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Date:      Thu, 21 Jan 2016 15:19:01 +0000
From:      Steven Hartland <steven.hartland@multiplay.co.uk>
To:        Slawa Olhovchenkov <slw@zxy.spb.ru>, alan somers <asomers@gmail.com>
Cc:        "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, Alan Somers <asomers@freebsd.org>, Andriy Gapon <avg@freebsd.org>
Subject:   Re: svn commit: r294329 - in head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys
Message-ID:  <56A0F6E5.2020406@multiplay.co.uk>
In-Reply-To: <20160121151010.GH37895@zxy.spb.ru>
References:  <201601191700.u0JH0P6k061610@repo.freebsd.org> <569E6DA0.9010300@pix.net> <CAOtMX2idrWOpWbkYxPFn3yur8w-vgfBryhT4_0yiBvg10sWWRA@mail.gmail.com> <569F516D.80303@FreeBSD.org> <CAOtMX2gs37OnLMXE4zCduZF94%2B5z-TgPW%2Bqg8K8BweauLCRgDQ@mail.gmail.com> <56A019A1.4030900@FreeBSD.org> <20160121113813.GG37895@zxy.spb.ru> <CAOtMX2jB_Zsy-inXHTrehGjN2Xd4f=4TOvd5g-ZB4ho==-psPA@mail.gmail.com> <20160121151010.GH37895@zxy.spb.ru>

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On 21/01/2016 15:10, Slawa Olhovchenkov wrote:
> On Thu, Jan 21, 2016 at 08:03:25AM -0700, alan somers wrote:
>
>> On Thu, Jan 21, 2016 at 4:38 AM, Slawa Olhovchenkov <slw@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@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?
> I am find PR 199189.
> My expirense slightly different: VirtualBox VM with test install (384M
> RAM) hang, not crashed, just infinite wait somewhere. Tested on 10.1.
>
Had the same on 10.2 last night.



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