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[Bug 1042551] os-prober + KVM on host kills btrfs in clients
  • From: bugzilla_noreply@xxxxxxxxxx
  • Date: Mon, 05 Jun 2017 08:17:30 +0000
  • Message-id: <>

Andreas Stieger <astieger@xxxxxxxx> changed:

What |Removed |Added
CC| |aj@xxxxxxxx,
| |arvidjaar@xxxxxxxxx,
| |astieger@xxxxxxxx,
| |mchang@xxxxxxxx
Assignee|bnc-team-screening@xxxxxxxx |mchang@xxxxxxxx
| |

--- Comment #1 from Andreas Stieger <astieger@xxxxxxxx> ---
(In reply to Thomas Wagner from comment #0)
Using ext4, this setup works well. Using btrfs it works until os-prober is
launched (IMHO due to kernel or grub update) on the host.
os-prober tries to mount all btrfs partitions regardless if they are already
mount in a client. This destroys the btrfs filesystem.


Looking at /usr/lib/os-probes/50mounted-tests it would seem that btrfs is
handled in a special fashion, in particular not being mounted read-only:

if [ "$types" = btrfs ]; then
if mount -o ro -t "$type" "$partition" "$tmpmnt" 2>/dev/null;

and later:

# all btrfs subvol processing here. Handle both unmounted and
# mounted subvolumes.
if [ "$types" = btrfs ]; then
debug "begin btrfs processing for $UUID"
# note that the btrfs volume must not be mounted ro
if mount -t btrfs -U "$UUID" "$tmpmnt" 2>/dev/null; then
debug "btrfs volume $UUID mounted"

So the developer must have been aware of a requirements of mounting btrfs
read-write here, which breaks the KVM scenario. Assigning to SLE maintainer.

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