Kernel 4.17.9, 11tb BTRFS device (md-backed, not btrfs raid) I was testing something out and enabled quota groups and started getting 2-5 minute long pauses where a btrfs-transaction thread spun at 100%. Post-reboot the mount process spinds at 100% CPU, occasinally yielding to a btrfs-transaction thread at 100% CPU. The switchover is marked by a burst of disk activity in btrace. Btrace shows all disk activity is returning promptly - no hanging submits. Currently the mount is at 6+ hours. Suggestions on how to go about debugging this?
