  #ifndef MADV_SOFT_OFFLINE
> @@ -31,6 +32,8 @@
>  
>  #define EPREFIX " !!! "
>  
> +#define ENABLE_SOFT_OFFLINE_PATH "/proc/sys/vm/enable_soft_offline"
> +
>  static int do_soft_offline(int fd, size_t len, int expect_errno)
>  {
>  	char *filemap = NULL;
> @@ -77,26 +80,12 @@ static int do_soft_offline(int fd, size_t len, int expect_errno)
>  	return ret;
>  }
>  
> -static int set_enable_soft_offline(int value)
> -{
> -	char cmd[256] = {0};
> -	FILE *cmdfile = NULL;
> -
> -	if (value != 0 && value != 1)
> -		return -EINVAL;
> -
> -	sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value);
> -	cmdfile = popen(cmd, "r");
> -
> -	if (cmdfile)
> -		ksft_print_msg("enable_soft_offline => %d\n", value);
> -	else {
> -		ksft_perror(EPREFIX "failed to set enable_soft_offline");
> -		return errno;
> -	}
> +static unsigned long orig_enable_soft_offline = -1UL;
>  
> -	pclose(cmdfile);
> -	return 0;
> +static void restore_enable_soft_offline(void)
> +{
> +	if (orig_enable_soft_offline != -1UL)
> +		write_num(ENABLE_SOFT_OFFLINE_PATH, orig_enable_soft_offline);
>  }
>  
>  static int create_hugetlbfs_file(struct statfs *file_stat)
> @@ -145,10 +134,7 @@ static void test_soft_offline_common(int enable_soft_offline)
>  	hugepagesize_kb = file_stat.f_bsize / 1024;
>  	ksft_print_msg("Hugepagesize is %ldkB\n", hugepagesize_kb);
>  
> -	if (set_enable_soft_offline(enable_soft_offline) != 0) {
> -		close(fd);
> -		ksft_exit_fail_msg("Failed to set enable_soft_offline\n");
> -	}
> +	write_num(ENABLE_SOFT_OFFLINE_PATH, enable_soft_offline);
>  
>  	nr_hugepages_before = hugetlb_nr_default_pages();
>  
> @@ -192,6 +178,9 @@ int main(int argc, char **argv)
>  
>  	ksft_set_plan(2);
>  
> +	orig_enable_soft_offline = read_num(ENABLE_SOFT_OFFLINE_PATH);
> +	atexit(restore_enable_soft_offline);
> +

Seems good. Thanks for fixing.

Reviewed-by: Muhammad Usama Anjum <[email protected]>
Tested-by: Muhammad Usama Anjum <[email protected]>

Thanks,
Usama