Instructions to use WOJ for light-weight deduplication to support data journaling mode in ext3.


WOJ is prototyped in the dmdedup framework and follows its read/write interfaces.  
We have ported dmdedup to support kernel 4.4. 


Sofeware requirement: 
The linux kernele vesion should be 4.4. If it is the latest kernel (for example 4.17), 
it cannot be compiled directly as the definition of struct bio has been changed in the latest kernel version.



The package includes:


1. source code of WOJ.
    
we do not remove the stock code of dmdedup as in our expeirments we need to compare WOJ with existing deduplication schemes provided by dmdedup. The code related to WOJ implementation is mainly in dm-dedup-sb.h (file system super block handler), dm-dedup-target-weak.h and dm-dedup-target).  



2. Test code and some helper files (written in shell) to ease the execution of WOJ.



Instructions to use WOJ.


1. Compile the source code of WOJ. 


cd source_code
make 
clean & make; 

It will generate a kernel module with WOJ functionality supported.



Note: if they cannot be sucessfully compiled, please check your kernel version.



### All operations below should be executed as root user.


2. Install the kernel mode.
    There is an example shell named install-uninstall.sh showing how to install or remove the module.

Following instructions are performed in test-code directory

3. Setup WOJ
    We use dmsetup command to setup WOJ, an example showing how to setup the WOJ target is "setup-mydedup-u11.sh".
    Use instructions in u11-enable_journal_mode.sh to enable WOJ journal mode, currently two kinds of weak hash functions (crc32 and xxh64) are supported.



4. setup ext3 filesystem on the WOJ-enabled disk
    Follow the instructions in lw.sh to setup a ext3 file system 



5. Mount the file system in data journaling mode.
   Follow the instructions in lw.sh to setup a ext3 file system

6. Do read/write test on the file system.
	You can do any normal file sytem operations on the ext3 file system, including creating files or directory, writing/reading files, etc.