Mercurial > hg
view tests/test-unified-test.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 | bd0f122f3f51 |
children | 1d075b857c90 |
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Test that the syntax of "unified tests" is properly processed ============================================================== Simple commands: $ echo foo foo $ printf 'oh no' oh no (no-eol) $ printf 'bar\nbaz\n' | cat bar baz Multi-line command: $ foo() { > echo bar > } $ foo bar Return codes before inline python: $ sh -c 'exit 1' [1] Doctest commands: >>> from __future__ import print_function >>> print('foo') foo $ echo interleaved interleaved >>> for c in 'xyz': ... print(c) x y z >>> print() >>> foo = 'global name' >>> def func(): ... print(foo, 'should be visible in func()') >>> func() global name should be visible in func() >>> print('''multiline ... string''') multiline string Regular expressions: $ echo foobarbaz foobar.* (re) $ echo barbazquux .*quux.* (re) Globs: $ printf '* \\foobarbaz {10}\n' \* \\fo?bar* {10} (glob) Literal match ending in " (re)": $ echo 'foo (re)' foo (re) Windows: \r\n is handled like \n and can be escaped: #if windows $ printf 'crlf\r\ncr\r\tcrlf\r\ncrlf\r\n' crlf cr\r (no-eol) (esc) \tcrlf (esc) crlf\r (esc) #endif Escapes: $ $PYTHON -c 'from mercurial.utils.procutil import stdout; stdout.write(b"\xff")' \xff (no-eol) (esc) Escapes with conditions: $ $PYTHON -c 'from mercurial.utils.procutil import stdout; stdout.write(b"\xff")' \xff (no-eol) (esc) (true !) Combining esc with other markups - and handling lines ending with \r instead of \n: $ printf 'foo/bar\r' fo?/bar\r (no-eol) (glob) (esc) #if windows $ printf 'foo\\bar\r' foo/bar\r (no-eol) (esc) #endif $ printf 'foo/bar\rfoo/bar\r' foo.bar\r [(]no-eol[)] (re) (esc) foo.bar\r \(no-eol\) (re) testing hghave $ hghave true $ hghave false skipped: missing feature: nail clipper [1] $ hghave no-true skipped: system supports yak shaving [1] $ hghave no-false Conditional sections based on hghave: #if true $ echo tested tested #else $ echo skipped #endif #if false $ echo skipped #else $ echo tested tested #endif #if no-false $ echo tested tested #else $ echo skipped #endif #if no-true $ echo skipped #else $ echo tested tested #endif Exit code: $ (exit 1) [1]