Error: could not do orphan cleanup -22

[Pavel Volkov <negaipub@gmail.com>]

There was a similar discussion about an error in January 2013 but it related to some kernel panic.
I don't know if I encountered the same thing.

These errors from system journal bother me:

 2月 09 22:18:53 melforce kernel: BTRFS error (device sdb3): Error removing orphan entry, stopping orphan cleanup
 2月 09 22:18:53 melforce kernel: BTRFS critical (device sdb3): could not do orphan cleanup -22

I run kernel 3.12.10.
I'll explain what I did at that moment.
Subvolumes were already mounted at /home and /var and I mounted the root subvolume at /mnt/btr2.
Then executed ls command on /home/btr2. ls gave me "invalid argument" errors, but still displayed the contents. 
Next time I ran ls (right away), there were no more errors.

Another example is a script that mounts the same thing and then takes snapshots.
If I run the script manually, it never fails. If I run it from cron job, one of the snapshot commands fails
telling me that /home/btr2/var isn't accesible (I don't remember the exact error message, I can look if it
shows up again).

Someone said in the January thread that -22 error messages are harmless but in this case userspace tools break
so I wouldn't consider this totally harmless.