[Qemu-devel] [Bug 1077838] Re: qemu-nbd -r -c taints device for subsequent usage, even after -d

[Launchpad Bug Tracker]

This bug was fixed in the package qemu-kvm - 1.2.0+noroms-0ubuntu4

---------------
qemu-kvm (1.2.0+noroms-0ubuntu4) raring; urgency=low

  [ Serge Hallyn ]
  * debian/qemu-kvm.postinst: use udevadm trigger to change /dev/kvm perms as
    recommended by Steve Langasek (LP: #1057024)
  * apply debian/patches/nbd-fixes-to-read-only-handling.patch from upstream to
    make read-write mount after read-only mount work.  (LP: #1077838)

  [ Robert Collins ]
  * Fix upstart job to succeed if ksm settings can't be altered in the same way
    other settings are handled. (LP: #1078530)
 -- Serge Hallyn <address@hidden>   Wed, 14 Nov 2012 11:30:14 -0600

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

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https://bugs.launchpad.net/bugs/1077838

Title:
  qemu-nbd -r -c taints device for subsequent usage, even after -d

Status in QEMU:
  In Progress
Status in “qemu-kvm” package in Ubuntu:
  Fix Released

Bug description:
  Something about qemu-nbd -r -c /dev/nbd0 someimg leaves cruft behind -
  subsequent connections get marked readonly.

  This is on quantal, haven't checked precise or raring.

  To demonstrate:
  # use one image
  qemu-img create -f qcow2 /tmp/1.qcow2 100M
  sudo qemu-nbd -c /dev/nbd2 /tmp/1.qcow2
  sudo mkfs -t ext4 /dev/nbd2
  sudo qemu-nbd -d /dev/nbd2
  # use a second one on the same nbd device, shows that reuse works:
  qemu-img create -f qcow2 /tmp/2.qcow2 100M
  sudo qemu-nbd -c /dev/nbd2 /tmp/2.qcow2
  sudo mkfs -t ext4 /dev/nbd2
  sudo qemu-nbd -d /dev/nbd2
  # connect an image in read only mode
  sudo qemu-nbd -r -c /dev/nbd2 /tmp/2.qcow2
  sudo dumpe2fs /dev/nbd2 | head -n 3
  sudo qemu-nbd -d /dev/nbd2
  # now try to reuse in read-write mode again:
  qemu-img create -f qcow2 /tmp/3.qcow2 100M
  sudo qemu-nbd -c /dev/nbd2 /tmp/3.qcow2
  sudo mkfs -t ext4 /dev/nbd2
  # here it goes boom:
  mke2fs 1.42.5 (29-Jul-2012)
  /dev/nbd2: Operation not permitted while setting up superblock
  # still need to cleanup
  sudo qemu-nbd -d /dev/nbd2

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