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#
# Copyright (C) 2017 Codethink Limited
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library. If not, see <http://www.gnu.org/licenses/>.
#
# Authors:
# Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
import os
from collections import OrderedDict
from contextlib import contextmanager, ExitStack
from .. import utils
from .._fuse import SafeHardlinks
# Mount()
#
# Helper data object representing a single mount point in the mount map
#
class Mount():
def __init__(self, sandbox, mount_point, safe_hardlinks):
scratch_directory = sandbox._get_scratch_directory()
# Getting external_directory here is acceptable as we're part of the sandbox code.
root_directory = sandbox.get_virtual_directory().external_directory
self.mount_point = mount_point
self.safe_hardlinks = safe_hardlinks
# FIXME: When the criteria for mounting something and it's parent
# mount is identical, then there is no need to mount an additional
# fuse layer (i.e. if the root is read-write and there is a directory
# marked for staged artifacts directly within the rootfs, they can
# safely share the same fuse layer).
#
# In these cases it would be saner to redirect the sub-mount to
# a regular mount point within the parent's redirected mount.
#
if self.safe_hardlinks:
# Redirected mount
self.mount_origin = os.path.join(root_directory, mount_point.lstrip(os.sep))
self.mount_base = os.path.join(scratch_directory, utils.url_directory_name(mount_point))
self.mount_source = os.path.join(self.mount_base, 'mount')
self.mount_tempdir = os.path.join(self.mount_base, 'temp')
os.makedirs(self.mount_origin, exist_ok=True)
os.makedirs(self.mount_tempdir, exist_ok=True)
else:
# No redirection needed
self.mount_source = os.path.join(root_directory, mount_point.lstrip(os.sep))
external_mount_sources = sandbox._get_mount_sources()
external_mount_source = external_mount_sources.get(mount_point)
if external_mount_source is None:
os.makedirs(self.mount_source, exist_ok=True)
else:
if os.path.isdir(external_mount_source):
os.makedirs(self.mount_source, exist_ok=True)
else:
# When mounting a regular file, ensure the parent
# directory exists in the sandbox; and that an empty
# file is created at the mount location.
parent_dir = os.path.dirname(self.mount_source.rstrip('/'))
os.makedirs(parent_dir, exist_ok=True)
if not os.path.exists(self.mount_source):
with open(self.mount_source, 'w'):
pass
@contextmanager
def mounted(self, sandbox):
if self.safe_hardlinks:
mount = SafeHardlinks(self.mount_origin, self.mount_tempdir)
with mount.mounted(self.mount_source):
yield
else:
# Nothing to mount here
yield
# MountMap()
#
# Helper object for mapping of the sandbox mountpoints
#
# Args:
# sandbox (Sandbox): The sandbox object
# root_readonly (bool): Whether the sandbox root is readonly
#
class MountMap():
def __init__(self, sandbox, root_readonly):
# We will be doing the mounts in the order in which they were declared.
self.mounts = OrderedDict()
# We want safe hardlinks on rootfs whenever root is not readonly
self.mounts['/'] = Mount(sandbox, '/', not root_readonly)
for mark in sandbox._get_marked_directories():
directory = mark['directory']
artifact = mark['artifact']
# We want safe hardlinks for any non-root directory where
# artifacts will be staged to
self.mounts[directory] = Mount(sandbox, directory, artifact)
# get_mount_source()
#
# Gets the host directory where the mountpoint in the
# sandbox should be bind mounted from
#
# Args:
# mountpoint (str): The absolute mountpoint path inside the sandbox
#
# Returns:
# The host path to be mounted at the mount point
#
def get_mount_source(self, mountpoint):
return self.mounts[mountpoint].mount_source
# mounted()
#
# A context manager which ensures all the mount sources
# were mounted with any fuse layers which may have been needed.
#
# Args:
# sandbox (Sandbox): The sandbox
#
@contextmanager
def mounted(self, sandbox):
with ExitStack() as stack:
for _, mount in self.mounts.items():
stack.enter_context(mount.mounted(sandbox))
yield
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