nbd device size not updated correctly

[Stefan Kooman]

nbd does not handle a disk resize correctly. This has been fixed upstream: https://github.com/torvalds/linux/commit/639812a1ed9bf49ae2c026086fbf975339cd1eef

On Ubuntu Bionic with a "4.15.0-34-generic #37-Ubuntu" kernel a resize of a (Ceph) rbd image does not propagate to a "rbd-nbd" mapped disk, until it's unmapped / remapped. See https://tracker.ceph.com/issues/23137. Other "nbd" mapped disks might suffer from the same behaviour (not tested).

Ubuntu mainline kernel (4.19-rc5) works correct with regards to this rbd resize rbd-nbd mapped image.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1794766

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Stefan Kooman (stefan-n1)]

Unable to send logs as this host is ipv6 only, and bugs.launchpad.net does not have a quad A record published (ERROR: connecting to Launchpad failed: [Errno 101] Network is unreachable).

Logs are not relevant IMHO as the fix is clear and only needs to get applied to the kernels affacted (at least Ubuntu Bionic with 4.15 kernel).

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Joseph Salisbury (jsalisbury)]

Bionic already has commit 639812a1ed9b since it was added to mainline as of v4.14-rc6:

639812a1ed9b nbd: don't set the device size until we're connected

Can you confirm Bionic has this bug after applying all the latest updates? If it does, we can perform a "Reverse" bisect, since you confirm this bug is fixed in 4.19-rc5.

[Stefan Kooman (stefan-n1)]

On Tue, Oct 02, 2018 at 03:01:13PM -0000, Joseph Salisbury wrote:
> Bionic already has commit 639812a1ed9b since it was added to mainline as
> of v4.14-rc6:
>
> 639812a1ed9b nbd: don't set the device size until we're connected
>
> Can you confirm Bionic has this bug after applying all the latest
> updates? If it does, we can perform a "Reverse" bisect, since you
> confirm this bug is fixed in 4.19-rc5.

Just tested again against kernel 4.15.0-36-generic #39-Ubuntu SMP
(linux-image-generic: Installed: 4.15.0.36.38) but a "rbd resize" on the
ceph cluster does *not* propagate to the rbd-nbd session. Bug is still
present.

Gr. Stefan