revlog: rewrite censoring logic
I was able to corrupt a revlog relatively easily with the existing
censoring code. The underlying problem is that the existing code
doesn't fully take delta chains into account. When copying revisions
that occur after the censored revision, the delta base can refer
to a censored revision. Then at read time, things blow up due to the
revision data not being a compressed delta.
This commit rewrites the revlog censoring code to take a higher-level
approach. We now create a new revlog instance pointing at temp files.
We iterate through each revision in the source revlog and insert
those revisions into the new revlog, replacing the censored revision's
data along the way.
The new implementation isn't as efficient as the old one. This is
because it will fully engage delta computation on insertion. But I
don't think it matters.
The new implementation is a bit hacky because it attempts to reload
the revlog instance with a new revlog index/data file. This is fragile.
But this is needed because the index (which could be backed by C) would
have a cached copy of the old, possibly changed data and that could
lead to problems accessing index or revision data later.
One benefit of the new approach is that we integrate with the
transaction. The old revlog is backed up and if the transaction is
rolled back, the original revlog is restored.
As part of this, we had to teach the transaction about the store
vfs. I'm not super keen about this. But this was the easiest way
to hook things up to the transaction. We /could/ just ignore the
transaction like we were doing before. But any file mutation should
be governed by transaction semantics, including undo during rollback.
Differential Revision: https://phab.mercurial-scm.org/D4869
# This test verifies the conformance of various classes to various
# storage interfaces.
from __future__ import absolute_import
import silenttestrunner
from mercurial import (
error,
filelog,
revlog,
transaction,
ui as uimod,
vfs as vfsmod,
)
from mercurial.testing import (
storage as storagetesting,
)
STATE = {
'lastindex': 0,
'ui': uimod.ui(),
'vfs': vfsmod.vfs(b'.', realpath=True),
}
def makefilefn(self):
"""Factory for filelog instances."""
fl = filelog.filelog(STATE['vfs'], b'filelog-%d' % STATE['lastindex'])
STATE['lastindex'] += 1
return fl
def maketransaction(self):
vfsmap = {'plain': STATE['vfs'], 'store': STATE['vfs']}
return transaction.transaction(STATE['ui'].warn, STATE['vfs'], vfsmap,
b'journal', b'undo')
def addrawrevision(self, fl, tr, node, p1, p2, linkrev, rawtext=None,
delta=None, censored=False, ellipsis=False, extstored=False):
flags = 0
if censored:
flags |= revlog.REVIDX_ISCENSORED
if ellipsis:
flags |= revlog.REVIDX_ELLIPSIS
if extstored:
flags |= revlog.REVIDX_EXTSTORED
if rawtext is not None:
fl._revlog.addrawrevision(rawtext, tr, linkrev, p1, p2, node, flags)
elif delta is not None:
raise error.Abort('support for storing raw deltas not yet supported')
else:
raise error.Abort('must supply rawtext or delta arguments')
# We may insert bad data. Clear caches to prevent e.g. cache hits to
# bypass hash verification.
fl._revlog.clearcaches()
# Assigning module-level attributes that inherit from unittest.TestCase
# is all that is needed to register tests.
filelogindextests = storagetesting.makeifileindextests(makefilefn,
maketransaction,
addrawrevision)
filelogdatatests = storagetesting.makeifiledatatests(makefilefn,
maketransaction,
addrawrevision)
filelogmutationtests = storagetesting.makeifilemutationtests(makefilefn,
maketransaction,
addrawrevision)
if __name__ == '__main__':
silenttestrunner.main(__name__)