svn commit: r294329 - inhead/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys

[Cy Schubert]

Just another thought. If we must do this, why not a sysctl to restore functionality to those of us who need it. If indeed there are panics and hangs due to zpools on vdevs, a sysctl to bypass the restriction, in effect saying "I understand the risk," would be a reasonable compromise. I'm willing to put together a patch to do this.

Sent from my cellphone,
~Cy

-----Original Message-----
From: Cy Schubert
Sent: 19/01/2016 10:27
To: Shawn Webb; Alan Somers
Cc: Kurt Lidl; svn-src-head at freebsd.org; svn-src-all at freebsd.org; src-committers at freebsd.org; cy at freebsd.org
Subject: RE: svn commit: r294329 - inhead/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys

Agreed, I do a fair bit of testing (nothing permanent) by putting zpools on zvols. I have never experienced a hang or panic due to zpools on zvols. This is a POLA violation.

Regarding zfs hangs, I only experience them with zpool vdevs on USB devices on my laptop when I forget to zpool export tpool prior to laptop shutdown/reboot. This is acceptable as I'm in front of it.

Sent from my cellphone,
~Cy

-----Original Message-----
From: Shawn Webb
Sent: 19/01/2016 10:07
To: Alan Somers
Cc: Kurt Lidl; svn-src-head at freebsd.org; svn-src-all at freebsd.org; src-committers at freebsd.org
Subject: Re: svn commit: r294329 - inhead/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys

On Tue, Jan 19, 2016 at 10:20:38AM -0700, Alan Somers wrote:
> On Tue, Jan 19, 2016 at 10:08 AM, Kurt Lidl <lidl at pix.net> wrote:
> > Removing the ability to run different zpools on top of a zvol is
> > a significant reduction in functionality of the entire system, and a huge
> > violation of the POLA.
> 
> The thing is, it never really worked in the first place.  Panics and
> deadlocks are so frequent that I don't think the feature was usable
> for anybody.

I actively use this every day and will be making even more use of it in
the very near future. I haven't had a single kernel panic. I have had
deadlocks at shutdown, but since it's a laptop and I'm sitting right in
front of it, it's not a big deal.

I'd say fix the underlying problem, don't prevent people from getting
work done.

> 
> >
> > At the very least, can you not add a sysctl that allows the
> > dangerous behavior (even if it defaults to off)?  Myself
> > and certainly others rely on having being able to use a zpool
> > installed into a zvol for hosting bhyve virtual machines.
> 
> Your use case should be unaffected.  The guest has a different ZFS
> instance than the host, so it should work just fine.  Please let me
> know if you have problems.

-- 
Shawn Webb
HardenedBSD

GPG Key ID:          0x6A84658F52456EEE
GPG Key Fingerprint: 2ABA B6BD EF6A F486 BE89  3D9E 6A84 658F 5245 6EEE