diff options
| -rw-r--r-- | nova/tests/test_libvirt.py | 26 | ||||
| -rw-r--r-- | nova/tests/test_virt_drivers.py | 5 | ||||
| -rw-r--r-- | nova/virt/libvirt.xml.template | 14 | ||||
| -rw-r--r-- | nova/virt/libvirt/connection.py | 47 |
4 files changed, 85 insertions, 7 deletions
diff --git a/nova/tests/test_libvirt.py b/nova/tests/test_libvirt.py index d388a1d4f..11aadc896 100644 --- a/nova/tests/test_libvirt.py +++ b/nova/tests/test_libvirt.py @@ -15,6 +15,7 @@ # under the License. import copy +import errno import eventlet import mox import os @@ -800,6 +801,19 @@ class LibvirtConnTestCase(test.TestCase): (check(tree), expected_result, i)) def _check_xml_and_disk_driver(self, image_meta): + os_open = os.open + directio_supported = True + + def os_open_stub(path, flags, *args, **kwargs): + if flags & os.O_DIRECT: + if not directio_supported: + raise OSError(errno.EINVAL, + '%s: %s' % (os.strerror(errno.EINVAL), path)) + flags &= ~os.O_DIRECT + return os_open(path, flags, *args, **kwargs) + + self.stubs.Set(os, 'open', os_open_stub) + user_context = context.RequestContext(self.user_id, self.project_id) instance_ref = db.instance_create(user_context, self.test_instance) network_info = _fake_network_info(self.stubs, 1) @@ -812,6 +826,18 @@ class LibvirtConnTestCase(test.TestCase): for disk in disks: self.assertEqual(disk.get("cache"), "none") + directio_supported = False + + # The O_DIRECT availability is cached on first use in + # LibvirtConnection, hence we re-create it here + xml = connection.LibvirtConnection(True).to_xml(instance_ref, + network_info, + image_meta) + tree = ElementTree.fromstring(xml) + disks = tree.findall('./devices/disk/driver') + for disk in disks: + self.assertEqual(disk.get("cache"), "writethrough") + def _check_xml_and_disk_bus(self, image_meta, device_type, bus): user_context = context.RequestContext(self.user_id, self.project_id) instance_ref = db.instance_create(user_context, self.test_instance) diff --git a/nova/tests/test_virt_drivers.py b/nova/tests/test_virt_drivers.py index 8018008a6..592926597 100644 --- a/nova/tests/test_virt_drivers.py +++ b/nova/tests/test_virt_drivers.py @@ -451,6 +451,11 @@ class LibvirtConnTestCase(_VirtDriverTestCase): nova.virt.libvirt.connection.libvirt_utils = fake_libvirt_utils nova.virt.libvirt.firewall.libvirt = fakelibvirt + # So that the _supports_direct_io does the test based + # on the current working directory, instead of the + # default instances_path which doesn't exist + FLAGS.instances_path = '' + # Point _VirtDriverTestCase at the right module self.driver_module = nova.virt.libvirt.connection super(LibvirtConnTestCase, self).setUp() diff --git a/nova/virt/libvirt.xml.template b/nova/virt/libvirt.xml.template index b3cc75580..225133eb5 100644 --- a/nova/virt/libvirt.xml.template +++ b/nova/virt/libvirt.xml.template @@ -66,40 +66,40 @@ #else #if $getVar('rescue', False) <disk type='file'> - <driver type='${driver_type}' cache='none'/> + <driver type='${driver_type}' cache='${cachemode}'/> <source file='${basepath}/disk.rescue'/> <target dev='${disk_prefix}a' bus='${ephemeral_disk_bus}'/> </disk> <disk type='file'> - <driver type='${driver_type}' cache='none'/> + <driver type='${driver_type}' cache='${cachemode}'/> <source file='${basepath}/disk'/> <target dev='${disk_prefix}b' bus='${ephemeral_disk_bus}'/> </disk> #else #if not ($getVar('ebs_root', False)) <disk type='file' device='${root_device_type}'> - <driver type='${driver_type}' cache='none'/> + <driver type='${driver_type}' cache='${cachemode}'/> <source file='${basepath}/disk'/> <target dev='${root_device}' bus='${root_disk_bus}'/> </disk> #end if #if $getVar('ephemeral_device', False) <disk type='file'> - <driver type='${driver_type}' cache='none'/> + <driver type='${driver_type}' cache='${cachemode}'/> <source file='${basepath}/disk.local'/> <target dev='${ephemeral_device}' bus='${ephemeral_disk_bus}'/> </disk> #end if #for $eph in $ephemerals <disk type='block'> - <driver type='${driver_type}' cache='none'/> + <driver type='${driver_type}' cache='${cachemode}'/> <source dev='${basepath}/${eph.device_path}'/> <target dev='${eph.device}' bus='${ephemeral_disk_bus}'/> </disk> #end for #if $getVar('swap_device', False) <disk type='file'> - <driver type='${driver_type}' cache='none'/> + <driver type='${driver_type}' cache='${cachemode}'/> <source file='${basepath}/disk.swap'/> <target dev='${swap_device}' bus='${ephemeral_disk_bus}'/> </disk> @@ -110,7 +110,7 @@ #end if #if $getVar('config_drive', False) <disk type='file'> - <driver type='raw' /> + <driver type='raw' cache='${cachemode}'/> <source file='${basepath}/disk.config' /> <target dev='${disk_prefix}z' bus='${ephemeral_disk_bus}' /> </disk> diff --git a/nova/virt/libvirt/connection.py b/nova/virt/libvirt/connection.py index 3aabfde13..f1e04d3f9 100644 --- a/nova/virt/libvirt/connection.py +++ b/nova/virt/libvirt/connection.py @@ -225,9 +225,25 @@ class LibvirtConnection(driver.ComputeDriver): self.default_second_device = self._disk_prefix + 'b' self.default_third_device = self._disk_prefix + 'c' + self._disk_cachemode = None self.image_cache_manager = imagecache.ImageCacheManager() @property + def disk_cachemode(self): + if self._disk_cachemode is None: + # We prefer 'none' for consistent performance, host crash + # safety & migration correctness by avoiding host page cache. + # Some filesystems (eg GlusterFS via FUSE) don't support + # O_DIRECT though. For those we fallback to 'writethrough' + # which gives host crash safety, and is safe for migration + # provided the filesystem is cache coherant (cluster filesystems + # typically are, but things like NFS are not). + self._disk_cachemode = "none" + if not self._supports_direct_io(FLAGS.instances_path): + self._disk_cachemode = "writethrough" + return self._disk_cachemode + + @property def host_state(self): if not self._host_state: self._host_state = HostState(self.read_only) @@ -996,6 +1012,36 @@ class LibvirtConnection(driver.ComputeDriver): return {'host': host, 'port': port, 'internal_access_path': None} @staticmethod + def _supports_direct_io(dirpath): + testfile = os.path.join(dirpath, ".directio.test") + hasDirectIO = True + try: + f = os.open(testfile, os.O_CREAT | os.O_WRONLY | os.O_DIRECT) + os.close(f) + LOG.debug(_("Path '%(path)s' supports direct I/O") % + {'path': dirpath}) + except OSError, e: + if e.errno == errno.EINVAL: + LOG.debug(_("Path '%(path)s' does not support direct I/O: " + "'%(ex)s'") % {'path': dirpath, 'ex': str(e)}) + hasDirectIO = False + else: + LOG.error(_("Error on '%(path)s' while checking direct I/O: " + "'%(ex)s'") % {'path': dirpath, 'ex': str(e)}) + raise e + except Exception, e: + LOG.error(_("Error on '%(path)s' while checking direct I/O: " + "'%(ex)s'") % {'path': dirpath, 'ex': str(e)}) + raise e + finally: + try: + os.unlink(testfile) + except: + pass + + return hasDirectIO + + @staticmethod def _cache_image(fn, target, fname, cow=False, size=None, *args, **kwargs): """Wrapper for a method that creates an image that caches the image. @@ -1374,6 +1420,7 @@ class LibvirtConnection(driver.ComputeDriver): xml_info = {'type': FLAGS.libvirt_type, 'name': instance['name'], 'uuid': instance['uuid'], + 'cachemode': self.disk_cachemode, 'basepath': os.path.join(FLAGS.instances_path, instance['name']), 'memory_kb': inst_type['memory_mb'] * 1024, |