commit_snapshot_to_raw_backing: add switch for size check

if image is a block device, the size check will fail the case because
QEMU fails to get correct size info from block device. So add a switch
to enable tester to turn off the snapshot size check.
Signed-off-by: Nlolyu <lolyu@redhat.com>

qemu/tests/cfg/commit_snapshot_to_raw_backing.cfg

@@ -21,6 +21,7 @@
     dd_total_size = "${dd_bs_val} * ${dd_bs_count} * 1024 ** 2"
     file_create_cmd = "dd if=/dev/urandom of=%s bs=${dd_bs_val}M count=${dd_bs_count}"
     guest_file_name = ${tmp_file_name}
+    snapshot_size_check_after_commit = yes
     Windows:
         guest_file_name = C:\testfile
         x86_64:

qemu/tests/commit_snapshot_to_raw_backing.py

@@ -82,18 +82,22 @@ def run(test, params, env):
     else:
         logging.info("Commit snapshot image %s back to %s.", snapshot, base)
 
-    org_size = json.loads(sn_img.info(output="json"))["actual-size"]
+    size_check = params.get("snapshot_size_check_after_commit") == "yes"
+    if size_check:
+        org_size = json.loads(sn_img.info(output="json"))["actual-size"]
     sn_img.commit(cache_mode=cache_mode)
-    remain_size = json.loads(sn_img.info(output="json"))["actual-size"]
-
-    """Verify the snapshot file whether emptied after committing"""
-    logging.info("Verify the snapshot file whether emptied after committing")
-    commit_size = org_size - remain_size
-    dd_size = eval(params["dd_total_size"])
-    if commit_size >= dd_size:
-        logging.info("The snapshot file was emptied!")
-    else:
-        test.fail("The snapshot file was not emptied, check pls!")
+
+    if size_check:
+        remain_size = json.loads(sn_img.info(output="json"))["actual-size"]
+
+        # Verify the snapshot file whether emptied after committing
+        logging.info("Verify the snapshot file whether emptied after committing")
+        commit_size = org_size - remain_size
+        dd_size = eval(params["dd_total_size"])
+        if commit_size >= dd_size:
+            logging.info("The snapshot file was emptied!")
+        else:
+            test.fail("The snapshot file was not emptied, check pls!")
 
     base_qit = QemuImgTest(test, params, env, base)
     base_qit.start_vm()