[DRBD-user] drbd-9.0.18-1 : BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0

[Joel Colledge]

On Tue, Jun 4, 2019 at 7:12 AM Rob van der Wal
<rob.vanderwal at surfsara.nl> wrote:
>
> drbd-9.0.18-1 does not seem to work with Suse Enterprise 12 SP4:
> 2019-06-03T09:34:26.602963+02:00 barentsz kern alert kernel - - - [
> 699.994957] BUG: unable to handle kernel NULL pointer dereference at
> 00000000000000b0
> 2019-06-03T09:34:26.602964+02:00 barentsz kern alert kernel - - - [
> 699.996005] IP: drbd_md_decode+0x17/0x4f0 [drbd]
> 2019-06-03T09:34:26.602966+02:00 barentsz kern info kernel - - - [
> 699.997027] PGD 800000085a46a067 P4D 800000085a46a067 PUD 85ae11067 PMD 0
> 2019-06-03T09:34:26.602967+02:00 barentsz kern warning kernel - - - [
> 699.998075] Oops: 0000 [#6] SMP PTI
> 2019-06-03T09:34:26.602969+02:00 barentsz kern warning kernel - - - [
> 699.999118] CPU: 14 PID: 3179 Comm: drbdsetup Tainted: G D OE
> 4.12.14-95.16-default #1 SLE12-SP4
> ...
>
> The status of the drbd devices are "diskless" now. Any ideas?
>

I have briefly tested drbd-9.0.18-1 on SLES12 SP4 and have not found
any problems. There is presumably a difference in your environment or
configuration which is triggering this issue.

Where did you get your DRBD module from?

What backing device are you using for DRBD? In case you have external
metadata - what backing device are you using for the DRBD metadata? Is
this a PMEM device?

Just before the crash, you should see "meta-data IO uses: ..." in your
kernel log. Please provide this log line.

Joel Colledge