I sent a patch that fixes the original problem that Maria reported. It's hard to say whether this is the same problem as you saw, Sam, but it's quite possible.
** Changed in: qemu Status: New => In Progress -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1349972 Title: qcow2-refcount: qemu-io crashes on 'discard' command Status in QEMU: In Progress Bug description: qemu-io is killed by SIGIOT at the 'discard' command on the image having no refcount information. Sequence: 1. Unpack test.img and backing_img.qed in the same directory (see the attached archives for images) 2. Make a copy of test.img to copy.img (qemu-io modifies the image before being kill, therefore the image backup is necessary) 3. Run the command qemu-io copy.img -c 'discard 2210816 2856448' Result: qemu-io is killed by SIGIOT with the reason: qemu-io: block/qcow2-refcount.c:468: update_refcount_discard: Assertion `d->bytes + length == new_end - new_start' failed. The image was generated by the image fuzzer. qemu.git HEAD: 1d80eb7a680d To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1349972/+subscriptions