qemu-iotests: make compare_images() common

The iotests.compare_images() function returns True if two image files
have the identical data.  Previously this was implemented by converting
images to raw and then comparing their contents using Python.  Since
"qemu-img compare" is now available and is more efficient, switch to it.

This function will be reused by the 'drive-backup' test case.
Suggested-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/041

@@ -80,27 +80,6 @@ class ImageMirroringTestCase(iotests.QMPTestCase):
             i = i + 512
         file.close()
 
-    def compare_images(self, img1, img2):
-        try:
-            qemu_img('convert', '-f', iotests.imgfmt, '-O', 'raw', img1, img1 + '.raw')
-            qemu_img('convert', '-f', iotests.imgfmt, '-O', 'raw', img2, img2 + '.raw')
-            file1 = open(img1 + '.raw', 'r')
-            file2 = open(img2 + '.raw', 'r')
-            return file1.read() == file2.read()
-        finally:
-            if file1 is not None:
-                file1.close()
-            if file2 is not None:
-                file2.close()
-            try:
-                os.remove(img1 + '.raw')
-            except OSError:
-                pass
-            try:
-                os.remove(img2 + '.raw')
-            except OSError:
-                pass
-
 class TestSingleDrive(ImageMirroringTestCase):
     image_len = 1 * 1024 * 1024 # MB
 
@@ -130,7 +109,7 @@ class TestSingleDrive(ImageMirroringTestCase):
         result = self.vm.qmp('query-block')
         self.assert_qmp(result, 'return[0]/inserted/file', target_img)
         self.vm.shutdown()
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
     def test_cancel(self):
@@ -156,7 +135,7 @@ class TestSingleDrive(ImageMirroringTestCase):
         result = self.vm.qmp('query-block')
         self.assert_qmp(result, 'return[0]/inserted/file', test_img)
         self.vm.shutdown()
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
     def test_pause(self):
@@ -182,7 +161,7 @@ class TestSingleDrive(ImageMirroringTestCase):
 
         self.complete_and_wait()
         self.vm.shutdown()
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
     def test_small_buffer(self):
@@ -197,7 +176,7 @@ class TestSingleDrive(ImageMirroringTestCase):
         result = self.vm.qmp('query-block')
         self.assert_qmp(result, 'return[0]/inserted/file', target_img)
         self.vm.shutdown()
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
     def test_small_buffer2(self):
@@ -213,7 +192,7 @@ class TestSingleDrive(ImageMirroringTestCase):
         result = self.vm.qmp('query-block')
         self.assert_qmp(result, 'return[0]/inserted/file', target_img)
         self.vm.shutdown()
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
     def test_large_cluster(self):
@@ -229,7 +208,7 @@ class TestSingleDrive(ImageMirroringTestCase):
         result = self.vm.qmp('query-block')
         self.assert_qmp(result, 'return[0]/inserted/file', target_img)
         self.vm.shutdown()
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
     def test_medium_not_found(self):
@@ -256,7 +235,7 @@ class TestMirrorNoBacking(ImageMirroringTestCase):
 
     def compare_images(self, img1, img2):
         self.create_image(target_backing_img, TestMirrorNoBacking.image_len)
-        return ImageMirroringTestCase.compare_images(self, img1, img2)
+        return iotests.compare_images(img1, img2)
 
     def setUp(self):
         self.create_image(backing_img, TestMirrorNoBacking.image_len)
@@ -353,7 +332,7 @@ class TestMirrorResized(ImageMirroringTestCase):
         result = self.vm.qmp('query-block')
         self.assert_qmp(result, 'return[0]/inserted/file', target_img)
         self.vm.shutdown()
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
     def test_complete_full(self):
@@ -367,7 +346,7 @@ class TestMirrorResized(ImageMirroringTestCase):
         result = self.vm.qmp('query-block')
         self.assert_qmp(result, 'return[0]/inserted/file', target_img)
         self.vm.shutdown()
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
 class TestReadErrors(ImageMirroringTestCase):
@@ -487,7 +466,7 @@ new_state = "1"
 
         # Detach blkdebug to compare images successfully
         qemu_img('rebase', '-f', iotests.imgfmt, '-u', '-b', backing_img, test_img)
-        self.assertTrue(self.compare_images(test_img, target_img),
+        self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')
 
     def test_stop_read(self):

tests/qemu-iotests/iotests.py

@@ -51,6 +51,11 @@ def qemu_io(*args):
     args = qemu_io_args + list(args)
     return subprocess.Popen(args, stdout=subprocess.PIPE).communicate()[0]
 
+def compare_images(img1, img2):
+    '''Return True if two image files are identical'''
+    return qemu_img('compare', '-f', imgfmt,
+                    '-F', imgfmt, img1, img2) == 0
+
 class VM(object):
     '''A QEMU VM'''