linux-ext4 - No data blocks at all in my ext4 journal

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Date:   Tue, 20 Mar 2018 07:31:56 +0800 (GMT+08:00)
From:   "Jidong Xiao" <0121167@...an.edu.cn>
To:     linux-ext4@...r.kernel.org
Subject: No data blocks at all in my ext4 journal

Hi,

When I use the dd command to examine the journal, it turns out every block starts with the jbd2 magic number, meaning they are either a superblock, a descriptor block, or a commit block, or a revoke block, but there is no data block.

I manually and randomly tried like 50 blocks after that superblock, but I haven't seen any data blocks.

The kernel version I am using is, 4.14. Is this a serious bug or am I doing something wrong? Anyone has any suggestions, or tell me how to find the data blocks in my journal, or are they actually missing from the journal? By data blocks, I mean metadata, as my system is using the default mode, i.e., the ordered journal mode, only metadata will be logged.

Thanks. Let me know if more information is needed.

-Jidong