Linux Kernel Development, Second Edition

Chapter 12. The Virtual Filesystem

The Virtual Filesystem (sometimes called the Virtual File Switch or more commonly simply the VFS) is the subsystem of the kernel that implements the filesystem-related interfaces provided to user-space programs. All filesystems rely on the VFS to allow them not only to coexist, but also to interoperate. This enables programs to use standard Unix system calls to read and write to different filesystems on different media, as shown in Figure 12.1.

Figure 12.1. The VFS in action: Using the cp(1) utility to move data from a hard disk mounted as ext3 to a removable disk mounted as ext2. Two different filesystems, two ...