Re: nfs problems with 2.6.18-rc1

[Neil Brown <neilb@suse.de>]

On Thursday July 13, chexum+dev@gmail.com wrote:
> Hi!
> 
> I recently updated two (old) hosts to 2.6.18-rc1, and started noticing
> weird things with the nfs mounted /home s.

So this is both the client and the server that you upgraded?  That
makes is harder to point the finger of blame :-)

> 
> I frequently face EACCESs where a few minutes ago there wasn't any
> problem, and after a retry everything does work again.
> 

I wonder if that is pointing the finger at

http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=8c7b389e532e964f07057dac8a56c43465544759

as that is a recent change that returns 'EACCES'... but I cannot see
that being relevant in this case as it only affects directories.

> 
> How can I help with tracing this?  git bisecting on these machines takes
> at least an hour per step, (and no reasonable connectivity either to
> compile elsewhere much quicker).

The standard answer for tracing nfs problems if 'tcpdump'.
e.g. 
  tcpdump -s 0 -w /tmp/trace host $CLIENT and host $SERVER and port 2049

that should show whether the error is coming from the server, or if
the client is generating it all by itself.
If you can get a reasonably small '/tmp/trace', compress it and attach
it to an email.

Also turn on tracing. Something like:
on server
   echo 32767 > /proc/sys/sunrpc/nfsd_debug
on client
   echo 32767 > /proc/sys/sunrpc/nfs_debug

You can be a bit more selective by only enabling individual flags.
For the server, these are in include/linux/nfsd/debug.h
You probably want FH, EXPORT AUTH PROC FILEOP

For the client, they are near the end of include/linux/nfs_fs.h
Not sure which to choose... maybe just all of them.

NeilBrown
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