Control: reassign -1 src:linux 4.6.1-1
Control: severity -1 important
Control: tag -1 confirmed upstream
On Mon, 2016-07-04 at 00:47 -0400, westlake wrote:
> Package: linux-image-4.6.0-0.bpo.1-amd64
> Version: 4.6.1-1~bpo8+1
> Severity: normal
>
> kernels 4.5 and 4.6 breaks qemu-nbd from mapping partitions
>
> qemu-nbd can map partitions from VM images and raw disk images to
> /dev/nbdNpM nodes, but proper module options have to be loaded prior so
> that qemu-nbd performs these additional mappings (the general consensus
> around mapping image files has users issuing "kpartx -a /dev/",
> but kpartx is not needed at all after issuing qemu-nbd)
>
> nothing is specially set up other than a module option file and that's
> pretty much it -- there's just 2 or 3 commands for the testing --- all
> which indicates the issue is more towards kernel than it is with qemu-nbd.
I can confirm this issue.
> after a modprobe nbd is issued, there is no "/dev/nbd0p1"-like devices,
That much is correct behaviour since no device is attached yet...
> so the main problem with kernels 4.5/4.6 is that qemu-nbd is not being
> allowed to generate any device nodes. ("partition" device nodes that is
> -- "/dev/nbd0" and "/dev/nbd1" nodes are generated by modprobe nbd)
[...]
...but the kernel should scan the partition table for an nbd as soon as
it is attached to a server. Currently that isn't happening. As a
workaround, running 'fdisk' and then re-writing the same partition
table triggers a rescan.
This is almost certainly caused by:
commit 37091fdd831f28a6509008542174ed324dd645bc
Author: Markus Pargmann
<mpa@pengutronix.de>
Date: Mon Jul 27 07:36:49 2015 +0200
nbd: Create size change events for userspace
I have a rough idea of how to fix it and will update you later.
Ben.
--
Ben Hutchings
Lowery's Law:
If it jams, force it. If it breaks, it needed replacing
anyway.
Attachment:
signature.asc
Description: This is a digitally signed message part