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

[alan somers]

On Thu, Jan 21, 2016 at 4:38 AM, Slawa Olhovchenkov <slw at zxy.spb.ru> wrote:
> On Thu, Jan 21, 2016 at 01:34:57AM +0200, Andriy Gapon wrote:
>
>> On 20/01/2016 22:03, Alan Somers wrote:
>> > On Wed, Jan 20, 2016 at 2:20 AM, Andriy Gapon <avg at freebsd.org> wrote:
>> >> On 19/01/2016 19:20, Alan Somers wrote:
>> >>> 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.
>> >>
>> >> The feature is perfectly usable for me.  I have never run into the problems that
>> >> you describe.  Why not fix the real bugs that you've run into?
>> >
>> > Spectra Logic and iXSystems both experienced many problems with this.
>> > The worst is a deadlock that can be triggered simply by pulling a
>> > drive from a redundant pool when there exists a zvol anywhere in the
>> > system (see https://reviews.freebsd.org/D4998 for a quick way to
>> > reproduce).  Fixing it correctly would likely require far more time
>> > than I have available.  I just want the bugs to go away.  See that
>> > same code review for a change to make the feature optional.
>>
>> I think that we all want all the bugs to go way.  One way to remove bugs is to
>> remove (disable) code that contains bugs.  That way the perfect bug-free
>> software is clearly achievable :-)  Unfortunately, that technique is not always
>> welcomed.
>>
>> P.S.
>> I think that the real problem here is that a method of a geom must never drop
>> topology_lock.  In other words, the GEOM management code (like g_xxx() stuff in
>> geom_subr.c) expects that a topology can not change underneath it.  But
>> zvol_geom_access() clearly breaks that contract.
>
> May be same cause problem with swap on zvol (don't test on latest
> -stable)?

I'm not familiar with that problem.  Is there a PR?