Deadlock on 5.13.8 when running bees?

Hi there,

Esteemed Zygo suggested that I report this here. I was running bees on
a btrfs volume that was a few days old after having transferred a
snapshot to it, and bees hung in a not seemingly healthy way. The
system load was 15 while not doing much else, and a bees process
seemed to be stuck consuming 100% CPU in a syscall that it would not
return from. Here are some relevant logs and dmesg excerpts:

"task blocked for more than ...":
https://dump.cy.md/464b43eec01aad04e762e6329323a309/15%3A42%3A20-upload.txt

echo w > /proc/sysrq-trigger:
https://dump.cy.md/6efc6a7116aebe9bbd4a6fb0b9e3d91e/15%3A43%3A02-upload.txt

Hope this helps!