On Thu, Aug 6, 2020 at 4:21 PM Andrea Bolognani <abologna@xxxxxxxxxx> wrote:
On Thu, 2020-08-06 at 15:45 +0200, Marc Hartmayer wrote:
> On Tue, Aug 04, 2020 at 11:39 PM +0200, Andrea Bolognani <abologna@xxxxxxxxxx> wrote:
> > This patch broke libvirt in Debian for certain setups.
> >
> > With AppArmor enabled (the default), the error is
> >
> > $ virsh start cirros
> > error: Failed to start domain cirros
> > error: internal error: Process exited prior to exec: libvirt:
> > error : Cannot delete directory '/run/libvirt/qemu/1-cirros.dev':
> > Device or resource busy
> >
> > If I disable AppArmor by passing security='' on the kernel command
> > line, the error message changes to
> >
> > $ virsh start cirros
> > error: Failed to start domain cirros
> > error: internal error: Process exited prior to exec: libvirt:
> > QEMU Driver error : Unable to get devmapper targets for
> > /var/lib/libvirt/images/cirros.qcow2: Success
> >
> > An effective workaround is to set namespaces=[] in qemu.conf, but
> > that's of course not something that we want users doing :)
> >
> > The underlying issue seems to be caused by the fact that, on a Debian
> > installation that uses plain partitions instead of LVM, /proc/devices
> > doesn't contain an entry for device-mapper right after boot, which...
> > ... this code expects.
> >
> > Running
> >
> > $ sudo dmsetup info
> > No devices found
>
> We see the same problem as mentioned by Andrea. The host kernel
> configuration used:
>
> …
> CONFIG_BLK_DEV_DM_BUILTIN=y
> CONFIG_BLK_DEV_DM=m
> …
>
> As soon as we load the kernel module ‘dm-mod‘ everything works because
> then ‘device-mapper‘ is listed in /proc/devices.
Thanks Marc! I have confirmed that Debian also uses the same kernel
configuration as the one you have reported above, and that running
dmsetup(8) causes the dm-mod kernel module to be loaded.
For comparison Fedora, where everything works fine, uses
CONFIG_BLK_DEV_DM_BUILTIN=y
CONFIG_BLK_DEV_DM=y
FYI even having the module loaded isn't the ultimate workaround as there is a further twist of the same issue. Ubuntu has: CONFIG_BLK_DEV_DM_BUILTIN=y CONFIG_BLK_DEV_DM=y And there is an entry in devices (in host and in the container) $ cat /proc/devices | grep map 253 device-mapper But libvirt 6.6 in this case running in a LXD system container (working before) now fails related to this with what seems to be the same high level symptom. # virsh start kvmguest-groovy-normal3 error: Failed to start domain kvmguest-groovy-normal3 error: internal error: Process exited prior to exec: libvirt: QEMU Driver error : Unable to get devmapper targets for /var/lib/uvtool/libvirt/images/kvmguest-groovy-normal3.qcow: No such file or directory
--
Andrea Bolognani / Red Hat / Virtualization
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd
Staff Engineer, Ubuntu Server
Canonical Ltd
