We tried to resize a 15TB ext4 partition to 16TB and accidentally managed to hit an old (and fixed in newer releases) off-by-one bug of ext4_resize_fs() which causes inode count to reset to 0 thanks to an overflow bug.
The fix can be seen here: https://github.com/torvalds/linux/commit/4f2f76f751433908364ccff82f437a57d0e6e9b7
As a result, our 16TB partition is unusable at the moment.
Are there any ways to recover from the situation? Even a read-only access to all files is more than enough in this case.