NewFS is created io/fs.FS for ext4 filesystem.

DirectoryEntry2 is more or less a flat file that maps an arbitrary byte string.

DirectoryEntryCsum is not use.

Extent is extent tree leaf nodes.

ExtentHeader is ...

ExtentInternal.

File is implemented io/fs File interface.

FileInfo is implemented io/fs FileInfo interface.

FileSystem is implemented io/fs interface.

GroupDescriptor is 64 byte.

GroupDescriptor32 is 32 byte.

Inode is index-node.

MoveExtent is not use.