added a test checks thin write in qemu-img commit

Signed-off-by: NHaotong Chen <hachen@redhat.com>

qemu/tests/cfg/thin_write_in_qemu_img_commit.cfg

+- thin_write_in_qemu_img_commit:
+    only qcow2
+    virt_test_type = qemu
+    type = thin_write_in_qemu_img_commit
+    kill_vm = yes
+    start_vm = no
+    force_create_image = no
+    create_image = yes
+    remove_image = yes
+    images = "base"
+    image_chain = "base sn"
+    image_name_base = "images/base"
+    image_size_base = 1G
+    image_name_sn = "images/sn"
+    # set size to "", so during snapshot creation
+    # the cmdline will not have speicfed size option
+    image_size_sn = ""
+    write_size = 64K

qemu/tests/thin_write_in_qemu_img_commit.py

+import logging
+import json
+
+from virttest import data_dir
+from virttest import utils_numeric
+from virttest.qemu_io import QemuIOSystem
+from virttest.qemu_storage import QemuImg
+
+from qemu.tests.qemu_disk_img import QemuImgTest
+from qemu.tests.qemu_disk_img import generate_base_snapshot_pair
+
+
+def run(test, params, env):
+    """
+    Check thin write in qemu-img commit.
+
+    1) write 0x1 into the entire base image through qemu-io
+    2) create a external snapshot sn of the base
+    3) write specific length zeros at the beginning of the snapshot
+    4) commit sn back to base
+    5) make sure the zeros have been committed into the base image
+
+    :param test: Qemu test object
+    :param params: Dictionary with the test parameters
+    :param env: Dictionary with test environment.
+    """
+    def _get_image_object(tag):
+        """Get QemuImg object by tag."""
+        img_param = params.object_params(tag)
+        return QemuImg(img_param, img_root_dir, tag)
+
+    def _create_external_snapshot(tag):
+        """Create an external snapshot based on tag."""
+        logging.info("Create external snapshot %s." % tag)
+        qit = QemuImgTest(test, params, env, snapshot)
+        qit.create_snapshot()
+
+    def _qemu_io(img, cmd):
+        """Run qemu-io cmd to a given img."""
+        logging.info("Run qemu-io %s" % img.image_filename)
+        q = QemuIOSystem(test, params, img.image_filename)
+        q.cmd_output(cmd, 120)
+
+    def _verify_map_output(output):
+        """"Verify qemu map output."""
+        expected = {
+            "length": int(utils_numeric.normalize_data_size(
+                params["write_size"], "B")),
+            "start": 0, "depth": 0, "zero": True, "data": False}
+        if expected not in json.loads(output.stdout_text):
+            test.fail("Commit failed, data from 0 to %s are not zero" %
+                      params["write_size"])
+
+    gen = generate_base_snapshot_pair(params["image_chain"])
+    img_root_dir = data_dir.get_data_dir()
+    base, snapshot = next(gen)
+
+    img_base = _get_image_object(base)
+    _qemu_io(img_base, 'write -P 1 0 %s' % params["image_size_base"])
+
+    _create_external_snapshot(snapshot)
+    img_sn = _get_image_object(snapshot)
+    _qemu_io(img_sn, 'write -z 0 %s' % params["write_size"])
+
+    img_sn.commit()
+    _verify_map_output(img_base.map(output="json"))