zpool create on md hangs

[Andreas Nilsson]

On Mon, Nov 10, 2014 at 7:37 AM, Curtis Villamizar <curtis at 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

Best regards
Andreas