Re: NFS caching bug is back

[David Warren <warren@atmos.washington.edu>]

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No it doesn't. I just let the changed file sit for about 45 minutes and 
the inode still has not changed. It is very similar to a bug I sent in 
for 2.6.11 that had been fixed.

I have also now verified that the same thing happens with a Solaris 10 
client, so it is likely to be the server side.

 From wireshark I see the client sending packets with:
PUTFH and GETATTR
then at the end
PUTFH and ACCESS

The return values for the ACCESS are:
access: 0x2d
.... .1 = allow READ
.... 0. = not allow LOOKUP
...1 .. = allow MODIFY
..1. .. = allow EXTEND
.0.. .. = not allow DELETE
1... .. = allow EXECUTE
The request had
Supported: 0x1f
.... .1 = allow READ
.... 1. = allow LOOKUP
...1 .. = allow MODIFY
..1. .. = allow EXTEND
.1.. .. = allow DELETE
0... .. = allow EXECUTE
Access: 0x1f
.... .1 = allow READ
.... 1. = allow LOOKUP
...1 .. = allow MODIFY
..1. .. = allow EXTEND
.1.. .. = allow DELETE
0... .. = allow EXECUTE

I don't know that much about the inner workings of the NFS protocol, but 
considering that the inode has been removed and replaced by a new one 
shouldn't all the return values from the access request be 0? It seems 
odd that read, modify, extend and execute are allowed for a nonexistent 
object.

Bryan O'Sullivan wrote:
> David Warren wrote:
>> A bug that we turned in a while ago is back in the 2.6.20 kernels, 
>> only worse. I have found it in 2.6.20.6 and 2.6.20.7.
>
> These symptoms look similar to this bug:
>
> http://bugzilla.kernel.org/show_bug.cgi?id=8305
>
> Which has been around since 2.6.17.  Do you find that the problem 
> magically resolves itself after a little while?
>
>     <b

Trond Myklebust wrote:
> On Thu, 2007-04-19 at 08:43 -0700, David Warren wrote:
>   
>> A bug that we turned in a while ago is back in the 2.6.20 kernels,
>> only worse. I have found it in 2.6.20.6 and 2.6.20.7. It happens with
>> both NFS4 and NFS3 mounts. Clients don't see inode changes (delete and
>> recreate file):
>>     
>
> Interesting. Do you see an OPEN request being sent to the server when
> you 'cat' the file on enkf2 or enkf3? You can check either using
> ethereal/wireshark, or by comparing the values in the OPEN column
> in /proc/self/mountstats on the client before and after issuing the
> 'cat' command.
>
> Trond


-- 
David Warren 		INTERNET: warren@atmos.washington.edu
(206) 543-0945		Fax: (206) 543-0308
University of Washington
Dept of Atmospheric Sciences, Box 351640
Seattle, WA 98195-1640
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