Always fall back from hard linking to copying files

The current check is insufficient: it passes for Kubernetes shared
volumes, although hard-linking between them is not possible.
This patch changes the approach to trying a hard link and falling
back to copyfile instead.

The patch relies on optimizations in Python 3.8 and thus should not
be backported beyond the Zed series to avoid performance regression.

Change-Id: I929944685b3ac61b2f63d2549198a2d8a1c8fe35

1 files changed, 21 insertions, 86 deletions

diff --git a/ironic/tests/unit/common/test_image_service.py b/ironic/tests/unit/common/test_image_service.py
index 197518e1a..297a1b4b9 100644
--- a/ironic/tests/unit/common/test_image_service.py
+++ b/ironic/tests/unit/common/test_image_service.py
@@ -10,7 +10,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import builtins
 import datetime
 from http import client as http_client
 import io
@@ -483,119 +482,55 @@ class FileImageServiceTestCase(base.TestCase):
                           'properties': {},
                           'no_cache': True}, result)
 
+    @mock.patch.object(shutil, 'copyfile', autospec=True)
     @mock.patch.object(os, 'link', autospec=True)
     @mock.patch.object(os, 'remove', autospec=True)
-    @mock.patch.object(os, 'access', return_value=True, autospec=True)
-    @mock.patch.object(os, 'stat', autospec=True)
     @mock.patch.object(image_service.FileImageService, 'validate_href',
                        autospec=True)
-    def test_download_hard_link(self, _validate_mock, stat_mock, access_mock,
-                                remove_mock, link_mock):
+    def test_download_hard_link(self, _validate_mock, remove_mock, link_mock,
+                                copy_mock):
         _validate_mock.return_value = self.href_path
-        stat_mock.return_value.st_dev = 'dev1'
         file_mock = mock.Mock(spec=io.BytesIO)
         file_mock.name = 'file'
         self.service.download(self.href, file_mock)
         _validate_mock.assert_called_once_with(mock.ANY, self.href)
-        self.assertEqual(2, stat_mock.call_count)
-        access_mock.assert_called_once_with(self.href_path, os.R_OK | os.W_OK)
         remove_mock.assert_called_once_with('file')
         link_mock.assert_called_once_with(self.href_path, 'file')
+        copy_mock.assert_not_called()
 
-    @mock.patch.object(os, 'sendfile', return_value=42, autospec=True)
-    @mock.patch.object(os.path, 'getsize', return_value=42, autospec=True)
-    @mock.patch.object(builtins, 'open', autospec=True)
-    @mock.patch.object(os, 'access', return_value=False, autospec=True)
-    @mock.patch.object(os, 'stat', autospec=True)
-    @mock.patch.object(image_service.FileImageService, 'validate_href',
-                       autospec=True)
-    def test_download_copy(self, _validate_mock, stat_mock, access_mock,
-                           open_mock, size_mock, copy_mock):
-        _validate_mock.return_value = self.href_path
-        stat_mock.return_value.st_dev = 'dev1'
-        file_mock = mock.MagicMock(spec=io.BytesIO)
-        file_mock.name = 'file'
-        input_mock = mock.MagicMock(spec=io.BytesIO)
-        open_mock.return_value = input_mock
-        self.service.download(self.href, file_mock)
-        _validate_mock.assert_called_once_with(mock.ANY, self.href)
-        self.assertEqual(2, stat_mock.call_count)
-        access_mock.assert_called_once_with(self.href_path, os.R_OK | os.W_OK)
-        copy_mock.assert_called_once_with(file_mock.fileno(),
-                                          input_mock.__enter__().fileno(),
-                                          0, 42)
-
-    @mock.patch.object(os, 'sendfile', autospec=True)
-    @mock.patch.object(os.path, 'getsize', return_value=42, autospec=True)
-    @mock.patch.object(builtins, 'open', autospec=True)
-    @mock.patch.object(os, 'access', return_value=False, autospec=True)
-    @mock.patch.object(os, 'stat', autospec=True)
+    @mock.patch.object(shutil, 'copyfile', autospec=True)
+    @mock.patch.object(os, 'link', autospec=True)
+    @mock.patch.object(os, 'remove', autospec=True)
     @mock.patch.object(image_service.FileImageService, 'validate_href',
                        autospec=True)
-    def test_download_copy_segmented(self, _validate_mock, stat_mock,
-                                     access_mock, open_mock, size_mock,
-                                     copy_mock):
-        # Fake a 3G + 1k image
-        chunk_size = image_service.SENDFILE_CHUNK_SIZE
-        fake_image_size = chunk_size * 3 + 1024
-        fake_chunk_seq = [chunk_size, chunk_size, chunk_size, 1024]
+    def test_download_copy(self, _validate_mock, remove_mock, link_mock,
+                           copy_mock):
         _validate_mock.return_value = self.href_path
-        stat_mock.return_value.st_dev = 'dev1'
+        link_mock.side_effect = PermissionError
         file_mock = mock.MagicMock(spec=io.BytesIO)
         file_mock.name = 'file'
-        input_mock = mock.MagicMock(spec=io.BytesIO)
-        open_mock.return_value = input_mock
-        size_mock.return_value = fake_image_size
-        copy_mock.side_effect = fake_chunk_seq
         self.service.download(self.href, file_mock)
         _validate_mock.assert_called_once_with(mock.ANY, self.href)
-        self.assertEqual(2, stat_mock.call_count)
-        access_mock.assert_called_once_with(self.href_path, os.R_OK | os.W_OK)
-        copy_calls = [mock.call(file_mock.fileno(),
-                                input_mock.__enter__().fileno(),
-                                chunk_size * i,
-                                fake_chunk_seq[i]) for i in range(4)]
-        copy_mock.assert_has_calls(copy_calls)
-        size_mock.assert_called_once_with(self.href_path)
-
-    @mock.patch.object(os, 'remove', side_effect=OSError, autospec=True)
-    @mock.patch.object(os, 'access', return_value=True, autospec=True)
-    @mock.patch.object(os, 'stat', autospec=True)
-    @mock.patch.object(image_service.FileImageService, 'validate_href',
-                       autospec=True)
-    def test_download_hard_link_fail(self, _validate_mock, stat_mock,
-                                     access_mock, remove_mock):
-        _validate_mock.return_value = self.href_path
-        stat_mock.return_value.st_dev = 'dev1'
-        file_mock = mock.MagicMock(spec=io.BytesIO)
-        file_mock.name = 'file'
-        self.assertRaises(exception.ImageDownloadFailed,
-                          self.service.download, self.href, file_mock)
-        _validate_mock.assert_called_once_with(mock.ANY, self.href)
-        self.assertEqual(2, stat_mock.call_count)
-        access_mock.assert_called_once_with(self.href_path, os.R_OK | os.W_OK)
+        link_mock.assert_called_once_with(self.href_path, 'file')
+        copy_mock.assert_called_once_with(self.href_path, 'file')
 
-    @mock.patch.object(os, 'sendfile', side_effect=OSError, autospec=True)
-    @mock.patch.object(os.path, 'getsize', return_value=42, autospec=True)
-    @mock.patch.object(builtins, 'open', autospec=True)
-    @mock.patch.object(os, 'access', return_value=False, autospec=True)
-    @mock.patch.object(os, 'stat', autospec=True)
+    @mock.patch.object(shutil, 'copyfile', autospec=True)
+    @mock.patch.object(os, 'link', autospec=True)
+    @mock.patch.object(os, 'remove', autospec=True)
     @mock.patch.object(image_service.FileImageService, 'validate_href',
                        autospec=True)
-    def test_download_copy_fail(self, _validate_mock, stat_mock, access_mock,
-                                open_mock, size_mock, copy_mock):
+    def test_download_copy_fail(self, _validate_mock, remove_mock, link_mock,
+                                copy_mock):
         _validate_mock.return_value = self.href_path
-        stat_mock.return_value.st_dev = 'dev1'
+        link_mock.side_effect = PermissionError
+        copy_mock.side_effect = PermissionError
         file_mock = mock.MagicMock(spec=io.BytesIO)
         file_mock.name = 'file'
-        input_mock = mock.MagicMock(spec=io.BytesIO)
-        open_mock.return_value = input_mock
         self.assertRaises(exception.ImageDownloadFailed,
                           self.service.download, self.href, file_mock)
         _validate_mock.assert_called_once_with(mock.ANY, self.href)
-        self.assertEqual(2, stat_mock.call_count)
-        access_mock.assert_called_once_with(self.href_path, os.R_OK | os.W_OK)
-        size_mock.assert_called_once_with(self.href_path)
+        link_mock.assert_called_once_with(self.href_path, 'file')
+        copy_mock.assert_called_once_with(self.href_path, 'file')
 
 
 class ServiceGetterTestCase(base.TestCase):