On 6/17/20 9:00 AM, Alberto Garcia wrote:
When resizing an image with qcow2_co_truncate() using the falloc or
full preallocation modes the code assumes that both the old and new
sizes are cluster-aligned.

There are two problems with this:

   1) The calculation of how many clusters are involved does not always
      get the right result.

      Example: creating a 60KB image and resizing it (with
      preallocation=full) to 80KB won't allocate the second cluster.

   2) No copy-on-write is performed, so in the previous example if
      there is a backing file then the first 60KB of the first cluster
      won't be filled with data from the backing file.

This patch fixes both issues.

Signed-off-by: Alberto Garcia <be...@igalia.com>
v2: iotests: don't check the image size if data_file is set [Max]

Reviewed-by: Eric Blake <ebl...@redhat.com>

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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