Commit 08ff89b5 authored by Donet Tom's avatar Donet Tom Committed by Andrew Morton
Browse files

selftests/mm: add fork inheritance test for ksm_merging_pages counter 

Add 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.

Link: https://lkml.kernel.org/r/e7bb17d374133bd31a3e423aa9e46e1122e74971.1758648700.git.donettom@linux.ibm.com


Signed-off-by: default avatarDonet Tom <donettom@linux.ibm.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Aboorva Devarajan <aboorvad@linux.ibm.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4d6fc29f

tools/testing/selftests/mm/ksm_functional_tests.c

+42 −1
Original line number Diff line number Diff line
@@ -602,6 +602,46 @@ static void test_prot_none(void) 
	munmap(map, size);

}



static void test_fork_ksm_merging_page_count(void)

{

	const unsigned int size = 2 * MiB;

	char *map;

	pid_t child_pid;

	int status;



	ksft_print_msg("[RUN] %s\n", __func__);



	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);

	if (map == MAP_FAILED)

		return;



	child_pid = 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 = 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 = open("/proc/self/mem", O_RDWR);
@@ -620,7 +660,7 @@ static void init_global_file_handles(void) 


int main(int argc, char **argv)

{

	unsigned int tests = 8;

	unsigned int tests = 9;

	int err;



	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();



	err = ksft_get_fail_cnt();

	if (err)