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

#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 ..