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

Hello,
I'm sorry to bother you, but you may not be aware of this thread and
this problem. We are several people experiencing deadlocks, kernel 
panics and other problems when creating sanpshots on file systems
with SU+J. It would be nice to get some feedback, e.g. how can we
help debugging and / or fixing this problem.

Thank you,
Yamagi

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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