I've no need for a fix. I know exactly what the underlying cause is:
Those Seagate 8TB Archive drives and their known compatibility issues
with some kernel versions. I just shared the log because it's a
situation that btrfs handles very, very poorly, and the error handling
could be improved.
I've finally finished deleting all those nasty unreliable Seagate drives
from my array. During the process I crashed my server - over, and over,
and over. Completely gone - screen blank, controls unresponsive, no
network activity (no, I don't have root on btrfs - data only). Most
annoying, but
I did suspect that NCQ may be involved, but I had no clear evidence -
until I noticed that my drives had also incremented the 'end to end
error' count in SMART, which does match accounts of the NCQ issue. That
suggests there are two interlinked issues: The issue with those Seagate
drives and
