On Thu, Aug 04, 2011 at 12:49:13PM -0400, J. Bruce Fields wrote:
> On Thu, Aug 04, 2011 at 06:43:13PM +0200, Frank van Maarseveen wrote:
> > On Thu, Aug 04, 2011 at 12:34:52PM -0400, J. Bruce Fields wrote:
> > > On Thu, Aug 04, 2011 at 12:30:19PM +0200, Frank van Maarseveen wrote:
> > > > Both client- and server run 2.6.39.3, NFSv3 over UDP (without the
> > > > relock_filesystem patch proposed earlier).
> > > >
> > > > A second client has an exclusive lock on a file on the server. The
> > > > client under test calls fcntl(F_SETLKW) to wait for the same exclusive
> > > > lock. Wireshark sees NLM V4 LOCK calls resulting in NLM_BLOCKED.
> > > >
> > > > Next the server is rebooted. The second client recovers the lock
> > > > correctly. The client under test now receives NLM_DENIED_GRACE_PERIOD for
> > > > every NLM V4 LOCK request resulting from the waiting fcntl(F_SETLKW). When
> > > > this changes to NLM_BLOCKED after grace period expiration the fcntl
> > > > returns -ENOLCK ("No locks available.") instead of continuing to wait.
> > >
> > > So that sounds like a client bug, and correct behavior from the server
> > > (assuming the second client was still holding the lock throughout).
> >
> > yes.
> >
> > >
> > > > server:/proc/locks shows two entries for the file after the -ENOLCK. When
> > > > the second client gives up its lock because the program running there
> > > > is killed one entry in server:/proc/locks remains indefinately: as a
> > > > result no NFS client can lock the file anymore.
> > >
> > > But that sounds like a server bug--what do the two entries look like?
> >
> > I think the server assumes correct client behavior; the client under
> > test resulted in a '->' prefixed entry. The fcntl at the client just
> > shouldn't have returned yet.
>
> Oh, right, so did you see a granted callback returned to the client?
Hmm no, maybe it is a server bug. These are the final request and reply
(which result in the incorrect -ENOLCK for F_SETLKW at the client under
test), decoded by wireshark:
No. Time Source Destination Protocol Info
529 225.386189 172.17.1.124 172.17.1.49 NLM V4 LOCK Call (Reply In 530) FH:0xb17f38ea svid:10 pos:0-0
Frame 529: 246 bytes on wire (1968 bits), 246 bytes captured (1968 bits)
Network Lock Manager Protocol
[Program Version: 4]
[V4 Procedure: LOCK (2)]
cookie: <DATA>
length: 4
contents: <DATA>
block: Yes
exclusive: Yes
lock
caller_name: lokka.tasking.nl
length: 16
contents: lokka.tasking.nl
fh
length: 28
[hash (CRC-32): 0xb17f38ea]
decode type as: unknown
filehandle: 01000601e66f5c256cb3414eba710fcd882a67201b000000...
owner: <DATA>
length: 19
contents: <DATA>
fill bytes: opaque data
svid: 10
l_offset: 0
l_len: 0
reclaim: No
state: 87
No. Time Source Destination Protocol Info
530 225.386368 172.17.1.49 172.17.1.124 NLM V4 LOCK Reply (Call In 529) NLM_BLOCKED
Frame 530: 78 bytes on wire (624 bits), 78 bytes captured (624 bits)
Network Lock Manager Protocol
[Program Version: 4]
[V4 Procedure: LOCK (2)]
cookie: <DATA>
length: 4
contents: <DATA>
stat: NLM_BLOCKED (3)
--
Frank
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