Activating autotrim results in high load average due to uninterruptible threads

[trackwitz]

When activating the autotrim feature on any ZFS version starting from 2.2.0 this will lead to a permanent increase of the load average (as diplayed in top) due to an uninterruptible vdev_autotrim thread for each vdev capable of TRIM.

This issue has been reported (https://github.com/openzfs/zfs/issues/15453) as well as fixed (https://github.com/openzfs/zfs/pull/15781) upstream but the fix is not yet backported to Ubuntu.

Since this bug was introduced with version 2.2.0 both mantic as well as noble are affected.

How to reproduce:
1. Create a pool with at least one TRIM-capable device
2. run "zpool set autotrim=on <pool>"
3. watch the output of "top" or "runtime" and see how the load average increases permanently even when the system is idle by one per vdev
4. running "ps aux | grep -w D" will show the broken threads:

[root@test ~]# ps aux | grep -w D\<
root 7193 0.0 0.0 0 0 ? D< 13:07 0:00 [vdev_autotrim]

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.