Mercurial > hg
view tests/test-mq-pull-from-bundle.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 | 89630d0b3e23 |
children |
line wrap: on
line source
#require repobundlerepo $ cat <<EOF >> $HGRCPATH > [extensions] > mq= > [alias] > tlog = log --template "{rev}: {node|short} {desc}\\n" > theads = heads --template "{rev}: {desc}\\n" > tincoming = incoming --template "{rev}: {desc}\\n" > EOF Setup main: $ hg init base $ cd base $ echo "One" > one $ hg add adding one $ hg ci -m "main: one added" $ echo "++" >> one $ hg ci -m "main: one updated" Bundle main: $ hg bundle --base=null ../main.hg 2 changesets found $ cd .. Incoming to fresh repo: $ hg init fresh $ hg -R fresh tincoming main.hg comparing with main.hg 0: main: one added 1: main: one updated $ test -f ./fresh/.hg/hg-bundle* && echo 'temp. bundle file remained' || true $ hg -R fresh tincoming bundle:fresh+main.hg comparing with bundle:fresh+main.hg 0: main: one added 1: main: one updated Setup queue: $ cd base $ hg qinit -c $ hg qnew -m "patch: two added" two.patch $ echo two > two $ hg add adding two $ hg qrefresh $ hg qcommit -m "queue: two.patch added" $ hg qpop -a popping two.patch patch queue now empty Bundle queue: $ hg -R .hg/patches bundle --base=null ../queue.hgq 1 changesets found $ test -f ./fresh/.hg/hg-bundle* && echo 'temp. bundle file remained' || true $ cd .. Clone base: $ hg clone base copy updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cd copy $ hg qinit -c Incoming queue bundle: $ hg -R .hg/patches tincoming ../queue.hgq comparing with ../queue.hgq 0: queue: two.patch added $ test -f .hg/hg-bundle* && echo 'temp. bundle file remained' || true Pull queue bundle: $ hg -R .hg/patches pull --update ../queue.hgq pulling from ../queue.hgq requesting all changes adding changesets adding manifests adding file changes added 1 changesets with 3 changes to 3 files new changesets d7553909353d (1 drafts) merging series 2 files updated, 1 files merged, 0 files removed, 0 files unresolved $ test -f .hg/patches/hg-bundle* && echo 'temp. bundle file remained' || true $ hg -R .hg/patches theads 0: queue: two.patch added $ hg -R .hg/patches tlog 0: d7553909353d queue: two.patch added $ hg qseries two.patch $ cd .. Clone base again: $ hg clone base copy2 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cd copy2 $ hg qinit -c Unbundle queue bundle: $ hg -R .hg/patches unbundle --update ../queue.hgq adding changesets adding manifests adding file changes added 1 changesets with 3 changes to 3 files new changesets d7553909353d (1 drafts) merging series 2 files updated, 1 files merged, 0 files removed, 0 files unresolved $ hg -R .hg/patches theads 0: queue: two.patch added $ hg -R .hg/patches tlog 0: d7553909353d queue: two.patch added $ hg qseries two.patch $ cd ..