To some extent it is a bug in the upstream kernel, which doesn't reset state properly. However, the qemu patch is also good. Thanks!
-- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1077838 Title: qemu-nbd -r -c taints device for subsequent usage, even after -d Status in QEMU: New Status in “qemu-kvm” package in Ubuntu: Triaged 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 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1077838/+subscriptions
