We should actually get this error
dd: writing to `myfile5': No space left on device
root@x300-qemu-image:~# mount /dev/hdc -t ext4dev -o delalloc,data=writeback /ext4
root@x300-qemu-image:/ext4# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/hdc 49M 46M 94K 100% /ext4
root@x300-qemu-image:/ext4#
root@x300-qemu-image:/ext4#
root@x300-qemu-image:/ext4#
root@x300-qemu-image:/ext4# dd if=/dev/zero of=myfile
34188+0 records in
34187+0 records out
17503744 bytes (18 MB) copied, 11.2724 seconds, 1.6 MB/s
root@x300-qemu-image:/ext4# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/hdc 49M 49M 0 100% /ext4
root@x300-qemu-image:/ext4# dd if=/dev/zero of=myfile5
49777+0 records in
49777+0 records out
25485824 bytes (25 MB) copied, 19.7667 seconds, 1.3 MB/s
root@x300-qemu-image:/ext4# df -h .
Filesystem Size Used Avail Use% Mounted on
/dev/hdc 49M 49M 0 100% /ext4
root@x300-qemu-image:/ext4#