Mercurial > hg
view tests/test-absorb-rename.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 | 31dfa7dac4c9 |
children |
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$ cat >> $HGRCPATH << EOF > [diff] > git=1 > [extensions] > absorb= > EOF $ sedi() { # workaround check-code > pattern="$1" > shift > for i in "$@"; do > sed "$pattern" "$i" > "$i".tmp > mv "$i".tmp "$i" > done > } rename a to b, then b to a $ hg init repo1 $ cd repo1 $ echo 1 > a $ hg ci -A a -m 1 $ hg mv a b $ echo 2 >> b $ hg ci -m 2 $ hg mv b a $ echo 3 >> a $ hg ci -m 3 $ hg annotate -ncf a 0 eff892de26ec a: 1 1 bf56e1f4f857 b: 2 2 0b888b00216c a: 3 $ sedi 's/$/a/' a $ hg absorb -apq showing changes for a @@ -0,3 +0,3 @@ eff892d -1 bf56e1f -2 0b888b0 -3 eff892d +1a bf56e1f +2a 0b888b0 +3a 3 changesets affected 0b888b0 3 bf56e1f 2 eff892d 1 $ hg status $ hg annotate -ncf a 0 5d1c5620e6f2 a: 1a 1 9a14ffe67ae9 b: 2a 2 9191d121a268 a: 3a when the first changeset is public $ hg phase --public -r 0 $ sedi 's/a/A/' a $ hg absorb -apq showing changes for a @@ -0,3 +0,3 @@ -1a 9a14ffe -2a 9191d12 -3a +1A 9a14ffe +2A 9191d12 +3A 2 changesets affected 9191d12 3 9a14ffe 2 $ hg diff diff --git a/a b/a --- a/a +++ b/a @@ -1,3 +1,3 @@ -1a +1A 2A 3A copy a to b $ cd .. $ hg init repo2 $ cd repo2 $ echo 1 > a $ hg ci -A a -m 1 $ hg cp a b $ echo 2 >> b $ hg ci -m 2 $ hg log -T '{rev}:{node|short} {desc}\n' 1:17b72129ab68 2 0:eff892de26ec 1 $ sedi 's/$/a/' a $ sedi 's/$/b/' b $ hg absorb -apq showing changes for a @@ -0,1 +0,1 @@ eff892d -1 eff892d +1a showing changes for b @@ -0,2 +0,2 @@ -1 17b7212 -2 +1b 17b7212 +2b 2 changesets affected 17b7212 2 eff892d 1 $ hg diff diff --git a/b b/b --- a/b +++ b/b @@ -1,2 +1,2 @@ -1 +1b 2b copy b to a $ cd .. $ hg init repo3 $ cd repo3 $ echo 1 > b $ hg ci -A b -m 1 $ hg cp b a $ echo 2 >> a $ hg ci -m 2 $ hg log -T '{rev}:{node|short} {desc}\n' 1:e62c256d8b24 2 0:55105f940d5c 1 $ sedi 's/$/a/' a $ sedi 's/$/a/' b $ hg absorb -apq showing changes for a @@ -0,2 +0,2 @@ -1 e62c256 -2 +1a e62c256 +2a showing changes for b @@ -0,1 +0,1 @@ 55105f9 -1 55105f9 +1a 2 changesets affected e62c256 2 55105f9 1 $ hg diff diff --git a/a b/a --- a/a +++ b/a @@ -1,2 +1,2 @@ -1 +1a 2a "move" b to both a and c, follow a - sorted alphabetically $ cd .. $ hg init repo4 $ cd repo4 $ echo 1 > b $ hg ci -A b -m 1 $ hg cp b a $ hg cp b c $ hg rm b $ echo 2 >> a $ echo 3 >> c $ hg commit -m cp $ hg log -T '{rev}:{node|short} {desc}\n' 1:366daad8e679 cp 0:55105f940d5c 1 $ sedi 's/$/a/' a $ sedi 's/$/c/' c $ hg absorb -apq showing changes for a @@ -0,2 +0,2 @@ 55105f9 -1 366daad -2 55105f9 +1a 366daad +2a showing changes for c @@ -0,2 +0,2 @@ -1 366daad -3 +1c 366daad +3c 2 changesets affected 366daad cp 55105f9 1 $ hg log -G -p -T '{rev}:{node|short} {desc}\n' @ 1:70606019f91b cp | diff --git a/b b/a | rename from b | rename to a | --- a/b | +++ b/a | @@ -1,1 +1,2 @@ | 1a | +2a | diff --git a/b b/c | copy from b | copy to c | --- a/b | +++ b/c | @@ -1,1 +1,2 @@ | -1a | +1 | +3c | o 0:bfb67c3539c1 1 diff --git a/b b/b new file mode 100644 --- /dev/null +++ b/b @@ -0,0 +1,1 @@ +1a run absorb again would apply the change to c $ hg absorb -apq showing changes for c @@ -0,1 +0,1 @@ 7060601 -1 7060601 +1c 1 changesets affected 7060601 cp $ hg log -G -p -T '{rev}:{node|short} {desc}\n' @ 1:8bd536cce368 cp | diff --git a/b b/a | rename from b | rename to a | --- a/b | +++ b/a | @@ -1,1 +1,2 @@ | 1a | +2a | diff --git a/b b/c | copy from b | copy to c | --- a/b | +++ b/c | @@ -1,1 +1,2 @@ | -1a | +1c | +3c | o 0:bfb67c3539c1 1 diff --git a/b b/b new file mode 100644 --- /dev/null +++ b/b @@ -0,0 +1,1 @@ +1a "move" b to a, c and d, follow d if a gets renamed to e, and c is deleted $ cd .. $ hg init repo5 $ cd repo5 $ echo 1 > b $ hg ci -A b -m 1 $ hg cp b a $ hg cp b c $ hg cp b d $ hg rm b $ echo 2 >> a $ echo 3 >> c $ echo 4 >> d $ hg commit -m cp $ hg mv a e $ hg rm c $ hg commit -m mv $ hg log -T '{rev}:{node|short} {desc}\n' 2:49911557c471 mv 1:7bc3d43ede83 cp 0:55105f940d5c 1 $ sedi 's/$/e/' e $ sedi 's/$/d/' d $ hg absorb -apq showing changes for d @@ -0,2 +0,2 @@ 55105f9 -1 7bc3d43 -4 55105f9 +1d 7bc3d43 +4d showing changes for e @@ -0,2 +0,2 @@ -1 7bc3d43 -2 +1e 7bc3d43 +2e 2 changesets affected 7bc3d43 cp 55105f9 1 $ hg diff diff --git a/e b/e --- a/e +++ b/e @@ -1,2 +1,2 @@ -1 +1e 2e $ hg log -G -p -T '{rev}:{node|short} {desc}\n' @ 2:34be9b0c786e mv | diff --git a/c b/c | deleted file mode 100644 | --- a/c | +++ /dev/null | @@ -1,2 +0,0 @@ | -1 | -3 | diff --git a/a b/e | rename from a | rename to e | o 1:13e56db5948d cp | diff --git a/b b/a | rename from b | rename to a | --- a/b | +++ b/a | @@ -1,1 +1,2 @@ | -1d | +1 | +2e | diff --git a/b b/c | copy from b | copy to c | --- a/b | +++ b/c | @@ -1,1 +1,2 @@ | -1d | +1 | +3 | diff --git a/b b/d | copy from b | copy to d | --- a/b | +++ b/d | @@ -1,1 +1,2 @@ | 1d | +4d | o 0:0037613a5dc6 1 diff --git a/b b/b new file mode 100644 --- /dev/null +++ b/b @@ -0,0 +1,1 @@ +1d