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

Joel Colledge joel.colledge at linbit.com
Tue Jun 11 15:57:14 CEST 2019

Hi Rob,

This is strange. It seems that your LV is reporting that it supports
PMEM/DAX. I suggest that you check that this issue also occurs without
DRBD. For example, create a filesystem and try to mount it with DAX
mkfs.ext4 -b 4K /dev/<your-lv>
mount -o dax /dev/<your-lv> <somewhere>

The check the syslog to see whether DAX was successfully enabled. You
can see the expected success and failure output here:

Best regards,

PS Please "reply all" to keep the mailing list in CC

On Tue, Jun 11, 2019 at 2:53 PM Rob van der Wal
<rob.vanderwal at surfsara.nl> wrote:
> Hi Joel,
> I've build the module from source (downloaded from https://www.linbit.com/en/drbd-community/drbd-download/).
> I think we don't use external metadata and we are using a ssd disk for storing. This is a part of our drbd.conf:
> drbd.conf:
>     on barentsz {
>         node-id 1;
>         device           /dev/drbd0 minor 0;
>         disk             /dev/vg_ssd/vm_prace-ldap;
>         meta-disk        internal;
>         address          ipv4;
>     }
> LVM info:
>   PV /dev/sdb2   VG vg_ssd          lvm2 [446.43 GiB / 102.43 GiB free]
>   ACTIVE            '/dev/vg_ssd/vm_prace-ldap' [38.00 GiB] inherit
> The requested line in the syslog is:
> [1037978.736262] drbd r0/0 drbd0: meta-data IO uses: dax-pmem
> But I don't think we are using a PMEM device so this looks not correct.
> Regards,
> Rob van der Wal

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