• get_sb_bdev calls read_super to read in the superblock structure

 union {
 ...
 struct ext2_sb_info ext2_sb;
 ...
 } u;

Superblocks

• The kernel reads in the superblock structure with a function read_super

• This function dispatches the FS-specific superblock-reading function:

 static struct super_block * read_super(kdev_t dev, struct block_device *bdev,
 struct file_system_type *type, int flags,
 void *data, int silent)
 {
 struct super_block * s;
 s = get_empty_super();
 ...
 s->s_type = type;
 ...
 if (!type->read_super(s, data, silent))
 goto out_fail;
 ...
 return s;
 } 

• For ext2fs, this actually invokes ext2_read_super.