Re: about NLM/NSM

[Peter Staubach <staubach@redhat.com>]

J. Bruce Fields wrote:
> On Mon, Oct 27, 2008 at 03:22:57PM -0400, Peter Staubach wrote:
>   
>> J. Bruce Fields wrote:
>>     
>>> On Mon, Oct 27, 2008 at 02:49:27PM +0800, hexf wrote:
>>>   
>>>       
>>>> We are using nfsv3. Now we meet a demand. If a client which hold a
>>>> lock crash, after it reboot, its statd daemon can notify the nfs
>>>> server to release the lock.  But if this client will not reboot for
>>>> some reason(or will reboot after a long time), then the lock it
>>>> holding will not be released.In nfsv3 and nlmv4,it seems there is no
>>>> time-out mechnism for this situation. How would we solve this
>>>> question? My colleague advise me to modify the code of NLM/NSM to meet
>>>> this demand,but is seems quite a complicated work.Can you give me some
>>>> advice?
>>>>     
>>>>         
>>> It might be possible to modify the server so that it dropped all locks
>>> from a client it hadn't heard from in a while.  However, nfsv2/v3
>>> clients are not required to contact the server regularly while they hold
>>> locks.  So you may end up revoking locks held by perfectly good
>>> functioning clients.
>>>
>>> As an ugly workaround, rebooting the server will clear the problem, as
>>> it will notify clients to recover their locks on restart, and any dead
>>> clients will fail to recover their locks.
>>>
>>>   
>>>       
>> Didn't Wendy Cheng submit some patches to implement a
>> "clearlocks" sort of functionality?  What happened with
>> them?
>>     
>
> Yes, but that's motivated by the case of migrating all clients using one
> export; so it'll drop all locks held on a single filesystem, or all
> locks acquired using a single server (not client!) ip address.
>
> So if we want some finer-grained interface then that's yet to be
> designed.
>   

Sorry, I guess that I was remembering incorrectly.  I was
thinking that she was looking for something like the clearlocks
functionality so that file systems could be migrated around
cleanly.

It seems for this situation, we could use this sort of variation.

       ps