Ubuntu
linux package

  1. Bug #1779156
  2. Comment #13

Comment 13 for bug 1779156

Revision history for this message
Colin Ian King (colin-king) wrote :

Been digging into this a bit further with lxc 3.17 on Eoan.

lxc launch ubuntu:bionic zfs-bug-test
Creating zfs-bug-test
Starting zfs-bug-test
lxc delete zfs-bug-test --force
Error: Failed to destroy ZFS filesystem: Failed to run: zfs destroy -r default/containers/z1: cannot destroy 'default/containers/z1': dataset is busy

However, re-running the delete works fine:
lxd.lxc delete z1 --force

Looking at system calls, it appears that the first failing delete --force command attempts to destroy the zfs file system multiple times and then gives up. In doing so, it umounts the zfs file system. Hence the second time the delete is issued it works fine because zfs is now umounted. So it appears that the ordering in the delete is not as it expected.

It seems to do:
zfs destroy x 10 (or so and then gives up because of errno 16 -EBUSY)
zfs umount

It should be doing:
zfs umount
zfs destroy

This matches the observed reference counting. The ref count is only dropped once the umount is complete. Attempts to destroy it before that will cause an -EBUSY.