On 2016-01-24 09:13, Shawn Webb wrote: > On Tue, Jan 19, 2016 at 05:00:25PM +0000, Alan Somers wrote: >> Author: asomers >> Date: Tue Jan 19 17:00:25 2016 >> New Revision: 294329 >> URL: https://svnweb.freebsd.org/changeset/base/294329 >> >> Log: >> Disallow zvol-backed ZFS pools >> >> Using zvols as backing devices for ZFS pools is fraught with panics and >> deadlocks. For example, attempting to online a missing device in the >> presence of a zvol can cause a panic when vdev_geom tastes the zvol. >> Better >> to completely disable vdev_geom from ever opening a zvol. The solution >> relies on setting a thread-local variable during vdev_geom_open, and >> returning EOPNOTSUPP during zvol_open if that thread-local variable is set. >> >> Remove the check for MUTEX_HELD(&zfsdev_state_lock) in zvol_open. Its >> intent >> was to prevent a recursive mutex acquisition panic. However, the new check >> for the thread-local variable also fixes that problem. >> >> Also, fix a panic in vdev_geom_taste_orphan. For an unknown reason, this >> function was set to panic. But it can occur that a device disappears during >> tasting, and it causes no problems to ignore this departure. >> >> Reviewed by: delphij >> MFC after: 1 week >> Relnotes: yes >> Sponsored by: Spectra Logic Corp >> Differential Revision: https://reviews.freebsd.org/D4986 > > I've just been bit by this pretty hard. I have a bhyve VM that's backed > by a zvol. The VM is running root-on-zfs. I wrote some experimental code > that's now preventing the VM from booting (kernel panic due to userland > change). Since I can't import the pool, I have no way of fixing the > problem. > > I'm probably just going to go revert this commit locally on my box so I > can get some work done. > > Thanks, >
Alan is working on making it a sysctl, so you can turn the old behaviour back on. You might want to test that patch: https://reviews.freebsd.org/D4998 -- Allan Jude
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