For ext4, reading the group descriptor table (GDT), it was assuming that the GDT always followed right after the superblock, which is right after the padding bytes. This is true when blocksize is 1024, as padding = block 0, superblock = block 1, GDT = block 2. However, if it is larger than 1024, then padding + superblock = block 0, GDT = block 1.
Fixes #231
For ext4, reading the group descriptor table (GDT), it was assuming that the GDT always followed right after the superblock, which is right after the padding bytes. This is true when blocksize is 1024, as padding = block 0, superblock = block 1, GDT = block 2. However, if it is larger than 1024, then padding + superblock = block 0, GDT = block 1.