Re: nfs + Reiser4

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Apr 07, 2010 at 02:59:36PM -0400, Chuck Lever wrote:
> On 04/07/2010 02:51 PM, J. Bruce Fields wrote:
>> On Wed, Apr 07, 2010 at 02:44:01PM -0400, Chuck Lever wrote:
>>> On 04/07/2010 01:34 PM, J. Bruce Fields wrote:
>>>> On Tue, Apr 06, 2010 at 07:52:21PM +0200, gg-B3jsHfKwJfLR7s880joybQ@public.gmane.org wrote:
>>>>> I am having serious headaches using nfs between a reiser4 server and arm
>>>>> client.
>>>>> Both on 2.6.29 vintage kernels.
>>>>>
>>>>> Files are constantly getting out of sync.
>>>>>
>>>>> Example :
>>>>>
>>>>> boot ARM via nfs
>>>>> edit lighttpd.conf on ARM
>>>>> check edit is visible on server. OK
>>>>>
>>>>> reboot ARM
>>>>> check file : reverted to an earlier state.
>>>>> check server: edited version still showing.
>>>>
>>>> So, on a freshly booted NFS client, you're opening and reading a file
>>>> and seeing file data that isn't even on the NFS server any more?
>>>>
>>>> That's beyond bizarre.  Do you have a reliable way to reproduce the
>>>> problem?
>>>
>>> Could be XID replay.
>>
>> I'm not following you.  You're thinking of a read request after the
>> reboot that unluckily reuses an old XID and gets stale data from the
>> servers reply cache?  Or something else?
>
> Nothing unlucky about it.  Just after a boot, if the client  
> implementation isn't careful about choosing an initial XID, (eg it  
> always starts with a psuedorandom number but uses the same seed every  
> time), it will hit the server's replay cache.

Hm, OK.

> This can be quite reproducible for NFSROOT and a quiescent server.

The Linux server doesn't cache READ results as far as I can tell.

--b.

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