[Pkg-virtualbox-devel] Bug#874105: virtualbox: Virtualbox seems to conflict with BTRFS when trying to install ReactOS 0.4.6

[Svein Engelsgjerd]

Package: virtualbox
Version: 5.1.26-dfsg-2
Severity: grave
Justification: causes non-serious data loss

Dear Maintainer,

   * What led up to the situation?
I wanted to try to install ReactOS 0.4.6. My rootfs is btrfs with metadata=raid10 and data=raid1
While VirtualBox was running dmesg showed a constant stream of csum failed root 5 ino XXX off XXX csum XXX expected csum XXX mirror 1 messages.
Note that the mirror was always 1.

   * What exactly did you do (or not do) that was effective (or
     ineffective)?
I stopped the VM that was running the ReactOS installer. All the errors stopped
I ran a scrub on my btrfs filesystem afterwards. No errors detected.
I checked smart data for my SSD's No errors detected, no sign of wear.
I tried various file operations (md5sum, sha1sum, cp, hexeditor etc...) on the .vdi file - no corruption messages

   * What was the outcome of this action?
While this could just as easily be a btrfs bug I suspect that  VirtualBox's vboxdrv is the cause here.
I may be wrong about this, so my apologies if that is the case.
Btrfs fixes the corruptions and appear to be in a good state as long as the VirutalBox VM is not running.
qemu/kvm works fine. Using that instead.

   * What outcome did you expect instead?
I expected no errors while running VirtualBox on top of my BTRFS rootfilessytem.

   * Other information:
While I did not experience any dataloss I fear that this is fragile and *might* cause dataloss for some.
this is the reason I classify this bug as grave. This is also causing me to avoid testing for a while
until I get some feedback on this one.

I am aware that BTRFS have it's share of bugs, but I run with a minimal configuration that have not caused
any issues for years (it has actually fixed a few silent data corruptions here and there).

So since my hardware and data checked out fine and the data is instact I think this could be a conflict
between the btrfs and/or vboxdrv module. I am not skilled enoguh to find that out for myself.

BTW: The VirtualBox vdi file contains a VFAT filesystem (reactos uses that). This does NOT appear to be
the issues as I have tested other stuff with VFAT without any issues.

-- System Information:
Debian Release: buster/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.12.0-1-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages virtualbox depends on:
ii  adduser                               3.116
ii  init-system-helpers                   1.49
ii  iproute2                              4.9.0-1
ii  libc6                                 2.24-14
ii  libcurl3-gnutls                       7.55.0-1
ii  libdevmapper1.02.1                    2:1.02.137-2+b1
ii  libgcc1                               1:7.2.0-1
ii  libgsoap-2.8.49                       2.8.49-1
ii  libpng16-16                           1.6.31-1
ii  libpython3.5                          3.5.4-2
ii  libsdl1.2debian                       1.2.15+dfsg2-0.1
ii  libssl1.1                             1.1.0f-4
ii  libstdc++6                            7.2.0-1
ii  libvncserver1                         0.9.11+dfsg-1
ii  libvpx4                               1.6.1-3
ii  libx11-6                              2:1.6.4-3
ii  libxcursor1                           1:1.1.14-1+b4
ii  libxext6                              2:1.3.3-1+b2
ii  libxml2                               2.9.4+dfsg1-3.1
ii  libxmu6                               2:1.1.2-2
ii  libxt6                                1:1.1.5-1
ii  procps                                2:3.3.12-3
ii  python3                               3.5.3-3
ii  python3.5                             3.5.4-2
ii  virtualbox-dkms [virtualbox-modules]  5.1.26-dfsg-2
ii  zlib1g                                1:1.2.8.dfsg-5

Versions of packages virtualbox recommends:
ii  libgl1-mesa-glx [libgl1]  13.0.6-1+b2
ii  libqt5core5a              5.9.1+dfsg-9
ii  libqt5opengl5             5.9.1+dfsg-9
ii  libqt5widgets5            5.9.1+dfsg-9
ii  virtualbox-qt             5.1.26-dfsg-2

Versions of packages virtualbox suggests:
ii  vde2                            2.3.2+r586-2.1
pn  virtualbox-guest-additions-iso  <none>

-- no debconf information