usage:

1. insert module
    sudo insmod yramfs.ko
2. mount file system
    sudo mount -t yramfs none /mnt/yramfs
3. unmount
    sudo unmout /mnt/yramfs
4. remove moudule
    sudo rmmod yramfs

The steps of registerring a file system with the kernel as a kernel module:
    1. During module initialization, kernel register the file system with a
    handler be called to fill the super block structure while mounting, also a
    handler to do the cleanup during unmounting the file system.
    2. the super block operations are set at the time of mounting. The operation
    tables for inodes and files are set when the inode is opend.
    3. The root most inode is allocated at the time of mounting during the super
    block initialization
    4. The first step before opening an inode is lookup. The inode of a file is
    looked up by calling the lookup handler of the parent inode.
    


Referenced documents on internet:
http://www.win.tue.nl/~aeb/linux/lk/lk-8.html
http://tldp.org/LDP/tlk/fs/filesystem.html
http://thecoffeedesk.com/geocities/rkfs.html

Referenced source code on internet:
http://pages.cpsc.ucalgary.ca/~crwth/programming/VFS/inodes.php