This is an academic project to create a simple file system that will union 2 
seperate file system and display to the user as a single one.
So the file system takes a left branch and right branch where the right branch
is considered to be read only.

The project uses the wrapfs file system as a template and modifies its code
to create a stackable file system U2fs


The directory includes a Makefile and all the other files required to create the module
for the filesystem


To mount the file systems there is a script inside the fs/wrapfs directory called
install_modules.sh. This module installs the module and mounts the u2fs filesystem


The u2fs file system takes 2 options the ldir for the left directory and the rdir for the
right directory. So to mount you have to provide the path for both left and right directories
seperated by a comma. There should be any spaces between the comma.
Also the left path should be written first and then the right.

eg: mount -f u2fs -o ldir=/path/left_dir,rdir=/path/right_dir none mount point


The mount point should be a directory which already exists.


Design Issues
-------------
The u2fs file system is built by extending the current functionality of wrapfs. The u2fs filesystem
combines 2 different file systems with the left branch or file system being read write and the right 
branch being read only.

So for every data structure in wrapfs I have added an extra variable that will hold the respective 
information about the left and right branch. The reason for doing it was to keep it simple and 
make sure the functionalities of the right branch are supported.

For whiteouts I create a file in the left branch starting with the prefix ".wh.parent_name.file_name"
I include the parent name to differentiate between files with the same name in 2 different directories
in the right branch.

 
I have added my own method for getting inodes and interposing with the u2fs file system

I have modified the lookup to make sure both the left and the right path are found.

I have been cautious about avoiding memory leaks so memory leaks are avoided.