So the change must be there. A short look at the ‘WIP’ (work-in-progress) branch of the e2fsprogrs confirmed the integration.

So i tried to build the most recent e2fsprogs (Remeber: This are *development* tools – use at your OWN RISK):

[root@vm-mkmoel ~] git clone git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git
[root@vm-mkmoel ~]# cd e2fsprogs
[root@vm-mkmoel e2fsprogs]# mkdir build ; cd build/
[root@vm-mkmoel build]# ../configure
[root@vm-mkmoel build]# make
[root@vm-mkmoel build]# make install

So let´s try to create a file system:

[root@vm-mkmoel misc]# ./mke2fs -O 64bit,has_journal,extents,huge_file,flex_bg, \
uninit_bg,dir_nlink,extra_isize -i 4194304 /dev/iscsi/test 

mke2fs 1.42-WIP (02-Jul-2011)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
4456448 inodes, 4563402752 blocks
228170137 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=6710886400
139264 block groups
32768 blocks per group, 32768 fragments per group
32 inodes per group

Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
102400000, 214990848, 512000000, 550731776, 644972544, 1934917632,
2560000000, 3855122432
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 0 mounts or 0 days,
whichever comes first.  Use tune2fs -c or -i to override.

OK. Seems to have worked. Lets check it:

[root@vm-mkmoel misc]# mount /dev/iscsi/test /mnt

[root@vm-mkmoel misc]# df -h
Filesystem                          Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00     18G  2.6G   14G  16% /
/dev/sda1                           99M  13M  82M    14% /boot
tmpfs                               502M 0    502M   0% /dev/shm
/dev/mapper/iscsi-test              17T  229M   17T   1% /mnt

[root@vm-mkmoel misc]# mount | grep mnt
/dev/mapper/iscsi-test on /mnt type ext4 (rw)

As you can see: With the most recent development e2fsprogrs it is possible to create ext4 file systems larger than 16 TB.

I even tried it with a 50 TB file system (because thats what i needed i my use case):

[root@vm-mkmoel misc]# df -h
Filesystem                          Size Used Avail Use% Mounted on
/dev/mapper/iscsi-test              50T  237M   48T   1% /mnt

Update:

Today i tested some more user space tools.

fsck

Maybe the most important tool in case the journaling fails. I copied some data to the file system (roughly about 2 TB) and had 73% of my 6.5 million inodes (one inode per 8 MB) allocated. Running fsck on my demo system with 1 GB memory yields: