Hi Ralf. Ralf Zerres - 19.12.19, 21:00:12 CET: > at customer site i can't mount a given btrfs device in rw mode. > this is production data and i do have a backup and managed to mount > the filesystem in ro mode. I did copy out relevant stuff. Having said > this, if btrfs --repair can't heal the situation, i could reformat > the filesystem and start all over. But i would prefere to save the > time and take the heeling as a proof of "production ready" status of > btrfs-progs. > > Here are the details: > > kernel: 5.2.2 (Ubuntu 18.04.3) > btrfs-progs: 5.2.1 […] > 4) As a forth step, i tried to repair it > > # btrfs check --mode lowmem --progress --repair /dev/<mydev> > # enabling repair mode > # WARNING: low-memory mode repair support is only partial > # Opening filesystem to check... > # Checking filesystem on /dev/<mydev> > # UUID: <my UUID> > # [1/7] checking root items (0:00:33 elapsed, > 20853512 items checked) > # Fixed 0 roots. > # ERROR: extent[1988733435904, 134217728] referencer count mismatch > (root: 261, owner: 286, offset: 5905580032) wanted: # 28, have: 34 > # ERROR: fail to allocate new chunk No space left on device Maybe the filesystem check failed due to that error? Just guess work tough! You could try adding a device to the filesystem and then check again. It could even be a good (!) USB stick. This way BTRFS would have some additional space and maybe 'btrfs check' would complete. May or may not work, no idea. But I noticed that the check itself mentioned an out of space condition so I thought I'd mention it. Best of success, -- Martin
