Mercurial > hg
view tests/test-convert-cvsnt-mergepoints.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 | e5e5ee2b60e4 |
children |
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#require cvs no-root $ filterpath() > { > eval "$@" | sed "s:$CVSROOT:*REPO*:g" > } $ cvscall() > { > cvs -f "$@" > } output of 'cvs ci' varies unpredictably, so discard most of it -- just keep the part that matters $ cvsci() > { > cvs -f ci -f "$@" > /dev/null > } $ hgcat() > { > hg --cwd src-hg cat -r tip "$1" > } $ echo "[extensions]" >> $HGRCPATH $ echo "convert = " >> $HGRCPATH create cvs repository $ mkdir cvsmaster $ cd cvsmaster $ CVSROOT=`pwd` $ export CVSROOT $ CVS_OPTIONS=-f $ export CVS_OPTIONS $ cd .. $ rmdir cvsmaster $ filterpath cvscall -Q -d "$CVSROOT" init checkout #1: add foo.txt $ cvscall -Q checkout -d cvsworktmp . $ cd cvsworktmp $ mkdir foo $ cvscall -Q add foo $ cd foo $ echo foo > foo.txt $ cvscall -Q add foo.txt $ cvsci -m "add foo.txt" foo.txt $ cd ../.. $ rm -rf cvsworktmp checkout #2: create MYBRANCH1 and modify foo.txt on it $ cvscall -Q checkout -d cvswork foo $ cd cvswork $ cvscall -q rtag -b -R MYBRANCH1 foo $ cvscall -Q update -P -r MYBRANCH1 $ echo bar > foo.txt $ cvsci -m "bar" foo.txt $ echo baz > foo.txt $ cvsci -m "baz" foo.txt create MYBRANCH1_2 and modify foo.txt some more $ cvscall -q rtag -b -R -r MYBRANCH1 MYBRANCH1_2 foo $ cvscall -Q update -P -r MYBRANCH1_2 $ echo bazzie > foo.txt $ cvsci -m "bazzie" foo.txt create MYBRANCH1_1 and modify foo.txt yet again $ cvscall -q rtag -b -R MYBRANCH1_1 foo $ cvscall -Q update -P -r MYBRANCH1_1 $ echo quux > foo.txt $ cvsci -m "quux" foo.txt merge MYBRANCH1 to MYBRANCH1_1 $ filterpath cvscall -Q update -P -jMYBRANCH1 rcsmerge: warning: conflicts during merge RCS file: *REPO*/foo/foo.txt,v retrieving revision 1.1 retrieving revision 1.1.2.2 Merging differences between 1.1 and 1.1.2.2 into foo.txt carefully placed sleep to dodge cvs bug (optimization?) where it sometimes ignores a "commit" command if it comes too fast (the -f option in cvsci seems to work for all the other commits in this script) $ sleep 1 $ echo xyzzy > foo.txt $ cvsci -m "merge1+clobber" foo.txt #if unix-permissions return to trunk and merge MYBRANCH1_2 $ cvscall -Q update -P -A $ filterpath cvscall -Q update -P -jMYBRANCH1_2 RCS file: *REPO*/foo/foo.txt,v retrieving revision 1.1 retrieving revision 1.1.2.2.2.1 Merging differences between 1.1 and 1.1.2.2.2.1 into foo.txt $ cvsci -m "merge2" foo.txt $ REALCVS=`which cvs` $ echo "for x in \$*; do if [ \"\$x\" = \"rlog\" ]; then echo \"RCS file: $CVSROOT/foo/foo.txt,v\"; cat \"$TESTDIR/test-convert-cvsnt-mergepoints.rlog\"; exit 0; fi; done; $REALCVS \$*" > ../cvs $ chmod +x ../cvs $ PATH=..:${PATH} hg debugcvsps --parents foo collecting CVS rlog 7 log entries creating changesets 7 changeset entries --------------------- PatchSet 1 Date: * (glob) Author: user Branch: HEAD Tag: (none) Branchpoints: MYBRANCH1, MYBRANCH1_1 Log: foo.txt Members: foo.txt:INITIAL->1.1 --------------------- PatchSet 2 Date: * (glob) Author: user Branch: MYBRANCH1 Tag: (none) Parent: 1 Log: bar Members: foo.txt:1.1->1.1.2.1 --------------------- PatchSet 3 Date: * (glob) Author: user Branch: MYBRANCH1 Tag: (none) Branchpoints: MYBRANCH1_2 Parent: 2 Log: baz Members: foo.txt:1.1.2.1->1.1.2.2 --------------------- PatchSet 4 Date: * (glob) Author: user Branch: MYBRANCH1_1 Tag: (none) Parent: 1 Log: quux Members: foo.txt:1.1->1.1.4.1 --------------------- PatchSet 5 Date: * (glob) Author: user Branch: MYBRANCH1_2 Tag: (none) Parent: 3 Log: bazzie Members: foo.txt:1.1.2.2->1.1.2.2.2.1 --------------------- PatchSet 6 Date: * (glob) Author: user Branch: HEAD Tag: (none) Parents: 1,5 Log: merge Members: foo.txt:1.1->1.2 --------------------- PatchSet 7 Date: * (glob) Author: user Branch: MYBRANCH1_1 Tag: (none) Parents: 4,3 Log: merge Members: foo.txt:1.1.4.1->1.1.4.2 #endif $ cd ..