On Mon, 13 Dec 2021 14:14:43 -1000, Tejun Heo wrote:

The donation calculation logic assumes that the donor has non-zero
after-donation hweight, so the lowest active hweight a donating cgroup can
have is 2 so that it can donate 1 while keeping the other 1 for itself.
Earlier, we only donated from cgroups with sizable surpluses so this
condition was always true. However, with the precise donation algorithm
implemented, f1de2439ec43 ("blk-iocost: revamp donation amount
determination") made the donation amount calculation exact enabling even low
hweight cgroups to donate.

[...]

Applied, thanks!

[1/1] iocost: Fix divide-by-zero on donation from low hweight cgroup
      commit: edaa26334c117a584add6053f48d63a988d25a6e

Best regards,
-- 
Jens Axboe