Wrong (or at least confusing) “Ext2 file too big” message from `mkfs.ext4`

[DemiMarie]

The following command fails to include a 18159239168-byte file into a 100GiB image:

mkfs.ext4 -t ext4 -L eosimages -Oextent,huge_file,orphan_file,\
has_journal,extent,flex_bg,metadata_csum,\
metadata_csum_seed,64bit,dir_nlink,extra_isize,\
sparse_super,large_file,filetype,resize_inode,\
dir_index,ext_attr -d . OUTPUT_FILE

Full output:

mke2fs 1.47.3 (8-Jul-2025)
Discarding device blocks: done             
Creating filesystem with 26214400 4k blocks and 6553600 inodes
Filesystem UUID: 9dd24827-d97b-47ea-8129-f2f76ee5b4b8
Superblock backups stored on blocks:
   32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
       4096000, 7962624, 11239424, 20480000, 23887872

Allocating group tables: done   
Writing inode tables: done   
Creating journal (131072 blocks): done
Copying files into the device: __populate_fs: Ext2 file too big while writing file "Spectrum-0.0-x86_64-generic.0.Live.img"
mkfs.ext4: Ext2 file too big while populating file system

Since 19GiB << 100GiB I suspect the command should succeed.

I don’t know if there is an mke2fs.conf, though. This is on NixOS so it might be somewhere else or not exist at all.