Another test with "--repair" make BUG_ON:
time btrfs check --mode=lowmem --progress --repair /dev/sda1
enabling repair mode
WARNING: low-memory mode repair support is only partial
Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969b58eff
[1/7] checking root items (0:04:08 elapsed,
10279825 items checked)
Fixed 0 roots.
ERROR: extent[1198869807104 16384] backref lost (owner: 2, level: 0)
root 2s checked)
ERROR: fail to allocate new chunk No space left on device
Try to exclude all metadata blcoks and extents, it may be slowd, 81140
items checked)
Added an extent item [1198869807104 16384] (2:16:04 elapsed, 81140
items checked)
Added one tree block ref start 1198869807104 root 26:05 elapsed, 81140
items checked)
ERROR: extent[81379328 16384] backref lost (owner: 2, level: 0) root 2
items checked)
Added an extent item [81379328 16384]
transaction.c:168: btrfs_commit_transaction: BUG_ON `ret` triggered,
value -17
btrfs(+0x3c0ad)[0x5320ad]
btrfs(btrfs_commit_transaction+0x68)[0x5324bb]
btrfs(+0x78c24)[0x56ec24]
btrfs(check_chunks_and_extents_lowmem+0x198)[0x572060]
btrfs(cmd_check+0x16e2)[0x554da5]
btrfs(main+0x22c)[0x502edc]
/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0xb7badb41]
btrfs(_start+0x31)[0x502f21]
Przerwane
real 140m42,553s
user 6m14,394s
sys 2m21,156s
