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.
# repair.py - functions for repository repair for mercurial
#
# Copyright 2005, 2006 Chris Mason <mason@suse.com>
# Copyright 2007 Matt Mackall
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
import changegroup, bookmarks
from node import nullrev, short
from i18n import _
import os
def _bundle(repo, bases, heads, node, suffix, compress=True):
"""create a bundle with the specified revisions as a backup"""
cg = repo.changegroupsubset(bases, heads, 'strip')
backupdir = repo.join("strip-backup")
if not os.path.isdir(backupdir):
os.mkdir(backupdir)
name = os.path.join(backupdir, "%s-%s.hg" % (short(node), suffix))
if compress:
bundletype = "HG10BZ"
else:
bundletype = "HG10UN"
return changegroup.writebundle(cg, name, bundletype)
def _collectfiles(repo, striprev):
"""find out the filelogs affected by the strip"""
files = set()
for x in xrange(striprev, len(repo)):
files.update(repo[x].files())
return sorted(files)
def _collectbrokencsets(repo, files, striprev):
"""return the changesets which will be broken by the truncation"""
def collectone(revlog):
startrev = count = len(revlog)
# find the truncation point of the revlog
for i in xrange(count):
lrev = revlog.linkrev(i)
if lrev >= striprev:
startrev = i + 1
break
# see if any revision after that point has a linkrev less than striprev
# (those will be broken by strip)
for i in xrange(startrev, count):
lrev = revlog.linkrev(i)
if lrev < striprev:
yield lrev
for rev in collectone(repo.manifest):
yield rev
for fname in files:
f = repo.file(fname)
for rev in collectone(f):
yield rev
def strip(ui, repo, node, backup="all"):
cl = repo.changelog
# TODO delete the undo files, and handle undo of merge sets
striprev = cl.rev(node)
keeppartialbundle = backup == 'strip'
# Some revisions with rev > striprev may not be descendants of striprev.
# We have to find these revisions and put them in a bundle, so that
# we can restore them after the truncations.
# To create the bundle we use repo.changegroupsubset which requires
# the list of heads and bases of the set of interesting revisions.
# (head = revision in the set that has no descendant in the set;
# base = revision in the set that has no ancestor in the set)
tostrip = set(cl.descendants(striprev))
tostrip.add(striprev)
files = _collectfiles(repo, striprev)
saverevs = set(_collectbrokencsets(repo, files, striprev))
# compute heads
saveheads = set(saverevs)
for r in xrange(striprev + 1, len(cl)):
if r not in tostrip:
saverevs.add(r)
saveheads.difference_update(cl.parentrevs(r))
saveheads.add(r)
saveheads = [cl.node(r) for r in saveheads]
# compute base nodes
if saverevs:
descendants = set(cl.descendants(*saverevs))
saverevs.difference_update(descendants)
savebases = [cl.node(r) for r in saverevs]
bm = repo._bookmarks
updatebm = []
for m in bm:
rev = repo[bm[m]].rev()
if rev in tostrip:
updatebm.append(m)
# create a changegroup for all the branches we need to keep
backupfile = None
if backup == "all":
backupfile = _bundle(repo, [node], cl.heads(), node, 'backup')
repo.ui.status(_("saved backup bundle to %s\n") % backupfile)
if saveheads or savebases:
# do not compress partial bundle if we remove it from disk later
chgrpfile = _bundle(repo, savebases, saveheads, node, 'temp',
compress=keeppartialbundle)
mfst = repo.manifest
tr = repo.transaction("strip")
offset = len(tr.entries)
try:
tr.startgroup()
cl.strip(striprev, tr)
mfst.strip(striprev, tr)
for fn in files:
repo.file(fn).strip(striprev, tr)
tr.endgroup()
try:
for i in xrange(offset, len(tr.entries)):
file, troffset, ignore = tr.entries[i]
repo.sopener(file, 'a').truncate(troffset)
tr.close()
except:
tr.abort()
raise
if saveheads or savebases:
ui.note(_("adding branch\n"))
f = open(chgrpfile, "rb")
gen = changegroup.readbundle(f, chgrpfile)
if not repo.ui.verbose:
# silence internal shuffling chatter
repo.ui.pushbuffer()
repo.addchangegroup(gen, 'strip', 'bundle:' + chgrpfile, True)
if not repo.ui.verbose:
repo.ui.popbuffer()
f.close()
if not keeppartialbundle:
os.unlink(chgrpfile)
for m in updatebm:
bm[m] = repo['.'].node()
bookmarks.write(repo)
except:
if backupfile:
ui.warn(_("strip failed, full bundle stored in '%s'\n")
% backupfile)
elif saveheads:
ui.warn(_("strip failed, partial bundle stored in '%s'\n")
% chgrpfile)
raise
repo.destroyed()