Understanding the Linux Kernel, 3rd Edition

Ext2 Methods

Many of the VFS methods described in Chapter 12 have a corresponding Ext2 implementation. Because it would take a whole book to describe all of them, we limit ourselves to briefly reviewing the methods implemented in Ext2. Once the disk and the memory data structures are clearly understood, the reader should be able to follow the code of the Ext2 functions that implement them.

Ext2 Superblock Operations

Many VFS superblock operations have a specific implementation in Ext2, namely alloc_inode, destroy_inode, read_inode, write_inode, delete_inode, put_super, write_super, statfs, remount_fs, and clear_inode. The addresses of the superblock methods are stored in the ext2_sops array of pointers.

Ext2 inode Operations

Some of the VFS inode operations have a specific implementation in Ext2, which depends on the type of the file to which the inode refers.

The inode operations for Ext2 regular files and Ext2 directories are shown in Table 18-8; the purpose of each method is described in the section "Inode Objects" in Chapter 12. The table does not show the methods that are undefined (a NULL pointer) for both regular files and directories; recall that if a method is undefined, the VFS either invokes a generic function or does nothing at all. The addresses of the Ext2 methods for regular files and directories are stored in the ext2_file_inode_operations and ext2_dir_inode_operations tables, respectively.

Table 18-8. Ext2 inode operations for regular files and directories

VFS inode ...