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Message-ID: <4FE13260.1050002@pml.ac.uk>
Date: Wed, 20 Jun 2012 03:16:00 +0100
From: Mike Grant <mggr@pml.ac.uk>
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To: Christoph Bartoschek <bartoschek@gmx.de>
CC: <linux-nfs@vger.kernel.org>
Subject: Re: Spurious permission denied
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On 06/19/2012 10:58 AM, Christoph Bartoschek wrote:
> we still have the problem that some users get permission denied for
> directories they normally can access. The problem only affects a single user
> at a time and automatically goes away after about 30 minutes.

We've seen this error quite a bit too, though never managed to pin it 
down well enough to report it as it's intermittent and unpredictable.  I 
agree that it seems to be server side and we tried a few things to get 
rid of it.  I'm not sure if they worked or if it's just in remission, 
but the two things that seemed to help most were:
  a) increase the amount of memory in the server (we went from 6 to 24GB)
  b) reduce dependence on NIS by (ick) hard coding key users into the 
server's /etc/passwd file.

We tried the latter because our NIS server was struggling a lot at the 
time and I'm not sure what happens if the NFS server fails to get a NIS 
response in a timely manner or gets a failed response (i,e. it can't 
identify the user).

It may be worth you seeing if the user id resolves correctly on the 
server at the time of the failure.  It might also be interesting to know 
what happens if you restart the NFS server when you have this problem. 
I'm wondering if the 30min thing indicates a cached bad credential or 
something that expires after a bit or perhaps the NFS server thread just 
gets recycled..

It may also be worth doing a capture on the server side at the same 
time, as that might show issues with NIS or whatever you use.  There's a 
good chance it may not be visible after the problem has occurred though, 
if it's cached somewhere.

Anyway, sorry that's not directly helpful, but maybe a few things to try!

Cheers,

Mike.

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