Mercurial > hg
view tests/test-merge-commit.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 | 69429972ff1f |
children | 38941a28406a |
line wrap: on
line source
Check that renames are correctly saved by a commit after a merge Test with the merge on 3 having the rename on the local parent $ hg init a $ cd a $ echo line1 > foo $ hg add foo $ hg ci -m '0: add foo' $ echo line2 >> foo $ hg ci -m '1: change foo' $ hg up -C 0 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg mv foo bar $ rm bar $ echo line0 > bar $ echo line1 >> bar $ hg ci -m '2: mv foo bar; change bar' created new head $ hg merge 1 merging bar and foo to bar 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat bar line0 line1 line2 $ hg ci -m '3: merge with local rename' $ hg debugindex bar rev linkrev nodeid p1 p2 0 2 d35118874825 000000000000 000000000000 1 3 5345f5ab8abd 000000000000 d35118874825 $ hg debugrename bar bar renamed from foo:9e25c27b87571a1edee5ae4dddee5687746cc8e2 $ hg debugindex foo rev linkrev nodeid p1 p2 0 0 690b295714ae 000000000000 000000000000 1 1 9e25c27b8757 690b295714ae 000000000000 Revert the content change from rev 2: $ hg up -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ rm bar $ echo line1 > bar $ hg ci -m '4: revert content change from rev 2' created new head $ hg log --template '{rev}:{node|short} {parents}\n' 4:2263c1be0967 2:0f2ff26688b9 3:0555950ead28 2:0f2ff26688b9 1:5cd961e4045d 2:0f2ff26688b9 0:2665aaee66e9 1:5cd961e4045d 0:2665aaee66e9 This should use bar@rev2 as the ancestor: $ hg --debug merge 3 resolving manifests branchmerge: True, force: False, partial: False ancestor: 0f2ff26688b9, local: 2263c1be0967+, remote: 0555950ead28 starting 4 threads for background file closing (?) preserving bar for resolve of bar bar: versions differ -> m (premerge) picked tool ':merge' for bar (binary False symlink False changedelete False) merging bar my bar@2263c1be0967+ other bar@0555950ead28 ancestor bar@0f2ff26688b9 premerge successful 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat bar line1 line2 $ hg ci -m '5: merge' $ hg debugindex bar rev linkrev nodeid p1 p2 0 2 d35118874825 000000000000 000000000000 1 3 5345f5ab8abd 000000000000 d35118874825 2 4 ff4b45017382 d35118874825 000000000000 3 5 3701b4893544 ff4b45017382 5345f5ab8abd Same thing, but with the merge on 3 having the rename on the remote parent: $ cd .. $ hg clone -U -r 1 -r 2 a b adding changesets adding manifests adding file changes added 3 changesets with 3 changes to 2 files (+1 heads) new changesets 2665aaee66e9:0f2ff26688b9 $ cd b $ hg up -C 1 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg merge 2 merging foo and bar to bar 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat bar line0 line1 line2 $ hg ci -m '3: merge with remote rename' $ hg debugindex bar rev linkrev nodeid p1 p2 0 2 d35118874825 000000000000 000000000000 1 3 5345f5ab8abd 000000000000 d35118874825 $ hg debugrename bar bar renamed from foo:9e25c27b87571a1edee5ae4dddee5687746cc8e2 $ hg debugindex foo rev linkrev nodeid p1 p2 0 0 690b295714ae 000000000000 000000000000 1 1 9e25c27b8757 690b295714ae 000000000000 Revert the content change from rev 2: $ hg up -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ rm bar $ echo line1 > bar $ hg ci -m '4: revert content change from rev 2' created new head $ hg log --template '{rev}:{node|short} {parents}\n' 4:2263c1be0967 2:0f2ff26688b9 3:3ffa6b9e35f0 1:5cd961e4045d 2:0f2ff26688b9 2:0f2ff26688b9 0:2665aaee66e9 1:5cd961e4045d 0:2665aaee66e9 This should use bar@rev2 as the ancestor: $ hg --debug merge 3 resolving manifests branchmerge: True, force: False, partial: False ancestor: 0f2ff26688b9, local: 2263c1be0967+, remote: 3ffa6b9e35f0 starting 4 threads for background file closing (?) preserving bar for resolve of bar bar: versions differ -> m (premerge) picked tool ':merge' for bar (binary False symlink False changedelete False) merging bar my bar@2263c1be0967+ other bar@3ffa6b9e35f0 ancestor bar@0f2ff26688b9 premerge successful 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat bar line1 line2 $ hg ci -m '5: merge' $ hg debugindex bar rev linkrev nodeid p1 p2 0 2 d35118874825 000000000000 000000000000 1 3 5345f5ab8abd 000000000000 d35118874825 2 4 ff4b45017382 d35118874825 000000000000 3 5 3701b4893544 ff4b45017382 5345f5ab8abd $ cd ..