Mercurial > hg
view tests/test-diff-upgrade.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 | 5abc47d4ca6b |
children | 0492002560f3 |
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#require execbit $ cat <<EOF >> $HGRCPATH > [extensions] > autodiff = $TESTDIR/autodiff.py > [diff] > nodates = 1 > EOF $ hg init repo $ cd repo make a combination of new, changed and deleted file $ echo regular > regular $ echo rmregular > rmregular $ "$PYTHON" -c "open('bintoregular', 'wb').write(b'\0')" $ touch rmempty $ echo exec > exec $ chmod +x exec $ echo rmexec > rmexec $ chmod +x rmexec $ echo setexec > setexec $ echo unsetexec > unsetexec $ chmod +x unsetexec $ echo binary > binary $ "$PYTHON" -c "open('rmbinary', 'wb').write(b'\0')" $ hg ci -Am addfiles adding binary adding bintoregular adding exec adding regular adding rmbinary adding rmempty adding rmexec adding rmregular adding setexec adding unsetexec $ echo regular >> regular $ echo newregular >> newregular $ rm rmempty $ touch newempty $ rm rmregular $ echo exec >> exec $ echo newexec > newexec $ echo bintoregular > bintoregular $ chmod +x newexec $ rm rmexec $ chmod +x setexec $ chmod -x unsetexec $ "$PYTHON" -c "open('binary', 'wb').write(b'\0\0')" $ "$PYTHON" -c "open('newbinary', 'wb').write(b'\0')" $ rm rmbinary $ hg addremove -s 0 adding newbinary adding newempty adding newexec adding newregular removing rmbinary removing rmempty removing rmexec removing rmregular git=no: regular diff for all files $ hg autodiff --git=no diff -r a66d19b9302d binary Binary file binary has changed diff -r a66d19b9302d bintoregular Binary file bintoregular has changed diff -r a66d19b9302d exec --- a/exec +++ b/exec @@ -1,1 +1,2 @@ exec +exec diff -r a66d19b9302d newbinary Binary file newbinary has changed diff -r a66d19b9302d newexec --- /dev/null +++ b/newexec @@ -0,0 +1,1 @@ +newexec diff -r a66d19b9302d newregular --- /dev/null +++ b/newregular @@ -0,0 +1,1 @@ +newregular diff -r a66d19b9302d regular --- a/regular +++ b/regular @@ -1,1 +1,2 @@ regular +regular diff -r a66d19b9302d rmbinary Binary file rmbinary has changed diff -r a66d19b9302d rmexec --- a/rmexec +++ /dev/null @@ -1,1 +0,0 @@ -rmexec diff -r a66d19b9302d rmregular --- a/rmregular +++ /dev/null @@ -1,1 +0,0 @@ -rmregular git=yes: git diff for single regular file $ hg autodiff --git=yes regular diff --git a/regular b/regular --- a/regular +++ b/regular @@ -1,1 +1,2 @@ regular +regular git=auto: regular diff for regular files and non-binary removals $ hg autodiff --git=auto regular newregular rmregular rmexec diff -r a66d19b9302d newregular --- /dev/null +++ b/newregular @@ -0,0 +1,1 @@ +newregular diff -r a66d19b9302d regular --- a/regular +++ b/regular @@ -1,1 +1,2 @@ regular +regular diff -r a66d19b9302d rmexec --- a/rmexec +++ /dev/null @@ -1,1 +0,0 @@ -rmexec diff -r a66d19b9302d rmregular --- a/rmregular +++ /dev/null @@ -1,1 +0,0 @@ -rmregular $ for f in exec newexec setexec unsetexec binary newbinary newempty rmempty rmbinary bintoregular; do > echo > echo '% git=auto: git diff for' $f > hg autodiff --git=auto $f > done % git=auto: git diff for exec diff -r a66d19b9302d exec --- a/exec +++ b/exec @@ -1,1 +1,2 @@ exec +exec % git=auto: git diff for newexec diff --git a/newexec b/newexec new file mode 100755 --- /dev/null +++ b/newexec @@ -0,0 +1,1 @@ +newexec % git=auto: git diff for setexec diff --git a/setexec b/setexec old mode 100644 new mode 100755 % git=auto: git diff for unsetexec diff --git a/unsetexec b/unsetexec old mode 100755 new mode 100644 % git=auto: git diff for binary diff --git a/binary b/binary index a9128c283485202893f5af379dd9beccb6e79486..09f370e38f498a462e1ca0faa724559b6630c04f GIT binary patch literal 2 Jc${Nk0000200961 % git=auto: git diff for newbinary diff --git a/newbinary b/newbinary new file mode 100644 index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..f76dd238ade08917e6712764a16a22005a50573d GIT binary patch literal 1 Ic${MZ000310RR91 % git=auto: git diff for newempty diff --git a/newempty b/newempty new file mode 100644 % git=auto: git diff for rmempty diff --git a/rmempty b/rmempty deleted file mode 100644 % git=auto: git diff for rmbinary diff --git a/rmbinary b/rmbinary deleted file mode 100644 index f76dd238ade08917e6712764a16a22005a50573d..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 GIT binary patch literal 0 Hc$@<O00001 % git=auto: git diff for bintoregular diff --git a/bintoregular b/bintoregular index f76dd238ade08917e6712764a16a22005a50573d..9c42f2b6427d8bf034b7bc23986152dc01bfd3ab GIT binary patch literal 13 Uc$`bh%qz(+N=+}#Ni5<5043uE82|tP git=warn: regular diff with data loss warnings $ hg autodiff --git=warn diff -r a66d19b9302d binary Binary file binary has changed diff -r a66d19b9302d bintoregular Binary file bintoregular has changed diff -r a66d19b9302d exec --- a/exec +++ b/exec @@ -1,1 +1,2 @@ exec +exec diff -r a66d19b9302d newbinary Binary file newbinary has changed diff -r a66d19b9302d newexec --- /dev/null +++ b/newexec @@ -0,0 +1,1 @@ +newexec diff -r a66d19b9302d newregular --- /dev/null +++ b/newregular @@ -0,0 +1,1 @@ +newregular diff -r a66d19b9302d regular --- a/regular +++ b/regular @@ -1,1 +1,2 @@ regular +regular diff -r a66d19b9302d rmbinary Binary file rmbinary has changed diff -r a66d19b9302d rmexec --- a/rmexec +++ /dev/null @@ -1,1 +0,0 @@ -rmexec diff -r a66d19b9302d rmregular --- a/rmregular +++ /dev/null @@ -1,1 +0,0 @@ -rmregular data lost for: binary data lost for: bintoregular data lost for: newbinary data lost for: newempty data lost for: newexec data lost for: rmbinary data lost for: rmempty data lost for: setexec data lost for: unsetexec git=abort: fail on execute bit change $ hg autodiff --git=abort regular setexec abort: losing data for setexec [255] git=abort: succeed on regular file $ hg autodiff --git=abort regular diff -r a66d19b9302d regular --- a/regular +++ b/regular @@ -1,1 +1,2 @@ regular +regular $ cd ..