Since the author of this post is Jeremy Allison, a major Samba contributor, I also suggest reading the Samba code. I've been working with it, and have found it clean and well-structured. A great example of how to write a networked filesystem.

These two books look interesting, too: http://www.spinellis.gr/codereading/ http://www.spinellis.gr/codequality/

As for your suggestion on reading Understanding the Linux Kernel, is it readable even if I haven't taken a course on Operating Systems or something equivalent?

Probably not. It's a walkthrough of how the Linux kernel is implemented, both in terms of design ideas and the code itself. They assume you already know operating systems basics.

I could be wrong, as I've also never read it cover-to-cover; I always dive into it when I specific questions about how things work. I've never read it from the perspective of how well it teaches OS concepts. But if you're interested, and you think you will remain interested in the future, then there's no harm in getting the book now. As you learn more, you'll be able to understand more.

The code for Lua, OCaml, and qmail are also quite good.