Every mounted file system is represented by a VFS superblock; amongst other information, the VFS superblock contains the:

Device

This is the device identifier for the block device that this file system is contained in. For example, /dev/hda1, the first IDE hard disk in the system has a device identifier of 0x301,

Inode pointers

The mounted inode pointer points at the first inode in this file system. The covered inode pointer points at the inode representing the directory that this file system is mounted on. The root file system’s VFS superblock does not have a covered pointer,

Blocksize

The block size in bytes of this file system, for example 1024 bytes,

Superblock operations

A pointer to a set of superblock routines for this file system. Amongst other things, these routines are used by the VFS to read and write inodes and superblocks.

File System type

A pointer to the mounted file system’s file_system_type data structure,

File System specific

A pointer to information needed by this file system,