ext2 File System, with immediate files and encryption added.

Final project for UQ's COMP3301 - Operating Systems Principles course.

Important files:

• file.c contains wrappers for file read and write, handling encryption and providing special methods for immediate files.
• ext2.h contains function prototypes, global variables, debug features, preprocessor utilities (all at the bottom) and the immediate file type.
• ext3301util.c contains utility functions: a suite of file operations, utilities for building and analysing file paths, and working with user-space buffers.
• namei.c contains the modified ext2_rename() function (handling encryption of moved files).
• super.c contains the modified parse_options() function (handling reading the encryption key).
• inode.c contains the modified ext2_iget() function (uses init_ext3301_inode() instead of init_special_inode())

Known bugs/incomplete features:

• Switching from regular files back to immediate doesn't copy the file contents correctly
• After the filesystem is unmounted and re-mounted, attempts to write/read immediate files created before mounting throw errors. Spent a long time on this, but never figured out how to get around it.

Comments:

• In my opinion, the decision to introduce a new file type (DT_IM) for immediate files is unwise. It causes unnecessary complications/problems with generic linux kernel code (outside the ext2 implementation), as nothing outside of ext2 knows about the immediate file type. We would have been better off taking advantage of one of the unused bits in the inode flag mask, e.g. the unused file compression bit (http://wiki.osdev.org/Ext2#Inode_Flags)