Mercurial > hg
view tests/test-import-merge.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 | f1186c292d03 |
children | 2f2682f40ea0 |
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$ echo "[extensions]" >> $HGRCPATH $ echo "mq=" >> $HGRCPATH $ tipparents() { > hg parents --template "{rev}:{node|short} {desc|firstline}\n" -r tip > } Test import and merge diffs $ hg init repo $ cd repo $ echo a > a $ hg ci -Am adda adding a $ echo a >> a $ hg ci -m changea $ echo c > c $ hg ci -Am addc adding c $ hg up 0 1 files updated, 0 files merged, 1 files removed, 0 files unresolved $ echo b > b $ hg ci -Am addb adding b created new head $ hg up 1 1 files updated, 0 files merged, 1 files removed, 0 files unresolved $ hg merge 3 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg ci -m merge $ hg export . > ../merge.diff $ grep -v '^merge$' ../merge.diff > ../merge.nomsg.diff $ cd .. $ hg clone -r2 repo repo2 adding changesets adding manifests adding file changes added 3 changesets with 3 changes to 2 files new changesets 07f494440405:890ecaa90481 updating to branch default 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cd repo2 $ hg pull -r3 ../repo pulling from ../repo searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files (+1 heads) new changesets 102a90ea7b4a (run 'hg heads' to see heads, 'hg merge' to merge) Test without --exact and diff.p1 == workingdir.p1 $ hg up 1 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ cat > $TESTTMP/editor.sh <<EOF > env | grep HGEDITFORM > echo merge > \$1 > EOF $ HGEDITOR="sh $TESTTMP/editor.sh" hg import --edit ../merge.nomsg.diff applying ../merge.nomsg.diff HGEDITFORM=import.normal.merge $ tipparents 1:540395c44225 changea 3:102a90ea7b4a addb $ hg strip --no-backup tip 0 files updated, 0 files merged, 1 files removed, 0 files unresolved Test without --exact and diff.p1 != workingdir.p1 $ hg up 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg import ../merge.diff applying ../merge.diff warning: import the patch as a normal revision (use --exact to import the patch as a merge) $ tipparents 2:890ecaa90481 addc $ hg strip --no-backup tip 0 files updated, 0 files merged, 1 files removed, 0 files unresolved Test with --exact $ hg import --exact ../merge.diff applying ../merge.diff 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ tipparents 1:540395c44225 changea 3:102a90ea7b4a addb $ hg strip --no-backup tip 0 files updated, 0 files merged, 1 files removed, 0 files unresolved Test with --bypass and diff.p1 == workingdir.p1 $ hg up 1 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg import --bypass ../merge.diff applying ../merge.diff $ tipparents 1:540395c44225 changea 3:102a90ea7b4a addb $ hg strip --no-backup tip Test with --bypass and diff.p1 != workingdir.p1 $ hg up 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg import --bypass ../merge.diff applying ../merge.diff warning: import the patch as a normal revision (use --exact to import the patch as a merge) $ tipparents 2:890ecaa90481 addc $ hg strip --no-backup tip Test with --bypass and --exact $ hg import --bypass --exact ../merge.diff applying ../merge.diff $ tipparents 1:540395c44225 changea 3:102a90ea7b4a addb $ hg strip --no-backup tip $ cd .. Test that --exact on a bad header doesn't corrupt the repo (issue3616) $ hg init repo3 $ cd repo3 $ echo a>a $ hg ci -Aqm0 $ echo a>>a $ hg ci -m1 $ echo a>>a $ hg ci -m2 $ echo a>a $ echo b>>a $ echo a>>a $ hg ci -m3 $ hg export 2 | head -7 > ../a.patch $ hg export tip > out >>> apatch = open("../a.patch", "ab") >>> apatch.write(b"".join(open("out", 'rb').readlines()[7:])) and None $ cd .. $ hg clone -qr0 repo3 repo3-clone $ cd repo3-clone $ hg pull -qr1 ../repo3 $ hg import --exact ../a.patch applying ../a.patch 1 files updated, 0 files merged, 0 files removed, 0 files unresolved patching file a Hunk #1 succeeded at 1 with fuzz 1 (offset -1 lines). transaction abort! rollback completed abort: patch is damaged or loses information [255] $ hg verify checking changesets checking manifests crosschecking files in changesets and manifests checking files checked 2 changesets with 2 changes to 1 files