conf-sanity test_87 calls umount_ldiskfs() and fails to find the function
The problem is that umount_ldiskfs() does not exist, but unmount_ldiskfs() does exist. conf-sanity test 87 is the only test and only test suite that calls unmount_ldiskfs().
umount_client() is another function that exists and is used throughout conf-sanity. Since the unmount command is umount, let’s be consistent and change unmount_ldiskfs() to umount_ldiskfs().