Please read the details on Ext2 and Ext3 file systems found on
line in chapter 18 of the following tutorial:


http://www.91kaifa.com/doc/ulk/0596005652/understandlk-chp-18.html

or

http://book.opensourceproject.org.cn/kernel/kernel3rd/index.html?page=opensource/0596005652/understandlk-chp-18.html



Make sure you read all the pages for this full chapter