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

Rob van der Wal rob.vanderwal at surfsara.nl
Wed Jun 12 10:00:29 CEST 2019


Hi Joel,

The additional debug setting gives one additional line:
2019-06-12T09:58:27.977088+02:00 barentsz kern warning kernel - - - 
[525370.955129] EXT4-fs (dm-16): DAX enabled. Warning: EXPERIMENTAL, use 
at your own risk
2019-06-12T09:58:27.977121+02:00 barentsz kern debug kernel - - - 
[525370.955135] dm-16: error: dax access failed (-95)
2019-06-12T09:58:27.977122+02:00 barentsz kern err kernel - - - 
[525370.955136] EXT4-fs (dm-16): DAX unsupported by block device. 
Turning off DAX.
2019-06-12T09:58:27.977124+02:00 barentsz kern info kernel - - - 
[525370.957006] EXT4-fs (dm-16): mounted filesystem with ordered data 
mode. Opts: dax

Regards,
Rob


On 6/12/19 9:50 AM, Joel Colledge wrote:
> Hi Rob,
>
> This is strange, since the filesystem DAX access uses essentially the 
> same checks as DRBD does. You can get more detail about the failure by 
> doing the mount test again after enabling the relevant debug logging 
> as follows:
> echo "file drivers/dax/super.c +p" > 
> /sys/kernel/debug/dynamic_debug/control
>
> Perhaps there is a subtle difference in the checks that DRBD does 
> which is relevant for your device on this kernel.
>
> Best regards,
> Joel
>
>
> On Wed, Jun 12, 2019 at 8:04 AM Rob van der Wal 
> <rob.vanderwal at surfsara.nl <mailto:rob.vanderwal at surfsara.nl>> wrote:
>
>     Hi Joel,
>
>     Yes, I can mount with "-o dax":
>
>     lvcreate -L 40G -n test-lv  vg_ssd
>       scan_dev_close /dev/sdb2 no DEV_IN_BCACHE set
>       Logical volume "test-lv" created.
>     mkfs.ext4 -b 4K /dev/vg_ssd/test-lv
>     mount -o dax /dev/vg_ssd/test-lv /mnt
>     df /mnt
>     Filesystem                  1K-blocks  Used Available Use% Mounted on
>     /dev/mapper/vg_ssd-test--lv  41022688 49176  38859976   1% /mnt
>
>     But it shows a failure in syslog:
>     [518270.833954] EXT4-fs (dm-16): DAX enabled. Warning:
>     EXPERIMENTAL, use at your own risk
>     [518270.833959] EXT4-fs (dm-16): DAX unsupported by block device.
>     Turning off DAX.
>     [518270.835599] EXT4-fs (dm-16): mounted filesystem with ordered
>     data mode. Opts: dax
>
>     Regards,
>     Rob
>
>
>     On 6/11/19 3:57 PM, Joel Colledge wrote:
>>     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
>>     enabled:
>>     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:
>>     https://nvdimm.wiki.kernel.org/#filesystems
>>
>>     Best regards,
>>     Joel
>>
>>     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>  <mailto:rob.vanderwal at surfsara.nl>  wrote:
>>>     Hi Joel,
>>>
>>>     I've build the module from source (downloaded fromhttps://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          ipv410.0.0.30:7788  <http://10.0.0.30:7788>;
>>>          }
>>>
>>>
>>>     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
>>>
>
>     -- 
>     Rob van der Wal
>     Supercomputing | SURFsara | Science Park 140 | 1098 XG Amsterdam |
>     T +31 20 800  1300 | Rob.vanderWal at surfsara.nl
>     <mailto:Rob.vanderWal at surfsara.nl> | www.surfsara.nl
>     <http://www.surfsara.nl> |
>
>                 We are ISO 27001 certified and meet the high
>     requirements for information security.
>
>
>
> -- 
> Joel Colledge - Software Developer
> +43-1-817-82-92 x53 <tel:+4318178292>
> joel.colledge at linbit.com <mailto:joel.colledge at linbit.com>
>
> LIN <http://www.linbit.com/en/>BIT <http://www.linbit.com/en/> | 
> Keeping the Digital World Running
> DRBD HA - Disaster Recovery - Software-defined Storage
> t <https://twitter.com/linbit> / f 
> <https://www.facebook.com/pg/linbitdrbd/posts/> / in 
> <https://www.linkedin.com/company/linbit> / y 
> <https://www.youtube.com/user/linbit> / g+ 
> <https://plus.google.com/+Linbit/about>
>
> DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.

-- 
Rob van der Wal
Supercomputing | SURFsara | Science Park 140 | 1098 XG Amsterdam | T +31 
20 800  1300 | Rob.vanderWal at surfsara.nl | www.surfsara.nl |

             We are ISO 27001 certified and meet the high requirements 
for information security.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20190612/d9920b4d/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SURFsara
Type: image/png
Size: 2515 bytes
Desc: not available
URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20190612/d9920b4d/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ISO27001
Type: image/png
Size: 1742 bytes
Desc: not available
URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20190612/d9920b4d/attachment-0003.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 3704 bytes
Desc: S/MIME Cryptographic Signature
URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20190612/d9920b4d/attachment-0001.bin>


More information about the drbd-user mailing list