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#!/usr/bin/env python3
#
# Copyright (C) 2016 Stavros Korokithakis
# 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>
#
# The filesystem operations implementation here is based
# on some example code written by Stavros Korokithakis.
import errno
import os
import shutil
import stat
import tempfile
from .fuse import FuseOSError, Operations
from .mount import Mount
# SafeHardlinks()
#
# A FUSE mount which implements a copy on write hardlink experience.
#
# Args:
# root (str): The underlying filesystem path to mirror
# tmp (str): A directory on the same filesystem for creating temp files
#
class SafeHardlinks(Mount):
def __init__(self, directory, tempdir):
self.directory = directory
self.tempdir = tempdir
def create_operations(self):
return SafeHardlinkOps(self.directory, self.tempdir)
# SafeHardlinkOps()
#
# The actual FUSE Operations implementation below.
#
class SafeHardlinkOps(Operations):
def __init__(self, root, tmp):
self.root = root
self.tmp = tmp
def _full_path(self, partial):
if partial.startswith("/"):
partial = partial[1:]
path = os.path.join(self.root, partial)
return path
def _ensure_copy(self, full_path):
try:
# Follow symbolic links manually here
real_path = os.path.realpath(full_path)
file_stat = os.stat(real_path)
# Dont bother with files that cannot be hardlinked, oddly it
# directories actually usually have st_nlink > 1 so just avoid
# that.
#
# We already wont get symlinks here, and stat will throw
# the FileNotFoundError below if a followed symlink did not exist.
#
if not stat.S_ISDIR(file_stat.st_mode) and file_stat.st_nlink > 1:
with tempfile.TemporaryDirectory(dir=self.tmp) as tempdir:
basename = os.path.basename(real_path)
temp_path = os.path.join(tempdir, basename)
# First copy, then unlink origin and rename
shutil.copy2(real_path, temp_path)
os.unlink(real_path)
os.rename(temp_path, real_path)
except FileNotFoundError:
# This doesnt exist yet, assume we're about to create it
# so it's not a problem.
pass
###########################################################
# Fuse Methods #
###########################################################
def access(self, path, mode):
full_path = self._full_path(path)
if not os.access(full_path, mode):
raise FuseOSError(errno.EACCES)
def chmod(self, path, mode):
full_path = self._full_path(path)
# Ensure copies on chmod
self._ensure_copy(full_path)
return os.chmod(full_path, mode)
def chown(self, path, uid, gid):
full_path = self._full_path(path)
# Ensure copies on chown
self._ensure_copy(full_path)
return os.chown(full_path, uid, gid)
def getattr(self, path, fh=None):
full_path = self._full_path(path)
st = os.lstat(full_path)
return dict((key, getattr(st, key)) for key in (
'st_atime', 'st_ctime', 'st_gid', 'st_mode',
'st_mtime', 'st_nlink', 'st_size', 'st_uid'))
def readdir(self, path, fh):
full_path = self._full_path(path)
dirents = ['.', '..']
if os.path.isdir(full_path):
dirents.extend(os.listdir(full_path))
for r in dirents:
yield r
def readlink(self, path):
pathname = os.readlink(self._full_path(path))
if pathname.startswith("/"):
# Path name is absolute, sanitize it.
return os.path.relpath(pathname, self.root)
else:
return pathname
def mknod(self, path, mode, dev):
return os.mknod(self._full_path(path), mode, dev)
def rmdir(self, path):
full_path = self._full_path(path)
return os.rmdir(full_path)
def mkdir(self, path, mode):
return os.mkdir(self._full_path(path), mode)
def statfs(self, path):
full_path = self._full_path(path)
stv = os.statvfs(full_path)
return dict((key, getattr(stv, key)) for key in (
'f_bavail', 'f_bfree', 'f_blocks', 'f_bsize', 'f_favail',
'f_ffree', 'f_files', 'f_flag', 'f_frsize', 'f_namemax'))
def unlink(self, path):
return os.unlink(self._full_path(path))
def symlink(self, name, target):
return os.symlink(target, self._full_path(name))
def rename(self, old, new):
return os.rename(self._full_path(old), self._full_path(new))
def link(self, target, name):
# When creating a hard link here, should we ensure the original
# file is not a hardlink itself first ?
#
return os.link(self._full_path(name), self._full_path(target))
def utimens(self, path, times=None):
return os.utime(self._full_path(path), times)
def open(self, path, flags):
full_path = self._full_path(path)
# If we're opening for writing, ensure it's a copy first
if flags & os.O_WRONLY or flags & os.O_RDWR:
self._ensure_copy(full_path)
return os.open(full_path, flags)
def create(self, path, mode, fi=None):
full_path = self._full_path(path)
# If it already exists, ensure it's a copy first
self._ensure_copy(full_path)
return os.open(full_path, os.O_WRONLY | os.O_CREAT, mode)
def read(self, path, length, offset, fh):
os.lseek(fh, offset, os.SEEK_SET)
return os.read(fh, length)
def write(self, path, buf, offset, fh):
os.lseek(fh, offset, os.SEEK_SET)
return os.write(fh, buf)
def truncate(self, path, length, fh=None):
full_path = self._full_path(path)
with open(full_path, 'r+') as f:
f.truncate(length)
def flush(self, path, fh):
return os.fsync(fh)
def release(self, path, fh):
return os.close(fh)
def fsync(self, path, fdatasync, fh):
return self.flush(path, fh)
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