The performance enhancements to the UNIX file system did not require any changes to the semantics or data structures visible to application programs. However, several changes had been generally desired for some time but had not been introduced because they would require users to dump and restore all their file systems. Since the new file system already required all existing file systems to be dumped and restored, these functional enhancements were introduced at this time.
File names can now be of nearly arbitrary length.
Only programs that read directories are affected by this change. Directories are allocated in 512 byte units called chunks. This size is chosen so that each allocation can be transferred to disk in a single operation. Chunks are broken up into variable length records termed directory entries. A directory entry contains the information necessary to map the name of a file to its associated inode.