[Qemu-devel] [Bug 1349972] Re: qcow2-refcount: qemu-io crashes on 'discard' command

[Sam Azer]

FWIW:

While trying to restore (apply) a snapshot on a Windows VM (ie: qemu-img
snapshot -a snapshotname windows.qcow2 where the image file is 150gb in
size,) I got the above error:

qemu-img: /build/buildd/qemu-2.0.0+dfsg/block/qcow2-refcount.c:467:
update_refcount_discard: Assertion `d->bytes + length == new_end -
new_start' failed.

(My VM is now broken.)

This is the only reference that I found using Google.

HTH

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https://bugs.launchpad.net/bugs/1349972

Title:
   qcow2-refcount: qemu-io crashes on 'discard' command

Status in QEMU:
  New

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

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