linux-kernel - Different value in journal block after crash?

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Message-ID: <4513B3CE.50805@ece.hanyang.ac.kr>
Date:	Fri, 22 Sep 2006 18:58:38 +0900
From:	a287848 <a287848@....hanyang.ac.kr>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Different value in journal block after crash?

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

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