Here is the HELP from a vanilla 2.4.16 source
CONFIG_EXT3_FS:
This is the journaling version of the Second extended file system (often called ext3), the de facto standard Linux file system (method to organize files on a storage device) for hard disks.
The journaling code included in this driver means you do not have to run e2fsck (file system checker) on your file systems after a crash. The journal keeps track of any changes that were being made at the time the system crashed, and can ensure that your file system is consistent without the need for a lengthy check.
Other than adding the journal to the file system, the on-disk format of ext3 is identical to ext2. It is possible to freely switch between using the ext3 driver and the ext2 driver, as long as the file system has been cleanly unmounted, or e2fsck is run on the file system.
To add a journal on an existing ext2 file system or change the behavior of ext3 file systems, you can use the tune2fs utility ("man tune2fs"). To modify attributes of files and directories on ext3 file systems, use chattr ("man chattr"). You need to be using e2fsprogs version 1.20 or later in order to create ext3 journals (available at <[link|http://sourceforge.net/projects/e2fsprogs/|http://sourceforge....s/e2fsprogs/]>).
If you want to compile this file system as a module ( = code which can be inserted in and removed from the running kernel whenever you want), say M here and read Documentation/modules.txt. The module will be called ext3.o. Be aware however that the file system of your root partition (the one containing the directory /) cannot be compiled as a module, and so this may be dangerous.