Mercurial > hg
view tests/test-symlinks.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 | 96ca817ec192 |
children | 93eb6c8035a9 |
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#require symlink == tests added in 0.7 == $ hg init test-symlinks-0.7; cd test-symlinks-0.7; $ touch foo; ln -s foo bar; ln -s nonexistent baz import with add and addremove -- symlink walking should _not_ screwup. $ hg add adding bar adding baz adding foo $ hg forget bar baz foo $ hg addremove adding bar adding baz adding foo commit -- the symlink should _not_ appear added to dir state $ hg commit -m 'initial' $ touch bomb again, symlink should _not_ show up on dir state $ hg addremove adding bomb Assert screamed here before, should go by without consequence $ hg commit -m 'is there a bug?' $ cd .. == fifo & ignore == $ hg init test; cd test; $ mkdir dir $ touch a.c dir/a.o dir/b.o test what happens if we want to trick hg $ hg commit -A -m 0 adding a.c adding dir/a.o adding dir/b.o $ echo "relglob:*.o" > .hgignore $ rm a.c $ rm dir/a.o $ rm dir/b.o $ mkdir dir/a.o $ ln -s nonexistent dir/b.o $ mkfifo a.c it should show a.c, dir/a.o and dir/b.o deleted $ hg status M dir/b.o ! a.c ! dir/a.o ? .hgignore $ hg status a.c a.c: unsupported file type (type is fifo) ! a.c $ cd .. == symlinks from outside the tree == test absolute path through symlink outside repo $ p=`pwd` $ hg init x $ ln -s x y $ cd x $ touch f $ hg add f $ hg status "$p"/y/f A f try symlink outside repo to file inside $ ln -s x/f ../z this should fail $ hg status ../z && { echo hg mistakenly exited with status 0; exit 1; } || : abort: ../z not under root '$TESTTMP/x' $ cd .. == cloning symlinks == $ hg init clone; cd clone; try cloning symlink in a subdir 1. commit a symlink $ mkdir -p a/b/c $ cd a/b/c $ ln -s /path/to/symlink/source demo $ cd ../../.. $ hg stat ? a/b/c/demo $ hg commit -A -m 'add symlink in a/b/c subdir' adding a/b/c/demo 2. clone it $ cd .. $ hg clone clone clonedest updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved == symlink and git diffs == git symlink diff $ cd clonedest $ hg diff --git -r null:tip diff --git a/a/b/c/demo b/a/b/c/demo new file mode 120000 --- /dev/null +++ b/a/b/c/demo @@ -0,0 +1,1 @@ +/path/to/symlink/source \ No newline at end of file $ hg export --git tip > ../sl.diff import git symlink diff $ hg rm a/b/c/demo $ hg commit -m'remove link' $ hg import ../sl.diff applying ../sl.diff $ hg diff --git -r 1:tip diff --git a/a/b/c/demo b/a/b/c/demo new file mode 120000 --- /dev/null +++ b/a/b/c/demo @@ -0,0 +1,1 @@ +/path/to/symlink/source \ No newline at end of file == symlinks and addremove == directory moved and symlinked $ mkdir foo $ touch foo/a $ hg ci -Ama adding foo/a $ mv foo bar $ ln -s bar foo $ hg status ! foo/a ? bar/a ? foo now addremove should remove old files $ hg addremove adding bar/a adding foo removing foo/a commit and update back $ hg ci -mb $ hg up '.^' 1 files updated, 0 files merged, 2 files removed, 0 files unresolved $ hg up tip 2 files updated, 0 files merged, 1 files removed, 0 files unresolved $ cd .. == root of repository is symlinked == $ hg init root $ ln -s root link $ cd root $ echo foo > foo $ hg status ? foo $ hg status ../link ? foo $ hg add foo $ hg cp foo "$TESTTMP/link/bar" foo has not been committed yet, so no copy data will be stored for bar. $ cd .. $ hg init b $ cd b $ ln -s nothing dangling $ hg commit -m 'commit symlink without adding' dangling abort: dangling: file not tracked! [10] $ hg add dangling $ hg commit -m 'add symlink' $ hg tip -v changeset: 0:cabd88b706fc tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 files: dangling description: add symlink $ hg manifest --debug 2564acbe54bbbedfbf608479340b359f04597f80 644 @ dangling $ readlink.py dangling dangling -> nothing $ rm dangling $ ln -s void dangling $ hg commit -m 'change symlink' $ readlink.py dangling dangling -> void modifying link $ rm dangling $ ln -s empty dangling $ readlink.py dangling dangling -> empty reverting to rev 0: $ hg revert -r 0 -a reverting dangling $ readlink.py dangling dangling -> nothing backups: $ readlink.py *.orig dangling.orig -> empty $ rm *.orig $ hg up -C 1 files updated, 0 files merged, 0 files removed, 0 files unresolved copies $ hg cp -v dangling dangling2 copying dangling to dangling2 $ hg st -Cmard A dangling2 dangling $ readlink.py dangling dangling2 dangling -> void dangling2 -> void Issue995: hg copy -A incorrectly handles symbolic links $ hg up -C 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ mkdir dir $ ln -s dir dirlink $ hg ci -qAm 'add dirlink' $ mkdir newdir $ mv dir newdir/dir $ mv dirlink newdir/dirlink $ hg mv -A dirlink newdir/dirlink $ cd ..