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charset="utf-8" Added a new selftest to verify whether the `ksm_merging_pages` counter in `mm_struct` is not inherited by a child process after fork. This helps ensure correctness of KSM accounting across process creation. Acked-by: David Hildenbrand Signed-off-by: Donet Tom --- .../selftests/mm/ksm_functional_tests.c | 43 ++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/test= ing/selftests/mm/ksm_functional_tests.c index 712f43c87736..ac136f04b8d6 100644 --- a/tools/testing/selftests/mm/ksm_functional_tests.c +++ b/tools/testing/selftests/mm/ksm_functional_tests.c @@ -602,6 +602,46 @@ static void test_prot_none(void) munmap(map, size); } =20 +static void test_fork_ksm_merging_page_count(void) +{ + const unsigned int size =3D 2 * MiB; + char *map; + pid_t child_pid; + int status; + + ksft_print_msg("[RUN] %s\n", __func__); + + map =3D mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERG= E_MADVISE); + if (map =3D=3D MAP_FAILED) + return; + + child_pid =3D fork(); + if (!child_pid) { + init_global_file_handles(); + exit(ksm_get_self_merging_pages()); + } else if (child_pid < 0) { + ksft_test_result_fail("fork() failed\n"); + goto unmap; + } + + if (waitpid(child_pid, &status, 0) < 0) { + ksft_test_result_fail("waitpid() failed\n"); + goto unmap; + } + + status =3D WEXITSTATUS(status); + if (status) { + ksft_test_result_fail("ksm_merging_page in child: %d\n", status); + goto unmap; + } + + ksft_test_result_pass("ksm_merging_pages is not inherited after fork\n"); + +unmap: + ksm_stop(); + munmap(map, size); +} + static void init_global_file_handles(void) { mem_fd =3D open("/proc/self/mem", O_RDWR); @@ -620,7 +660,7 @@ static void init_global_file_handles(void) =20 int main(int argc, char **argv) { - unsigned int tests =3D 8; + unsigned int tests =3D 9; int err; =20 if (argc > 1 && !strcmp(argv[1], FORK_EXEC_CHILD_PRG_NAME)) { @@ -652,6 +692,7 @@ int main(int argc, char **argv) test_prctl_fork(); test_prctl_fork_exec(); test_prctl_unmerge(); + test_fork_ksm_merging_page_count(); =20 err =3D ksft_get_fail_cnt(); if (err) --=20 2.51.0