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Date:      Mon, 10 Nov 2014 10:32:54 +0100
From:      Andreas Nilsson <andrnils@gmail.com>
To:        Steven Hartland <killing@multiplay.co.uk>
Cc:        "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org>, curtis@ipv6.occnc.com
Subject:   Re: zpool create on md hangs
Message-ID:  <CAPS9%2BStTY2g=qze9qTi9jtkTs4735MZytLFcDb7-9-N8YW7AQw@mail.gmail.com>
In-Reply-To: <546084FE.80300@multiplay.co.uk>
References:  <201411100637.sAA6bJnR051011@maildrop31.somerville.occnc.com> <CAPS9%2BSvm32uX23tUQfismQ%2B1_aiQDe1gyHWQ_BneWSV-cSRhow@mail.gmail.com> <546084FE.80300@multiplay.co.uk>

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On Mon, Nov 10, 2014 at 10:27 AM, Steven Hartland <killing@multiplay.co.uk>
wrote:

>
> On 10/11/2014 06:48, Andreas Nilsson wrote:
>
>> On Mon, Nov 10, 2014 at 7:37 AM, Curtis Villamizar <curtis@ipv6.occnc.com
>> >
>> wrote:
>>
>>  The following shell program produces a hang.  Its reproducible (hangs
>>> every time).
>>>
>>>      #!sh
>>>
>>>      set -e
>>>      set -x
>>>
>>>      truncate -s `expr 10 \* 1024 \* 1024 \* 1024` /image-file
>>>      md_unit=`mdconfig -a -n -t vnode -f /image-file`
>>>      echo "md device is /dev/md$md_unit"
>>>      zpool create test md$md_unit
>>>
>>> The zpool command hangs.  Kill or kill -9 has no effect.  All
>>> filesystems are unaffected but any other zpool or zfs command will
>>> hang and be unkillable.  A reboot is needed.
>>>
>>> This is running on:
>>>
>>>     FreeBSD 10.0-STABLE (GENERIC) #0 r270645: Wed Aug 27 00:54:29 EDT
>>> 2014
>>>
>>> When I get a chance, I will try again with a 10.1 RC3 kernel I
>>> recently built.  If this still doesn't work, I'll build an r11 kernel
>>> since the code differs from 10.1, not having the svm code merged in.
>>> I'm asking before poking around further in case anyone has insights
>>> into why this might happen.
>>>
>>> BTW- The reason to create a zfs filesystem on an vnode type md is to
>>> create an image that can run under bhyve using a zfs root fs.  This
>>> works quite nicely for combinations geom types (gmirror, gstripe,
>>> gjournal, gcache) but zpool hangs when trying this with zfs.
>>>
>>> Curtis
>>>
>>> ps- please keep me on the Cc as I'm not subscribed to freebsd-fs.
>>>
>>>  Freezes here on 10.1-RC2-p1 (amd64) as well.
>> ^T says:
>> load: 0.21  cmd: zpool 74063 [zio->io_cv] 8.84r 0.00u 0.00s 0% 3368k
>>
>>  I suspect your just seeing the delay as it trim's the file and it will
> complete in time.
>
> Try setting vfs.zfs.vdev.trim_on_init=0 before running the create and see
> if it completes quickly after that.
>
> I tested this on HEAD and confirmed it was the case there.
>
>     Regards
>     Steve
>

Sure enough, it has since completed on my box at least.

Best regards
Andreas



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