[RFC PATCH v2 17/19] selftests/vm: add KSM get merge type test

[Stefan Roesch <shr@devkernel.io>]

This adds the -G flag to the ksm_tests to query if prctl has been used
to enable ksm merging.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 tools/testing/selftests/mm/ksm_tests.c | 37 ++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c
index 386a0929c8a3..9667cb3b8c6a 100644
--- a/tools/testing/selftests/mm/ksm_tests.c
+++ b/tools/testing/selftests/mm/ksm_tests.c
@@ -45,6 +45,7 @@ enum ksm_merge_type {
 enum ksm_test_name {
 	CHECK_KSM_MERGE,
 	CHECK_KSM_UNMERGE,
+	CHECK_KSM_GET_MERGE_TYPE,
 	CHECK_KSM_ZERO_PAGE_MERGE,
 	CHECK_KSM_NUMA_MERGE,
 	KSM_MERGE_TIME,
@@ -124,7 +125,8 @@ static void print_help(void)
 	       " -D evaluate unmerging time and speed when disabling KSM.\n"
 	       "    For this test, the size of duplicated memory area (in MiB)\n"
 	       "    must be provided using -s option\n"
-	       " -C evaluate the time required to break COW of merged pages.\n\n");
+	       " -C evaluate the time required to break COW of merged pages.\n"
+	       " -G query merge mode\n\n");
 
 	printf(" -a: specify the access protections of pages.\n"
 	       "     <prot> must be of the form [rwx].\n"
@@ -323,6 +325,31 @@ static int check_ksm_merge(int merge_type, int mapping, int prot,
 	return KSFT_FAIL;
 }
 
+static int check_ksm_get_merge_type(void)
+{
+	if (prctl(PR_SET_MEMORY_MERGE, 1)) {
+		perror("prctl set");
+		return 1;
+	}
+
+	int is_on = prctl(PR_GET_MEMORY_MERGE, 0);
+
+	if (prctl(PR_SET_MEMORY_MERGE, 0)) {
+		perror("prctl set");
+		return 1;
+	}
+
+	int is_off = prctl(PR_GET_MEMORY_MERGE, 0);
+
+	if (is_on && is_off) {
+		printf("OK\n");
+		return KSFT_PASS;
+	}
+
+	printf("Not OK\n");
+	return KSFT_FAIL;
+}
+
 static int check_ksm_unmerge(int merge_type, int mapping, int prot, int timeout, size_t page_size)
 {
 	void *map_ptr;
@@ -733,7 +760,7 @@ int main(int argc, char *argv[])
 	bool merge_across_nodes = KSM_MERGE_ACROSS_NODES_DEFAULT;
 	long size_MB = 0;
 
-	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:t:MUZNPCHD")) != -1) {
+	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:t:GMUZNPCHD")) != -1) {
 		switch (opt) {
 		case 'a':
 			prot = str_to_prot(optarg);
@@ -792,6 +819,9 @@ int main(int argc, char *argv[])
 		case 'Z':
 			test_name = CHECK_KSM_ZERO_PAGE_MERGE;
 			break;
+		case 'G':
+			test_name = CHECK_KSM_GET_MERGE_TYPE;
+			break;
 		case 'N':
 			test_name = CHECK_KSM_NUMA_MERGE;
 			break;
@@ -841,6 +871,9 @@ int main(int argc, char *argv[])
 		ret = check_ksm_unmerge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
 					ksm_scan_limit_sec, page_size);
 		break;
+	case CHECK_KSM_GET_MERGE_TYPE:
+		ret = check_ksm_get_merge_type();
+		break;
 	case CHECK_KSM_ZERO_PAGE_MERGE:
 		ret = check_ksm_zero_page_merge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
 						page_count, ksm_scan_limit_sec, use_zero_pages,
-- 
2.30.2