Re: FS hang when creating snapshots on a UFS SU+J setup

Hi,
I've seen this too (and other problems with SU+J and snapshots) and was
able to reproduce it fairly easy. I wrote a PR:

 http://www.freebsd.org/cgi/query-pr.cgi?pr=163310 

Never received any feedback until now...

On Mon, 2 Jan 2012 23:27:57 -0600
Bryce Edwards <bryce_at_bryce.net> wrote:

> I have a RELENG_9 machine that hangs when a snapshot is created on the
> root fs (UFS, with SU+J).  More accurately, all the processes show a
> state of "suspfs" (with ^T) and no fs activity is completed from then
> on.  A hard reboot (power cycle) was the only way to proceed.
> 
> Here's some reference info - let me know what else I should provide.
> 
> $uname -a
> FreeBSD xxx.xxx.net 9.0-PRERELEASE FreeBSD 9.0-PRERELEASE #0: Sun Dec
> 25 05:04:37 UTC 2011     root_at_xxx.xxx.net:/usr/obj/usr/src/sys/GENERIC
> amd64
> 
> csup was run just before build[world|kernel] so you have reference on
> the version information.
> 
> $mount
> /dev/gpt/root on / (ufs, local, journaled soft-updates)
> devfs on /dev (devfs, local, multilabel)
> linprocfs on /compat/linux/proc (linprocfs, local)
> { zfs info removed }
> 
> $df -h
> Filesystem                  Size    Used   Avail Capacity  Mounted on
> /dev/gpt/root               454G    9.1G    409G     2%    /
> devfs                       1.0k    1.0k      0B   100%    /dev
> linprocfs                   4.0k    4.0k      0B   100%    /compat/linux/proc
> { zfs info removed }
> 
> After the hard reset, there was a snapshot file listed in /.snap and
> it was ~465 GB, iirc.  Unfortunately, I needed to get things going
> again so I was not able to debug or diagnose further.  I may be able
> to schedule a time that I could recreate the issue and diagnose
> better, but I wanted to get your input on what data points and/or
> command you would be interested in.
> 
> Thanks in advance,
> 
> Bryce
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