[Bug 1189926] Re: data corruption in storage attached to VM using KVM

[Adam Conrad]

Hello Chris, or anyone else affected,

Accepted qemu-kvm into precise-proposed. The package will build now and
be available at http://launchpad.net/ubuntu/+source/qemu-kvm/1.0+noroms-
0ubuntu14.9 in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to
enable and use -proposed.  Your feedback will aid us getting this update
out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, and change the tag
from verification-needed to verification-done. If it does not fix the
bug for you, please add a comment stating that, and change the tag to
verification-failed.  In either case, details of your testing will help
us make a better decision.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance!

** Changed in: qemu-kvm (Ubuntu Precise)
       Status: In Progress => Fix Committed

** Tags added: verification-needed

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https://bugs.launchpad.net/bugs/1189926

Title:
  data corruption in storage attached to VM using KVM

Status in “qemu-kvm” package in Ubuntu:
  Fix Released
Status in “qemu-kvm” source package in Precise:
  Fix Committed
Status in “qemu-kvm” source package in Quantal:
  Fix Released

Bug description:
  [Impact]

  When using qemu-kvm-1.0 occasionally qcow2 disks will be corrupted.

  [Test Case]

  A test case can be downloaded here:
      http://people.canonical.com/~arges/lp1189926/lnv-382.tgz
  Extract the contents and run ./create-disk, then ./test-kvm to test the currently installed KVM. Keep in mind that 100GB+ of disk is required to run the test.

  [Regression Potential]

  The patch is a backport of commit
  143550a83ef4eef86a847d00023d148e1f59f743 upstream, which changes the
  way that the number of available clusters are counted. While the
  original patch has assumptions that certain functions are available,
  the backport had to change these to be able to apply to v1.0.

  --

  When using io_perf corruption can be detected when using qemu-kvm-1.0.
  A test case can be downloaded here:
      http://people.canonical.com/~arges/lp1189926/lnv-382.tgz
  Extract the contents and run ./create-disk, then ./test-kvm to test the currently installed KVM. Keep in mind that 100GB+ of disk is required to run the test.

  This affects the qemu-kvm version in Precise, but is fixed in Quantal
  and beyond.

  It is expected that running the test case results in no disk
  corruption; however we detect corruption on Precise.

  Running git bisect on this test finds that commit 68d100e905453ebbeea8e915f4f18a2bd4339fe8 introduced the problem between v0.15.0 and v1.0.
  Running git bisect in reverse finds that commit b7ab0fea37c15ca9e249c42c46f5c48fd1a0943c fixes the issue between v1.1.2 and v1.2.0.

  However, b7ab0fea cannot be easily backported to v1.0 and 68d100e9 is
  a large change to revert. However, both changes seem to indicate that
  the problem lies in the qcow2 parts of the code.

  bug 1040033 seems to be a related issue.

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