[DRBD-user] Can't unload ib_sdp module after "drbdadm down all" (fishy module refcount)

[Florian Haas]

Hi,

DRBD 8.3.12 on CentOS 6.2; SDP from kernel-ib-1.5.3, built locally
from ofa_kernel-1.5.3-OFED srpm. DRBD resource config is as follows:

resource vg_cluster1 {
    on alice {
        device           /dev/drbd1 minor 1;
        disk             /dev/sda;
        address          sdp 192.168.100.12:7789;
        meta-disk        internal;
    }
    on bob {
        device           /dev/drbd1 minor 1;
        disk             /dev/sdb;
        address          sdp 192.168.100.13:7789;
        meta-disk        internal;
    }
}

The 192.168.100.0/24 network is a directly connected IB link, and DRBD
demonstrably does use SDP:

# sdpnetstat -Sn
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
sdp        0      0 192.168.100.13:55825    192.168.100.12:7788     ESTABLISHED
sdp        0      0 192.168.100.13:55826    192.168.100.12:7789     ESTABLISHED
sdp        0      0 192.168.100.13:7789     192.168.100.12:41104    ESTABLISHED
sdp        0      0 192.168.100.13:7788     192.168.100.12:41105    ESTABLISHED


The ib_sdp module refcount looks normal at this time (at least, I
would expect the 2 in lsmod's "used by" column, one per SDP-enabled
DRBD resource -- but please correct me if this is a misconception):

lsmod | grep ib_sdp
ib_sdp                130827  2


Now, "drbdadm down" all seems to not have the expected effect on the refcount:

# drbdadm down all; lsmod | grep ib_sdp
ib_sdp                130827  4294967294

4 billion references on that module look excessive. :) I suppose the
refcount incorrectly goes negative.


This is inconvenient as you're now unable to unload ib_sdp. I presume
this is a bug; if I can provide any traces or debug logs to narrow
down the issue I'll be happy to.

Cheers,
Florian

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