130 lines
5.1 KiB
Python
130 lines
5.1 KiB
Python
# Copyright 2018 Michael Still and Aptira
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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Helpers for qemu tasks.
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"""
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import os
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from oslo_concurrency import processutils
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from oslo_log import log as logging
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from oslo_utils import units
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from nova import exception
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from nova.i18n import _
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import nova.privsep.utils
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LOG = logging.getLogger(__name__)
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QEMU_IMG_LIMITS = processutils.ProcessLimits(
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cpu_time=30,
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address_space=1 * units.Gi)
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@nova.privsep.sys_admin_pctxt.entrypoint
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def convert_image(source, dest, in_format, out_format, instances_path,
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compress):
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unprivileged_convert_image(source, dest, in_format, out_format,
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instances_path, compress)
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# NOTE(mikal): this method is deliberately not wrapped in a privsep entrypoint
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def unprivileged_convert_image(source, dest, in_format, out_format,
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instances_path, compress):
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# NOTE(mdbooth, kchamart): `qemu-img convert` defaults to
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# 'cache=writeback' for the source image, and 'cache=unsafe' for the
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# target, which means that data is not synced to disk at completion.
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# We explicitly use 'cache=none' here, for the target image, to (1)
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# ensure that we don't interfere with other applications using the
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# host's I/O cache, and (2) ensure that the data is on persistent
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# storage when the command exits. Without (2), a host crash may
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# leave a corrupt image in the image cache, which Nova cannot
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# recover automatically.
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# NOTE(zigo, kchamart): We cannot use `qemu-img convert -t none` if
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# the 'instance_dir' is mounted on a filesystem that doesn't support
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# O_DIRECT, which is the case, for example, with 'tmpfs'. This
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# simply crashes `openstack server create` in environments like live
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# distributions. In such cases, the best choice is 'writeback',
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# which (a) makes the conversion multiple times faster; and (b) is
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# as safe as it can be, because at the end of the conversion it,
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# just like 'writethrough', calls fsync(2)|fdatasync(2), which
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# ensures to safely write the data to the physical disk.
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# NOTE(mikal): there is an assumption here that the source and destination
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# are in the instances_path. Is that worth enforcing?
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if nova.privsep.utils.supports_direct_io(instances_path):
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cache_mode = 'none'
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else:
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cache_mode = 'writeback'
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cmd = ('qemu-img', 'convert', '-t', cache_mode, '-O', out_format)
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if in_format is not None:
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cmd = cmd + ('-f', in_format)
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if compress:
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cmd += ('-c',)
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cmd = cmd + (source, dest)
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processutils.execute(*cmd)
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@nova.privsep.sys_admin_pctxt.entrypoint
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def privileged_qemu_img_info(path, format=None):
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"""Return an oject containing the parsed output from qemu-img info
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This is a privileged call to qemu-img info using the sys_admin_pctxt
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entrypoint allowing host block devices etc to be accessed.
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"""
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return unprivileged_qemu_img_info(path, format=format)
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def unprivileged_qemu_img_info(path, format=None):
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"""Return an object containing the parsed output from qemu-img info."""
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try:
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# The following check is about ploop images that reside within
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# directories and always have DiskDescriptor.xml file beside them
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if (os.path.isdir(path) and
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os.path.exists(os.path.join(path, "DiskDescriptor.xml"))):
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path = os.path.join(path, "root.hds")
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cmd = (
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'env', 'LC_ALL=C', 'LANG=C', 'qemu-img', 'info', path,
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'--force-share', '--output=json',
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)
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if format is not None:
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cmd = cmd + ('-f', format)
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out, err = processutils.execute(*cmd, prlimit=QEMU_IMG_LIMITS)
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except processutils.ProcessExecutionError as exp:
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if exp.exit_code == -9:
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# this means we hit prlimits, make the exception more specific
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msg = (_("qemu-img aborted by prlimits when inspecting "
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"%(path)s : %(exp)s") % {'path': path, 'exp': exp})
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elif exp.exit_code == 1 and 'No such file or directory' in exp.stderr:
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# The os.path.exists check above can race so this is a simple
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# best effort at catching that type of failure and raising a more
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# specific error.
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raise exception.DiskNotFound(location=path)
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else:
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msg = (_("qemu-img failed to execute on %(path)s : %(exp)s") %
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{'path': path, 'exp': exp})
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raise exception.InvalidDiskInfo(reason=msg)
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if not out:
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msg = (_("Failed to run qemu-img info on %(path)s : %(error)s") %
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{'path': path, 'error': err})
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raise exception.InvalidDiskInfo(reason=msg)
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return out
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