+ *
+ * If @index_type is INDEX_TYPE_ALLOCATION, @ia_page is the locked page
+ * containing the index allocation block containing the index entry @ie.
+ * Otherwise, @ia_page is NULL.
+ *
+ * Note, we drop (and then reacquire) the page lock on @ia_page across the
+ * @filldir() call otherwise we would deadlock with NFSd when it calls ->lookup
+ * since ntfs_lookup() will lock the same page. As an optimization, we do not
+ * retake the lock if we are returning a non-zero value as ntfs_readdir()
+ * would need to drop the lock immediately anyway.