umount: dataset is busy

[TimLand]

System information

Type	Version/Name
Distribution Name	ubuntu
Distribution Version	14.04
Kernel Version	4.4.0-24-generic
Architecture	amd
OpenZFS Version	0.8.6

Describe the problem you're observing

We have a zvol which cant not be umount:

Have no process which is accessing the zvol. The dataset does not have any snapshots.

And there is no any lvm opening this dataset

Describe how to reproduce the problem

This problem is occurred for the first time

Include any warning/errors/backtraces from the system logs

[gertvdijk]

There can be tons of reasons for this, even outside of ZFS. But please, this is on an unsupported OS, on a kernel built in 2016; please just try to upgrade?

[stale[bot]]

This issue has been automatically marked as "stale" because it has not had any activity for a while. It will be closed in 90 days if no further activity occurs. Thank you for your contributions.