60 lines
2.4 KiB
Python
60 lines
2.4 KiB
Python
# Copyright 2018 Michael Still and Aptira
|
|
#
|
|
# Licensed under the Apache License, Version 2.0 (the "License"); you may
|
|
# not use this file except in compliance with the License. You may obtain
|
|
# a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
# License for the specific language governing permissions and limitations
|
|
# under the License.
|
|
|
|
"""
|
|
Helpers for qemu tasks.
|
|
"""
|
|
|
|
from oslo_concurrency import processutils
|
|
from oslo_log import log as logging
|
|
|
|
import nova.privsep.utils
|
|
|
|
|
|
LOG = logging.getLogger(__name__)
|
|
|
|
|
|
@nova.privsep.sys_admin_pctxt.entrypoint
|
|
def convert_image(source, dest, in_format, out_format, instances_path):
|
|
unprivileged_convert_image(source, dest, in_format, out_format,
|
|
instances_path)
|
|
|
|
|
|
# NOTE(mikal): this method is deliberately not wrapped in a privsep entrypoint
|
|
def unprivileged_convert_image(source, dest, in_format, out_format,
|
|
instances_path):
|
|
# NOTE(mdbooth): qemu-img convert defaults to cache=unsafe, which means
|
|
# that data is not synced to disk at completion. We explicitly use
|
|
# cache=none here to (1) ensure that we don't interfere with other
|
|
# applications using the host's io cache, and (2) ensure that the data is
|
|
# on persistent storage when the command exits. Without (2), a host crash
|
|
# may leave a corrupt image in the image cache, which Nova cannot recover
|
|
# automatically.
|
|
# NOTE(zigo): we cannot use -t none if the instances dir is mounted on a
|
|
# filesystem that doesn't have support for O_DIRECT, which is the case
|
|
# for example with tmpfs. This simply crashes "openstack server create"
|
|
# in environments like live distributions. In such case, the best choice
|
|
# is writethrough, which is power-failure safe, but still faster than
|
|
# writeback.
|
|
if nova.privsep.utils.supports_direct_io(instances_path):
|
|
cache_mode = 'none'
|
|
else:
|
|
cache_mode = 'writethrough'
|
|
cmd = ('qemu-img', 'convert', '-t', cache_mode, '-O', out_format)
|
|
|
|
if in_format is not None:
|
|
cmd = cmd + ('-f', in_format)
|
|
cmd = cmd + (source, dest)
|
|
processutils.execute(*cmd)
|