066 was supposed to be a test "for discarding preallocated zero
clusters", but it did so incompletely: While it did check the image
file's integrity after the operation, it did not confirm that the
clusters are indeed freed. This patch adds this test.

In addition, new cases for writing to preallocated zero clusters are
added.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

As mentioned in commit 0c1bd469, we ignored requests to
discard the trailing cluster of an unaligned image.  While
discard is an advisory operation from the guest standpoint,
(and we are therefore free to ignore any request), our
qcow2 implementation exploits the fact that a discarded
cluster reads back as 0.  As long as we discard on cluster
boundaries, we are fine; but that means we could observe
non-zero data leaked at the tail of an unaligned image.

Enhance iotest 66 to cover this case, and fix the implementation
to honor a discard request on the final partial cluster.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-id: 20170407013709.18440-1-eblake@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

This is simply:

  $ cd tests/qemu-iotests; sed -i -e 's/ *$//' *.out
Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Message-id: 1418110684-19528-2-git-send-email-famz@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Add a new test case for discarding preallocated zero clusters; doing
this should not result in any leaks.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

This test creates an image with unallocated zero clusters, then creates
a snapshot. Afterwards, there should be neither any errors nor leaks.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>