-Data is stored in ext4 dirent after file-name, this space is accounted
-in de->rec_len. Flag EXT4_DIRENT_LUFID is added to d_type when extra
-data is present.
+Allows ext4 to store extra data records inside the ext4_dirent
+along with the regular directory entry (type, length, filename).
+Data is stored in ext4 dirent after filename, with a bit flag in
+de->file_type to indicate if any record after de->name is used.
+Each in-use record is variable length and must store a 1-byte
+length (including the length byte itself) at the start so that it
+can be skipped if the record type is unknown/uneeded. The record
+starts after a NUL byte terminator for the filename. This extra
+space is accounted in de->rec_len but not de->name_len.