Re: NFSv4 client locks up on larger writes with Kerberos enabled

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Bruce,

Yes. It’s a Dell EMC Unity 300 storage appliance. 

>From what I have gathered, under the hood it is running SLES12SP1

3.12.74-60.64.66.1.NEOKERNEL_SLES12SP1 #2 SMP Fri May 17 06;41:36 EDT 2019 x86_64

Unfortunately I only have limited access to the appliance through a “service” account. I do not have root privileges and I can only run certain commands under the service account. 

I’ve got a ticket open with them and it’s been escalated to their “engineering” department but they haven’t provided much insight as of yet.

If you give me some idea on what might help I’ll try to get more info if I can.


-Kevin

> On Sep 26, 2019, at 11:06 AM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> 
> On Thu, Sep 26, 2019 at 08:55:17AM -0700, Chuck Lever wrote:
>>>> On Sep 25, 2019, at 1:07 PM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>>> 
>>> On Wed, Sep 25, 2019 at 11:49:14AM -0700, Chuck Lever wrote:
>>>> Sounds like the NFS server is dropping the connection. With
>>>> GSS enabled, that's usually a sign that the GSS window has
>>>> overflowed.
>>> 
>>> Would that show up in the rpc statistics on the client somehow?
>> 
>> More likely on the server. The client just sees a disconnect
>> without any explanation attached.
> 
> So watching a count of disconnects might at least tell us something?
> 
>> gss_verify_header is where the checking is done on the server.
>> Disappointingly, I see some dprintk's in there, but no static
>> trace events.
> 
> Kevin, was this a Linux server?
> 
> --b.
> 
>>> In that case--I seem to remember there's a way to configure the size of
>>> the client's slot table, maybe lowering that (decreasing the number of
>>> rpc's allowed to be outstanding at a time) would work around the
>>> problem.
>> 
>>> Should the client be doing something different to avoid or recover from
>>> overflows of the gss window?
>> 
>> The client attempts to meter the request stream so that it stays
>> within the bounds of the GSS sequence number window. The stream
>> of requests is typically unordered coming out of the transmit
>> queue.
>> 
>> There is some new code (since maybe v5.0?) that handles the
>> metering: gss_xmit_need_reencode().




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