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

[Durham Goode]

On 10/26/16 5:54 AM, Yuya Nishihara wrote:
> 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().
Ah, yes manifestctx's may be held for longer than the manifestlog lives, 
by code that is out of our control.  I'm not aware of specific cases 
where this is happening, but it could.

I'm less concerned with stale manifestlogs, since most everything 
accesses it through repo.manifestlog already.