122 lines
4.9 KiB
Python
122 lines
4.9 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2011 Red Hat, Inc.
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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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"""Support for mounting images with libguestfs"""
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import os
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from nova import exception
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from nova import utils
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from nova.virt.disk.mount import api
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class GuestFSMount(api.Mount):
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"""libguestfs support for arbitrary images."""
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mode = 'guestfs'
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device_id_string = 'guest'
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def map_dev(self):
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self.mapped = True
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return True
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def unmap_dev(self):
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self.mapped = False
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def mnt_dev(self):
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try:
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partition = int(self.partition or 0)
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except ValueError:
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self.error = _('unsupported partition: %s') % self.partition
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return False
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args = ('guestmount', '--rw', '-a', self.image)
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if partition == -1:
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args += ('-i',) # find the OS partition
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elif partition:
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args += ('-m', '/dev/sda%d' % partition)
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else:
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# We don't resort to -i for this case yet,
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# as some older versions of libguestfs
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# have problems identifying ttylinux images for example
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args += ('-m', '/dev/sda')
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args += (self.mount_dir,)
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# root access should not required for guestfs (if the user
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# has permissions to fusermount (by being part of the fuse
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# group for example)). Also note the image and mount_dir
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# have appropriate creditials at this point for read/write
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# mounting by the nova user. However currently there are
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# subsequent access issues by both the nova and root users
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# if the nova user mounts the image, as detailed here:
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# https://bugzilla.redhat.com/show_bug.cgi?id=765814
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_out, err = utils.trycmd(*args, discard_warnings=True,
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run_as_root=True)
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if err:
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self.error = _('Failed to mount filesystem: %s') % err
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# Be defensive and ensure this is unmounted,
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# as I'm not sure guestmount will never have
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# mounted when it returns EXIT_FAILURE.
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# This is required if discard_warnings=False above
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utils.trycmd('fusermount', '-u', self.mount_dir, run_as_root=True)
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return False
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# More defensiveness as there are edge cases where
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# guestmount can return success while not mounting
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try:
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if not os.listdir(self.mount_dir):
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# Assume we've just got the original empty temp dir
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err = _('unknown guestmount error')
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self.error = _('Failed to mount filesystem: %s') % err
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return False
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except OSError:
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# This is the usual path and means root has
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# probably mounted fine
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pass
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self.mounted = True
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return True
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def unmnt_dev(self):
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if not self.mounted:
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return
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umount_cmd = ['fusermount', '-u', self.mount_dir]
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try:
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# We make a few attempts to work around other
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# processes temporarily scanning the mount_dir etc.
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utils.execute(*umount_cmd, attempts=5, run_as_root=True)
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except exception.ProcessExecutionError:
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# If we still can't umount, then do a lazy umount
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# (in the background), so that mounts might eventually
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# be cleaned up. Note we'll wait 10s below for the umount to
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# complete, after which we'll raise an exception.
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umount_cmd.insert(1, '-z')
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utils.execute(*umount_cmd, run_as_root=True)
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# Unfortunately FUSE has an issue where it doesn't wait
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# for processes associated with the mount to terminate.
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# Therefore we do this manually here. Note later versions
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# of guestmount have the --pid-file option to help with this.
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# Here we check every .2 seconds whether guestmount is finished
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# but do this for at most 10 seconds.
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wait_cmd = 'until ! ps -C guestmount -o args= | grep -qF "%s"; '
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wait_cmd += 'do sleep .2; done'
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wait_cmd %= self.mount_dir
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try:
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utils.execute('timeout', '10s', 'sh', '-c', wait_cmd)
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self.mounted = False
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except exception.ProcessExecutionError:
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msg = _("Failed to umount image at %s, guestmount was "
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"still running after 10s") % (self.mount_dir)
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raise exception.NovaException(msg)
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