pending adds now retried for kqueue

Rethought how to keep track of pending adds that need to be retried later.
The commit thread already run up every second when there are changes,
so let's keep pending adds queued as changes until they're safe to add.

Also, the committer is now smarter about avoiding empty commits when
all the adds are currently unsafe, or in the rare case that an add event
for a symlink is not received in time. It may avoid them entirely.

This seems to work as before for inotify, and is untested for kqueue.

(Actually commit batching seems to be improved for inotify, although I'm
not sure why. I'm seeing only two commits made during large batch
operations, and the first of those is the non-batch mode commit.)

1 files changed, 85 insertions, 77 deletions

diff --git a/Assistant/Committer.hs b/Assistant/Committer.hs
index 600034a0a..46fee1b74 100644
--- a/Assistant/Committer.hs
+++ b/Assistant/Committer.hs
@@ -7,7 +7,6 @@ module Assistant.Committer where
 
 import Common.Annex
 import Assistant.Changes
-import Assistant.DaemonStatus
 import Assistant.ThreadedMonad
 import Assistant.Watcher
 import qualified Annex
@@ -24,20 +23,25 @@ import Types.KeySource
 import Data.Time.Clock
 import Data.Tuple.Utils
 import qualified Data.Set as S
+import Data.Either
 
 {- This thread makes git commits at appropriate times. -}
-commitThread :: ThreadState -> DaemonStatusHandle -> ChangeChan -> IO ()
-commitThread st dstatus changechan = runEvery (Seconds 1) $ do
+commitThread :: ThreadState -> ChangeChan -> IO ()
+commitThread st changechan = runEvery (Seconds 1) $ do
 	-- We already waited one second as a simple rate limiter.
-	-- Next, wait until at least one change has been made.
-	cs <- getChanges changechan
+	-- Next, wait until at least one change is available for
+	-- processing.
+	changes <- getChanges changechan
 	-- Now see if now's a good time to commit.
 	time <- getCurrentTime
-	if shouldCommit time cs
+	if shouldCommit time changes
 		then do
-			handleAdds st dstatus changechan cs
-			void $ tryIO $ runThreadState st commitStaged
-		else refillChanges changechan cs
+			readychanges <- handleAdds st changechan changes
+			if shouldCommit time readychanges
+				then do
+					void $ tryIO $ runThreadState st commitStaged
+				else refillChanges changechan readychanges
+		else refillChanges changechan changes
 
 commitStaged :: Annex ()
 commitStaged = do
@@ -83,95 +87,99 @@ shouldCommit now changes
  - staged before returning, and will be committed immediately.
  -
  - OTOH, for kqueue, eventsCoalesce, so instead the symlink is directly
- - created and staged, if the file is not open.
+ - created and staged.
+ -
+ - Returns a list of all changes that are ready to be committed.
+ - Any pending adds that are not ready yet are put back into the ChangeChan,
+ - where they will be retried later.
  -}
-handleAdds :: ThreadState -> DaemonStatusHandle -> ChangeChan -> [Change] -> IO ()
-handleAdds st dstatus changechan cs
-	| null toadd = noop
-	| otherwise = do
-		toadd' <- safeToAdd st dstatus toadd
-		unless (null toadd') $ do
-			added <- filter id <$> forM toadd' add
-			unless (DirWatcher.eventsCoalesce || null added) $
-				handleAdds st dstatus changechan
+handleAdds :: ThreadState -> ChangeChan -> [Change] -> IO [Change]
+handleAdds st changechan cs = returnWhen (null pendingadds) $ do
+	(postponed, toadd) <- partitionEithers <$>
+		safeToAdd st pendingadds
+
+	unless (null postponed) $
+		refillChanges changechan postponed
+
+	returnWhen (null toadd) $ do
+		added <- catMaybes <$> forM toadd add
+		if (DirWatcher.eventsCoalesce || null added)
+			then return $ added ++ otherchanges
+			else do
+				r <- handleAdds st changechan
 					=<< getChanges changechan
+				return $ r ++ added ++ otherchanges
 	where
-		toadd = map changeFile $ filter isPendingAdd cs
+		(pendingadds, otherchanges) = partition isPendingAddChange cs
+
+		returnWhen c a
+			| c = return otherchanges
+			| otherwise = a
 
-		isPendingAdd (Change { changeType = PendingAddChange }) = True
-		isPendingAdd _ = False
+		add :: Change -> IO (Maybe Change)
+		add change@(PendingAddChange { keySource = ks }) = do
+			r <- catchMaybeIO $ runThreadState st $ do
+				showStart "add" $ keyFilename ks
+				handle (finishedChange change) (keyFilename ks)
+					=<< Command.Add.ingest ks
+			return $ maybeMaybe r
+		add _ = return Nothing
 
-		add keysource = catchBoolIO $ runThreadState st $ do
-			showStart "add" $ keyFilename keysource
-			handle (keyFilename keysource)
-				=<< Command.Add.ingest keysource
+		maybeMaybe (Just j@(Just _)) = j
+		maybeMaybe _ = Nothing
 
-		handle _ Nothing = do
+		handle _ _ Nothing = do
 			showEndFail
-			return False
-		handle file (Just key) = do
+			return Nothing
+		handle change file (Just key) = do
 			link <- Command.Add.link file key True
 			when DirWatcher.eventsCoalesce $ do
 				sha <- inRepo $
 					Git.HashObject.hashObject BlobObject link
 				stageSymlink file sha
 			showEndOk
-			return True
+			return $ Just change
 
-{- Checks which of a set of files can safely be added.
- - Files are locked down as hard links in a temp directory,
- - with their write bits disabled. But some may still be
- - opened for write, so lsof is run on the temp directory
- - to check them.
+{- PendingAddChanges can Either be Right to be added now,
+ - or are unsafe, and must be Left for later.
+ -
+ - Check by running lsof on the temp directory, which
+ - the KeySources are locked down in.
  -}
-safeToAdd :: ThreadState -> DaemonStatusHandle -> [FilePath] -> IO [KeySource]
-safeToAdd st dstatus files = do
-	locked <- catMaybes <$> lockdown files
-	runThreadState st $ ifM (Annex.getState Annex.force)
-		( return locked -- force bypasses lsof check
+safeToAdd :: ThreadState -> [Change] -> IO [Either Change Change]
+safeToAdd st changes = runThreadState st $
+	ifM (Annex.getState Annex.force)
+		( allRight changes -- force bypasses lsof check
 		, do
 			tmpdir <- fromRepo gitAnnexTmpDir
-			open <- S.fromList . map fst3 . filter openwrite <$>
+			openfiles <- S.fromList . map fst3 . filter openwrite <$>
 				liftIO (Lsof.queryDir tmpdir)
-			catMaybes <$> forM locked (go open)
+			
+			let checked = map (check openfiles) changes
+
+			{- If new events are received when files are closed,
+			 - there's no need to retry any changes that cannot
+			 - be done now. -}
+			if DirWatcher.closingTracked
+				then do
+					mapM_ canceladd $ lefts checked
+					allRight $ rights checked
+				else return checked
 		)
 	where
- 		{- When a file is still open, it can be put into pendingAdd
-		 - to be checked again later. However when closingTracked
-		 - is supported, another event will be received once it's
-		 - closed, so there's no point in doing so. -}
-		go open keysource
-			| S.member (contentLocation keysource) open = do
-				if DirWatcher.closingTracked
-					then do
-						warning $ keyFilename keysource
-							++ " still has writers, not adding"
-						void $ liftIO $ canceladd keysource
-					else void $ addpending keysource
-				return Nothing
-			| otherwise = return $ Just keysource
-
-		canceladd keysource = tryIO $
+		check openfiles change@(PendingAddChange { keySource = ks })
+			| S.member (contentLocation ks) openfiles = Left change
+		check _ change = Right change
+
+		canceladd (PendingAddChange { keySource = ks }) = do
+			warning $ keyFilename ks
+				++ " still has writers, not adding"
 			-- remove the hard link
-			removeFile $ contentLocation keysource
-
-		{- The same file (or a file with the same name)
-		 - could already be pending add; if so this KeySource
-		 - superscedes the old one. -}
-		addpending keysource = modifyDaemonStatusM dstatus $ \s -> do
-			let set = pendingAdd s
-			mapM_ canceladd $ S.toList $ S.filter (== keysource) set
-			return $ s { pendingAdd = S.insert keysource set }
-
-		lockdown = mapM $ \file -> do
-			ms <- catchMaybeIO $ getSymbolicLinkStatus file
-			case ms of
-				Just s
-					| isRegularFile s -> 
-						catchMaybeIO $ runThreadState st $
-							Command.Add.lockDown file
-				_ -> return Nothing
-	
+			void $ liftIO $ tryIO $
+				removeFile $ contentLocation ks
+		canceladd _ = noop
 
 		openwrite (_file, mode, _pid) =
 			mode == Lsof.OpenWriteOnly || mode == Lsof.OpenReadWrite
+
+		allRight = return . map Right