Mercurial > hg
view tests/test-filebranch.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 | 07e181ed82ef |
children | 42d2b31cee0b |
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This test makes sure that we don't mark a file as merged with its ancestor when we do a merge. $ cat <<EOF > merge > from __future__ import print_function > import sys, os > print("merging for", os.path.basename(sys.argv[1])) > EOF $ HGMERGE="\"$PYTHON\" ../merge"; export HGMERGE Creating base: $ hg init a $ cd a $ echo 1 > foo $ echo 1 > bar $ echo 1 > baz $ echo 1 > quux $ hg add foo bar baz quux $ hg commit -m "base" $ cd .. $ hg clone a b updating to branch default 4 files updated, 0 files merged, 0 files removed, 0 files unresolved Creating branch a: $ cd a $ echo 2a > foo $ echo 2a > bar $ hg commit -m "branch a" Creating branch b: $ cd .. $ cd b $ echo 2b > foo $ echo 2b > baz $ hg commit -m "branch b" We shouldn't have anything but n state here: $ hg debugstate --no-dates | grep -v "^n" [1] Merging: $ hg pull ../a pulling from ../a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 2 changes to 2 files (+1 heads) new changesets bdd988058d16 (run 'hg heads' to see heads, 'hg merge' to merge) $ hg merge -v resolving manifests getting bar merging foo merging for foo 1 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ echo 2m > foo $ echo 2b > baz $ echo new > quux $ hg ci -m "merge" main: we should have a merge here: $ hg debugindex --changelog rev linkrev nodeid p1 p2 0 0 cdca01651b96 000000000000 000000000000 1 1 f6718a9cb7f3 cdca01651b96 000000000000 2 2 bdd988058d16 cdca01651b96 000000000000 3 3 d8a521142a3c f6718a9cb7f3 bdd988058d16 log should show foo and quux changed: $ hg log -v -r tip changeset: 3:d8a521142a3c tag: tip parent: 1:f6718a9cb7f3 parent: 2:bdd988058d16 user: test date: Thu Jan 01 00:00:00 1970 +0000 files: foo quux description: merge foo: we should have a merge here: $ hg debugindex foo rev linkrev nodeid p1 p2 0 0 b8e02f643373 000000000000 000000000000 1 1 2ffeddde1b65 b8e02f643373 000000000000 2 2 33d1fb69067a b8e02f643373 000000000000 3 3 aa27919ee430 2ffeddde1b65 33d1fb69067a bar: we should not have a merge here: $ hg debugindex bar rev linkrev nodeid p1 p2 0 0 b8e02f643373 000000000000 000000000000 1 2 33d1fb69067a b8e02f643373 000000000000 baz: we should not have a merge here: $ hg debugindex baz rev linkrev nodeid p1 p2 0 0 b8e02f643373 000000000000 000000000000 1 1 2ffeddde1b65 b8e02f643373 000000000000 quux: we should not have a merge here: $ hg debugindex quux rev linkrev nodeid p1 p2 0 0 b8e02f643373 000000000000 000000000000 1 3 6128c0f33108 b8e02f643373 000000000000 Manifest entries should match tips of all files: $ hg manifest --debug 33d1fb69067a0139622a3fa3b7ba1cdb1367972e 644 bar 2ffeddde1b65b4827f6746174a145474129fa2ce 644 baz aa27919ee4303cfd575e1fb932dd64d75aa08be4 644 foo 6128c0f33108e8cfbb4e0824d13ae48b466d7280 644 quux Everything should be clean now: $ hg status $ hg verify checking changesets checking manifests crosschecking files in changesets and manifests checking files checked 4 changesets with 10 changes to 4 files $ cd ..