after calling fork() in the test_prctl_fork_exec() function, the global variable ksm_full_scans_fd is initialized to 0 in the child process upon entering the main function of ./ksm_functional_tests. In the function call chain test_child_ksm() -> __mmap_and_merge_range -> ksm_merge-> ksm_get_full_scans, start_scans = ksm_get_full_scans() will return an error. Therefore, the value of ksm_full_scans_fd needs to be initialized before calling test_child_ksm in the child process.

Signed-off-by: aigourensheng shechenglong001@gmail.com --- .../selftests/mm/ksm_functional_tests.c | 38 +++++++++++-------- 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c index 37de82da9be7..b61803e36d1c 100644 --- a/tools/testing/selftests/mm/ksm_functional_tests.c +++ b/tools/testing/selftests/mm/ksm_functional_tests.c @@ -656,12 +656,33 @@ static void test_prot_none(void) munmap(map, size); }

+static void init_global_file_handles(void) +{ + mem_fd = open("/proc/self/mem", O_RDWR); + if (mem_fd < 0) + ksft_exit_fail_msg("opening /proc/self/mem failed\n"); + ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR); + if (ksm_fd < 0) + ksft_exit_skip("open("/sys/kernel/mm/ksm/run") failed\n"); + ksm_full_scans_fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY); + if (ksm_full_scans_fd < 0) + ksft_exit_skip("open("/sys/kernel/mm/ksm/full_scans") failed\n"); + pagemap_fd = open("/proc/self/pagemap", O_RDONLY); + if (pagemap_fd < 0) + ksft_exit_skip("open("/proc/self/pagemap") failed\n"); + proc_self_ksm_stat_fd = open("/proc/self/ksm_stat", O_RDONLY); + proc_self_ksm_merging_pages_fd = open("/proc/self/ksm_merging_pages", + O_RDONLY); + ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR); +} + int main(int argc, char **argv) { unsigned int tests = 8; int err;

if (argc > 1 && !strcmp(argv[1], FORK_EXEC_CHILD_PRG_NAME)) { + init_global_file_handles(); exit(test_child_ksm()); }

@@ -674,22 +695,7 @@ int main(int argc, char **argv)

pagesize = getpagesize();

- mem_fd = open("/proc/self/mem", O_RDWR); - if (mem_fd < 0) - ksft_exit_fail_msg("opening /proc/self/mem failed\n"); - ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR); - if (ksm_fd < 0) - ksft_exit_skip("open("/sys/kernel/mm/ksm/run") failed\n"); - ksm_full_scans_fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY); - if (ksm_full_scans_fd < 0) - ksft_exit_skip("open("/sys/kernel/mm/ksm/full_scans") failed\n"); - pagemap_fd = open("/proc/self/pagemap", O_RDONLY); - if (pagemap_fd < 0) - ksft_exit_skip("open("/proc/self/pagemap") failed\n"); - proc_self_ksm_stat_fd = open("/proc/self/ksm_stat", O_RDONLY); - proc_self_ksm_merging_pages_fd = open("/proc/self/ksm_merging_pages", - O_RDONLY); - ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR); + init_global_file_handles();

test_unmerge(); test_unmerge_zero_pages();