Chapter6.Filesystems

Chapter 6. Filesystems

In this chapter

• 6.1 General Filesystem Concepts 296

• 6.2 Linux Virtual Filesystem 302

• 6.3 Structures Associated with VFS 324

• 6.4 Page Cache 330

• 6.5 VFS System Calls and the Filesystem Layer 336

• Summary 371

• Exercises 372

Computing revolves around the storage, retrieval, and manipulation of information.

In Chapter 3, "Processes: The Principal Model of Execution," we talked about how processes are the basic unit of execution and looked at how a process manipulates information by storing it in its address space. However, the process address space is limited in that it lasts only as long as the process is alive and it holds a fraction of the size of the system memory. The filesystem evolved from the need for large capacity, non-volatile storage of information in media other than system registers or memory. Non-volatile information is data that persists despite the termination of the process that manipulates it or operating-system shutdown.

The storage of information on external media presents the problem of how to represent the information. The basic unit of information storage is the file. The filesystem, or file-management subsystem, is the operating-system component that deals with the file structure, manipulation, and protection. This chapter covers the topics related to the Linux filesystem implementation.