[Drbd-dev] possible FIX [Xen - DRBD issue / panic in skb_copy_bits]

Valentin Vidic Valentin.Vidic at CARNet.hr
Tue Jun 23 10:01:09 CEST 2009

On Mon, Jun 15, 2009 at 01:58:57PM +0200, Valentin Vidic wrote:
> I've reproduced the problem with Debian lenny versions of kernel (2.6.26)
> and DRBD (8.0.14). Unfortunately it seems the patches don't help. I've
> tried both and the ooops still happens: 

And here is the setup I used to reproduce the problem: two machines
(node1, node2) running Debian lenny with DRBD v8.0.14, Xen v3.2.1,
Heartbeat v2.1.4 and kernel v2.6.26-2-xen-amd64. On these nodes I have
two domU machines (child1, child2) running and managed by Hearbeat:

* node1: child1
* node2: child2

The problem is reproduced as follows:

* Turn on scatter-gather on dom0 machines: ethtool -K xenbr0 sg on
* Disconnect all DRBD devices on both nodes: drbdadm disconnect drbdX
* Connect all DRBD devices on both nodes: drbdadm connect drbdX
* Start some heavy disk IO in child1: dd if=/dev/zero of=/tmp/zero
* Force reboot the node2: reboot -f -n
* After some time Heartbeat starts child2 on node1
* Some seconds later kernel on node1 ooopses

It is not clear which of the DRBD devices causes the ooops but I couldn't
reproduce it with only child1 or child2. Also here is a DRBD config used
on these nodes:

resource drbd0 {
  protocol C;

  startup {
    wfc-timeout 60;
    degr-wfc-timeout 30;

  disk {
    on-io-error detach;
    fencing resource-and-stonith;

  net {
    cram-hmac-alg sha1;
    shared-secret "somethinglong";
    after-sb-0pri discard-older-primary;
    after-sb-1pri consensus;
    after-sb-2pri disconnect;

  handlers {
    outdate-peer /usr/local/sbin/hb2drbd;

  on node1 {
    device     /dev/drbd0;
    disk       /dev/vg0/child1;
    meta-disk  internal;

  on node2 {
    device     /dev/drbd0;
    disk       /dev/vg0/child1;
    meta-disk  internal;

Valentin Vidic
Computer systems engineer
Computer and IT Systems and Services Department
Croatian Academic and Research Network - CARNet
Josipa Marohnica 5, HR-10000 Zagreb, Croatia
tel: +385 1 6661 714, fax. +385 1 6661 766

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