I was having the same issue with kernels 4.19.2 and 4.19.4. I don’t appear to have the issue with 4.20.0-0.rc1 on Fedora Server 29.
The issue is very easy to reproduce on my setup, not sure how much of it is actually relevant, but here it is: - 3 drive RAID5 created - Some data moved to it - Expanded to 7 drives - No balancing The issue is easily reproduced (within 30 mins) by starting multiple transfers to the volume (several TB in the form of many 30GB+ files). Multiple concurrent ‘rsync’ transfers seems to take a bit longer to trigger the issue, but multiple ‘cp’ commands will do it much quicker (again not sure if relevant). I have not seen the issue occur with a single ‘rsync’ or ‘cp’ transfer, but I haven’t left one running alone for too long (copying the data from multiple drives, so there is a lot to be gained from parallelizing the transfers). I’m not sure what state the FS is left in after Magic SysRq reboot after it deadlocks, but seemingly it’s fine. No problems mounting and ‘btrfs check’ passes OK. I’m sure some of the data doesn’t get flushed, but it’s no problem for my use case. I’ve been running nonstop concurrent transfers with kernel 4.20.0-0.rc1 for 24hr nonstop and I haven’t experienced the issue. Hope this helps.
