Metadata balance fails ENOSPC

[Stefan Priebe - Profihost AG <s.priebe@profihost.ag>]

Hello,

# btrfs balance start -v -dusage=0 -musage=1 /ssddisk/
Dumping filters: flags 0x7, state 0x0, force is off
  DATA (flags 0x2): balancing, usage=0
  METADATA (flags 0x2): balancing, usage=1
  SYSTEM (flags 0x2): balancing, usage=1
ERROR: error during balancing '/ssddisk/': No space left on device
There may be more info in syslog - try dmesg | tail

# btrfs filesystem show /ssddisk/
Label: none  uuid: a69d2e90-c2ca-4589-9876-234446868adc
        Total devices 1 FS bytes used 305.67GiB
        devid    1 size 500.00GiB used 500.00GiB path /dev/vdb1

# btrfs filesystem usage /ssddisk/
Overall:
    Device size:                 500.00GiB
    Device allocated:            500.00GiB
    Device unallocated:            1.05MiB
    Device missing:                  0.00B
    Used:                        305.69GiB
    Free (estimated):            185.78GiB      (min: 185.78GiB)
    Data ratio:                       1.00
    Metadata ratio:                   1.00
    Global reserve:              512.00MiB      (used: 608.00KiB)

Data,single: Size:483.97GiB, Used:298.18GiB
   /dev/vdb1     483.97GiB

Metadata,single: Size:16.00GiB, Used:7.51GiB
   /dev/vdb1      16.00GiB

System,single: Size:32.00MiB, Used:144.00KiB
   /dev/vdb1      32.00MiB

Unallocated:
   /dev/vdb1       1.05MiB

How can i make it balancing again?

Greets,
Stefan