/usr/share/pyshared/obnamlib/vfs_local.py is in obnam 1.6.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
import errno
import fcntl
import grp
import logging
import math
import os
import pwd
import tempfile
import time
import tracing
import obnamlib
# O_NOATIME is Linux specific:
EXTRA_OPEN_FLAGS = getattr(os, "O_NOATIME", 0)
class LocalFSFile(file):
def read(self, amount=-1):
offset = self.tell()
data = file.read(self, amount)
if data:
fd = self.fileno()
obnamlib._obnam.fadvise_dontneed(fd, offset, len(data))
return data
def write(self, data):
offset = self.tell()
file.write(self, data)
fd = self.fileno()
obnamlib._obnam.fadvise_dontneed(fd, offset, len(data))
class LocalFS(obnamlib.VirtualFileSystem):
"""A VFS implementation for local filesystems."""
chunk_size = 1024 * 1024
def __init__(self, baseurl, create=False):
tracing.trace('baseurl=%s', baseurl)
tracing.trace('create=%s', create)
obnamlib.VirtualFileSystem.__init__(self, baseurl)
self.reinit(baseurl, create=create)
# For checking that we do not unlock something we didn't lock
# ourselves.
self.our_locks = set()
# For testing purposes, allow setting a limit on write operations
# after which an exception gets raised. If set to None, no crash.
self.crash_limit = None
self.crash_counter = 0
# Do we have lchmod?
self.got_lchmod = hasattr(os, 'lchmod')
def maybe_crash(self): # pragma: no cover
if self.crash_limit is not None:
self.crash_counter += 1
if self.crash_counter >= self.crash_limit:
raise Exception('Crashing as requested after %d writes' %
self.crash_counter)
def reinit(self, baseurl, create=False):
# We fake chdir so that it doesn't mess with the caller's
# perception of current working directory. This also benefits
# unit tests. To do this, we store the baseurl as the cwd.
tracing.trace('baseurl=%s', baseurl)
tracing.trace('create=%s', create)
self.cwd = os.path.abspath(baseurl)
if not self.isdir('.'):
if create:
tracing.trace('creating %s', baseurl)
try:
os.mkdir(baseurl)
except OSError, e: # pragma: no cover
# The directory might have been created concurrently
# by someone else!
if e.errno != errno.EEXIST:
raise
else:
err = errno.ENOENT
raise OSError(err, os.strerror(err), self.cwd)
def getcwd(self):
return self.cwd
def chdir(self, pathname):
tracing.trace('LocalFS(%s).chdir(%s)', self.baseurl, pathname)
newcwd = os.path.abspath(self.join(pathname))
if not os.path.isdir(newcwd):
raise OSError('%s is not a directory' % newcwd)
self.cwd = newcwd
def lock(self, lockname, data):
tracing.trace('attempting lockname=%s', lockname)
try:
self.write_file(lockname, data)
except OSError, e:
if e.errno == errno.EEXIST:
raise obnamlib.LockFail("Lock %s already exists" % lockname)
else:
raise # pragma: no cover
tracing.trace('got lockname=%s', lockname)
tracing.trace('time=%f' % time.time())
self.our_locks.add(lockname)
def unlock(self, lockname):
tracing.trace('lockname=%s', lockname)
assert lockname in self.our_locks
self.remove(lockname)
self.our_locks.remove(lockname)
tracing.trace('time=%f' % time.time())
def join(self, pathname):
return os.path.join(self.cwd, pathname)
def remove(self, pathname):
tracing.trace('remove %s', pathname)
os.remove(self.join(pathname))
self.maybe_crash()
def rename(self, old, new):
tracing.trace('rename %s %s', old, new)
os.rename(self.join(old), self.join(new))
self.maybe_crash()
def lstat(self, pathname):
(ret, dev, ino, mode, nlink, uid, gid, rdev, size, blksize, blocks,
atime_sec, atime_nsec, mtime_sec, mtime_nsec,
ctime_sec, ctime_nsec) = obnamlib._obnam.lstat(self.join(pathname))
if ret != 0:
raise OSError(ret, os.strerror(ret), pathname)
return obnamlib.Metadata(
st_dev=dev,
st_ino=ino,
st_mode=mode,
st_nlink=nlink,
st_uid=uid,
st_gid=gid,
st_rdev=rdev,
st_size=size,
st_blksize=blksize,
st_blocks=blocks,
st_atime_sec=atime_sec,
st_atime_nsec=atime_nsec,
st_mtime_sec=mtime_sec,
st_mtime_nsec=mtime_nsec,
st_ctime_sec=ctime_sec,
st_ctime_nsec=ctime_nsec
)
def get_username(self, uid):
return pwd.getpwuid(uid)[0]
def get_groupname(self, gid):
return grp.getgrgid(gid)[0]
def llistxattr(self, filename): # pragma: no cover
ret = obnamlib._obnam.llistxattr(self.join(filename))
if type(ret) is int:
raise OSError(ret, os.strerror(ret), filename)
return [s for s in ret.split('\0') if s]
def lgetxattr(self, filename, attrname): # pragma: no cover
ret = obnamlib._obnam.lgetxattr(self.join(filename), attrname)
if type(ret) is int:
raise OSError(ret, os.strerror(ret), filename)
return ret
def lsetxattr(self, filename, attrname, attrvalue): # pragma: no cover
ret = obnamlib._obnam.lsetxattr(self.join(filename),
attrname, attrvalue)
if ret != 0:
raise OSError(ret, os.strerror(ret), filename)
def lchown(self, pathname, uid, gid): # pragma: no cover
tracing.trace('lchown %s %d %d', pathname, uid, gid)
os.lchown(self.join(pathname), uid, gid)
# This method is excluded from test coverage because the platform
# either has lchmod or doesn't, and accordingly either branch of
# the if statement is taken, and the other branch shows up as not
# being tested by the unit tests.
def chmod_symlink(self, pathname, mode): # pragma: no cover
tracing.trace('chmod_symlink %s %o', pathname, mode)
if self.got_lchmod:
os.lchmod(self.join(pathname), mode)
else:
self.lstat(pathname)
def chmod_not_symlink(self, pathname, mode):
tracing.trace('chmod_not_symlink %s %o', pathname, mode)
os.chmod(self.join(pathname), mode)
def lutimes(self, pathname, atime_sec, atime_nsec, mtime_sec, mtime_nsec):
assert atime_sec is not None
assert atime_nsec is not None
assert mtime_sec is not None
assert mtime_nsec is not None
ret = obnamlib._obnam.utimensat(self.join(pathname),
atime_sec, atime_nsec,
mtime_sec, mtime_nsec)
if ret != 0:
raise OSError(ret, os.strerror(ret), pathname)
def link(self, existing, new):
tracing.trace('existing=%s', existing)
tracing.trace('new=%s', new)
os.link(self.join(existing), self.join(new))
self.maybe_crash()
def readlink(self, pathname):
return os.readlink(self.join(pathname))
def symlink(self, existing, new):
tracing.trace('existing=%s', existing)
tracing.trace('new=%s', new)
os.symlink(existing, self.join(new))
self.maybe_crash()
def open(self, pathname, mode):
tracing.trace('pathname=%s', pathname)
tracing.trace('mode=%s', mode)
f = LocalFSFile(self.join(pathname), mode)
tracing.trace('opened %s', pathname)
try:
flags = fcntl.fcntl(f.fileno(), fcntl.F_GETFL)
flags |= EXTRA_OPEN_FLAGS
fcntl.fcntl(f.fileno(), fcntl.F_SETFL, flags)
except IOError, e: # pragma: no cover
tracing.trace('fcntl F_SETFL failed: %s', repr(e))
return f # ignore any problems setting flags
tracing.trace('returning ok')
return f
def exists(self, pathname):
return os.path.exists(self.join(pathname))
def isdir(self, pathname):
return os.path.isdir(self.join(pathname))
def mknod(self, pathname, mode):
tracing.trace('pathmame=%s', pathname)
tracing.trace('mode=%o', mode)
os.mknod(self.join(pathname), mode)
def mkdir(self, pathname):
tracing.trace('mkdir %s', pathname)
os.mkdir(self.join(pathname))
self.maybe_crash()
def makedirs(self, pathname):
tracing.trace('makedirs %s', pathname)
os.makedirs(self.join(pathname))
self.maybe_crash()
def rmdir(self, pathname):
tracing.trace('rmdir %s', pathname)
os.rmdir(self.join(pathname))
self.maybe_crash()
def cat(self, pathname):
tracing.trace('pathname=%s' % pathname)
pathname = self.join(pathname)
f = self.open(pathname, 'rb')
chunks = []
while True:
chunk = f.read(self.chunk_size)
if not chunk:
break
chunks.append(chunk)
self.bytes_read += len(chunk)
f.close()
data = ''.join(chunks)
return data
def write_file(self, pathname, contents): # pragma: no cover
# This is tricky. We need to at least try to support NFS, and
# various filesystems that do not support hardlinks. On NFS,
# creating a file with O_EXCL is not guaranteed to be atomic,
# but adding a link with link(2) is. However, that doesn't work
# on VFAT, for example. So we try do both: first create a
# temporary file with a name guaranteed to not be a name we
# want to use, and then we rename it using link(2) and remove(2).
# If that fails, we try to create the target file with O_EXCL
# and rename the temporary file to that. This is still not 100%
# reliable: someone could be mounting VFAT across NFS, for
# example, but it's the best we can do. If this paragraph is
# wrong, tell the authors.
tracing.trace('write_file %s', pathname)
tempname = self._write_to_tempfile(pathname, contents)
path = self.join(pathname)
# Try link(2) for creating target file.
try:
os.link(tempname, path)
except OSError, e:
pass
else:
os.remove(tempname)
tracing.trace('link+remove worked')
return
# Nope, didn't work. Now try with O_EXCL instead.
try:
fd = os.open(path, os.O_CREAT | os.O_EXCL | os.O_WRONLY, 0666)
os.close(fd)
os.rename(tempname, path)
except OSError, e:
# Give up.
os.remove(tempname)
raise
tracing.trace('O_EXCL+rename worked')
self.maybe_crash()
def overwrite_file(self, pathname, contents):
tracing.trace('overwrite_file %s', pathname)
tempname = self._write_to_tempfile(pathname, contents)
path = self.join(pathname)
os.rename(tempname, path)
self.maybe_crash()
def _write_to_tempfile(self, pathname, contents):
path = self.join(pathname)
dirname = os.path.dirname(path)
if not os.path.exists(dirname):
tracing.trace('os.makedirs(%s)' % dirname)
os.makedirs(dirname)
fd, tempname = tempfile.mkstemp(dir=dirname)
os.close(fd)
f = self.open(tempname, 'wb')
pos = 0
while pos < len(contents):
chunk = contents[pos:pos+self.chunk_size]
f.write(chunk)
pos += len(chunk)
self.bytes_written += len(chunk)
f.close()
return tempname
def listdir(self, dirname):
return os.listdir(self.join(dirname))
def listdir2(self, dirname):
result = []
for name in self.listdir(dirname):
try:
st = self.lstat(os.path.join(dirname, name))
except OSError, e: # pragma: no cover
st = e
ino = -1
else:
ino = st.st_ino
result.append((ino, name, st))
# We sort things in inode order, for speed when doing namei lookups
# when backing up.
result.sort()
return [(name, st) for ino, name, st in result]
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