Read: Journaling the Linux ext2fs Filesystem.

The paper uses "journal" to refer to the same idea that xv6 calls a "log". The file system described in the paper is now called ext3.

To help you read the paper, try to answer the following question for yourself:

Mid-way down the left column on page 6, the Journaling paper says "However, until we have finished syncing those buffers, we cannot delete the copy of the data in the journal." Give a concrete example in which removing this rule would lead to disaster.

You don't have submit your answer.