ZFS and deadlock with {nullfs,NFS}

[Kris Kennaway]

On Wed, Jun 20, 2007 at 11:53:43AM -0400, Joe Marcus Clarke wrote:
> I've resurrected by amd64 Tinderbox with a ZFS base, and I've been
> seeing a 100% reproducible deadlock when I use it with either localhost
> NFS or nullfs.  When this occurs, the CPU is 100% idle, but I can no
> longer connect via SSH, and the box will only reboot from the debugger.
> I know there are some tuning bits I can tweak, but all I've run across
> is for memory consumption.  Any pointers would be helpful.  I'm also at
> the debugger, so if there is anything I can do to help troubleshoot why
> this is happening, please let me know.  
> 
> This box is -CURRENT as of June 19, 2007.  It has a GENERIC kernel minus
> devices I do not have (i.e. SMP kernel).  I am currently using nullfs
> for the Tinderbox.  The process that most regularly locks up is mtree.
> Here is the trace:

> A full process list from the debugger can be found at
> http://www.marcuscom.com/downloads/cobbler_proc.txt .

404 at the moment, but look for processes involving zil* in the
backtrace.  I had to disable zil (vfs.zfs.zil_disable=1 tunable) to
prevent low-memory deadlocks on my machines.  Since then it's been
fine.

You may also wish to use my patches (see the archives) to improve
performance and low-memory behaviour.

Kris
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