No space left on device

[Jakob Truelsen <antialize@gmail.com>]

Hello. I am experiencing "No space left on device" with a btrfs file
system, yet I cannot seem to find any exhausted resource. Could some
resource I do not know about be exhausted, or is this caused by
something else. Below is a trace of information that might be usefull,
please let me know if there is anything I can do to resolve the issue.

/Jakob

[jakobt@soda ~]$ uname -a
Linux soda 3.12.8-1-ARCH #1 SMP PREEMPT Thu Jan 16 09:16:34 CET 2014
x86_64 GNU/Linux

[jakobt@soda ~]$ btrfs --version
Btrfs v3.12

[jakobt@soda ~]$ mount
...
/dev/sda on /data type btrfs (rw,relatime,nospace_cache)

[jakobt@soda ~]$ df /data
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sdb2       76594224 49247368  23433028  68% /

[jakobt@soda ~]$ btrfs filesystem df /data
Data, single: total=1.82TiB, used=518.04GiB
System, DUP: total=8.00MiB, used=204.00KiB
System, single: total=4.00MiB, used=0.00
Metadata, DUP: total=1.00GiB, used=767.70MiB
Metadata, single: total=8.00MiB, used=0.00

[jakobt@soda ~]$ touch /data/jakobt/hat
touch: cannot touch ‘/data/jakobt/hat’: No space left on device

[jakobt@soda ~]$ sudo btrfs fi balance start /data
ERROR: error during balancing '/data' - No space left on device
There may be more info in syslog - try dmesg | tail

[jakobt@soda ~]$ dmesg | grep tail -n 2
[1113177.878157] btrfs: device label Data devid 1 transid 44784 /dev/sda
[1113507.641752] btrfs: 1866 enospc errors during balance

[jakobt@soda ~]$ sudo umount /data

[jakobt@soda ~]$ sudo btrfsck /dev/sda
...
cache and super generation don't match, space cache will be invalidated
..
found 172181366447 bytes used err is 0
total csum bytes: 418841160
total tree bytes: 805187584
total fs tree bytes: 247164928
total extent tree bytes: 26329088
btree space waste bytes: 164771401
file data blocks allocated: 561564688384
 referenced 511759908864
Btrfs v3.12