path: root/rdiff-backup/src/Hardlink.py

# Copyright 2002 Ben Escoto
#
# This file is part of rdiff-backup.
#
# rdiff-backup 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, Inc., 675 Mass Ave, Cambridge MA
# 02139, USA; either version 2 of the License, or (at your option) any
# later version; incorporated herein by reference.

"""Preserve and restore hard links

If the preserve_hardlinks option is selected, linked files in the
source directory will be linked in the mirror directory.  Linked files
are treated like any other with respect to incrementing, but a
database of all links will be recorded at each session, so linked
files can still be restored from the increments.

All these functions are meant to be executed on the destination
side.  The source side should only transmit inode information.

"""

from __future__ import generators
import cPickle


# In all of these lists of indicies are the values.  The keys in
# _inode_ ones are (inode, devloc) pairs.
_src_inode_indicies = {}
_dest_inode_indicies = {}

# The keys for these two are just indicies.  They share values
# with the earlier dictionaries.
_src_index_indicies = {}
_dest_index_indicies = {}

# When a linked file is restored, its path is added to this dict,
# so it can be found when later paths being restored are linked to
# it.
_restore_index_path = {}

def get_inode_key(rorp):
	"""Return rorp's key for _inode_ dictionaries"""
	return (rorp.getinode(), rorp.getdevloc())

def get_indicies(rorp, source):
	"""Return a list of similarly linked indicies, using rorp's index"""
	if source: dict = _src_index_indicies
	else: dict = _dest_index_indicies
	try: return dict[rorp.index]
	except KeyError: return []

def add_rorp(rorp, source):
	"""Process new rorp and update hard link dictionaries

	First enter it into src_inode_indicies.  If we have already
	seen all the hard links, then we can delete the entry.
	Everything must stay recorded in src_index_indicies though.

	"""
	if not rorp.isreg() or rorp.getnumlinks() < 2: return

	if source:
		inode_dict, index_dict = _src_inode_indicies, _src_index_indicies
	else: inode_dict, index_dict = _dest_inode_indicies, _dest_index_indicies

	rp_inode_key = get_inode_key(rorp)
	if inode_dict.has_key(rp_inode_key):
		index_list = inode_dict[rp_inode_key]
		index_list.append(rorp.index)
		if len(index_list) == rorp.getnumlinks():
			del inode_dict[rp_inode_key]
	else: # make new entry in both src dicts
		index_list = [rorp.index]
		inode_dict[rp_inode_key] = index_list
	index_dict[rorp.index] = index_list

def add_rorp_iter(iter, source):
	"""Return new rorp iterator like iter that add_rorp's first"""
	for rorp in iter:
		add_rorp(rorp, source)
		yield rorp

def rorp_eq(src_rorp, dest_rorp):
	"""Compare hardlinked for equality

	Two files may otherwise seem equal but be hardlinked in
	different ways.  This function considers them equal enough if
	they have been hardlinked correctly to the previously seen
	indicies.

	"""
	if not src_rorp.index == dest_rorp.index: return None
	if (not src_rorp.isreg() or not dest_rorp.isreg() or
		src_rorp.getnumlinks() == dest_rorp.getnumlinks() == 1):
		return 1 # Hard links don't apply

	src_index_list = get_indicies(src_rorp, 1)
	dest_index_list = get_indicies(dest_rorp, None)

	# If a list only has one element, then it is only hardlinked
	# to itself so far, so that is not a genuine difference yet.
	if not src_index_list or len(src_index_list) == 1:
		return not dest_index_list or len(dest_index_list) == 1
	if not dest_index_list or len(dest_index_list) == 1: return None

	# Both index lists exist and are non-empty
	return src_index_list == dest_index_list # they are always sorted

def islinked(rorp):
	"""True if rorp's index is already linked to something on src side"""
	return len(get_indicies(rorp, 1)) >= 2

def restore_link(index, rpath):
	"""Restores a linked file by linking it

	When restoring, all the hardlink data is already present, and
	we can only link to something already written.  In either
	case, add to the _restore_index_path dict, so we know later
	that the file is available for hard
	linking.

	Returns true if succeeded in creating rpath, false if must
	restore rpath normally.

	"""
	if index not in _src_index_indicies: return None
	for linked_index in _src_index_indicies[index]:
		if linked_index in _restore_index_path:
			srcpath = _restore_index_path[linked_index]
			Log("Restoring %s by hard linking to %s" %
				(rpath.path, srcpath), 6)
			rpath.hardlink(srcpath)
			return 1
	_restore_index_path[index] = rpath.path
	return None

def link_rp(src_rorp, dest_rpath, dest_root = None):
	"""Make dest_rpath into a link analogous to that of src_rorp"""
	if not dest_root: dest_root = dest_rpath # use base of dest_rpath
	dest_link_rpath = RPath(dest_root.conn, dest_root.base,
							get_indicies(src_rorp, 1)[0])
	dest_rpath.hardlink(dest_link_rpath.path)

def write_linkdict(rpath, dict, compress = None):
	"""Write link data to the rbdata dir

	It is stored as the a big pickled dictionary dated to match
	the current hardlinks.

	"""
	assert (Globals.isbackup_writer and
			rpath.conn is Globals.local_connection)
	tf = TempFileManager.new(rpath)
	def init():
		fp = tf.open("wb", compress)
		cPickle.dump(dict, fp)
		assert not fp.close()
		tf.setdata()
	Robust.make_tf_robustaction(init, (tf,), (rpath,)).execute()

def get_linkrp(data_rpath, time, prefix):
	"""Return RPath of linkdata, or None if cannot find"""
	for rp in map(data_rpath.append, data_rpath.listdir()):
		if (rp.isincfile() and rp.getincbase_str() == prefix and
			(rp.getinctype() == 'snapshot' or rp.getinctype() == 'data')
			and Time.stringtotime(rp.getinctime()) == time):
			return rp
	return None

def get_linkdata(data_rpath, time, prefix = 'hardlink_data'):
	"""Return index dictionary written by write_linkdata at time"""
	rp = get_linkrp(data_rpath, time, prefix)
	if not rp: return None
	fp = rp.open("rb", rp.isinccompressed())
	index_dict = cPickle.load(fp)
	assert not fp.close()
	return index_dict

def final_writedata():
	"""Write final checkpoint data to rbdir after successful backup"""
	global final_inc
	if _src_index_indicies:
		Log("Writing hard link data", 6)
		if Globals.compression:
			final_inc = Globals.rbdir.append("hardlink_data.%s.data.gz" %
											 Time.curtimestr)
		else: final_inc = Globals.rbdir.append("hardlink_data.%s.data" %
											   Time.curtimestr)
		write_linkdict(final_inc, _src_index_indicies, Globals.compression)
	else: # no hardlinks, so writing unnecessary
		final_inc = None

def retrieve_final(time):
	"""Set source index dictionary from hardlink_data file if avail"""
	global _src_index_indicies
	hd = get_linkdata(Globals.rbdir, time)
	if hd is None: return None
	_src_index_indicies = hd
	return 1

def final_checkpoint(data_rpath):
	"""Write contents of the four dictionaries to the data dir

	If rdiff-backup receives a fatal error, it may still be able
	to save the contents of the four hard link dictionaries.
	Because these dictionaries may be big, they are not saved
	after every 20 seconds or whatever, but just at the end.

	"""
	Log("Writing intermediate hard link data to disk", 2)
	src_inode_rp = data_rpath.append("hardlink_source_inode_checkpoint."
									 "%s.data" % Time.curtimestr)
	src_index_rp = data_rpath.append("hardlink_source_index_checkpoint."
									 "%s.data" % Time.curtimestr)
	dest_inode_rp = data_rpath.append("hardlink_dest_inode_checkpoint."
									  "%s.data" % Time.curtimestr)
	dest_index_rp = data_rpath.append("hardlink_dest_index_checkpoint."
									  "%s.data" % Time.curtimestr)
	for (rp, dict) in ((src_inode_rp, _src_inode_indicies),
					   (src_index_rp, _src_index_indicies),
					   (dest_inode_rp, _dest_inode_indicies),
					   (dest_index_rp, _dest_index_indicies)):
		write_linkdict(rp, dict)

def retrieve_checkpoint(data_rpath, time):
	"""Retrieve hardlink data from final checkpoint

	Return true if the retrieval worked, false otherwise.

	"""
	global _src_inode_indicies, _src_index_indicies
	global _dest_inode_indicies, _dest_index_indicies
	try:
		src_inode = get_linkdata(data_rpath, time,
								 "hardlink_source_inode_checkpoint")
		src_index = get_linkdata(data_rpath, time,
								 "hardlink_source_index_checkpoint")
		dest_inode = get_linkdata(data_rpath, time,
								  "hardlink_dest_inode_checkpoint")
		dest_index = get_linkdata(data_rpath, time,
								  "hardlink_dest_index_checkpoint")
	except cPickle.UnpicklingError:
		Log("Unpickling Error", 2)
		return None
	if (src_inode is None or src_index is None or
		dest_inode is None or dest_index is None): return None
	_src_inode_indicies, _src_index_indicies = src_inode, src_index
	_dest_inode_indicies, _dest_index_indicies = dest_inode, dest_index
	return 1

def remove_all_checkpoints():
	"""Remove all hardlink checkpoint information from directory"""
	prefix_list = ["hardlink_source_inode_checkpoint",
				   "hardlink_source_index_checkpoint",
				   "hardlink_dest_inode_checkpoint",
				   "hardlink_dest_index_checkpoint"]
	for rp in map(Globals.rbdir.append, Globals.rbdir.listdir()):
		if (rp.isincfile() and rp.getincbase_str() in prefix_list and
			(rp.getinctype() == 'snapshot' or rp.getinctype() == 'data')):
			rp.delete()


from log import *
from robust import *
from rpath import *
import Globals, Time