[PATCH 3 of 4 STABLE] manifest: make manifestctx store the repo

[Yuya Nishihara]

On Tue, 25 Oct 2016 12:46:58 -0700, Durham Goode wrote:
> On 10/22/16 1:59 AM, Yuya Nishihara wrote:
> > On Tue, 18 Oct 2016 17:50:16 -0700, Durham Goode wrote:
> >> # HG changeset patch
> >> # User Durham Goode <durham at fb.com>
> >> # Date 1476837866 25200
> >> #      Tue Oct 18 17:44:26 2016 -0700
> >> # Branch stable
> >> # Node ID 3efece5c59853908d65de53635488361dbf20c49
> >> # Parent  ed607426a3ff4deda8c7f2de8b86d5b6ca976d67
> >> manifest: make manifestctx store the repo
> >>
> >> The old manifestctx stored a reference to the revlog. If the inmemory revlog
> >> became invalid, the ctx now held an old copy and would be incorrect. To fix
> >> this, we need the ctx to go through the manifestlog for each access.
> >>
> >> This is the same pattern that changectx already uses (it stores the repo, and
> >> accesses commit data through self._repo.changelog).
> >>
> >> diff --git a/mercurial/manifest.py b/mercurial/manifest.py
> >> --- a/mercurial/manifest.py
> >> +++ b/mercurial/manifest.py
> >> @@ -1276,7 +1276,7 @@ class manifestlog(object):
> >>           if self._treeinmem:
> >>               m = treemanifestctx(self._revlog, '', node)
> >>           else:
> >> -            m = manifestctx(self._revlog, node)
> >> +            m = manifestctx(self._repo, node)
> >>           if node != revlog.nullid:
> >>               self._mancache[node] = m
> > This will create a reference cycle, but I don't know if the situation gets
> > better or worse after this patch.
> >
> >    repo -> manifestlog -> _mancache -> manifestctx -> repo
> >
> > Is _mancache valid after the manifestlog is recreated?
> _mancache is not really valid after manifestlog is recreated, since it 
> may contain manifest entries that no longer exist in the file. Even if 
> it didn't contain bad entries, the manifestctx itself needs up-to-date 
> access to the manifest revlog, which is only available through the repo 
> object (since the repo object's property is what handles manifest revlog 
> cache checking).

Perhaps I miss the point. Do we have stale copies of manifestlog and manifestctx
somewhere? My understanding is we've moved the @storecache to manifestlog() at
3c8811efdddc, so manifestlog, _revlog (and _mancache) should be accessible only
when they are valid, and manifestlog doesn't live longer than repo.manifest().