svn commit: r294329 - inhead/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys
Cy Schubert
cschuber at gmail.com
Sun Jan 24 14:35:23 UTC 2016
A previous email in this thread said that a sysctl will be committed before MFC.
I personally have never encountered this particular problem.
Sent from my cellphone,
~Cy
-----Original Message-----
From: Julian Elischer
Sent: 24/01/2016 06:20
To: Shawn Webb; Alan Somers
Cc: src-committers at freebsd.org; svn-src-all at freebsd.org; svn-src-head at freebsd.org; Xin LI
Subject: Re: svn commit: r294329 - inhead/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys
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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