qemu-iotests: Test rebase with short backing file

This tests that qemu-img rebase doesn't assume that the backing file has
the same size as the image, but considers that it can be smaller.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

tests/qemu-iotests/028

@@ -96,6 +96,11 @@ io_zero readv $(( offset + 32 * 1024 )) 512 1024 32
 
 _check_test_img
 
+# Rebase it on top of its base image
+$QEMU_IMG rebase -b $TEST_IMG.base $TEST_IMG
+
+_check_test_img
+
 # success, all done
 echo "*** done"
 rm -f $seq.full

tests/qemu-iotests/028.out

@@ -465,4 +465,5 @@ qemu-io> read 512/512 bytes at offset 3221257728
 qemu-io> read 512/512 bytes at offset 3221258752
 512.000000 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qemu-io> No errors were found on the image.
+No errors were found on the image.
 *** done