The Linux kernel contains a Virtual File System layer which is used during system calls acting on files. The VFS is an indirection layer which handles the file oriented system calls and calls the necessary functions in the physical filesystem code to do the I/O.
This indirection mechanism is frequently used in Unix-like operating systems to ease the integration and the use of several filesystem types [, ].
When a process issues a file oriented system call, the kernel calls
a function contained in the VFS. This function handles the structure
independent manipulations and redirects the call to a function contained
in the physical
filesystem code, which is responsible for handling the structure dependent
operations. Filesystem code uses the buffer cache functions to request
I/O on devices. This scheme is illustrated on figure 
.
ext2fs/vfs 7cm 9cm The VFS Layer