view tests/test-remotefilelog-linknodes.t @ 49000:dd6b67d5c256 stable

rust: fix unsound `OwningDirstateMap`

As per the previous patch, `OwningDirstateMap` is unsound. Self-referential
structs are difficult to implement correctly in Rust since the compiler is
free to move structs around as much as it wants to. They are also very rarely
needed in practice, so the state-of-the-art on how they should be done within
the Rust rules is still a bit new.

The crate `ouroboros` is an attempt at providing a safe way (in the Rust sense)
of declaring self-referential structs. It is getting a lot attention and was
improved very quickly when soundness issues were found in the past: rather than
relying on our own (limited) review circle, we might as well use the de-facto
common crate to fix this problem. This will give us a much better chance of
finding issues should any new ones be discovered as well as the benefit of
fewer `unsafe` APIs of our own.

I was starting to think about how I would present a safe API to the old struct
but soon realized that the callback-based approach was already done in
`ouroboros`, along with a lot more care towards refusing incorrect structs.

In short: we don't return a mutable reference to the `DirstateMap` anymore, we
expect users of its API to pass a `FnOnce` that takes the map as an argument.
This allows our `OwningDirstateMap` to control the input and output lifetimes
of the code that modifies it to prevent such issues.

Changing to `ouroboros` meant changing every API with it, but it is relatively
low churn in the end. It correctly identified the example buggy modification of
`copy_map_insert` outlined in the previous patch as violating the borrow rules.

Differential Revision: https://phab.mercurial-scm.org/D12429

#require no-windows

# Tests for the complicated linknode logic in remotefilelog.py::ancestormap()

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

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > serverexpiration=-1
  > EOF
  $ echo x > x
  $ hg commit -qAm x
  $ cd ..

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

# Rebase produces correct log -f linknodes

  $ cd shallow
  $ echo y > y
  $ hg commit -qAm y
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo x >> x
  $ hg commit -qAm xx
  $ hg log -f x --template "{node|short}\n"
  0632994590a8
  b292c1e3311f

  $ hg rebase -d 1
  rebasing 2:0632994590a8 tip "xx"
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/0632994590a8-0bc786d8-rebase.hg (glob)
  $ hg log -f x --template "{node|short}\n"
  81deab2073bc
  b292c1e3311f

# Rebase back, log -f still works

  $ hg rebase -d 0 -r 2
  rebasing 2:81deab2073bc tip "xx"
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/81deab2073bc-80cb4fda-rebase.hg (glob)
  $ hg log -f x --template "{node|short}\n"
  b3fca10fb42d
  b292c1e3311f

  $ hg rebase -d 1 -r 2
  rebasing 2:b3fca10fb42d tip "xx"
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/b3fca10fb42d-da73a0c7-rebase.hg (glob)

  $ cd ..

# Reset repos
  $ clearcache

  $ rm -rf master
  $ rm -rf shallow
  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > serverexpiration=-1
  > EOF
  $ echo x > x
  $ hg commit -qAm x
  $ cd ..

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

# Rebase stack onto landed commit

  $ cd master
  $ echo x >> x
  $ hg commit -Aqm xx

  $ cd ../shallow
  $ echo x >> x
  $ hg commit -Aqm xx2
  $ echo y >> x
  $ hg commit -Aqm xxy

  $ hg pull -q
  $ hg rebase -d tip
  rebasing 1:4549721d828f "xx2"
  note: not rebasing 1:4549721d828f "xx2", its destination already has all its changes
  rebasing 2:5ef6d97e851c "xxy"
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/4549721d828f-b084e33c-rebase.hg (glob)
  $ hg log -f x --template '{node|short}\n'
  4ae8e31c85ef
  0632994590a8
  b292c1e3311f

  $ cd ..

# system cache has invalid linknode, but .hg/store/data has valid

  $ cd shallow
  $ hg strip -r 1 -q
  $ rm -rf .hg/store/data/*
  $ echo x >> x
  $ hg commit -Aqm xx_local
  $ hg log -f x --template '{rev}:{node|short}\n'
  1:21847713771d
  0:b292c1e3311f

  $ cd ..
  $ rm -rf shallow

/* Local linknode is invalid; remote linknode is valid (formerly slow case) */

  $ hgcloneshallow ssh://user@dummy/master shallow -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over * (glob)
  $ cd shallow
  $ echo x >> x
  $ hg commit -Aqm xx2
  $ cd ../master
  $ echo y >> y
  $ hg commit -Aqm yy2
  $ echo x >> x
  $ hg commit -Aqm xx2-fake-rebased
  $ echo y >> y
  $ hg commit -Aqm yy3
  $ cd ../shallow
  $ hg pull --config remotefilelog.debug=True
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 0 changes to 0 files (+1 heads)
  new changesets 01979f9404f8:7200df4e0aca
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg update tip -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ echo x > x
  $ hg commit -qAm xx3

# At this point, the linknode points to c1254e70bad1 instead of 32e6611f6149
  $ hg log -G -T '{node|short} {desc} {phase} {files}\n'
  @  a5957b6bf0bd xx3 draft x
  |
  o  7200df4e0aca yy3 public y
  |
  o  32e6611f6149 xx2-fake-rebased public x
  |
  o  01979f9404f8 yy2 public y
  |
  | o  c1254e70bad1 xx2 draft x
  |/
  o  0632994590a8 xx public x
  |
  o  b292c1e3311f x public x
  
# Check the contents of the local blob for incorrect linknode
  $ hg debugremotefilelog .hg/store/data/11f6ad8ec52a2984abaafd7c3b516503785c2072/d4a3ed9310e5bd9887e3bf779da5077efab28216
  size: 6 bytes
  path: .hg/store/data/11f6ad8ec52a2984abaafd7c3b516503785c2072/d4a3ed9310e5bd9887e3bf779da5077efab28216 
  key: d4a3ed9310e5 
  
          node =>           p1            p2      linknode     copyfrom
  d4a3ed9310e5 => aee31534993a  000000000000  c1254e70bad1  
  aee31534993a => 1406e7411862  000000000000  0632994590a8  
  1406e7411862 => 000000000000  000000000000  b292c1e3311f  

# Verify that we do a fetch on the first log (remote blob fetch for linkrev fix)
  $ hg log -f x -T '{node|short} {desc} {phase} {files}\n'
  a5957b6bf0bd xx3 draft x
  32e6611f6149 xx2-fake-rebased public x
  0632994590a8 xx public x
  b292c1e3311f x public x
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

# But not after that
  $ hg log -f x -T '{node|short} {desc} {phase} {files}\n'
  a5957b6bf0bd xx3 draft x
  32e6611f6149 xx2-fake-rebased public x
  0632994590a8 xx public x
  b292c1e3311f x public x

# Check the contents of the remote blob for correct linknode
  $ hg debugremotefilelog $CACHEDIR/master/11/f6ad8ec52a2984abaafd7c3b516503785c2072/d4a3ed9310e5bd9887e3bf779da5077efab28216
  size: 6 bytes
  path: $TESTTMP/hgcache/master/11/f6ad8ec52a2984abaafd7c3b516503785c2072/d4a3ed9310e5bd9887e3bf779da5077efab28216 
  key: d4a3ed9310e5 
  
          node =>           p1            p2      linknode     copyfrom
  d4a3ed9310e5 => aee31534993a  000000000000  32e6611f6149  
  aee31534993a => 1406e7411862  000000000000  0632994590a8  
  1406e7411862 => 000000000000  000000000000  b292c1e3311f