Note that the editlog initialization will be done separately.
There are some code refactoring in the patch. I am think about doing it on trunk first.
I like the idea of refactoring the code in trunk first and bringing it in.
I created HDFS-3273 for refactoring. Then, I am going to work on editlog initialization here.
Hari's patch in HDFS-3274 has editlog initialization. We should simply use it in JournalDiskWriter.
h3196_20120416.patch: adds a Journal class so that reader and writer can use it.
Thanks Hari and Suresh for reviewing this.
I have committed this.