Hello all. It seems that the zone map, inodes, inode maps and superblock
aren't included in the zone map. At least it's the impression I've got from:
        Super3.s_zmap_blocks = UPPER(BLOCKS -
(1+get_nimaps()+inode_blocks()),
                         BITS_PER_BLOCK+1);
However, in another place the assumption is opposite and this leads to
an attempt to write outside the allocated buffer. Attached patch fixes it.

-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko