Mercurial > hg
view tests/test-committer.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 | 17a695357270 |
children |
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$ unset HGUSER $ EMAIL="My Name <myname@example.com>" $ export EMAIL $ hg init test $ cd test $ touch asdf $ hg add asdf $ hg commit -m commit-1 $ hg tip changeset: 0:53f268a58230 tag: tip user: My Name <myname@example.com> date: Thu Jan 01 00:00:00 1970 +0000 summary: commit-1 $ unset EMAIL $ echo 1234 > asdf $ hg commit -u "foo@bar.com" -m commit-1 $ hg tip changeset: 1:3871b2a9e9bf tag: tip user: foo@bar.com date: Thu Jan 01 00:00:00 1970 +0000 summary: commit-1 $ echo "[ui]" >> .hg/hgrc $ echo "username = foobar <foo@bar.com>" >> .hg/hgrc $ echo 12 > asdf $ hg commit -m commit-1 $ hg tip changeset: 2:8eeac6695c1c tag: tip user: foobar <foo@bar.com> date: Thu Jan 01 00:00:00 1970 +0000 summary: commit-1 $ echo 1 > asdf $ hg commit -u "foo@bar.com" -m commit-1 $ hg tip changeset: 3:957606a725e4 tag: tip user: foo@bar.com date: Thu Jan 01 00:00:00 1970 +0000 summary: commit-1 $ echo 123 > asdf $ echo "[ui]" > .hg/hgrc $ echo "username = " >> .hg/hgrc $ hg commit -m commit-1 abort: no username supplied (use 'hg config --edit' to set your username) [255] # test alternate config var $ echo 1234 > asdf $ echo "[ui]" > .hg/hgrc $ echo "user = Foo Bar II <foo2@bar.com>" >> .hg/hgrc $ hg commit -m commit-1 $ hg tip changeset: 4:6f24bfb4c617 tag: tip user: Foo Bar II <foo2@bar.com> date: Thu Jan 01 00:00:00 1970 +0000 summary: commit-1 # test prompt username $ cat > .hg/hgrc <<EOF > [ui] > askusername = True > EOF $ echo 12345 > asdf $ hg commit --config ui.interactive=False -m ask enter a commit username: no username found, using '[^']*' instead (re) $ hg rollback -q $ hg commit --config ui.interactive=True -m ask <<EOF > Asked User <ask@example.com> > EOF enter a commit username: Asked User <ask@example.com> $ hg tip changeset: 5:84c91d963b70 tag: tip user: Asked User <ask@example.com> date: Thu Jan 01 00:00:00 1970 +0000 summary: ask # test no .hg/hgrc (uses generated non-interactive username) $ echo space > asdf $ rm .hg/hgrc $ hg commit -m commit-1 2>&1 no username found, using '[^']*' instead (re) $ echo space2 > asdf $ hg commit -u ' ' -m commit-1 transaction abort! rollback completed abort: empty username [50] # don't add tests here, previous test is unstable $ cd ..