tools/cgget: fix '-m' option usage

'-m' is logically an independent option and should not be mixed and
matched with other options and also when used with '-h', help always
takes precedence over other options. Fix both cases of usage with
a bool flag, that gets set when parsing the command line option but
executes only it meets the rules of not mixing with other options.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
(cherry picked from commit ce809ea)

src/tools/cgget.c

@@ -398,6 +398,7 @@ static int parse_opts(int argc, char *argv[], struct cgroup **cg_list[], int * c
 {
 	bool do_not_fill_controller = false;
 	bool first_cgroup_is_dummy = false;
+	bool cgroup_mount_type = false;
 	bool fill_controller = false;
 	int ret = 0;
 	int c;
@@ -451,9 +452,7 @@ static int parse_opts(int argc, char *argv[], struct cgroup **cg_list[], int * c
 				goto err;
 			break;
 		case 'm':
-			ret = find_cgroup_mount_type();
-			if (ret)
-				goto err;
+			cgroup_mount_type = true;
 			break;
 		default:
 			usage(1, argv[0]);
@@ -467,6 +466,18 @@ static int parse_opts(int argc, char *argv[], struct cgroup **cg_list[], int * c
 		exit(EXIT_BADARGS);
 	}
 
+	/* '-m' should not used with other options */
+	if (cgroup_mount_type && (fill_controller || do_not_fill_controller)) {
+		usage(1, argv[0]);
+		exit(EXIT_BADARGS);
+	}
+
+	if (cgroup_mount_type) {
+		ret = find_cgroup_mount_type();
+		if (ret)
+			goto err;
+	}
+
 	ret = parse_opt_args(argc, argv, cg_list, cg_list_len, first_cgroup_is_dummy);
 	if (ret)
 		goto err;