Comment # 99 on bug 1017461 from Oliver Kurz

(In reply to Edmund Nadolski from comment #98)
> The patches listed in comment #94 have been merged into upstream 4.14.
> Otherwise one of the kernels mentioned in the previous comment has them.
> 
> It should be safe to disable quotas as far as btrfs itself is concerned.

I would not recommend disabling quotas (in case you mean btrfs qgroups) as IIUC
they are implicitly used to prevent snapshots filling up the hard disk by
cleaning them up if they reach *their* quota.

To me it seems the issue is not really resolved even though I think the patches
provided in the kernel by enadolski@suse.com should help. I guess one has to
look at a more whole system level. Would it make sense to lower the I/O prio of
background jobs?