MFC r349802 (from fsu@):
Add additional check for 'blocks per group' and 'fragments per group'
These fields will not be equal only in case if bigalloc filesystem feature is
turned on. This feature is not supported for now.
Reported by: Christopher Krah, Thomas Barabosch, and Jan-Niclas Hilgert of Fraunhofer FKIE
Reported as: FS-27-EXT2-12: Denial of Service in openat-0 (vm_fault_hold/ext2_clusteracct)