Patchwork [5,of,9,V2] manifest: specify checkambig=True to revlog.__init__, to avoid ambiguity

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Submitter Katsunori FUJIWARA
Date Sept. 22, 2016, 12:59 p.m.
Message ID <f41572305dfab3686526.1474549164@feefifofum>
Download mbox | patch
Permalink /patch/16753/
State Accepted
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Katsunori FUJIWARA - Sept. 22, 2016, 12:59 p.m.
# HG changeset patch
# User FUJIWARA Katsunori <foozy@lares.dti.ne.jp>
# Date 1474548718 -32400
#      Thu Sep 22 21:51:58 2016 +0900
# Node ID f41572305dfab3686526fcc3a1339689542b6b53
# Parent  770044f70593a8f3932e176784ed09e33d734ddf
manifest: specify checkambig=True to revlog.__init__, to avoid ambiguity

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 00manifest.i (and close transaction)
  2. discard appended data by truncation (strip or rollback)
  3. append same size but different data to 00manifest.i again

Therefore, cache validation doesn't work after (3) as expected.

To avoid such file stat ambiguity around truncation, this patch
specifies checkambig=True to revlog.__init__(). This makes revlog
write changes out with checkambig=True.

Even after this patch, avoiding file stat ambiguity of 00manifest.i
around truncation isn't yet completed, because truncation side isn't
aware of this issue.

This is a part of ExactCacheValidationPlan.

    https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan

Patch

diff --git a/mercurial/manifest.py b/mercurial/manifest.py
--- a/mercurial/manifest.py
+++ b/mercurial/manifest.py
@@ -927,7 +927,8 @@  class manifestrevlog(revlog.revlog):
         else:
             self._dirlogcache = {'': self}
 
-        super(manifestrevlog, self).__init__(opener, indexfile)
+        super(manifestrevlog, self).__init__(opener, indexfile,
+                                             checkambig=bool(dir))
 
     @property
     def fulltextcache(self):