Mercurial > hg
view tests/test-repair-strip.t @ 46607:e9901d01d135
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
author | Kyle Lippincott <spectral@google.com> |
---|---|
date | Wed, 03 Feb 2021 16:33:10 -0800 |
parents | 7a4e1d245f19 |
children | c84844cd523a |
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#require unix-permissions no-root reporevlogstore $ cat > $TESTTMP/dumpjournal.py <<EOF > import sys > for entry in sys.stdin.read().split('\n'): > if entry: > print(entry.split('\x00')[0]) > EOF $ echo "[extensions]" >> $HGRCPATH $ echo "mq=">> $HGRCPATH $ teststrip() { > hg -q up -C $1 > echo % before update $1, strip $2 > hg parents > chmod -$3 $4 > hg strip $2 2>&1 | sed 's/\(bundle\).*/\1/' | sed 's/Permission denied.*\.hg\/store\/\(.*\)/Permission denied \.hg\/store\/\1/' > echo % after update $1, strip $2 > chmod +$3 $4 > hg verify > echo % journal contents > if [ -f .hg/store/journal ]; then > cat .hg/store/journal | "$PYTHON" $TESTTMP/dumpjournal.py > else > echo "(no journal)" > fi > if ls .hg/store/journal >/dev/null 2>&1; then > hg recover --verify > fi > ls .hg/strip-backup/* >/dev/null 2>&1 && hg unbundle -q .hg/strip-backup/* > rm -rf .hg/strip-backup > } $ hg init test $ cd test $ echo a > a $ hg -q ci -m "a" -A $ echo b > b $ hg -q ci -m "b" -A $ echo b2 >> b $ hg -q ci -m "b2" -A $ echo c > c $ hg -q ci -m "c" -A $ teststrip 0 2 w .hg/store/data/b.i % before update 0, strip 2 changeset: 0:cb9a9f314b8b user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: a saved backup bundle transaction abort! failed to truncate data/b.i rollback failed - please run hg recover (failure reason: [Errno *] Permission denied .hg/store/data/b.i') (glob) strip failed, backup bundle abort: Permission denied .hg/store/data/b.i' % after update 0, strip 2 abandoned transaction found - run hg recover checking changesets checking manifests crosschecking files in changesets and manifests checking files b@?: rev 1 points to nonexistent changeset 2 (expected 1) b@?: 736c29771fba not in manifests warning: orphan data file 'data/c.i' checked 2 changesets with 3 changes to 2 files 2 warnings encountered! 2 integrity errors encountered! % journal contents 00changelog.i 00manifest.i data/b.i data/c.i rolling back interrupted transaction checking changesets checking manifests crosschecking files in changesets and manifests checking files checked 2 changesets with 2 changes to 2 files $ teststrip 0 2 r .hg/store/data/b.i % before update 0, strip 2 changeset: 0:cb9a9f314b8b user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: a abort: Permission denied .hg/store/data/b.i' % after update 0, strip 2 checking changesets checking manifests crosschecking files in changesets and manifests checking files checked 4 changesets with 4 changes to 3 files % journal contents (no journal) $ teststrip 0 2 w .hg/store/00manifest.i % before update 0, strip 2 changeset: 0:cb9a9f314b8b user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: a saved backup bundle transaction abort! failed to truncate 00manifest.i rollback failed - please run hg recover (failure reason: [Errno *] Permission denied .hg/store/00manifest.i') (glob) strip failed, backup bundle abort: Permission denied .hg/store/00manifest.i' % after update 0, strip 2 abandoned transaction found - run hg recover checking changesets checking manifests manifest@?: rev 2 points to nonexistent changeset 2 manifest@?: 3362547cdf64 not in changesets manifest@?: rev 3 points to nonexistent changeset 3 manifest@?: 265a85892ecb not in changesets crosschecking files in changesets and manifests c@3: in manifest but not in changeset checking files b@?: rev 1 points to nonexistent changeset 2 (expected 1) c@?: rev 0 points to nonexistent changeset 3 checked 2 changesets with 4 changes to 3 files 1 warnings encountered! 7 integrity errors encountered! (first damaged changeset appears to be 3) % journal contents 00changelog.i 00manifest.i data/b.i data/c.i rolling back interrupted transaction checking changesets checking manifests crosschecking files in changesets and manifests checking files checked 2 changesets with 2 changes to 2 files $ cd ..