Centos and Reiserfs.
There were lots of horror stories all over the web from different people who had tried to compile the kernel on Centos. It's littered with pitfalls for the unwary (and even the wary). Apparently the best thing to do, is to install what is known as the Centos Plus kernel.
It can be installed using yum by the following command:
The tricky bit is to reboot the server. It's never a good idea to install a kernel when you do not have physical access to it. In this case I felt that I have no choice, so I changed grub.conf and did a reboot. Predictably the server failed to come up.