sysctl: Add a selftest for handling empty dirs

Basic test to ensure that empty directories can be registered and that
they in turn can serve as a base dir for other registrations.

Add one test to the sysctl selftest module. It first registers an empty
directory under "empty_add" and then uses that as a base to register
another empty dir.
The sysctl bash script then checks that "empty_add" is present and that
there an empty directory within it.

Signed-off-by: Joel Granados <[e-mail]>
Signed-off-by: Luis Chamberlain <[e-mail]>

lib/test_sysctl.c

···
 	struct ctl_table_header *test_h_setup_node;
 	struct ctl_table_header *test_h_mnt;
 	struct ctl_table_header *test_h_mnterror;
+	struct ctl_table_header *empty_add;
+	struct ctl_table_header *empty;
 } sysctl_test_headers;
 
 struct test_sysctl_data {
···
 	return 0;
 }
 
+static struct ctl_table test_table_empty[] = { };
+
+static int test_sysctl_run_register_empty(void)
+{
+	/* Tets that an empty dir can be created */
+	sysctl_test_headers.empty_add
+		= register_sysctl("debug/test_sysctl/empty_add", test_table_empty);
+	if (!sysctl_test_headers.empty_add)
+		return -ENOMEM;
+
+	/* Test that register on top of an empty dir works */
+	sysctl_test_headers.empty
+		= register_sysctl("debug/test_sysctl/empty_add/empty", test_table_empty);
+	if (!sysctl_test_headers.empty)
+		return -ENOMEM;
+
+	return 0;
+}
+
 static int __init test_sysctl_init(void)
 {
 	int err;
···
 		goto out;
 
 	err = test_sysctl_run_register_mount_point();
+	if (err)
+		goto out;
+
+	err = test_sysctl_run_register_empty();
 
 out:
 	return err;
···
 		unregister_sysctl_table(sysctl_test_headers.test_h_mnt);
 	if (sysctl_test_headers.test_h_mnterror)
 		unregister_sysctl_table(sysctl_test_headers.test_h_mnterror);
+	if (sysctl_test_headers.empty)
+		unregister_sysctl_table(sysctl_test_headers.empty);
+	if (sysctl_test_headers.empty_add)
+		unregister_sysctl_table(sysctl_test_headers.empty_add);
 }
 
 module_exit(test_sysctl_exit);

tools/testing/selftests/sysctl/sysctl.sh

···
 ALL_TESTS="$ALL_TESTS 0008:1:1:match_int:1"
 ALL_TESTS="$ALL_TESTS 0009:1:1:unregister_error:0"
 ALL_TESTS="$ALL_TESTS 0010:1:1:mnt/mnt_error:0"
+ALL_TESTS="$ALL_TESTS 0011:1:1:empty_add:0"
 
 function allow_user_defaults()
 {
···
 	return 0
 }
 
+sysctl_test_0011()
+{
+	TARGET="${SYSCTL}/$(get_test_target 0011)"
+	echo -n "Testing empty dir handling in ${TARGET} ... "
+	if [ ! -d ${TARGET} ]; then
+		echo -e "FAIL\nCould not create ${TARGET}" >&2
+		rc=1
+		test_rc
+	fi
+
+	TARGET2="${TARGET}/empty"
+	if [ ! -d ${TARGET2} ]; then
+		echo -e "FAIL\nCould not create ${TARGET2}" >&2
+		rc=1
+		test_rc
+	fi
+
+	echo "OK"
+	return 0
+}
+
 list_tests()
 {
 	echo "Test ID list:"
···
 	echo "0008 x $(get_test_count 0008) - tests sysctl macro values match"
 	echo "0009 x $(get_test_count 0009) - tests sysct unregister"
 	echo "0010 x $(get_test_count 0010) - tests sysct mount point"
+	echo "0011 x $(get_test_count 0011) - tests empty directories"
 }
 
 usage()