##// END OF EJS Templates
revlog: add a mechanism to verify expected file position before appending...
revlog: add a mechanism to verify expected file position before appending If someone uses `hg debuglocks`, or some non-hg process writes to the .hg directory without respecting the locks, or if the repo's on a networked filesystem, it's possible for the revlog code to write out corrupted data. The form of this corruption can vary depending on what data was written and how that happened. We are in the "networked filesystem" case (though I've had users also do this to themselves with the "`hg debuglocks`" scenario), and most often see this with the changelog. What ends up happening is we produce two items (let's call them rev1 and rev2) in the .i file that have the same linkrev, baserev, and offset into the .d file, while the data in the .d file is appended properly. rev2's compressed_size is accurate for rev2, but when we go to decompress the data in the .d file, we use the offset that's recorded in the index file, which is the same as rev1, and attempt to decompress rev2.compressed_size bytes of rev1's data. This usually does not succeed. :) When using inline data, this also fails, though I haven't investigated why too closely. This shows up as a "patch decode" error. I believe what's happening there is that we're basically ignoring the offset field, getting the data properly, but since baserev != rev, it thinks this is a delta based on rev (instead of a full text) and can't actually apply it as such. For now, I'm going to make this an optional component and default it to entirely off. I may increase the default severity of this in the future, once I've enabled it for my users and we gain more experience with it. Luckily, most of my users have a versioned filesystem and can roll back to before the corruption has been written, it's just a hassle to do so and not everyone knows how (so it's a support burden). Users on other filesystems will not have that luxury, and this can cause them to have a corrupted repository that they are unlikely to know how to resolve, and they'll see this as a data-loss event. Refusing to create the corruption is a much better user experience. This mechanism is not perfect. There may be false-negatives (racy writes that are not detected). There should not be any false-positives (non-racy writes that are detected as such). This is not a mechanism that makes putting a repo on a networked filesystem "safe" or "supported", just *less* likely to cause corruption. Differential Revision: https://phab.mercurial-scm.org/D9952

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transport.py
158 lines | 5.2 KiB | text/x-python | PythonLexer
# -*- coding: utf-8 -*-
# Copyright (C) 2007 Daniel Holth <dholth@fastmail.fm>
# This is a stripped-down version of the original bzr-svn transport.py,
# Copyright (C) 2006 Jelmer Vernooij <jelmer@samba.org>
# This program 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; either version 2 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.
from __future__ import absolute_import
import svn.client
import svn.core
import svn.ra
Pool = svn.core.Pool
SubversionException = svn.core.SubversionException
from mercurial.pycompat import getattr
from mercurial import util
# Some older versions of the Python bindings need to be
# explicitly initialized. But what we want to do probably
# won't work worth a darn against those libraries anyway!
svn.ra.initialize()
svn_config = None
def _create_auth_baton(pool):
"""Create a Subversion authentication baton. """
import svn.client
# Give the client context baton a suite of authentication
# providers.h
providers = [
svn.client.get_simple_provider(pool),
svn.client.get_username_provider(pool),
svn.client.get_ssl_client_cert_file_provider(pool),
svn.client.get_ssl_client_cert_pw_file_provider(pool),
svn.client.get_ssl_server_trust_file_provider(pool),
]
# Platform-dependent authentication methods
getprovider = getattr(
svn.core, 'svn_auth_get_platform_specific_provider', None
)
if getprovider:
# Available in svn >= 1.6
for name in (b'gnome_keyring', b'keychain', b'kwallet', b'windows'):
for type in (b'simple', b'ssl_client_cert_pw', b'ssl_server_trust'):
p = getprovider(name, type, pool)
if p:
providers.append(p)
else:
if util.safehasattr(svn.client, b'get_windows_simple_provider'):
providers.append(svn.client.get_windows_simple_provider(pool))
return svn.core.svn_auth_open(providers, pool)
class NotBranchError(SubversionException):
pass
class SvnRaTransport(object):
"""
Open an ra connection to a Subversion repository.
"""
def __init__(self, url=b"", ra=None):
self.pool = Pool()
self.svn_url = url
self.username = b''
self.password = b''
# Only Subversion 1.4 has reparent()
if ra is None or not util.safehasattr(svn.ra, b'reparent'):
self.client = svn.client.create_context(self.pool)
ab = _create_auth_baton(self.pool)
self.client.auth_baton = ab
global svn_config
if svn_config is None:
svn_config = svn.core.svn_config_get_config(None)
self.client.config = svn_config
try:
self.ra = svn.client.open_ra_session(
self.svn_url, self.client, self.pool
)
except SubversionException as xxx_todo_changeme:
(inst, num) = xxx_todo_changeme.args
if num in (
svn.core.SVN_ERR_RA_ILLEGAL_URL,
svn.core.SVN_ERR_RA_LOCAL_REPOS_OPEN_FAILED,
svn.core.SVN_ERR_BAD_URL,
):
raise NotBranchError(url)
raise
else:
self.ra = ra
svn.ra.reparent(self.ra, self.svn_url.encode('utf8'))
class Reporter(object):
def __init__(self, reporter_data):
self._reporter, self._baton = reporter_data
def set_path(self, path, revnum, start_empty, lock_token, pool=None):
svn.ra.reporter2_invoke_set_path(
self._reporter,
self._baton,
path,
revnum,
start_empty,
lock_token,
pool,
)
def delete_path(self, path, pool=None):
svn.ra.reporter2_invoke_delete_path(
self._reporter, self._baton, path, pool
)
def link_path(
self, path, url, revision, start_empty, lock_token, pool=None
):
svn.ra.reporter2_invoke_link_path(
self._reporter,
self._baton,
path,
url,
revision,
start_empty,
lock_token,
pool,
)
def finish_report(self, pool=None):
svn.ra.reporter2_invoke_finish_report(
self._reporter, self._baton, pool
)
def abort_report(self, pool=None):
svn.ra.reporter2_invoke_abort_report(
self._reporter, self._baton, pool
)
def do_update(self, revnum, path, *args, **kwargs):
return self.Reporter(
svn.ra.do_update(self.ra, revnum, path, *args, **kwargs)
)