import errno import io import os import stat import struct import sys import tempfile import time from collections import defaultdict from signal import SIGINT import llfuse from .logger import create_logger logger = create_logger() from .crypto.low_level import blake2b_128 from .archiver import Archiver from .archive import Archive from .hashindex import FuseVersionsIndex from .helpers import daemonize, hardlinkable, signal_handler, format_file_size, Error from .helpers import msgpack from .item import Item from .lrucache import LRUCache from .remote import RemoteRepository # Does this version of llfuse support ns precision? have_fuse_xtime_ns = hasattr(llfuse.EntryAttributes, 'st_mtime_ns') # Does this version of llfuse support birthtime? have_fuse_birthtime = hasattr(llfuse.EntryAttributes, 'st_birthtime') # never? have_fuse_birthtime_ns = hasattr(llfuse.EntryAttributes, 'st_birthtime_ns') # since llfuse 1.3 def fuse_main(): return llfuse.main(workers=1) # size of some LRUCaches (1 element per simultaneously open file) # note: _inode_cache might have rather large elements - Item.chunks can be large! # also, simultaneously reading too many files should be avoided anyway. # thus, do not set FILES to high values. FILES = 4 class ItemCache: """ This is the "meat" of the file system's metadata storage. This class generates inode numbers that efficiently index items in archives, and retrieves items from these inode numbers. """ # 2 MiB are approximately ~230000 items (depends on the average number of items per metadata chunk). # # Since growing a bytearray has to copy it, growing it will converge to O(n^2), however, # this is not yet relevant due to the swiftness of copying memory. If it becomes an issue, # use an anonymous mmap and just resize that (or, if on 64 bit, make it so big you never need # to resize it in the first place; that's free). GROW_META_BY = 2 * 1024 * 1024 indirect_entry_struct = struct.Struct('=cII') assert indirect_entry_struct.size == 9 def __init__(self, decrypted_repository): self.decrypted_repository = decrypted_repository # self.meta, the "meta-array" is a densely packed array of metadata about where items can be found. # It is indexed by the inode number minus self.offset. (This is in a way eerily similar to how the first # unices did this). # The meta-array contains chunk IDs and item entries (described in iter_archive_items). # The chunk IDs are referenced by item entries through relative offsets, # which are bounded by the metadata chunk size. self.meta = bytearray() # The current write offset in self.meta self.write_offset = 0 # Offset added to meta-indices, resulting in inodes, # or subtracted from inodes, resulting in meta-indices. # XXX: Merge FuseOperations.items and ItemCache to avoid # this implicit limitation / hack (on the number of synthetic inodes, degenerate # cases can inflate their number far beyond the number of archives). self.offset = 1000000 # A temporary file that contains direct items, i.e. items directly cached in this layer. # These are items that span more than one chunk and thus cannot be efficiently cached # by the object cache (self.decrypted_repository), which would require variable-length structures; # possible but not worth the effort, see iter_archive_items. self.fd = tempfile.TemporaryFile(prefix='borg-tmp') # A small LRU cache for chunks requested by ItemCache.get() from the object cache, # this significantly speeds up directory traversal and similar operations which # tend to re-read the same chunks over and over. # The capacity is kept low because increasing it does not provide any significant advantage, # but makes LRUCache's square behaviour noticeable and consumes more memory. self.chunks = LRUCache(capacity=10, dispose=lambda _: None) # Instrumentation # Count of indirect items, i.e. data is cached in the object cache, not directly in this cache self.indirect_items = 0 # Count of direct items, i.e. data is in self.fd self.direct_items = 0 def get(self, inode): offset = inode - self.offset if offset < 0: raise ValueError('ItemCache.get() called with an invalid inode number') if self.meta[offset] == ord(b'I'): _, chunk_id_relative_offset, chunk_offset = self.indirect_entry_struct.unpack_from(self.meta, offset) chunk_id_offset = offset - chunk_id_relative_offset # bytearray slices are bytearrays as well, explicitly convert to bytes() chunk_id = bytes(self.meta[chunk_id_offset:chunk_id_offset + 32]) chunk = self.chunks.get(chunk_id) if not chunk: csize, chunk = next(self.decrypted_repository.get_many([chunk_id])) self.chunks[chunk_id] = chunk data = memoryview(chunk)[chunk_offset:] unpacker = msgpack.Unpacker() unpacker.feed(data) return Item(internal_dict=next(unpacker)) elif self.meta[offset] == ord(b'S'): fd_offset = int.from_bytes(self.meta[offset + 1:offset + 9], 'little') self.fd.seek(fd_offset, io.SEEK_SET) return Item(internal_dict=next(msgpack.Unpacker(self.fd, read_size=1024))) else: raise ValueError('Invalid entry type in self.meta') def iter_archive_items(self, archive_item_ids, filter=None, consider_part_files=False): unpacker = msgpack.Unpacker() # Current offset in the metadata stream, which consists of all metadata chunks glued together stream_offset = 0 # Offset of the current chunk in the metadata stream chunk_begin = 0 # Length of the chunk preciding the current chunk last_chunk_length = 0 msgpacked_bytes = b'' write_offset = self.write_offset meta = self.meta pack_indirect_into = self.indirect_entry_struct.pack_into def write_bytes(append_msgpacked_bytes): # XXX: Future versions of msgpack include an Unpacker.tell() method that provides this for free. nonlocal msgpacked_bytes nonlocal stream_offset msgpacked_bytes += append_msgpacked_bytes stream_offset += len(append_msgpacked_bytes) for key, (csize, data) in zip(archive_item_ids, self.decrypted_repository.get_many(archive_item_ids)): # Store the chunk ID in the meta-array if write_offset + 32 >= len(meta): self.meta = meta = meta + bytes(self.GROW_META_BY) meta[write_offset:write_offset + 32] = key current_id_offset = write_offset write_offset += 32 # The chunk boundaries cannot be tracked through write_bytes, because the unpack state machine # *can* and *will* consume partial items, so calls to write_bytes are unrelated to chunk boundaries. chunk_begin += last_chunk_length last_chunk_length = len(data) unpacker.feed(data) while True: try: item = unpacker.unpack(write_bytes) except msgpack.OutOfData: # Need more data, feed the next chunk break item = Item(internal_dict=item) if filter and not filter(item) or not consider_part_files and 'part' in item: msgpacked_bytes = b'' continue current_item = msgpacked_bytes current_item_length = len(current_item) current_spans_chunks = stream_offset - current_item_length < chunk_begin msgpacked_bytes = b'' if write_offset + 9 >= len(meta): self.meta = meta = meta + bytes(self.GROW_META_BY) # item entries in the meta-array come in two different flavours, both nine bytes long. # (1) for items that span chunks: # # 'S' + 8 byte offset into the self.fd file, where the msgpacked item starts. # # (2) for items that are completely contained in one chunk, which usually is the great majority # (about 700:1 for system backups) # # 'I' + 4 byte offset where the chunk ID is + 4 byte offset in the chunk # where the msgpacked items starts # # The chunk ID offset is the number of bytes _back_ from the start of the entry, i.e.: # # |Chunk ID| .... |S1234abcd| # ^------ offset ----------^ if current_spans_chunks: pos = self.fd.seek(0, io.SEEK_END) self.fd.write(current_item) meta[write_offset:write_offset + 9] = b'S' + pos.to_bytes(8, 'little') self.direct_items += 1 else: item_offset = stream_offset - current_item_length - chunk_begin pack_indirect_into(meta, write_offset, b'I', write_offset - current_id_offset, item_offset) self.indirect_items += 1 inode = write_offset + self.offset write_offset += 9 yield inode, item self.write_offset = write_offset class FuseOperations(llfuse.Operations): """Export archive as a FUSE filesystem """ # mount options allow_damaged_files = False versions = False uid_forced = None gid_forced = None umask = 0 def __init__(self, key, repository, manifest, args, decrypted_repository): super().__init__() self.repository_uncached = repository self.decrypted_repository = decrypted_repository self.args = args self.manifest = manifest self.key = key # Maps inode numbers to Item instances. This is used for synthetic inodes, # i.e. file-system objects that are made up by FuseOperations and are not contained # in the archives. For example archive directories or intermediate directories # not contained in archives. self.items = {} # cache up to <FILES> Items self._inode_cache = LRUCache(capacity=FILES, dispose=lambda _: None) # _inode_count is the current count of synthetic inodes, i.e. those in self.items self._inode_count = 0 # Maps inode numbers to the inode number of the parent self.parent = {} # Maps inode numbers to a dictionary mapping byte directory entry names to their inode numbers, # i.e. this contains all dirents of everything that is mounted. (It becomes really big). self.contents = defaultdict(dict) self.default_uid = os.getuid() self.default_gid = os.getgid() self.default_dir = None self.pending_archives = {} self.cache = ItemCache(decrypted_repository) data_cache_capacity = int(os.environ.get('BORG_MOUNT_DATA_CACHE_ENTRIES', os.cpu_count() or 1)) logger.debug('mount data cache capacity: %d chunks', data_cache_capacity) self.data_cache = LRUCache(capacity=data_cache_capacity, dispose=lambda _: None) self._last_pos = LRUCache(capacity=FILES, dispose=lambda _: None) def _create_filesystem(self): self._create_dir(parent=1) # first call, create root dir (inode == 1) if self.args.location.archive: if self.versions: raise Error("for versions view, do not specify a single archive, " "but always give the repository as location.") self.process_archive(self.args.location.archive) else: self.versions_index = FuseVersionsIndex() for archive in self.manifest.archives.list_considering(self.args): if self.versions: # process archives immediately self.process_archive(archive.name) else: # lazily load archives, create archive placeholder inode archive_inode = self._create_dir(parent=1, mtime=int(archive.ts.timestamp() * 1e9)) self.contents[1][os.fsencode(archive.name)] = archive_inode self.pending_archives[archive_inode] = archive.name def sig_info_handler(self, sig_no, stack): logger.debug('fuse: %d synth inodes, %d edges (%s)', self._inode_count, len(self.parent), # getsizeof is the size of the dict itself; key and value are two small-ish integers, # which are shared due to code structure (this has been verified). format_file_size(sys.getsizeof(self.parent) + len(self.parent) * sys.getsizeof(self._inode_count))) logger.debug('fuse: %d pending archives', len(self.pending_archives)) logger.debug('fuse: ItemCache %d entries (%d direct, %d indirect), meta-array size %s, direct items size %s', self.cache.direct_items + self.cache.indirect_items, self.cache.direct_items, self.cache.indirect_items, format_file_size(sys.getsizeof(self.cache.meta)), format_file_size(os.stat(self.cache.fd.fileno()).st_size)) logger.debug('fuse: data cache: %d/%d entries, %s', len(self.data_cache.items()), self.data_cache._capacity, format_file_size(sum(len(chunk) for key, chunk in self.data_cache.items()))) self.decrypted_repository.log_instrumentation() def mount(self, mountpoint, mount_options, foreground=False): """Mount filesystem on *mountpoint* with *mount_options*.""" def pop_option(options, key, present, not_present, wanted_type, int_base=0): assert isinstance(options, list) # we mutate this for idx, option in enumerate(options): if option == key: options.pop(idx) return present if option.startswith(key + '='): options.pop(idx) value = option.split('=', 1)[1] if wanted_type is bool: v = value.lower() if v in ('y', 'yes', 'true', '1'): return True if v in ('n', 'no', 'false', '0'): return False raise ValueError('unsupported value in option: %s' % option) if wanted_type is int: try: return int(value, base=int_base) except ValueError: raise ValueError('unsupported value in option: %s' % option) from None try: return wanted_type(value) except ValueError: raise ValueError('unsupported value in option: %s' % option) from None else: return not_present # default_permissions enables permission checking by the kernel. Without # this, any umask (or uid/gid) would not have an effect and this could # cause security issues if used with allow_other mount option. # When not using allow_other or allow_root, access is limited to the # mounting user anyway. options = ['fsname=borgfs', 'ro', 'default_permissions'] if mount_options: options.extend(mount_options.split(',')) ignore_permissions = pop_option(options, 'ignore_permissions', True, False, bool) if ignore_permissions: # in case users have a use-case that requires NOT giving "default_permissions", # this is enabled by the custom "ignore_permissions" mount option which just # removes "default_permissions" again: pop_option(options, 'default_permissions', True, False, bool) self.allow_damaged_files = pop_option(options, 'allow_damaged_files', True, False, bool) self.versions = pop_option(options, 'versions', True, False, bool) self.uid_forced = pop_option(options, 'uid', None, None, int) self.gid_forced = pop_option(options, 'gid', None, None, int) self.umask = pop_option(options, 'umask', 0, 0, int, int_base=8) # umask is octal, e.g. 222 or 0222 dir_uid = self.uid_forced if self.uid_forced is not None else self.default_uid dir_gid = self.gid_forced if self.gid_forced is not None else self.default_gid dir_mode = 0o40755 & ~self.umask self.default_dir = Item(mode=dir_mode, mtime=int(time.time() * 1e9), uid=dir_uid, gid=dir_gid) self._create_filesystem() llfuse.init(self, mountpoint, options) if not foreground: old_id, new_id = daemonize() if not isinstance(self.repository_uncached, RemoteRepository): # local repo and the locking process' PID just changed, migrate it: self.repository_uncached.migrate_lock(old_id, new_id) # If the file system crashes, we do not want to umount because in that # case the mountpoint suddenly appears to become empty. This can have # nasty consequences, imagine the user has e.g. an active rsync mirror # job - seeing the mountpoint empty, rsync would delete everything in the # mirror. umount = False try: with signal_handler('SIGUSR1', self.sig_info_handler), \ signal_handler('SIGINFO', self.sig_info_handler): signal = fuse_main() # no crash and no signal (or it's ^C and we're in the foreground) -> umount request umount = (signal is None or (signal == SIGINT and foreground)) finally: llfuse.close(umount) def _create_dir(self, parent, mtime=None): """Create directory """ ino = self.allocate_inode() if mtime is not None: self.items[ino] = Item(**self.default_dir.as_dict()) self.items[ino].mtime = mtime else: self.items[ino] = self.default_dir self.parent[ino] = parent return ino def process_archive(self, archive_name, prefix=[]): """Build FUSE inode hierarchy from archive metadata """ self.file_versions = {} # for versions mode: original path -> version t0 = time.perf_counter() archive = Archive(self.repository_uncached, self.key, self.manifest, archive_name, consider_part_files=self.args.consider_part_files) strip_components = self.args.strip_components matcher = Archiver.build_matcher(self.args.patterns, self.args.paths) partial_extract = not matcher.empty() or strip_components hardlink_masters = {} if partial_extract else None def peek_and_store_hardlink_masters(item, matched): if (partial_extract and not matched and hardlinkable(item.mode) and item.get('hardlink_master', True) and 'source' not in item): hardlink_masters[item.get('path')] = (item.get('chunks'), None) filter = Archiver.build_filter(matcher, peek_and_store_hardlink_masters, strip_components) for item_inode, item in self.cache.iter_archive_items(archive.metadata.items, filter=filter, consider_part_files=self.args.consider_part_files): if strip_components: item.path = os.sep.join(item.path.split(os.sep)[strip_components:]) path = os.fsencode(item.path) is_dir = stat.S_ISDIR(item.mode) if is_dir: try: # This can happen if an archive was created with a command line like # $ borg create ... dir1/file dir1 # In this case the code below will have created a default_dir inode for dir1 already. inode = self._find_inode(path, prefix) except KeyError: pass else: self.items[inode] = item continue segments = prefix + path.split(b'/') parent = 1 for segment in segments[:-1]: parent = self.process_inner(segment, parent) self.process_leaf(segments[-1], item, parent, prefix, is_dir, item_inode, hardlink_masters, strip_components) duration = time.perf_counter() - t0 logger.debug('fuse: process_archive completed in %.1f s for archive %s', duration, archive.name) def process_leaf(self, name, item, parent, prefix, is_dir, item_inode, hardlink_masters, stripped_components): path = item.path del item.path # save some space hardlink_masters = hardlink_masters or {} def file_version(item, path): if 'chunks' in item: file_id = blake2b_128(path) current_version, previous_id = self.versions_index.get(file_id, (0, None)) chunk_ids = [chunk_id for chunk_id, _, _ in item.chunks] contents_id = blake2b_128(b''.join(chunk_ids)) if contents_id != previous_id: current_version += 1 self.versions_index[file_id] = current_version, contents_id return current_version def make_versioned_name(name, version, add_dir=False): if add_dir: # add intermediate directory with same name as filename path_fname = name.rsplit(b'/', 1) name += b'/' + path_fname[-1] # keep original extension at end to avoid confusing tools name, ext = os.path.splitext(name) version_enc = os.fsencode('.%05d' % version) return name + version_enc + ext if 'source' in item and hardlinkable(item.mode): source = os.sep.join(item.source.split(os.sep)[stripped_components:]) chunks, link_target = hardlink_masters.get(item.source, (None, source)) if link_target: # Hard link was extracted previously, just link link_target = os.fsencode(link_target) if self.versions: # adjust link target name with version version = self.file_versions[link_target] link_target = make_versioned_name(link_target, version, add_dir=True) try: inode = self._find_inode(link_target, prefix) except KeyError: logger.warning('Skipping broken hard link: %s -> %s', path, source) return item = self.get_item(inode) item.nlink = item.get('nlink', 1) + 1 self.items[inode] = item elif chunks is not None: # assign chunks to this item, since the item which had the chunks was not extracted item.chunks = chunks inode = item_inode self.items[inode] = item if hardlink_masters: # Update master entry with extracted item path, so that following hardlinks don't extract twice. hardlink_masters[item.source] = (None, path) else: inode = item_inode if self.versions and not is_dir: parent = self.process_inner(name, parent) enc_path = os.fsencode(path) version = file_version(item, enc_path) if version is not None: # regular file, with contents - maybe a hardlink master name = make_versioned_name(name, version) self.file_versions[enc_path] = version self.parent[inode] = parent if name: self.contents[parent][name] = inode def process_inner(self, name, parent_inode): dir = self.contents[parent_inode] if name in dir: inode = dir[name] else: inode = self._create_dir(parent_inode) if name: dir[name] = inode return inode def allocate_inode(self): self._inode_count += 1 return self._inode_count def statfs(self, ctx=None): 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 if hasattr(stat_, 'f_namemax'): # since llfuse 1.3.0 stat_.f_namemax = 255 # == NAME_MAX (depends on archive source OS / FS) return stat_ def get_item(self, inode): item = self._inode_cache.get(inode) if item is not None: return item try: # this is a cheap get-from-dictionary operation, no need to cache the result. return self.items[inode] except KeyError: # while self.cache does some internal caching, it has still quite some overhead, so we cache the result. item = self.cache.get(inode) self._inode_cache[inode] = item return item def _find_inode(self, path, prefix=[]): segments = prefix + path.split(b'/') inode = 1 for segment in segments: inode = self.contents[inode][segment] return inode def getattr(self, inode, ctx=None): item = self.get_item(inode) entry = llfuse.EntryAttributes() entry.st_ino = inode entry.generation = 0 entry.entry_timeout = 300 entry.attr_timeout = 300 entry.st_mode = item.mode & ~self.umask entry.st_nlink = item.get('nlink', 1) entry.st_uid = self.uid_forced if self.uid_forced is not None else item.uid if item.uid >= 0 else self.default_uid entry.st_gid = self.gid_forced if self.gid_forced is not None else item.gid if item.gid >= 0 else self.default_gid entry.st_rdev = item.get('rdev', 0) entry.st_size = item.get_size() entry.st_blksize = 512 entry.st_blocks = (entry.st_size + entry.st_blksize - 1) // entry.st_blksize # note: older archives only have mtime (not atime nor ctime) mtime_ns = item.mtime if have_fuse_xtime_ns: entry.st_mtime_ns = mtime_ns entry.st_atime_ns = item.get('atime', mtime_ns) entry.st_ctime_ns = item.get('ctime', mtime_ns) if have_fuse_birthtime_ns: entry.st_birthtime_ns = item.get('birthtime', mtime_ns) else: entry.st_mtime = mtime_ns / 1e9 entry.st_atime = item.get('atime', mtime_ns) / 1e9 entry.st_ctime = item.get('ctime', mtime_ns) / 1e9 if have_fuse_birthtime: entry.st_birthtime = item.get('birthtime', mtime_ns) / 1e9 return entry def listxattr(self, inode, ctx=None): item = self.get_item(inode) return item.get('xattrs', {}).keys() def getxattr(self, inode, name, ctx=None): item = self.get_item(inode) try: return item.get('xattrs', {})[name] or b'' except KeyError: raise llfuse.FUSEError(llfuse.ENOATTR) from None def _load_pending_archive(self, inode): # Check if this is an archive we need to load archive_name = self.pending_archives.pop(inode, None) if archive_name: self.process_archive(archive_name, [os.fsencode(archive_name)]) def lookup(self, parent_inode, name, ctx=None): self._load_pending_archive(parent_inode) if name == b'.': inode = parent_inode elif name == b'..': inode = self.parent[parent_inode] else: inode = self.contents[parent_inode].get(name) if not inode: raise llfuse.FUSEError(errno.ENOENT) return self.getattr(inode) def open(self, inode, flags, ctx=None): if not self.allow_damaged_files: item = self.get_item(inode) if 'chunks_healthy' in item: # Processed archive items don't carry the path anymore; for converting the inode # to the path we'd either have to store the inverse of the current structure, # or search the entire archive. So we just don't print it. It's easy to correlate anyway. logger.warning('File has damaged (all-zero) chunks. Try running borg check --repair. ' 'Mount with allow_damaged_files to read damaged files.') raise llfuse.FUSEError(errno.EIO) return inode def opendir(self, inode, ctx=None): self._load_pending_archive(inode) return inode def read(self, fh, offset, size): parts = [] item = self.get_item(fh) # optimize for linear reads: # we cache the chunk number and the in-file offset of the chunk in _last_pos[fh] chunk_no, chunk_offset = self._last_pos.get(fh, (0, 0)) if chunk_offset > offset: # this is not a linear read, so we lost track and need to start from beginning again... chunk_no, chunk_offset = (0, 0) offset -= chunk_offset chunks = item.chunks # note: using index iteration to avoid frequently copying big (sub)lists by slicing for idx in range(chunk_no, len(chunks)): id, s, csize = chunks[idx] if s < offset: offset -= s chunk_offset += s chunk_no += 1 continue n = min(size, s - offset) if id in self.data_cache: data = self.data_cache[id] if offset + n == len(data): # evict fully read chunk from cache del self.data_cache[id] else: data = self.key.decrypt(id, self.repository_uncached.get(id)) if offset + n < len(data): # chunk was only partially read, cache it self.data_cache[id] = data parts.append(data[offset:offset + n]) offset = 0 size -= n if not size: if fh in self._last_pos: self._last_pos.upd(fh, (chunk_no, chunk_offset)) else: self._last_pos[fh] = (chunk_no, chunk_offset) break return b''.join(parts) def readdir(self, fh, off): entries = [(b'.', fh), (b'..', self.parent[fh])] entries.extend(self.contents[fh].items()) for i, (name, inode) in enumerate(entries[off:], off): yield name, self.getattr(inode), i + 1 def readlink(self, inode, ctx=None): item = self.get_item(inode) return os.fsencode(item.source)
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