Possible Ubuntu 20.04 problem on kernel upgrade - containers with limits.disk.priority set fail to start

Unfortunately I don’t have time to debug this further right now, but (in case anyone wants to try and reproduce this) I appear to have hit a problem like https://github.com/lxc/lxd/issues/7420 on an Ubuntu 20.04 server (Dell PowerEdge R210 II, lxd 4.0.3) and a single SATA SSD. After a kernel upgrade (but as far as I know, without any other configuration changes which may have triggered this).

The problem looks similar to this: https://github.com/lxc/lxd/issues/7420

All of the containers which had limits.disk.priority configured failed to start following a reboot.

New kernel package was linux-image-5.4.0-45-generic I’m not sure what the previous running kernel version was - may have been linux-image-5.4.0-42-generic or maybe linux-image-5.4.0-40-generic.

I can probably do some debugging on this some point next week if you think its useful, and this hasn’t shown up for anyone else by that time.

@brauner can you take a look?
@TimSmall what’s the error you’re getting exactly?

Hm, can you show

cat /sys/block/sda/queue/scheduler 

before and after the kernel upgrade?