borg/attic/fuse.py

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from collections import defaultdict
import errno
import io
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import llfuse
import msgpack
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import os
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import stat
import tempfile
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import time
from attic.archive import Archive
from attic.helpers import daemonize
from attic.remote import cache_if_remote
# Does this version of llfuse support ns precision?
have_fuse_mtime_ns = hasattr(llfuse.EntryAttributes, 'st_mtime_ns')
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class ItemCache:
def __init__(self):
self.fd = tempfile.TemporaryFile()
self.offset = 1000000
def add(self, item):
pos = self.fd.seek(0, io.SEEK_END)
self.fd.write(msgpack.packb(item))
return pos + self.offset
def get(self, inode):
self.fd.seek(inode - self.offset, io.SEEK_SET)
return next(msgpack.Unpacker(self.fd))
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class AtticOperations(llfuse.Operations):
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"""Export Attic archive as a fuse filesystem
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"""
def __init__(self, key, repository, manifest, archive):
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super(AtticOperations, self).__init__()
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self._inode_count = 0
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self.key = key
self.repository = cache_if_remote(repository)
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self.items = {}
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self.parent = {}
self.contents = defaultdict(dict)
self.default_dir = {b'mode': 0o40755, b'mtime': int(time.time() * 1e9), b'uid': os.getuid(), b'gid': os.getgid()}
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self.pending_archives = {}
self.cache = ItemCache()
if archive:
self.process_archive(archive)
else:
# Create root inode
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self.parent[1] = self.allocate_inode()
self.items[1] = self.default_dir
for archive_name in manifest.archives:
# Create archive placeholder inode
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archive_inode = self.allocate_inode()
self.items[archive_inode] = self.default_dir
self.parent[archive_inode] = 1
self.contents[1][os.fsencode(archive_name)] = archive_inode
self.pending_archives[archive_inode] = Archive(repository, key, manifest, archive_name)
def process_archive(self, archive, prefix=[]):
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"""Build fuse inode hierarchy from archive metadata
"""
unpacker = msgpack.Unpacker()
for key, chunk in zip(archive.metadata[b'items'], self.repository.get_many(archive.metadata[b'items'])):
data = self.key.decrypt(key, chunk)
unpacker.feed(data)
for item in unpacker:
segments = prefix + os.fsencode(os.path.normpath(item[b'path'])).split(b'/')
del item[b'path']
num_segments = len(segments)
parent = 1
for i, segment in enumerate(segments, 1):
# Insert a default root inode if needed
if self._inode_count == 0 and segment:
archive_inode = self.allocate_inode()
self.items[archive_inode] = self.default_dir
self.parent[archive_inode] = parent
# Leaf segment?
if i == num_segments:
if b'source' in item and stat.S_ISREG(item[b'mode']):
inode = self._find_inode(item[b'source'], prefix)
item = self.cache.get(inode)
item[b'nlink'] = item.get(b'nlink', 1) + 1
self.items[inode] = item
else:
inode = self.cache.add(item)
self.parent[inode] = parent
if segment:
self.contents[parent][segment] = inode
elif segment in self.contents[parent]:
parent = self.contents[parent][segment]
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else:
inode = self.allocate_inode()
self.items[inode] = self.default_dir
self.parent[inode] = parent
if segment:
self.contents[parent][segment] = inode
parent = inode
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def allocate_inode(self):
self._inode_count += 1
return self._inode_count
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def statfs(self):
stat_ = llfuse.StatvfsData()
stat_.f_bsize = 512
stat_.f_frsize = 512
stat_.f_blocks = 0
stat_.f_bfree = 0
stat_.f_bavail = 0
stat_.f_files = 0
stat_.f_ffree = 0
stat_.f_favail = 0
return stat_
def get_item(self, inode):
try:
return self.items[inode]
except KeyError:
return self.cache.get(inode)
def _find_inode(self, path, prefix=[]):
segments = prefix + os.fsencode(os.path.normpath(path)).split(b'/')
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inode = 1
for segment in segments:
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inode = self.contents[inode][segment]
return inode
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def getattr(self, inode):
item = self.get_item(inode)
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size = 0
try:
size = sum(size for _, size, _ in item[b'chunks'])
except KeyError:
pass
entry = llfuse.EntryAttributes()
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entry.st_ino = inode
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entry.generation = 0
entry.entry_timeout = 300
entry.attr_timeout = 300
entry.st_mode = item[b'mode']
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entry.st_nlink = item.get(b'nlink', 1)
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entry.st_uid = item[b'uid']
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entry.st_gid = item[b'gid']
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entry.st_rdev = item.get(b'rdev', 0)
entry.st_size = size
entry.st_blksize = 512
entry.st_blocks = 1
if have_fuse_mtime_ns:
entry.st_atime_ns = item[b'mtime']
entry.st_mtime_ns = item[b'mtime']
entry.st_ctime_ns = item[b'mtime']
else:
entry.st_atime = item[b'mtime'] / 1e9
entry.st_mtime = item[b'mtime'] / 1e9
entry.st_ctime = item[b'mtime'] / 1e9
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return entry
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def listxattr(self, inode):
item = self.get_item(inode)
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return item.get(b'xattrs', {}).keys()
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def getxattr(self, inode, name):
item = self.get_item(inode)
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try:
return item.get(b'xattrs', {})[name]
except KeyError:
raise llfuse.FUSEError(errno.ENODATA)
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def _load_pending_archive(self, inode):
# Check if this is an archive we need to load
archive = self.pending_archives.pop(inode, None)
if archive:
self.process_archive(archive, [os.fsencode(archive.name)])
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def lookup(self, parent_inode, name):
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self._load_pending_archive(parent_inode)
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if name == b'.':
inode = parent_inode
elif name == b'..':
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inode = self.parent[parent_inode]
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else:
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inode = self.contents[parent_inode].get(name)
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if not inode:
raise llfuse.FUSEError(errno.ENOENT)
return self.getattr(inode)
def open(self, inode, flags):
return inode
def opendir(self, inode):
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self._load_pending_archive(inode)
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return inode
def read(self, fh, offset, size):
parts = []
item = self.get_item(fh)
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for id, s, csize in item[b'chunks']:
if s < offset:
offset -= s
continue
n = min(size, s - offset)
chunk = self.key.decrypt(id, self.repository.get(id))
parts.append(chunk[offset:offset+n])
offset = 0
size -= n
if not size:
break
return b''.join(parts)
def readdir(self, fh, off):
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entries = [(b'.', fh), (b'..', self.parent[fh])]
entries.extend(self.contents[fh].items())
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for i, (name, inode) in enumerate(entries[off:], off):
yield name, self.getattr(inode), i + 1
def readlink(self, inode):
item = self.get_item(inode)
return os.fsencode(item[b'source'])
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def mount(self, mountpoint, extra_options, foreground=False):
options = ['fsname=atticfs', 'ro']
if extra_options:
options.extend(extra_options.split(','))
llfuse.init(self, mountpoint, options)
if not foreground:
daemonize()
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try:
llfuse.main(single=True)
except:
llfuse.close()
raise
llfuse.close()