Re: [NFS] NFS rpc and stale handles on 2.6.x servers

From: Roman Kagan (Roman.Kagan_at_itep.ru)
Date: 01/30/04

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    Date:	Fri, 30 Jan 2004 14:55:36 +0300
To: Neil Brown <neilb@cse.unsw.edu.au>

    On Fri, Jan 30, 2004 at 10:16:05AM +0000, Neil Brown wrote:
    > The "RPC request reserved 0 ..." is very odd. It does immediately
    > indicate a major problem, but it should be fixed, if only I could
    > figure out what was causing it.

    In case it helps: having enabled svcsock debugging by

      echo $[0x0100] > /proc/sys/sunrpc/rpc_debug

    I've noticed that those messages always appear in the same pattern:

    svc: server c7a3d200 waiting for data (to = 3600000)
    svc: socket c6dbfb00(inet c769f220), write_space busy=0
    svc: socket c2a9fac0 TCP data ready (svsk c6dbf980)
    svc: socket c2a9fac0 served by daemon c7a3d200
    svc: socket c2a9fac0 TCP data ready (svsk c6dbf980)
    svc: socket c2a9fac0 busy, not enqueued
    svc: server c7a3d200, socket c6dbf980, inuse=1
    svc: tcp_recv c6dbf980 data 1 conn 0 close 0
    svc: socket c6dbf980 recvfrom(c6dbf9d8, 0) = 4
    svc: TCP record, 2584 bytes
    svc: socket c6dbf980 recvfrom(c6d06a18, 1512) = 2584
    svc: TCP complete record (2584 bytes)
    svc: socket c2a9fac0 served by daemon c6efe000
    svc: got len=2584
    svc: socket c2a9fac0 busy, not enqueued
    svc: socket c6dbf980 sendto([c436b000 140... ], 140) = 140 (addr 43e17cc1)
    svc: socket c2a9fac0 busy, not enqueued
    svc: server c7a3d200 waiting for data (to = 3600000)
    svc: server c7a3d200, socket c25007a0, inuse=1
    svc: tcp_recv c25007a0 data 0 conn 0 close 1
    svc: svc_delete_socket(c25007a0)
    svc: server socket destroy delayed
    svc: got len=0
    RPC request reserved 0 but used 140
    svc: releasing dead socket
    svc: server c7a3d200 waiting for data (to = 3600000)

    Note that "tcp_recv" with this set of parameters (data=0 conn=0 close=1)
    is always correlated with "RPC request reserved ...", and also the
    "used" request length matches the message length in "sendto" on the
    seemingly unrelated socket.

    Unfortunately I don't understand the code well enough to make a better
    bug report, but feel free to ask me to test your patches if you can't
    reproduce the problem in your setup.

      Roman.
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