Re: NFSv4 file lock reporting interface request

[Tom Tucker <tom@opengridcomputing.com>]

Hi Bruce,

FWIW, I don't think dtrace does/did what NASA is asking for, but that's 
really irrelevant. The locks in NFSv4 are application specific locks, 
not generic kernel locks, so a service looking for spinlocks, mutexes, 
etc... wouldn't really be helpful I don't think.  However implementing a 
/sys/class, debugfs thingy that dumped the nfsv4 locks held is fairly 
simple, although I would think there are security implications.

Tom

On 8/7/2018 3:34 PM, J. Bruce Fields wrote:
> On Thu, Aug 02, 2018 at 08:50:20PM +0200, Cedric Blancher wrote:
>> Solaris and FreeBSD dtrace facility supports this functionality.
>> Unfortunately, Linux rejected dtrace for license issues, and instead
>> did... nothing.
> I didn't think was this sort of question tracing was designed to
> answer--it's a question about the system state at a given time (who
> holds what locks), rather than a list of events.  But I know nothing
> about dtrace.
>
> --b.
>
>> Ced
>>
>> On 10 July 2018 at 04:28, Peter Scott <pjscott@jpl.nasa.gov> wrote:
>>> Hello.  I am with the institutional hosting service at NASA's Jet Propulsion
>>> Laboratory and we have been trying to find the answer to an apparently
>>> simple question.
>>>
>>> We are running an NFSv4 server on Centos 7 and we need to get the server to
>>> tell us which files it thinks are locked by which clients.  This is because
>>> we have observed failure modes where something apparently has a lock
>>> (because attempting to lock the file again blocks) but we can't find a
>>> client that has the lock. Finding out what the server believes would be
>>> critical to troubleshooting this.
>>>
>>> We tracked down Trond Myklebust and Neil Brown and conversation suggests
>>> that this is a function that is (a) not currently available and (b)
>>> reasonable to ask for.  So this is me suggesting that an interface be
>>> provided to have knfsd output its list of locked files and clients.
>>>
>>> Regards,
>>> Peter Scott
>>> Office of the CIO
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>>
>>
>> -- 
>> Cedric Blancher <cedric.blancher@gmail.com>
>> [https://plus.google.com/u/0/+CedricBlancher/]
>> Institute Pasteur
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-- 
Thomas Tucker
President
Open Grid Computing, Inc.
(m) 512-826-7622
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