On Tue, Mar 28, 2023 at 05:18:43PM -0400, Chris Mason wrote: > Is btrfs really the only place using worker threads to submit IO, or are > we just the only ones looking for the priority inversions w/resource > control in place? btrfs is the only place offloading writes from the per-cgroup writeback to it's own not cgroup aware workqueues. Offloading from one writeback thread to another threadpool to just offload back to another thread to not deadlock is obviously not an actual smart thing to do, and fortunately no one else is doing this. For btrfs it is on it's way out by not doing the offload just for checksumming in a little bit, and even for compression the right fix is just to allow more than one thread per device and cgroup. I plan to look into that, but there's plenty higher priority work right now.