Re: about NLM/NSM

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

On Mon, Oct 27, 2008 at 05:14:38PM -0400, Peter Staubach wrote:
> 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.

That's what she was working on (and we merged), yes.

But it doesn't help clear just the set of locks held by a single client.

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

I'm losing track of what those two "this"'s refer to!

--b.