Internals of ext2fs

Inodes

The following elements are not stored on the disk; they're in the struct inode only:

        struct inode_operations *i_op;
        struct file_operations  *i_fop; /* former ->i_op->default_file_ops */
        struct super_block      *i_sb;

These are the virtual method tables for operations like chmod and read
i_sb points back to the superblock structure we saw before

        struct file_lock        *i_flock;

Here's where the file lock is stored, if the file is locked
- (In memory only, not on the disk.)
Each filesystem has its own inode structure
ext2fs has some additional fields to support things like ACLs
- These were not yet implemented in the kernel I studied:

        plover% wc acl.c
             17      53     350 acl.c