dirstate: avoid a race with multiple commits in the same process
(issue2264, issue2516)
The race happens when two commits in a row change the same file
without changing its size, *if* those two commits happen in the same
second in the same process while holding the same repo lock. For
example:
commit 1:
M a
M b
commit 2: # same process, same second, same repo lock
M b # modify b without changing its size
M c
This first manifested in transplant, which is the most common way to
do multiple commits in the same process. But it can manifest in any
script or extension that does multiple commits under the same repo
lock. (Thus, the test script tests both transplant and a custom script.)
The problem was that dirstate.status() failed to notice the change to
b when localrepo is about to do the second commit, meaning that change
gets left in the working directory. In the context of transplant, that
means either a crash ("RuntimeError: nothing committed after
transplant") or a silently inaccurate transplant, depending on whether
any other files were modified by the second transplanted changeset.
The fix is to make status() work a little harder when we have
previously marked files as clean (state 'normal') in the same process.
Specifically, dirstate.normal() adds files to self._lastnormal, and
other state-changing methods remove them. Then dirstate.status() puts
any files in self._lastnormal into state 'lookup', which will make
localrepository.status() read file contents to see if it has really
changed. So we pay a small performance penalty for the second (and
subsequent) commits in the same process, without affecting the common
case. Anything that does lots of status updates and checks in the
same process could suffer a performance hit.
Incidentally, there is a simpler fix: call dirstate.normallookup() on
every file updated by commit() at the end of the commit. The trouble
with that solution is that it imposes a performance penalty on the
common case: it means the next status-dependent hg command after every
"hg commit" will be a little bit slower. The patch here is more
complex, but only affects performance for the uncommon case.
# dirstate.py - working directory tracking for mercurial
#
# Copyright 2005-2007 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from node import nullid
from i18n import _
import util, ignore, osutil, parsers, encoding
import struct, os, stat, errno
import cStringIO
_format = ">cllll"
propertycache = util.propertycache
def _finddirs(path):
pos = path.rfind('/')
while pos != -1:
yield path[:pos]
pos = path.rfind('/', 0, pos)
def _incdirs(dirs, path):
for base in _finddirs(path):
if base in dirs:
dirs[base] += 1
return
dirs[base] = 1
def _decdirs(dirs, path):
for base in _finddirs(path):
if dirs[base] > 1:
dirs[base] -= 1
return
del dirs[base]
class dirstate(object):
def __init__(self, opener, ui, root, validate):
'''Create a new dirstate object.
opener is an open()-like callable that can be used to open the
dirstate file; root is the root of the directory tracked by
the dirstate.
'''
self._opener = opener
self._validate = validate
self._root = root
self._rootdir = os.path.join(root, '')
self._dirty = False
self._dirtypl = False
self._lastnormal = set() # files believed to be normal
self._ui = ui
@propertycache
def _map(self):
'''Return the dirstate contents as a map from filename to
(state, mode, size, time).'''
self._read()
return self._map
@propertycache
def _copymap(self):
self._read()
return self._copymap
@propertycache
def _foldmap(self):
f = {}
for name in self._map:
f[os.path.normcase(name)] = name
return f
@propertycache
def _branch(self):
try:
return self._opener("branch").read().strip() or "default"
except IOError:
return "default"
@propertycache
def _pl(self):
try:
fp = self._opener("dirstate")
st = fp.read(40)
fp.close()
l = len(st)
if l == 40:
return st[:20], st[20:40]
elif l > 0 and l < 40:
raise util.Abort(_('working directory state appears damaged!'))
except IOError, err:
if err.errno != errno.ENOENT:
raise
return [nullid, nullid]
@propertycache
def _dirs(self):
dirs = {}
for f, s in self._map.iteritems():
if s[0] != 'r':
_incdirs(dirs, f)
return dirs
@propertycache
def _ignore(self):
files = [self._join('.hgignore')]
for name, path in self._ui.configitems("ui"):
if name == 'ignore' or name.startswith('ignore.'):
files.append(util.expandpath(path))
return ignore.ignore(self._root, files, self._ui.warn)
@propertycache
def _slash(self):
return self._ui.configbool('ui', 'slash') and os.sep != '/'
@propertycache
def _checklink(self):
return util.checklink(self._root)
@propertycache
def _checkexec(self):
return util.checkexec(self._root)
@propertycache
def _checkcase(self):
return not util.checkcase(self._join('.hg'))
def _join(self, f):
# much faster than os.path.join()
# it's safe because f is always a relative path
return self._rootdir + f
def flagfunc(self, fallback):
if self._checklink:
if self._checkexec:
def f(x):
p = self._join(x)
if os.path.islink(p):
return 'l'
if util.is_exec(p):
return 'x'
return ''
return f
def f(x):
if os.path.islink(self._join(x)):
return 'l'
if 'x' in fallback(x):
return 'x'
return ''
return f
if self._checkexec:
def f(x):
if 'l' in fallback(x):
return 'l'
if util.is_exec(self._join(x)):
return 'x'
return ''
return f
return fallback
def getcwd(self):
cwd = os.getcwd()
if cwd == self._root:
return ''
# self._root ends with a path separator if self._root is '/' or 'C:\'
rootsep = self._root
if not util.endswithsep(rootsep):
rootsep += os.sep
if cwd.startswith(rootsep):
return cwd[len(rootsep):]
else:
# we're outside the repo. return an absolute path.
return cwd
def pathto(self, f, cwd=None):
if cwd is None:
cwd = self.getcwd()
path = util.pathto(self._root, cwd, f)
if self._slash:
return util.normpath(path)
return path
def __getitem__(self, key):
'''Return the current state of key (a filename) in the dirstate.
States are:
n normal
m needs merging
r marked for removal
a marked for addition
? not tracked
'''
return self._map.get(key, ("?",))[0]
def __contains__(self, key):
return key in self._map
def __iter__(self):
for x in sorted(self._map):
yield x
def parents(self):
return [self._validate(p) for p in self._pl]
def branch(self):
return encoding.tolocal(self._branch)
def setparents(self, p1, p2=nullid):
self._dirty = self._dirtypl = True
self._pl = p1, p2
def setbranch(self, branch):
if branch in ['tip', '.', 'null']:
raise util.Abort(_('the name \'%s\' is reserved') % branch)
self._branch = encoding.fromlocal(branch)
self._opener("branch", "w").write(self._branch + '\n')
def _read(self):
self._map = {}
self._copymap = {}
try:
st = self._opener("dirstate").read()
except IOError, err:
if err.errno != errno.ENOENT:
raise
return
if not st:
return
p = parsers.parse_dirstate(self._map, self._copymap, st)
if not self._dirtypl:
self._pl = p
def invalidate(self):
for a in ("_map", "_copymap", "_foldmap", "_branch", "_pl", "_dirs",
"_ignore"):
if a in self.__dict__:
delattr(self, a)
self._dirty = False
def copy(self, source, dest):
"""Mark dest as a copy of source. Unmark dest if source is None."""
if source == dest:
return
self._dirty = True
if source is not None:
self._copymap[dest] = source
elif dest in self._copymap:
del self._copymap[dest]
def copied(self, file):
return self._copymap.get(file, None)
def copies(self):
return self._copymap
def _droppath(self, f):
if self[f] not in "?r" and "_dirs" in self.__dict__:
_decdirs(self._dirs, f)
def _addpath(self, f, check=False):
oldstate = self[f]
if check or oldstate == "r":
if '\r' in f or '\n' in f:
raise util.Abort(
_("'\\n' and '\\r' disallowed in filenames: %r") % f)
if f in self._dirs:
raise util.Abort(_('directory %r already in dirstate') % f)
# shadows
for d in _finddirs(f):
if d in self._dirs:
break
if d in self._map and self[d] != 'r':
raise util.Abort(
_('file %r in dirstate clashes with %r') % (d, f))
if oldstate in "?r" and "_dirs" in self.__dict__:
_incdirs(self._dirs, f)
def normal(self, f):
'''Mark a file normal and clean.'''
self._dirty = True
self._addpath(f)
s = os.lstat(self._join(f))
self._map[f] = ('n', s.st_mode, s.st_size, int(s.st_mtime))
if f in self._copymap:
del self._copymap[f]
# Right now, this file is clean: but if some code in this
# process modifies it without changing its size before the clock
# ticks over to the next second, then it won't be clean anymore.
# So make sure that status() will look harder at it.
self._lastnormal.add(f)
def normallookup(self, f):
'''Mark a file normal, but possibly dirty.'''
if self._pl[1] != nullid and f in self._map:
# if there is a merge going on and the file was either
# in state 'm' (-1) or coming from other parent (-2) before
# being removed, restore that state.
entry = self._map[f]
if entry[0] == 'r' and entry[2] in (-1, -2):
source = self._copymap.get(f)
if entry[2] == -1:
self.merge(f)
elif entry[2] == -2:
self.otherparent(f)
if source:
self.copy(source, f)
return
if entry[0] == 'm' or entry[0] == 'n' and entry[2] == -2:
return
self._dirty = True
self._addpath(f)
self._map[f] = ('n', 0, -1, -1)
if f in self._copymap:
del self._copymap[f]
self._lastnormal.discard(f)
def otherparent(self, f):
'''Mark as coming from the other parent, always dirty.'''
if self._pl[1] == nullid:
raise util.Abort(_("setting %r to other parent "
"only allowed in merges") % f)
self._dirty = True
self._addpath(f)
self._map[f] = ('n', 0, -2, -1)
if f in self._copymap:
del self._copymap[f]
self._lastnormal.discard(f)
def add(self, f):
'''Mark a file added.'''
self._dirty = True
self._addpath(f, True)
self._map[f] = ('a', 0, -1, -1)
if f in self._copymap:
del self._copymap[f]
self._lastnormal.discard(f)
def remove(self, f):
'''Mark a file removed.'''
self._dirty = True
self._droppath(f)
size = 0
if self._pl[1] != nullid and f in self._map:
# backup the previous state
entry = self._map[f]
if entry[0] == 'm': # merge
size = -1
elif entry[0] == 'n' and entry[2] == -2: # other parent
size = -2
self._map[f] = ('r', 0, size, 0)
if size == 0 and f in self._copymap:
del self._copymap[f]
self._lastnormal.discard(f)
def merge(self, f):
'''Mark a file merged.'''
self._dirty = True
s = os.lstat(self._join(f))
self._addpath(f)
self._map[f] = ('m', s.st_mode, s.st_size, int(s.st_mtime))
if f in self._copymap:
del self._copymap[f]
self._lastnormal.discard(f)
def forget(self, f):
'''Forget a file.'''
self._dirty = True
try:
self._droppath(f)
del self._map[f]
except KeyError:
self._ui.warn(_("not in dirstate: %s\n") % f)
self._lastnormal.discard(f)
def _normalize(self, path, knownpath):
norm_path = os.path.normcase(path)
fold_path = self._foldmap.get(norm_path, None)
if fold_path is None:
if knownpath or not os.path.lexists(os.path.join(self._root, path)):
fold_path = path
else:
fold_path = self._foldmap.setdefault(norm_path,
util.fspath(path, self._root))
return fold_path
def clear(self):
self._map = {}
if "_dirs" in self.__dict__:
delattr(self, "_dirs")
self._copymap = {}
self._pl = [nullid, nullid]
self._dirty = True
def rebuild(self, parent, files):
self.clear()
for f in files:
if 'x' in files.flags(f):
self._map[f] = ('n', 0777, -1, 0)
else:
self._map[f] = ('n', 0666, -1, 0)
self._pl = (parent, nullid)
self._dirty = True
def write(self):
if not self._dirty:
return
st = self._opener("dirstate", "w", atomictemp=True)
# use the modification time of the newly created temporary file as the
# filesystem's notion of 'now'
now = int(util.fstat(st).st_mtime)
cs = cStringIO.StringIO()
copymap = self._copymap
pack = struct.pack
write = cs.write
write("".join(self._pl))
for f, e in self._map.iteritems():
if e[0] == 'n' and e[3] == now:
# The file was last modified "simultaneously" with the current
# write to dirstate (i.e. within the same second for file-
# systems with a granularity of 1 sec). This commonly happens
# for at least a couple of files on 'update'.
# The user could change the file without changing its size
# within the same second. Invalidate the file's stat data in
# dirstate, forcing future 'status' calls to compare the
# contents of the file. This prevents mistakenly treating such
# files as clean.
e = (e[0], 0, -1, -1) # mark entry as 'unset'
self._map[f] = e
if f in copymap:
f = "%s\0%s" % (f, copymap[f])
e = pack(_format, e[0], e[1], e[2], e[3], len(f))
write(e)
write(f)
st.write(cs.getvalue())
st.rename()
self._dirty = self._dirtypl = False
def _dirignore(self, f):
if f == '.':
return False
if self._ignore(f):
return True
for p in _finddirs(f):
if self._ignore(p):
return True
return False
def walk(self, match, subrepos, unknown, ignored):
'''
Walk recursively through the directory tree, finding all files
matched by match.
Return a dict mapping filename to stat-like object (either
mercurial.osutil.stat instance or return value of os.stat()).
'''
def fwarn(f, msg):
self._ui.warn('%s: %s\n' % (self.pathto(f), msg))
return False
def badtype(mode):
kind = _('unknown')
if stat.S_ISCHR(mode):
kind = _('character device')
elif stat.S_ISBLK(mode):
kind = _('block device')
elif stat.S_ISFIFO(mode):
kind = _('fifo')
elif stat.S_ISSOCK(mode):
kind = _('socket')
elif stat.S_ISDIR(mode):
kind = _('directory')
return _('unsupported file type (type is %s)') % kind
ignore = self._ignore
dirignore = self._dirignore
if ignored:
ignore = util.never
dirignore = util.never
elif not unknown:
# if unknown and ignored are False, skip step 2
ignore = util.always
dirignore = util.always
matchfn = match.matchfn
badfn = match.bad
dmap = self._map
normpath = util.normpath
listdir = osutil.listdir
lstat = os.lstat
getkind = stat.S_IFMT
dirkind = stat.S_IFDIR
regkind = stat.S_IFREG
lnkkind = stat.S_IFLNK
join = self._join
work = []
wadd = work.append
exact = skipstep3 = False
if matchfn == match.exact: # match.exact
exact = True
dirignore = util.always # skip step 2
elif match.files() and not match.anypats(): # match.match, no patterns
skipstep3 = True
if self._checkcase:
normalize = self._normalize
skipstep3 = False
else:
normalize = lambda x, y: x
files = sorted(match.files())
subrepos.sort()
i, j = 0, 0
while i < len(files) and j < len(subrepos):
subpath = subrepos[j] + "/"
if files[i] < subpath:
i += 1
continue
while i < len(files) and files[i].startswith(subpath):
del files[i]
j += 1
if not files or '.' in files:
files = ['']
results = dict.fromkeys(subrepos)
results['.hg'] = None
# step 1: find all explicit files
for ff in files:
nf = normalize(normpath(ff), False)
if nf in results:
continue
try:
st = lstat(join(nf))
kind = getkind(st.st_mode)
if kind == dirkind:
skipstep3 = False
if nf in dmap:
#file deleted on disk but still in dirstate
results[nf] = None
match.dir(nf)
if not dirignore(nf):
wadd(nf)
elif kind == regkind or kind == lnkkind:
results[nf] = st
else:
badfn(ff, badtype(kind))
if nf in dmap:
results[nf] = None
except OSError, inst:
if nf in dmap: # does it exactly match a file?
results[nf] = None
else: # does it match a directory?
prefix = nf + "/"
for fn in dmap:
if fn.startswith(prefix):
match.dir(nf)
skipstep3 = False
break
else:
badfn(ff, inst.strerror)
# step 2: visit subdirectories
while work:
nd = work.pop()
skip = None
if nd == '.':
nd = ''
else:
skip = '.hg'
try:
entries = listdir(join(nd), stat=True, skip=skip)
except OSError, inst:
if inst.errno == errno.EACCES:
fwarn(nd, inst.strerror)
continue
raise
for f, kind, st in entries:
nf = normalize(nd and (nd + "/" + f) or f, True)
if nf not in results:
if kind == dirkind:
if not ignore(nf):
match.dir(nf)
wadd(nf)
if nf in dmap and matchfn(nf):
results[nf] = None
elif kind == regkind or kind == lnkkind:
if nf in dmap:
if matchfn(nf):
results[nf] = st
elif matchfn(nf) and not ignore(nf):
results[nf] = st
elif nf in dmap and matchfn(nf):
results[nf] = None
# step 3: report unseen items in the dmap hash
if not skipstep3 and not exact:
visit = sorted([f for f in dmap if f not in results and matchfn(f)])
for nf, st in zip(visit, util.statfiles([join(i) for i in visit])):
if not st is None and not getkind(st.st_mode) in (regkind, lnkkind):
st = None
results[nf] = st
for s in subrepos:
del results[s]
del results['.hg']
return results
def status(self, match, subrepos, ignored, clean, unknown):
'''Determine the status of the working copy relative to the
dirstate and return a tuple of lists (unsure, modified, added,
removed, deleted, unknown, ignored, clean), where:
unsure:
files that might have been modified since the dirstate was
written, but need to be read to be sure (size is the same
but mtime differs)
modified:
files that have definitely been modified since the dirstate
was written (different size or mode)
added:
files that have been explicitly added with hg add
removed:
files that have been explicitly removed with hg remove
deleted:
files that have been deleted through other means ("missing")
unknown:
files not in the dirstate that are not ignored
ignored:
files not in the dirstate that are ignored
(by _dirignore())
clean:
files that have definitely not been modified since the
dirstate was written
'''
listignored, listclean, listunknown = ignored, clean, unknown
lookup, modified, added, unknown, ignored = [], [], [], [], []
removed, deleted, clean = [], [], []
dmap = self._map
ladd = lookup.append # aka "unsure"
madd = modified.append
aadd = added.append
uadd = unknown.append
iadd = ignored.append
radd = removed.append
dadd = deleted.append
cadd = clean.append
lastnormal = self._lastnormal.__contains__
lnkkind = stat.S_IFLNK
for fn, st in self.walk(match, subrepos, listunknown,
listignored).iteritems():
if fn not in dmap:
if (listignored or match.exact(fn)) and self._dirignore(fn):
if listignored:
iadd(fn)
elif listunknown:
uadd(fn)
continue
state, mode, size, time = dmap[fn]
if not st and state in "nma":
dadd(fn)
elif state == 'n':
# The "mode & lnkkind != lnkkind or self._checklink"
# lines are an expansion of "islink => checklink"
# where islink means "is this a link?" and checklink
# means "can we check links?".
if (size >= 0 and
(size != st.st_size
or ((mode ^ st.st_mode) & 0100 and self._checkexec))
and (mode & lnkkind != lnkkind or self._checklink)
or size == -2 # other parent
or fn in self._copymap):
madd(fn)
elif (time != int(st.st_mtime)
and (mode & lnkkind != lnkkind or self._checklink)):
ladd(fn)
elif lastnormal(fn):
# If previously in this process we recorded that
# this file is clean, think twice: intervening code
# may have modified the file in the same second
# without changing its size. So force caller to
# check file contents. Because we're not updating
# self._map, this only affects the current process.
# That should be OK because this mainly affects
# multiple commits in the same process, and each
# commit by definition makes the committed files
# clean.
ladd(fn)
elif listclean:
cadd(fn)
elif state == 'm':
madd(fn)
elif state == 'a':
aadd(fn)
elif state == 'r':
radd(fn)
return (lookup, modified, added, removed, deleted, unknown, ignored,
clean)