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, as hugepage_restore_settings_atexit() in hugepage_settings.c already does. Use read_num()/write_num() from vm_util instead of hand-rolled popen()/fopen() helpers. The restore handler must not call write_num(): on failure it re-enters exit() through ksft_exit_fail_msg(), which is undefined behavior from inside an atexit handler. A non-root run hits it directly - the restore write fails the same way the write that triggered the exit did. Restore with plain open()/write(), best effort. Signed-off-by: Song Hu <[email protected]> --- Changes since v3: the restore handler no longer uses write_num(), whose failure path calls exit() from inside an atexit handler - undefined behavior on a non-root run. Restore with plain open()/write(), best effort. .../selftests/mm/hugetlb-soft-offline.c | 49 +++++++++++-------- 1 file changed, 28 insertions(+), 21 deletions(-) diff --git a/tools/testing/selftests/mm/hugetlb-soft-offline.c b/tools/testing/selftests/mm/hugetlb-soft-offline.c index bc202e4ed2bd..4af9d3db7b5b 100644 --- a/tools/testing/selftests/mm/hugetlb-soft-offline.c +++ b/tools/testing/selftests/mm/hugetlb-soft-offline.c @@ -11,6 +11,7 @@ #define _GNU_SOURCE #include <errno.h> +#include <fcntl.h> #include <stdlib.h> #include <stdio.h> #include <string.h> @@ -23,6 +24,7 @@ #include <sys/types.h> #include "kselftest.h" +#include "vm_util.h" #include "hugepage_settings.h" #ifndef MADV_SOFT_OFFLINE @@ -31,6 +33,8 @@ #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 +81,29 @@ 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; +static unsigned long orig_enable_soft_offline = -1UL; - sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value); - cmdfile = popen(cmd, "r"); +/* + * Runs from an atexit handler, so it must not call anything that + * exits on failure: write_num() would re-enter exit() through + * ksft_exit_fail_msg(). + */ +static void restore_enable_soft_offline(void) +{ + char buf[24]; + int fd, len; - if (cmdfile) - ksft_print_msg("enable_soft_offline => %d\n", value); - else { - ksft_perror(EPREFIX "failed to set enable_soft_offline"); - return errno; - } + if (orig_enable_soft_offline == -1UL) + return; - pclose(cmdfile); - return 0; + len = snprintf(buf, sizeof(buf), "%lu", orig_enable_soft_offline); + fd = open(ENABLE_SOFT_OFFLINE_PATH, O_WRONLY); + if (fd < 0) + return; + if (write(fd, buf, len) != len) + ksft_print_msg("failed to restore enable_soft_offline: %s\n", + strerror(errno)); + close(fd); } static int create_hugetlbfs_file(struct statfs *file_stat) @@ -145,10 +152,7 @@ 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 +196,9 @@ 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); + test_soft_offline_common(1); test_soft_offline_common(0); -- 2.43.0
