xfs+nfs crash in 2.6.30 and 2.6.30.1

[Christoph Hellwig]

On Wed, Jul 15, 2009 at 05:00:47AM +0200, Michael Ole Olsen wrote:
> Everything was stable on server+client until the server got 2.6.30 kernel, 
> the mdadm raid6 only works in 2.6.30 or above - mdadm fails to initialize it in 
> anything else, so cannot downgrade (custom reshape to raid6 using echo into /sys,
>  all Q blocks on one disk).
> 
> I have experimented with mount options on the client, and the client has 
> been stable with these mount options before, when the server had a kernel
>  below 2.6.30

Yes, we had a few reports of this already, but not been able to track it
down.  Your instrcution below will be very helpful to reproduce and test
it, I will looks at it on thursday when I get back home to my test
systems.

> I saw someone talking about kernel stack size would be the cause for this xfs+nfs problem, 
> is there anything to this?

Unlikely, it looks like problem in the XFS inode cache code introduced
in 2.6.29.