Internals of ext2fs

Superblocks

Each time you mount a filesystem, the kernel builds a struct super_block
- This struct contains a method table of superblock operations
- The structs are linked into a list
- mount's job is to build this struct and put it into the list
Typical mount call:

        mount("/dev/hdb2", "/home", "ext2", ...);

The code for mount is in super.c:

        long do_mount(char * dev_name, char * dir_name, char *type_page,
                          unsigned long flags, void *data_page)
        {
            ...
            fstype = get_fs_type(type_page);
            if (!fstype)            
                return -ENODEV;
            ...
            if (...) ...
            else if (fstype->fs_flags & FS_REQUIRES_DEV)
                sb = get_sb_bdev(fstype, dev_name, flags, data_page);
            ...
        }

get_sb_bdev calls read_super to read in the superblock structure