This is xnu-11215.1.10. See this file in: 
/* compile: xcrun -sdk macosx.internal clang -ldarwintest -o getattrlist_fstype getattrlist_fstype.c -g -Weverything */

#include <darwintest.h>
#include <darwintest_utils.h>
#include <darwintest_multiprocess.h>
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/attr.h>
#include <sys/event.h>
#include <sys/resource.h>
#include <sys/mount.h>

#ifndef ATTR_VOL_FSTYPENAME
#define ATTR_VOL_FSTYPENAME 0x00100000
#endif

#ifndef ATTR_VOL_FSSUBTYPE
#define ATTR_VOL_FSSUBTYPE 0x00200000
#endif

T_GLOBAL_META(
	T_META_NAMESPACE("xnu.vfs"),
	T_META_RADAR_COMPONENT_NAME("xnu"),
	T_META_RADAR_COMPONENT_VERSION("vfs"),
	T_META_ASROOT(false),
	T_META_CHECK_LEAKS(false));

T_DECL(getattrlist_fstype,
    "test ATTR_VOL_FSTYPENAME and ATTR_VOL_FSSUBTYPE",
    T_META_ASROOT(false))
{
	struct myattrbuf {
		uint32_t length;
		attribute_set_t returned_attrs;
		vol_attributes_attr_t vol_attributes;
		attrreference_t fstypename_ref;
		uint32_t fssubtype;
		char fstypename[MFSTYPENAMELEN];
	} attrbuf;
	struct attrlist attrs = {
		.bitmapcount = ATTR_BIT_MAP_COUNT,
		.commonattr = ATTR_CMN_RETURNED_ATTRS,
		/*
		 * Request ATTR_VOL_ATTRIBUTES to ensure that
		 * ATTR_VOL_FSTYPENAME and ATTR_VOL_FSSUBTYPE
		 * are packed into the buffer *after*.
		 */
		.volattr = ATTR_VOL_INFO | ATTR_VOL_ATTRIBUTES |
	    ATTR_VOL_FSTYPENAME | ATTR_VOL_FSSUBTYPE,
	};
	const char *tmpdir = dt_tmpdir();
	struct statfs sfs;

	T_SETUPBEGIN;

	T_WITH_ERRNO;
	T_ASSERT_POSIX_ZERO(statfs(tmpdir, &sfs),
	    "Setup: statfs'ing tmpdir: %s", tmpdir);

	T_SETUPEND;

	memset(&attrbuf, 0, sizeof(attrbuf));
	T_WITH_ERRNO;
	T_ASSERT_POSIX_ZERO(getattrlist(tmpdir, &attrs, &attrbuf,
	    sizeof(attrbuf), FSOPT_REPORT_FULLSIZE | FSOPT_PACK_INVAL_ATTRS),
	    "Calling getattrlist on tmpdir: %s", tmpdir);

	T_ASSERT_TRUE(attrbuf.length <= sizeof(attrbuf),
	    "Asserting attrbuf.length <= sizeof(attrbuf)");
	T_ASSERT_TRUE(attrbuf.returned_attrs.volattr & ATTR_VOL_FSTYPENAME,
	    "Asserting ATTR_VOL_FSTYPENAME was returned");
	T_ASSERT_TRUE(attrbuf.returned_attrs.volattr & ATTR_VOL_FSSUBTYPE,
	    "Asserting ATTR_VOL_FSSUBTYPE was returned");
	T_ASSERT_TRUE(attrbuf.fstypename_ref.attr_dataoffset + offsetof(struct myattrbuf, fstypename_ref) == offsetof(struct myattrbuf, fstypename),
	    "Asserting fstypename in expected place (%d + %lu == %lu)",
	    attrbuf.fstypename_ref.attr_dataoffset,
	    offsetof(struct myattrbuf, fstypename_ref),
	    offsetof(struct myattrbuf, fstypename));
	T_ASSERT_TRUE(attrbuf.fstypename_ref.attr_length <= MFSTYPENAMELEN,
	    "Asserting fstypename length is valid");
	T_ASSERT_TRUE(strcmp(attrbuf.fstypename, sfs.f_fstypename) == 0,
	    "Asserting that fstypename matches");
	T_ASSERT_TRUE(attrbuf.fssubtype == sfs.f_fssubtype,
	    "Asserting that fssubtype matches");
}