Cannot create filesystem with requested number of inodes while setting up superblock

commit 1abdd04eb1d19488493022f81c03f5b80aa7fcc7
Author: Darrick J. Wong <darrick.wong@oracle.com>
Date: Sat Oct 24 00:24:57 2015 -0400
libext2fs: fix maximum bg overhead calculation with meta_bg enabled
When meta_bg is enabled at mkfs time, we put at most one group
descriptor block in each blockgroup. Unfortunately, the calculation
of max overhead per bg doesn't know this, so mkfs fails when it isn't
strictly necessary. Fix it, since Dave reported that he couldn't
create a 500TB ext4 filesystem.
Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>