assistant: Fix race in v6 mode that caused downloaded file content to sometimes not replace pointer files.

The keys database handle needs to be closed after merging, because the
smudge filter, in another process, updates the database. Old cached info
can be read for a while from the open database handle; closing it ensures
that the info written by the smudge filter is available.

This is pretty horribly ad-hoc, and it's especially nasty that the
transferrer closes the database every time.

5 files changed, 38 insertions, 4 deletions

diff --git a/Assistant/Threads/Merger.hs b/Assistant/Threads/Merger.hs
index 521e5bda6..0080ef964 100644
--- a/Assistant/Threads/Merger.hs
+++ b/Assistant/Threads/Merger.hs
@@ -19,6 +19,7 @@ import qualified Annex.Branch
 import qualified Git
 import qualified Git.Branch
 import qualified Command.Sync
+import qualified Database.Keys
 import Annex.TaggedPush
 import Remote (remoteFromUUID)
 
@@ -89,6 +90,12 @@ onChange file
 					currbranch mergeConfig
 					Git.Branch.AutomaticCommit
 					changedbranch
+				-- Merging can cause new associated files
+				-- to appear and the smudge filter will
+				-- add them to the database. To ensure that
+				-- this process sees those changes, close
+				-- the database if it was open.
+				liftAnnex $ Database.Keys.closeDb
 	mergecurrent _ = noop
 
 	handleDesynced = case fromTaggedBranch changedbranch of
diff --git a/Command/TransferKeys.hs b/Command/TransferKeys.hs
index 005e491b4..82dc15032 100644
--- a/Command/TransferKeys.hs
+++ b/Command/TransferKeys.hs
@@ -16,6 +16,7 @@ import Annex.Transfer
 import qualified Remote
 import Utility.SimpleProtocol (dupIoHandles)
 import Git.Types (RemoteName)
+import qualified Database.Keys
 
 data TransferRequest = TransferRequest Direction Remote Key AssociatedFile
 
@@ -41,8 +42,13 @@ start = do
 				return ok
 		| otherwise = notifyTransfer direction file $
 			download (Remote.uuid remote) key file forwardRetry observer $ \p ->
-				getViaTmp (RemoteVerify remote) key $ \t -> 
-					Remote.retrieveKeyFile remote key file t p
+				getViaTmp (RemoteVerify remote) key $ \t -> do
+					r <- Remote.retrieveKeyFile remote key file t p
+					-- Make sure we get the current
+					-- associated files data for the key,
+					-- not old cached data.
+					Database.Keys.closeDb			
+					return r
 	
 	observer False t tinfo = recordFailedTransfer t tinfo
 	observer True _ _ = noop
diff --git a/Database/Keys.hs b/Database/Keys.hs
index ed3878161..778540137 100644
--- a/Database/Keys.hs
+++ b/Database/Keys.hs
@@ -9,6 +9,7 @@
 
 module Database.Keys (
 	DbHandle,
+	closeDb,
 	addAssociatedFile,
 	getAssociatedFiles,
 	getAssociatedKey,
@@ -137,6 +138,16 @@ openDb createdb _ = catchPermissionDenied permerr $ withExclusiveLock gitAnnexKe
 		False -> return DbUnavailable
 		True -> throwM e
 
+{- Closes the database if it was open. Any writes will be flushed to it.
+ -
+ - This does not normally need to be called; the database will auto-close
+ - when the handle is garbage collected. However, this can be used to
+ - force a re-read of the database, in case another process has written
+ - data to it.
+ -}
+closeDb :: Annex ()
+closeDb = liftIO . closeDbHandle =<< getDbHandle
+
 addAssociatedFile :: Key -> TopFilePath -> Annex ()
 addAssociatedFile k f = runWriterIO $ SQL.addAssociatedFile (toIKey k) f
 
diff --git a/Database/Keys/Handle.hs b/Database/Keys/Handle.hs
index 51de58fa8..1ef16d031 100644
--- a/Database/Keys/Handle.hs
+++ b/Database/Keys/Handle.hs
@@ -11,6 +11,7 @@ module Database.Keys.Handle (
 	DbState(..),
 	withDbState,
 	flushDbQueue,
+	closeDbHandle,
 ) where
 
 import qualified Database.Queue as H
@@ -38,8 +39,7 @@ newDbHandle = DbHandle <$> newMVar DbClosed
 withDbState
 	:: (MonadIO m, MonadCatch m)
 	=> DbHandle
-	-> (DbState
-	-> m (v, DbState))
+	-> (DbState -> m (v, DbState))
 	-> m v
 withDbState (DbHandle mvar) a = do
 	st <- liftIO $ takeMVar mvar
@@ -55,3 +55,11 @@ flushDbQueue (DbHandle mvar) = go =<< readMVar mvar
   where
 	go (DbOpen qh) = H.flushDbQueue qh
 	go _ = return ()
+
+closeDbHandle :: DbHandle -> IO ()
+closeDbHandle h = withDbState h go
+  where
+	go (DbOpen qh) = do
+		H.closeDbQueue qh
+		return ((), DbClosed)
+	go st = return ((), st)
diff --git a/debian/changelog b/debian/changelog
index af54ed566..e9de8bce8 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -8,6 +8,8 @@ git-annex (6.20160512) UNRELEASED; urgency=medium
     original branch.
   * assistant: Fix bug that caused v6 pointer files to be annexed by the
     assistant.
+  * assistant: Fix race in v6 mode that caused downloaded file content to
+    sometimes not replace pointer files.
 
  -- Joey Hess <id@joeyh.name>  Wed, 11 May 2016 16:08:38 -0400