Stale fcntl lock never released

Stale fcntl lock never released

[Christian Reis]

Just saw this from one of the diskless boxes on our system (clients
using vanilla 2.4.21, server running 2.4.20-rc3). The client was running
mutt and was editing a message when it hung. We shut down the box and
started another one up, but when the user tried to read his mail, mutt
was hanging upon fcntl(); strace shows it was returning Resource
temporarily unavailable (ENOLCK IIRC). 

On the server side, we have:

    kiko@anthem:~$ cat /proc/locks  | grep 09:06
    1: POSIX  ADVISORY  WRITE 11771 09:06:60316 0 EOF d0d51300 c02d1048
    d0d51424 00000000 d0d5130c
    2: POSIX  ADVISORY  WRITE 11752 09:06:60311 0 EOF d0d51420 d0d51304
    f7c367e4 00000000 d0d5142c
    4: POSIX  ADVISORY  WRITE 10560 09:06:60312 0 EOF f7c36840 f7c367e4
    f7c36f64 00000000 f7c3684c
    5: POSIX  ADVISORY  WRITE 599 09:06:30193 0 EOF f7c36f60 f7c36844
    f7c36964 00000000 f7c36eac
    5: -> POSIX  ADVISORY  WRITE 10569 09:06:30193 191252 EOF f7c36ea0
    f7c36604 c02d1050 f7c36f60 f7c3660c
    5: -> POSIX  ADVISORY  WRITE 11787 09:06:30193 191252 EOF f7c36600
    c02d1050 f7c36ea4 f7c36f60 f7c36f6c

(All these locks were held only by the crashed workstation)

Client mount options are:

    anthem:/var/spool/mail on /var/mail type nfs 
    (rw,sync,v3,rsize=8192,wsize=8192,acregmin=0,acregmax=0,
     acdirmin=0,acdirmax=0,hard,udp,noac,lock,addr=anthem)

Restarting the nfs service frees the locks, but shouldn't it be done
automatically? I'm not sure if it's a case of the server not clearing
the lock, or the client not tickling the server into it.. any ideas?

(Trond, do any of the lockd patches in
http://www.fys.uio.no/~trondmy/src/2.4.21/ fix something like this?)

Take care,
--
Christian Reis, Senior Engineer, Async Open Source, Brazil.
http://async.com.br/~kiko/ | [+55 16] 261 2331 | NMFL


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Re: Stale fcntl lock never released

[Trond Myklebust]

>>>>> " " == Christian Reis <kiko@async.com.br> writes:

     > (Trond, do any of the lockd patches in
     > http://www.fys.uio.no/~trondmy/src/2.4.21/ fix something like
     > this?)

No. This is what rpc.statd is supposed to do. When a client reboots,
it is supposed to notify the server that it should remove all locks
belonging to that client.

Cheers,
  Trond


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Re: Stale fcntl lock never released

[Christian Reis]

On Tue, Jun 24, 2003 at 09:02:10PM +0200, Trond Myklebust wrote:
> >>>>> " " == Christian Reis <kiko@async.com.br> writes:
> 
>      > (Trond, do any of the lockd patches in
>      > http://www.fys.uio.no/~trondmy/src/2.4.21/ fix something like
>      > this?)
> 
> No. This is what rpc.statd is supposed to do. When a client reboots,
> it is supposed to notify the server that it should remove all locks
> belonging to that client.

What if the client never reboots, but instead is turned off and another
client turned on? Should the lock persist? For how long?

Take care,
--
Christian Reis, Senior Engineer, Async Open Source, Brazil.
http://async.com.br/~kiko/ | [+55 16] 261 2331 | NMFL


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Re: Stale fcntl lock never released

[Trond Myklebust]

>>>>> " " == Christian Reis <kiko@async.com.br> writes:

     > What if the client never reboots, but instead is turned off and
     > another client turned on? Should the lock persist? For how
     > long?

It will persist forever.

Cheers,
  Trond


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Re: Stale fcntl lock never released

[Christian Reis]

On Tue, Jun 24, 2003 at 09:14:10PM +0200, Trond Myklebust wrote:
> >>>>> " " == Christian Reis <kiko@async.com.br> writes:
> 
>      > What if the client never reboots, but instead is turned off and
>      > another client turned on? Should the lock persist? For how
>      > long?
> 
> It will persist forever.

How odd.

Is the only solution is to restart the server-side statd, or knfsd?

Take care,
--
Christian Reis, Senior Engineer, Async Open Source, Brazil.
http://async.com.br/~kiko/ | [+55 16] 261 2331 | NMFL


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Re: Stale fcntl lock never released

[Steve Dickson]

The statd in nfs-utils-1.0.3 has a new -N flag that might work...

       -N     Causes statd to run in the notify-only  mode.  When  
started  in
              this  mode,  the  statd  program will check its state 
directory,
              send notifications to any monitored nodes,  and  exit  
once  the
              notifications have been sent. This mode is used to enable 
Highly
              Available NFS implementations (i.e. HA-NFS).

SteveD.

Christian Reis wrote:

>On Tue, Jun 24, 2003 at 09:14:10PM +0200, Trond Myklebust wrote:
>  
>
>>>>>>>" " == Christian Reis <kiko@async.com.br> writes:
>>>>>>>              
>>>>>>>
>>     > What if the client never reboots, but instead is turned off and
>>     > another client turned on? Should the lock persist? For how
>>     > long?
>>
>>It will persist forever.
>>    
>>
>
>How odd.
>
>Is the only solution is to restart the server-side statd, or knfsd?
>
>Take care,
>--
>Christian Reis, Senior Engineer, Async Open Source, Brazil.
>http://async.com.br/~kiko/ | [+55 16] 261 2331 | NMFL
>
>
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>



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Re: Stale fcntl lock never released

[Spencer Shepler]

Some server implementations provide a administrative command 
to release NFS locks held at the server for a specific client
for this scenario where the client is turned off or will never
contact the server again.

Spencer

Christian Reis wrote:
> 
> On Tue, Jun 24, 2003 at 09:14:10PM +0200, Trond Myklebust wrote:
> > >>>>> " " == Christian Reis <kiko@async.com.br> writes:
> >
> >      > What if the client never reboots, but instead is turned off and
> >      > another client turned on? Should the lock persist? For how
> >      > long?
> >
> > It will persist forever.
> 
> How odd.
> 
> Is the only solution is to restart the server-side statd, or knfsd?
> 
> Take care,
> --
> Christian Reis, Senior Engineer, Async Open Source, Brazil.
> http://async.com.br/~kiko/ | [+55 16] 261 2331 | NMFL
> 
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