Fresh boot, this time no compression, everything else the same. Time to delete both directories takes as long as it takes to copy one of them ~1m17s. This time I took an early and late sysrq t pair, and maybe caught some extra stuff.
[ 1190.094618] kernel: Workqueue: events_unbound btrfs_preempt_reclaim_metadata_space [ 1190.094633] kernel: Call Trace: [ 1190.094641] kernel: ? find_extent_buffer+0x5/0x200 [ 1190.094656] kernel: ? find_held_lock+0x32/0x90 [ 1190.094683] kernel: ? __lock_acquire+0x172/0x1e10 [ 1190.094694] kernel: ? lock_is_held_type+0xa7/0x120 [ 1190.094714] kernel: ? btrfs_search_slot+0x6d2/0x9f0 [ 1190.094729] kernel: ? btrfs_get_64+0x5e/0x100 [ 1190.094751] kernel: ? lock_acquire+0xc2/0x3a0 [ 1190.094768] kernel: ? _raw_spin_unlock+0x1f/0x30 [ 1190.094779] kernel: ? rcu_read_lock_sched_held+0x3f/0x80 [ 1190.094798] kernel: ? __lock_acquire+0x172/0x1e10 [ 1190.094811] kernel: ? lookup_extent_backref+0x43/0xd0 [ 1190.094829] kernel: ? release_extent_buffer+0xa3/0xe0 [ 1190.094846] kernel: ? __btrfs_free_extent+0x49c/0x8f0 [ 1190.094878] kernel: ? __btrfs_run_delayed_refs+0x29a/0x1270 [ 1190.094912] kernel: ? _raw_spin_unlock+0x1f/0x30 [ 1190.094934] kernel: ? btrfs_run_delayed_refs+0x86/0x210 [ 1190.094954] kernel: ? flush_space+0x570/0x6d0 [ 1190.094966] kernel: ? lock_release+0x280/0x410 [ 1190.094987] kernel: ? btrfs_preempt_reclaim_metadata_space+0x170/0x2f0 [ 1190.095007] kernel: ? process_one_work+0x2b0/0x5e0 [ 1190.095035] kernel: ? worker_thread+0x55/0x3c0 [ 1190.095045] kernel: ? process_one_work+0x5e0/0x5e0 [ 1190.095060] kernel: ? kthread+0x13a/0x150 [ 1190.095070] kernel: ? __kthread_bind_mask+0x60/0x60 [ 1190.095085] kernel: ? ret_from_fork+0x1f/0x30 dmesg https://drive.google.com/file/d/1VQNAVynVTJo6VqsRX9K5-Z0dMsLmb-vH/view?usp=sharing