Merge "libvirt: consider minimal I/O size when selecting cache type"

nova/tests/virt/libvirt/test_libvirt.py

@@ -2590,6 +2590,44 @@ class LibvirtConnTestCase(test.TestCase):
         self.assertEqual(len(interfaces), 2)
         self.assertEqual(interfaces[0].get('type'), 'bridge')
 
+    def _behave_supports_direct_io(self, raise_open=False, raise_write=False,
+                                   exc=ValueError()):
+        open_behavior = os.open(os.path.join('.', '.directio.test'),
+                                os.O_CREAT | os.O_WRONLY | os.O_DIRECT)
+        if raise_open:
+            open_behavior.AndRaise(exc)
+        else:
+            open_behavior.AndReturn(3)
+            write_bahavior = os.write(3, mox.IgnoreArg())
+            if raise_write:
+                write_bahavior.AndRaise(exc)
+            else:
+                os.close(3)
+        os.unlink(3)
+
+    def test_supports_direct_io(self):
+        einval = OSError()
+        einval.errno = errno.EINVAL
+        self.mox.StubOutWithMock(os, 'open')
+        self.mox.StubOutWithMock(os, 'write')
+        self.mox.StubOutWithMock(os, 'close')
+        self.mox.StubOutWithMock(os, 'unlink')
+        _supports_direct_io = libvirt_driver.LibvirtDriver._supports_direct_io
+
+        self._behave_supports_direct_io()
+        self._behave_supports_direct_io(raise_write=True)
+        self._behave_supports_direct_io(raise_open=True)
+        self._behave_supports_direct_io(raise_write=True, exc=einval)
+        self._behave_supports_direct_io(raise_open=True, exc=einval)
+
+        self.mox.ReplayAll()
+        self.assertTrue(_supports_direct_io('.'))
+        self.assertRaises(ValueError, _supports_direct_io, '.')
+        self.assertRaises(ValueError, _supports_direct_io, '.')
+        self.assertFalse(_supports_direct_io('.'))
+        self.assertFalse(_supports_direct_io('.'))
+        self.mox.VerifyAll()
+
     def _check_xml_and_container(self, instance):
         user_context = context.RequestContext(self.user_id,
                                               self.project_id)

nova/virt/libvirt/driver.py

@@ -44,6 +44,7 @@ import errno
 import eventlet
 import functools
 import glob
+import mmap
 import os
 import shutil
 import socket
@@ -2319,6 +2320,11 @@ class LibvirtDriver(driver.ComputeDriver):
         hasDirectIO = True
         try:
             f = os.open(testfile, os.O_CREAT | os.O_WRONLY | os.O_DIRECT)
+            # Check is the write allowed with 512 byte alignment
+            align_size = 512
+            m = mmap.mmap(-1, align_size)
+            m.write(r"x" * align_size)
+            os.write(f, m)
             os.close(f)
             LOG.debug(_("Path '%(path)s' supports direct I/O") %
                       {'path': dirpath})