I am now learning the source code of ext2. I think the best way to understand it is to play with it, but I never built a Linux kernel before, so I was wondering if somebody could give me some detailed instructions on how to build the Linux kernel from the source code. I've created a VM with centos 6.8 as the compiling environment.  
After modifing the source code of existing file system (such as ext2), how to rebuild and install it?
filesystems;linux kernel;kernel modules