ddf96bcd31
This is the first stage of the power management series. In order to be able to switch the CPU state or change the governor, we need a framework to access sysfs. As some bits can be reused, let's create a nova.filesystem helper module that will define read-write mechanisms for accessing sysfs-specific commands. Partially-Implements: blueprint libvirt-cpu-state-mgmt Change-Id: Icb913ed9be8d508de35e755a9c650ba25e45aca2
60 lines
2.2 KiB
Python
60 lines
2.2 KiB
Python
# 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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"""Functions to address filesystem calls, particularly sysfs."""
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import os
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from oslo_log import log as logging
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from nova import exception
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LOG = logging.getLogger(__name__)
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SYS = '/sys'
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# NOTE(bauzas): this method is deliberately not wrapped in a privsep entrypoint
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def read_sys(path: str) -> str:
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"""Reads the content of a file in the sys filesystem.
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:param path: relative or absolute. If relative, will be prefixed by /sys.
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:returns: contents of that file.
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:raises: nova.exception.FileNotFound if we can't read that file.
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"""
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try:
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# The path can be absolute with a /sys prefix but that's fine.
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with open(os.path.join(SYS, path), mode='r') as data:
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return data.read()
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except (OSError, ValueError) as exc:
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raise exception.FileNotFound(file_path=path) from exc
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# NOTE(bauzas): this method is deliberately not wrapped in a privsep entrypoint
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# In order to correctly use it, you need to decorate the caller with a specific
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# privsep entrypoint.
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def write_sys(path: str, data: str) -> None:
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"""Writes the content of a file in the sys filesystem with data.
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:param path: relative or absolute. If relative, will be prefixed by /sys.
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:param data: the data to write.
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:returns: contents of that file.
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:raises: nova.exception.FileNotFound if we can't write that file.
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"""
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try:
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# The path can be absolute with a /sys prefix but that's fine.
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with open(os.path.join(SYS, path), mode='w') as fd:
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fd.write(data)
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except (OSError, ValueError) as exc:
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raise exception.FileNotFound(file_path=path) from exc
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