btrfs scrub can neither start nor cancel

I just tried this script:
http://marc.merlins.org/perso/btrfs/2014-03.html#Btrfs-Tips_-Btrfs-Scrub-and-Btrfs-Filesystem-Repair

but I did not pass the directory where the filesystem is mounted.

Next I called it correctly: btrfs-scrub /t4
I also tried btrfs scrub start / cancel directly, but I am not really sure what I did in which order.

Anyway now I can neither cancel nor start btrfs scrub. Rebooting did not help. Running unmodified Linux 4.3

It seems like scrub stopped and did not clean up. Maybe because:

Dec  8 21:07:41 s5 kernel: [17833.840868] btrfs[23746]: segfault at ffffffffffffff98 ip 00000000004079e1 sp 00007fffafa27510 error 5 in btrfs[400000+53000]

How can I now clean this up?

root@s5:~# btrfs --version
Btrfs v3.12

root@s5:~# btrfs scrub status /t4
scrub status for 700900de-e35f-4264-8f5d-1b2b249a5c3a
        scrub started at Tue Dec  8 21:05:31 2015, running for 20 seconds
        total bytes scrubbed: 3.09GiB with 0 errors

root@s5:~# btrfs scrub cancel /t4
ERROR: scrub cancel failed on /t4: not running

root@s5:~# btrfs scrub start /t4
ERROR: scrub is already running.
To cancel use 'btrfs scrub cancel /t4'.
To see the status use 'btrfs scrub status [-d] /t4'.

Wolfgang

It might be that the userspace tools has got confused and left
behind a lock/pid/progress file in /var/lib/btrfs/

Take a look in there and see if there's anything that you can
delete to good effect?

Hugo.

Hugo Mills             | Go not to the elves for counsel, for they will say
hugo@... carfax.org.uk | both no and yes.
http://carfax.org.uk/  |
PGP: E2AB1DE4          |

Am Dienstag, 8. Dezember 2015, 20:51:08 schrieb Hugo Mills:

root@s5:/var/lib/btrfs# ls -l
insgesamt 4
srwxr-xr-x 1 root root   0 Dez  8 21:05 scrub.progress.700900de-e35f-4264-8f5d-1b2b249a5c3a
-rw------- 1 root root 394 Dez  8 21:05 scrub.status.700900de-e35f-4264-8f5d-1b2b249a5c3a

that fixed it, thanks!

I would have expected that such temporary files are deleted at reboot, so ẗo me this looks like a bug in user-space.

Wolfgang