Linux Virtual File System (VFS) is an abstraction layer that provides a unified interface for file systems in the Linux kernel. It allows different file systems, such as ext4, NTFS, and FAT, to be accessed using a consistent set of system calls regardless of their underlying implementation.
Here are some key points about the Linux Virtual File System:
Abstraction Layer: VFS acts as an abstraction layer between the file systems and the kernel. It provides a common interface that enables applications and processes to interact with different file systems without needing to know their specific details.
File System Operations: VFS defines a set of operations that all file systems must implement, such as file opening, reading, writing, and closing. These operations are represented by function pointers in the file system's superblock, allowing the kernel to invoke the appropriate functions for a specific file system.
Superblock and Inode Structures: VFS uses two main data structures: the superblock and the inode. The superblock contains information about the file system, such as its type and mount options. The inode represents an individual file or directory and contains metadata like file size, permissions, and pointers to the actual data blocks.
File System Registration: When a new file system is added to the Linux kernel, it needs to register itself with VFS. This registration process involves providing function pointers to the file system operations, allowing VFS to invoke the correct functions when interacting with files on that file system.
Mounting and File System Hierarchy: VFS handles the mounting of file systems onto specific directories in the file system hierarchy. Each mounted file system is represented by a mount structure that contains information about the mounted device and the associated file system type.
File System Caching: VFS employs a caching mechanism to improve performance. It caches file system data in memory, including directory entries, file attributes, and file data. This caching reduces the need for frequent disk accesses, improving overall system performance.
File System Modules: VFS supports dynamically loadable file system modules, allowing additional file system types to be added to the kernel without recompiling it. This modularity enhances the flexibility and extensibility of the Linux file system.