On 24/01/2016 10:13 PM, 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.
I use an md device to do this in bhyve but I was considering using a zvol.
Populating it in the host system and then presenting it to the VM as a
disk.
maybe it could be enabled with a sysctl? Is the problem always present?
Thanks,
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