[PATCH 5 of 7 V2] fncache: move fncache writing to be in a transaction

[Durham Goode]

# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1395700933 25200
#      Mon Mar 24 15:42:13 2014 -0700
# Node ID 23c4a802f5179a96dcc0ae26ce97671b675d87e3
# Parent  498a1087dd60ec7234c4352e566abe977eb63332
fncache: move fncache writing to be in a transaction

Previously the fncache was written at lock.release time. This meant it was not
tracked by a transaction, and if an error occurred during the fncache write it
would fail to update the fncache, but would not rollback the transaction,
resulting in an fncache that was not in sync with the files on disk (which
causes verify to fail, and causes streaming clones to not copy all the revlogs).

This uses the new transaction backup mechanism to make the fncache transacted.
It also moves the fncache from being written at lock.release time, to being
written at transaction.close time.

diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -823,13 +823,17 @@
             raise error.RepoError(
                 _("abandoned transaction found - run hg recover"))
 
+        def onclose():
+            self.store.write(tr)
+
         self._writejournal(desc)
         renames = [(vfs, x, undoname(x)) for vfs, x in self._journalfiles()]
         rp = report and report or self.ui.warn
         tr = transaction.transaction(rp, self.sopener,
                                      "journal",
                                      aftertrans(renames),
-                                     self.store.createmode)
+                                     self.store.createmode,
+                                     onclose)
         self._transref = weakref.ref(tr)
         return tr
 
@@ -1037,7 +1041,6 @@
             return l
 
         def unlock():
-            self.store.write()
             if hasunfilteredcache(self, '_phasecache'):
                 self._phasecache.write()
             for k, ce in self._filecache.items():
diff --git a/mercurial/store.py b/mercurial/store.py
--- a/mercurial/store.py
+++ b/mercurial/store.py
@@ -337,7 +337,7 @@
     def copylist(self):
         return ['requires'] + _data.split()
 
-    def write(self):
+    def write(self, tr):
         pass
 
     def __contains__(self, path):
@@ -402,16 +402,14 @@
                     raise util.Abort(t)
         fp.close()
 
-    def _write(self, files, atomictemp):
-        fp = self.vfs('fncache', mode='wb', atomictemp=atomictemp)
-        if files:
-            fp.write(encodedir('\n'.join(files) + '\n'))
-        fp.close()
-        self._dirty = False
-
-    def write(self):
+    def write(self, tr):
         if self._dirty:
-            self._write(self.entries, True)
+            tr.addbackup('fncache')
+            fp = self.vfs('fncache', mode='wb', atomictemp=True)
+            if self.entries:
+                fp.write(encodedir('\n'.join(self.entries) + '\n'))
+            fp.close()
+            self._dirty = False
 
     def add(self, fn):
         if self.entries is None:
@@ -488,8 +486,8 @@
         return (['requires', '00changelog.i'] +
                 ['store/' + f for f in d.split()])
 
-    def write(self):
-        self.fncache.write()
+    def write(self, tr):
+        self.fncache.write(tr)
 
     def _exists(self, f):
         ef = self.encode(f)
diff --git a/tests/test-fncache.t b/tests/test-fncache.t
--- a/tests/test-fncache.t
+++ b/tests/test-fncache.t
@@ -177,4 +177,62 @@
 
   $ cd ..
 
+Aborting lock does not prevent fncache writes
 
+  $ cat > exceptionext.py <<EOF
+  > import os
+  > from mercurial import commands, util
+  > from mercurial.extensions import wrapfunction
+  > 
+  > def lockexception(orig, vfs, lockname, wait, releasefn, acquirefn, desc):
+  >     def releasewrap():
+  >         raise util.Abort("forced lock failure")
+  >     return orig(vfs, lockname, wait, releasewrap, acquirefn, desc)
+  > 
+  > def reposetup(ui, repo):
+  >     wrapfunction(repo, '_lock', lockexception)
+  > 
+  > cmdtable = {}
+  > 
+  > EOF
+  $ extpath=`pwd`/exceptionext.py
+  $ hg init fncachetxn
+  $ cd fncachetxn
+  $ printf "[extensions]\nexceptionext=$extpath\n" >> .hg/hgrc
+  $ touch y
+  $ hg ci -qAm y
+  abort: forced lock failure
+  [255]
+  $ cat .hg/store/fncache
+  data/y.i
+
+Aborting tranaction prevents fncache change
+
+  $ cat > ../exceptionext.py <<EOF
+  > import os
+  > from mercurial import commands, util, transaction
+  > from mercurial.extensions import wrapfunction
+  > 
+  > def wrapper(orig, self, *args, **kwargs):
+  >     origonclose = self.onclose
+  >     def onclose():
+  >         origonclose()
+  >         raise util.Abort("forced transaction failure")
+  >     self.onclose = onclose
+  >     return orig(self, *args, **kwargs)
+  > 
+  > def uisetup(ui):
+  >     wrapfunction(transaction.transaction, 'close', wrapper)
+  > 
+  > cmdtable = {}
+  > 
+  > EOF
+  $ rm "${extpath}c"
+  $ touch z
+  $ hg ci -qAm z
+  transaction abort!
+  rollback completed
+  abort: forced transaction failure
+  [255]
+  $ cat .hg/store/fncache
+  data/y.i