Different value in journal block after crash?

[a287848 <a287848@ece.hanyang.ac.kr>]

Hi I'm moweon.

Now I'm making redundancy module in my jbd based file system.

When I tesed and dumped its block, I found one funny stuation.


First I modified */commit.c/* in jbd directory to print commit complete
message and it's block number.
( add printk after wait_on_buffer )


After I saw this message from kernel just like this

(*NOTICE: Commit complete , its block number : 560 *)

I read its contents from block number 1 to 101 into file

And I read it again after suddenly turn off my work station.

, I think it must has same value becuase journal commit block was
already written behind block number 101 .


But when I campared two file, it's different .

Why it happen? Does jbd use some trick in block management?

Dear