Where It All Starts From – The Virtual Filesystem

Even with astronomical advances in software development, the Linux kernel remains one of the most complex pieces of code. Developers, programmers, and would-be kernel hackers constantly look to dive into kernel code and push for new features, whereas hobbyists and enthusiasts try to understand and unravel those mysteries.

Naturally, a lot has been written on Linux and its internal workings, from general administration to kernel programming. Over the decades, hundreds of books have been published, which cover a diverse range of important operating system topics, such as process creation, threading, memory management, virtualization, filesystem implementations, and CPU scheduling. This book that you’ve picked up (thank you!) will focus on the storage stack in Linux and its multilayered organization.

We’ll start by introducing the Virtual Filesystem in the Linux kernel and its pivotal role in allowing end user programs to access data on filesystems. Since we intend to cover the entire storage stack in this book, from top to bottom, getting a deeper understanding of the Virtual Filesystem is extremely important, as it is the starting point of an I/O request in the kernel. We’ll introduce the concept of user space and kernel space, understand system calls, and see how the Everything is a file philosophy in Linux is tied to the Virtual Filesystem.

In this chapter, we’re going to cover the following main topics:

• Understanding storage in a modern-day data center
• Defining system calls
• Explaining the need for a Virtual Filesystem
• Describing the Virtual Filesystem
• Explaining the Everything is a file philosophy