Re: stuck/hung nfsv4 mounts

[Peter Staubach <staubach@redhat.com>]

Chuck Lever wrote:
> On Nov 3, 2008, at Nov 3, 2008, 5:20 PM, Peter Staubach wrote:
>> Chuck Lever wrote:
>>> On Nov 3, 2008, at Nov 3, 2008, 12:37 PM, Trond Myklebust wrote:
>>>> On Mon, 2008-11-03 at 12:25 -0500, Jim Rees wrote:
>>>>> Trond Myklebust wrote:
>>>>>
>>>>> BTW: NFSv4 + soft == BAD BAD BAD!
>>>>>
>>>>> Maybe this combination should be prohibited.  Does it make any 
>>>>> sense given
>>>>> the stateful nature of v4?
>>>>
>>>> It might make sense if we were to fix up the granularity of the 
>>>> recovery
>>>> routines so that we are able to recover all the state associated with
>>>> just a single open owner or lock owner. Currently we'd have to recover
>>>> all the state associated with that server.
>>>>
>>>> IOW: we might be able to fix things up in the future, but right now,
>>>> NFSv4+soft is not a good idea.
>>>
>>> Two cents worth:  Until NFSv4+soft works reasonably well, I wouldn't 
>>> have any problem with making "soft" a no-op for nfs4 mounts.
>>
>> It may be the right thing to do in the short term, but it will
>> generate calls to support organizations.
>
> As opposed to the support "call" we got today?  ;-)
>

Well, at least, you have an answer today.

>> Anyone trying it will
>> wonder why it doesn't work "as it used to".  That sort of thing.
>> When that happens, we will be forced to do something and not at
>> our choice of time.
>
> I think our petard is hoist either way.  Better to avoid data 
> corruption, by whatever means.
>

Then it is probably time to fix it, sooner as opposed to later.

I don't have the resources at this time to put into doing this work,
so I am just expressing opinions.

I do know that it caused quite the flood of interest when it was
discovered that the superblock sharing stuff had broken a lot of
customers who expected to be able mount the same file system from
a server, multiple times, in different places, with different
options, and it stopped using the options beyond the first mount.

I am thinking that perhaps we can take something from this experience
and do better this next time.  This time, we know that we are making
an incompatible change and can do better.

       ps

>> Perhaps we should deny such mount attempts because at least that
>> would be obvious what was happening?  Perhaps we should also
>> deny NFSv4 mounting over UDP?
>