I had a quick look at there are quite a few differences between the Delphix ZFS git repo and the upstream ZFS git repo. Github states: "This branch is 376 commits ahead of zfsonlinux:master.".
So: 1. Does this issue occur with stock ZFS rather than Delphix ZFS? 2. With the activity you are performing to trigger the bug it does seem like there is a race condition occurring on mnt_count so this does look like a kernel bug. One way to quickly sanity check this is with a coarse bisect using some pre-build ubuntu kernels based on the mainline kernels. The wiki page https://wiki.ubuntu.com/Kernel/MainlineBuilds details our mainline builds, you can select a mainline kernel from: https://kernel.ubuntu.com/~kernel-ppa/mainline/?C=N;O=D - install it, run the tests and see if the problem is fixed or still persists. I suggest trying a recent (say 5.1) kernel build, and if that works, bisect on that between 4.15 and 5.1 etc until you find the earliest fix point. If the problem still occurs with a 5.1 kernel, then we need to start digging a bit deeper. But I think it is definitely worth trying a recent kernel first as the fix may be already be in an upstream kernel. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1832384 Title: Unable to unmount apparently unused filesystem To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1832384/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
