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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
Joerg Sonnenberger - - Load All Authors

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debugcommands.py
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/ hgext / remotefilelog / debugcommands.py
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# debugcommands.py - debug logic for remotefilelog
#
# Copyright 2013 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
import os
import zlib
from mercurial.node import (
bin,
hex,
nullid,
short,
)
from mercurial.i18n import _
from mercurial.pycompat import open
from mercurial import (
error,
filelog,
lock as lockmod,
pycompat,
revlog,
)
from mercurial.utils import hashutil
from . import (
constants,
datapack,
fileserverclient,
historypack,
repack,
shallowutil,
)
def debugremotefilelog(ui, path, **opts):
decompress = opts.get('decompress')
size, firstnode, mapping = parsefileblob(path, decompress)
ui.status(_(b"size: %d bytes\n") % size)
ui.status(_(b"path: %s \n") % path)
ui.status(_(b"key: %s \n") % (short(firstnode)))
ui.status(_(b"\n"))
ui.status(
_(b"%12s => %12s %13s %13s %12s\n")
% (b"node", b"p1", b"p2", b"linknode", b"copyfrom")
)
queue = [firstnode]
while queue:
node = queue.pop(0)
p1, p2, linknode, copyfrom = mapping[node]
ui.status(
_(b"%s => %s %s %s %s\n")
% (short(node), short(p1), short(p2), short(linknode), copyfrom)
)
if p1 != nullid:
queue.append(p1)
if p2 != nullid:
queue.append(p2)
def buildtemprevlog(repo, file):
# get filename key
filekey = hex(hashutil.sha1(file).digest())
filedir = os.path.join(repo.path, b'store/data', filekey)
# sort all entries based on linkrev
fctxs = []
for filenode in os.listdir(filedir):
if b'_old' not in filenode:
fctxs.append(repo.filectx(file, fileid=bin(filenode)))
fctxs = sorted(fctxs, key=lambda x: x.linkrev())
# add to revlog
temppath = repo.sjoin(b'data/temprevlog.i')
if os.path.exists(temppath):
os.remove(temppath)
r = filelog.filelog(repo.svfs, b'temprevlog')
class faket(object):
def add(self, a, b, c):
pass
t = faket()
for fctx in fctxs:
if fctx.node() not in repo:
continue
p = fctx.filelog().parents(fctx.filenode())
meta = {}
if fctx.renamed():
meta[b'copy'] = fctx.renamed()[0]
meta[b'copyrev'] = hex(fctx.renamed()[1])
r.add(fctx.data(), meta, t, fctx.linkrev(), p[0], p[1])
return r
def debugindex(orig, ui, repo, file_=None, **opts):
"""dump the contents of an index file"""
if (
opts.get('changelog')
or opts.get('manifest')
or opts.get('dir')
or not shallowutil.isenabled(repo)
or not repo.shallowmatch(file_)
):
return orig(ui, repo, file_, **opts)
r = buildtemprevlog(repo, file_)
# debugindex like normal
format = opts.get(b'format', 0)
if format not in (0, 1):
raise error.Abort(_(b"unknown format %d") % format)
generaldelta = r.version & revlog.FLAG_GENERALDELTA
if generaldelta:
basehdr = b' delta'
else:
basehdr = b' base'
if format == 0:
ui.write(
(
b" rev offset length " + basehdr + b" linkrev"
b" nodeid p1 p2\n"
)
)
elif format == 1:
ui.write(
(
b" rev flag offset length"
b" size " + basehdr + b" link p1 p2"
b" nodeid\n"
)
)
for i in r:
node = r.node(i)
if generaldelta:
base = r.deltaparent(i)
else:
base = r.chainbase(i)
if format == 0:
try:
pp = r.parents(node)
except Exception:
pp = [nullid, nullid]
ui.write(
b"% 6d % 9d % 7d % 6d % 7d %s %s %s\n"
% (
i,
r.start(i),
r.length(i),
base,
r.linkrev(i),
short(node),
short(pp[0]),
short(pp[1]),
)
)
elif format == 1:
pr = r.parentrevs(i)
ui.write(
b"% 6d %04x % 8d % 8d % 8d % 6d % 6d % 6d % 6d %s\n"
% (
i,
r.flags(i),
r.start(i),
r.length(i),
r.rawsize(i),
base,
r.linkrev(i),
pr[0],
pr[1],
short(node),
)
)
def debugindexdot(orig, ui, repo, file_):
"""dump an index DAG as a graphviz dot file"""
if not shallowutil.isenabled(repo):
return orig(ui, repo, file_)
r = buildtemprevlog(repo, os.path.basename(file_)[:-2])
ui.writenoi18n(b"digraph G {\n")
for i in r:
node = r.node(i)
pp = r.parents(node)
ui.write(b"\t%d -> %d\n" % (r.rev(pp[0]), i))
if pp[1] != nullid:
ui.write(b"\t%d -> %d\n" % (r.rev(pp[1]), i))
ui.write(b"}\n")
def verifyremotefilelog(ui, path, **opts):
decompress = opts.get('decompress')
for root, dirs, files in os.walk(path):
for file in files:
if file == b"repos":
continue
filepath = os.path.join(root, file)
size, firstnode, mapping = parsefileblob(filepath, decompress)
for p1, p2, linknode, copyfrom in pycompat.itervalues(mapping):
if linknode == nullid:
actualpath = os.path.relpath(root, path)
key = fileserverclient.getcachekey(
b"reponame", actualpath, file
)
ui.status(
b"%s %s\n" % (key, os.path.relpath(filepath, path))
)
def _decompressblob(raw):
return zlib.decompress(raw)
def parsefileblob(path, decompress):
f = open(path, b"rb")
try:
raw = f.read()
finally:
f.close()
if decompress:
raw = _decompressblob(raw)
offset, size, flags = shallowutil.parsesizeflags(raw)
start = offset + size
firstnode = None
mapping = {}
while start < len(raw):
divider = raw.index(b'\0', start + 80)
currentnode = raw[start : (start + 20)]
if not firstnode:
firstnode = currentnode
p1 = raw[(start + 20) : (start + 40)]
p2 = raw[(start + 40) : (start + 60)]
linknode = raw[(start + 60) : (start + 80)]
copyfrom = raw[(start + 80) : divider]
mapping[currentnode] = (p1, p2, linknode, copyfrom)
start = divider + 1
return size, firstnode, mapping
def debugdatapack(ui, *paths, **opts):
for path in paths:
if b'.data' in path:
path = path[: path.index(b'.data')]
ui.write(b"%s:\n" % path)
dpack = datapack.datapack(path)
node = opts.get('node')
if node:
deltachain = dpack.getdeltachain(b'', bin(node))
dumpdeltachain(ui, deltachain, **opts)
return
if opts.get('long'):
hashformatter = hex
hashlen = 42
else:
hashformatter = short
hashlen = 14
lastfilename = None
totaldeltasize = 0
totalblobsize = 0
def printtotals():
if lastfilename is not None:
ui.write(b"\n")
if not totaldeltasize or not totalblobsize:
return
difference = totalblobsize - totaldeltasize
deltastr = b"%0.1f%% %s" % (
(100.0 * abs(difference) / totalblobsize),
(b"smaller" if difference > 0 else b"bigger"),
)
ui.writenoi18n(
b"Total:%s%s %s (%s)\n"
% (
b"".ljust(2 * hashlen - len(b"Total:")),
(b'%d' % totaldeltasize).ljust(12),
(b'%d' % totalblobsize).ljust(9),
deltastr,
)
)
bases = {}
nodes = set()
failures = 0
for filename, node, deltabase, deltalen in dpack.iterentries():
bases[node] = deltabase
if node in nodes:
ui.write((b"Bad entry: %s appears twice\n" % short(node)))
failures += 1
nodes.add(node)
if filename != lastfilename:
printtotals()
name = b'(empty name)' if filename == b'' else filename
ui.write(b"%s:\n" % name)
ui.write(
b"%s%s%s%s\n"
% (
b"Node".ljust(hashlen),
b"Delta Base".ljust(hashlen),
b"Delta Length".ljust(14),
b"Blob Size".ljust(9),
)
)
lastfilename = filename
totalblobsize = 0
totaldeltasize = 0
# Metadata could be missing, in which case it will be an empty dict.
meta = dpack.getmeta(filename, node)
if constants.METAKEYSIZE in meta:
blobsize = meta[constants.METAKEYSIZE]
totaldeltasize += deltalen
totalblobsize += blobsize
else:
blobsize = b"(missing)"
ui.write(
b"%s %s %s%s\n"
% (
hashformatter(node),
hashformatter(deltabase),
(b'%d' % deltalen).ljust(14),
pycompat.bytestr(blobsize),
)
)
if filename is not None:
printtotals()
failures += _sanitycheck(ui, set(nodes), bases)
if failures > 1:
ui.warn((b"%d failures\n" % failures))
return 1
def _sanitycheck(ui, nodes, bases):
"""
Does some basic sanity checking on a packfiles with ``nodes`` ``bases`` (a
mapping of node->base):
- Each deltabase must itself be a node elsewhere in the pack
- There must be no cycles
"""
failures = 0
for node in nodes:
seen = set()
current = node
deltabase = bases[current]
while deltabase != nullid:
if deltabase not in nodes:
ui.warn(
(
b"Bad entry: %s has an unknown deltabase (%s)\n"
% (short(node), short(deltabase))
)
)
failures += 1
break
if deltabase in seen:
ui.warn(
(
b"Bad entry: %s has a cycle (at %s)\n"
% (short(node), short(deltabase))
)
)
failures += 1
break
current = deltabase
seen.add(current)
deltabase = bases[current]
# Since ``node`` begins a valid chain, reset/memoize its base to nullid
# so we don't traverse it again.
bases[node] = nullid
return failures
def dumpdeltachain(ui, deltachain, **opts):
hashformatter = hex
hashlen = 40
lastfilename = None
for filename, node, filename, deltabasenode, delta in deltachain:
if filename != lastfilename:
ui.write(b"\n%s\n" % filename)
lastfilename = filename
ui.write(
b"%s %s %s %s\n"
% (
b"Node".ljust(hashlen),
b"Delta Base".ljust(hashlen),
b"Delta SHA1".ljust(hashlen),
b"Delta Length".ljust(6),
)
)
ui.write(
b"%s %s %s %d\n"
% (
hashformatter(node),
hashformatter(deltabasenode),
hex(hashutil.sha1(delta).digest()),
len(delta),
)
)
def debughistorypack(ui, path):
if b'.hist' in path:
path = path[: path.index(b'.hist')]
hpack = historypack.historypack(path)
lastfilename = None
for entry in hpack.iterentries():
filename, node, p1node, p2node, linknode, copyfrom = entry
if filename != lastfilename:
ui.write(b"\n%s\n" % filename)
ui.write(
b"%s%s%s%s%s\n"
% (
b"Node".ljust(14),
b"P1 Node".ljust(14),
b"P2 Node".ljust(14),
b"Link Node".ljust(14),
b"Copy From",
)
)
lastfilename = filename
ui.write(
b"%s %s %s %s %s\n"
% (
short(node),
short(p1node),
short(p2node),
short(linknode),
copyfrom,
)
)
def debugwaitonrepack(repo):
with lockmod.lock(repack.repacklockvfs(repo), b"repacklock", timeout=-1):
return
def debugwaitonprefetch(repo):
with repo._lock(
repo.svfs,
b"prefetchlock",
True,
None,
None,
_(b'prefetching in %s') % repo.origroot,
):
pass