Re: Random ESTALE due to lookup "/" in mount point?

[Frank van Maarseveen <frankvm@frankvm.com>]

On Wed, Aug 23, 2006 at 12:20:25PM -0400, Trond Myklebust wrote:
> On Wed, 2006-08-23 at 17:09 +0200, Frank van Maarseveen wrote:
> > NFSv3, udp, client=2.6.17.8, server=tru64
> > 
> > On the client I started to get some random ESTALE errors which disappeared
> > quickly afterwards without a remount. The errors only occurred when typing
> > 
> > 	stat ..
> > 
> > in a subdirectory of a mountpoint. Doing ls -al in that subdirectory
> > gave an ESTALE only on "..". I could even change directory to / and back
> > without an ESTALE but the "stat .." command still gave an ESTALE.
> > 
> > A "tcpdump -i eth0 udp port 2049 -n -s 1500" showed something which is
> > unusual to my knowledge. The kernel tried to lookup "/" in the mount
> > point as it seems:
> 
> I've never seen that, and my own kernel certainly appears to do no such
> thing when I stat '..'.
> 
> Any chance of a 'strace' with that?

It's reproduceable now but it appears that there's a nonstandard kernel
patch from me involved to do a selective "noac" (www.frankvm.com/nfs-noac,
it's a bit hackish...).  I think this results in an incorrect revalidation
of the mount point and I guess "/" is coming from the dcache: the fake
name of any root inode IIRC.

In short, I have to sort it out but it's probably only my patch at
fault. Sorry for the disturbance.

-- 
Frank

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