view tests/test-remotefilelog-local.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

#require no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > x
  $ echo y > y
  $ echo z > z
  $ hg commit -qAm xy

  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow -q
  3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over *s (glob)
  $ cd shallow

# status

  $ clearcache
  $ echo xx > x
  $ echo yy > y
  $ touch a
  $ hg status
  M x
  M y
  ? a
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ hg add a
  $ hg status
  M x
  M y
  A a

# diff

  $ hg debugrebuilddirstate # fixes dirstate non-determinism
  $ hg add a
  $ clearcache
  $ hg diff
  diff -r f3d0bb0d1e48 x
  --- a/x* (glob)
  +++ b/x* (glob)
  @@ -1,1 +1,1 @@
  -x
  +xx
  diff -r f3d0bb0d1e48 y
  --- a/y* (glob)
  +++ b/y* (glob)
  @@ -1,1 +1,1 @@
  -y
  +yy
  3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over *s (glob)

# local commit

  $ clearcache
  $ echo a > a
  $ echo xxx > x
  $ echo yyy > y
  $ hg commit -m a
  ? files fetched over 1 fetches - (? misses, 0.00% hit ratio) over *s (glob)

# local commit where the dirstate is clean -- ensure that we do just one fetch
# (update to a commit on the server first)

  $ hg --config debug.dirstate.delaywrite=1 up 0
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ clearcache
  $ hg debugdirstate
  n 644          2 * x (glob)
  n 644          2 * y (glob)
  n 644          2 * z (glob)
  $ echo xxxx > x
  $ echo yyyy > y
  $ hg commit -m x
  created new head
  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)

# restore state for future tests

  $ hg -q strip .
  $ hg -q up tip

# rebase

  $ clearcache
  $ cd ../master
  $ echo w > w
  $ hg commit -qAm w

  $ cd ../shallow
  $ hg pull
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)
  new changesets fed61014d323
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg rebase -d tip
  rebasing 1:9abfe7bca547 "a"
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/9abfe7bca547-8b11e5ff-rebase.hg (glob)
  3 files fetched over 2 fetches - (3 misses, 0.00% hit ratio) over *s (glob)

# strip

  $ clearcache
  $ hg debugrebuilddirstate # fixes dirstate non-determinism
  $ hg strip -r .
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/19edf50f4de7-df3d0f74-backup.hg (glob)
  4 files fetched over 2 fetches - (4 misses, 0.00% hit ratio) over *s (glob)

# unbundle

  $ clearcache
  $ ls -A
  .hg
  w
  x
  y
  z

  $ hg debugrebuilddirstate # fixes dirstate non-determinism
  $ hg unbundle .hg/strip-backup/19edf50f4de7-df3d0f74-backup.hg
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets 19edf50f4de7 (1 drafts)
  (run 'hg update' to get a working copy)

  $ hg up
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  4 files fetched over 1 fetches - (4 misses, 0.00% hit ratio) over *s (glob)
  $ cat a
  a

# revert

  $ clearcache
  $ hg revert -r .~2 y z
  no changes needed to z
  2 files fetched over 2 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
  $ hg checkout -C -r . -q

# explicit bundle should produce full bundle file

  $ hg bundle -r 2 --base 1 ../local.bundle
  1 changesets found
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow2 -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ cd shallow2
  $ hg unbundle ../local.bundle
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 3 changes to 3 files
  new changesets 19edf50f4de7 (1 drafts)
  (run 'hg update' to get a working copy)

  $ hg log -r 2 --stat
  changeset:   2:19edf50f4de7
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     a
  
   a |  1 +
   x |  2 +-
   y |  2 +-
   3 files changed, 3 insertions(+), 2 deletions(-)
  
# Merge

  $ echo merge >> w
  $ hg commit -m w
  created new head
  $ hg merge 2
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m merge
  $ hg strip -q -r ".^"

# commit without producing new node

  $ cd $TESTTMP
  $ hgcloneshallow ssh://user@dummy/master shallow3 -q
  $ cd shallow3
  $ echo 1 > A
  $ hg commit -m foo -A A
  $ hg log -r . -T '{node}\n'
  383ce605500277f879b7460a16ba620eb6930b7f
  $ hg update -r '.^' -q
  $ echo 1 > A
  $ hg commit -m foo -A A
  warning: commit already existed in the repository!
  $ hg log -r . -T '{node}\n'
  383ce605500277f879b7460a16ba620eb6930b7f