At Tue, 20 Sep 2016 18:12:58 +0200,
Pierre-Yves David wrote:
> 
> On 09/16/2016 10:51 PM, FUJIWARA Katsunori wrote:
> > # HG changeset patch
> > # User FUJIWARA Katsunori <fo...@lares.dti.ne.jp>
> > # Date 1474057495 -32400
> > #      Sat Sep 17 05:24:55 2016 +0900
> > # Node ID 71b6b49f8a7ab6c894028b9153290f4bbf0f54f6
> > # Parent  ad999fb789fcb86b11c98334ab98b31a17ee2d25
> > vfs: use checkambigatclosing in checkambig=True but atomictemp=False case
> >
> > In Mercurial source tree, opening a file in "a"/"a+" mode like below
> > doesn't specify atomictemp=True for vfs, and this avoids file stat
> > ambiguity check by atomictempfile.
> >
> >   - writing changes out in revlog layer uses "a+" mode
> >   - truncation in repair.strip() uses "a" mode
> >   - truncation in transaction._playback() uses "a" mode
> >
> > If steps below occurs at "the same time in sec", all of mtime, ctime
> > and size are same between (1) and (3).
> >
> >   1. append data to revlog-style file (and close transaction)
> >   2. discard appended data by truncation (strip or rollback)
> >   3. append same size but different data to revlog-style file again
> >
> > Therefore, cache validation doesn't work after (3) as expected.
> >
> > This patch uses checkambigatclosing in checkambig=True but
> > atomictemp=False case, to check (and get rid of) file stat ambiguity
> > at closing.
> >
> > This is a part of ExactCacheValidationPlan.
> >
> >     https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan
> >
> > diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
> > --- a/mercurial/scmutil.py
> > +++ b/mercurial/scmutil.py
> > @@ -587,6 +587,10 @@ class vfs(abstractvfs):
> >          if nlink == 0:
> >              self._fixfilemode(f)
> >
> > +        if checkambig:
> > +            assert mode not in ('r', 'rb'), "valid only at writing"
> > +            fp = checkambigatclosing(fp)
> 
> It sound a bit too much like a real logic check with assert. Instead we 
> should probably either:
> - have a hard check with an abort.
> - ignore the bad state with a devel warning (probably the best).

OK, I'll send revised one with the latter.


> Cheers,
> 
> -- 
> Pierre-Yves David
> 

----------------------------------------------------------------------
[FUJIWARA Katsunori]                             fo...@lares.dti.ne.jp
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