better optimisation of add check

Now really only done in the startup scan.

It turns out to be quite hard for event handlers to know when the startup
scan is complete. I tried to make addWatch pass that info, but found
threading the state very difficult. For now, a quick hack, using the fast
flag.

Note that it's actually possible for inotify events to come in while the
startup scan is still ongoing. Due to my hack, the expensive check will
be done for files added in such inotify events.

Command/Watch.hs

@@ -68,7 +68,7 @@ import System.INotify
 
 type ChangeChan = TChan Change
 
-type Handler = FilePath -> Bool -> Annex (Maybe Change)
+type Handler = FilePath -> Annex (Maybe Change)
 
 data Change = Change
 	{ changeTime :: UTCTime
@@ -122,18 +122,25 @@ watch st = withINotify $ \i -> do
 		}
 	-- The commit thread is started early, so that the user
 	-- can immediately begin adding files and having them
-	-- committed, even while the inotify scan is taking place.
+	-- committed, even while the startup scan is taking place.
 	_ <- forkIO $ commitThread st changechan
-	-- This does not return until the inotify scan is done.
+	-- The fast flag is abused somewhat, to tell when the startup
+	-- scan is still running.
+	runStateMVar st $ do
+		setfast False
+		showAction "scanning"
+	-- This does not return until the startup scan is done.
 	-- That can take some time for large trees.
 	watchDir i "." (ignored . takeFileName) hooks
-	runStateMVar st $ showAction "scanning"
+	runStateMVar st $ setfast True
 	-- Notice any files that were deleted before inotify
 	-- was started.
 	runStateMVar st $ do
 		inRepo $ Git.Command.run "add" [Param "--update"]
 		showAction "started"
 	waitForTermination
+	where
+		setfast v= Annex.changeState $ \s -> s { Annex.fast = v }
 #else
 watch = error "watch mode is so far only available on Linux"
 #endif
@@ -174,9 +181,9 @@ runChangeChan = atomically
  -
  - Exceptions are ignored, otherwise a whole watcher thread could be crashed.
  -}
-runHandler :: MVar Annex.AnnexState -> ChangeChan -> Handler -> FilePath -> Bool -> IO ()
-runHandler st changechan handler file inscan = void $ do
-	r <- tryIO (runStateMVar st $ handler file inscan)
+runHandler :: MVar Annex.AnnexState -> ChangeChan -> Handler -> FilePath -> IO ()
+runHandler st changechan handler file = void $ do
+	r <- tryIO (runStateMVar st $ handler file)
 	case r of
 		Left e -> print e
 		Right Nothing -> noop
@@ -200,34 +207,38 @@ noChange = return Nothing
  -
  - Inotify will notice the new symlink, so this Handler does not stage it
  - or return a Change, leaving that to onAddSymlink.
+ -
+ - During initial directory scan, this will be run for any files that
+ - are already checked into git. We don't want to turn those into symlinks,
+ - so do a check. This is rather expensive, but only happens during
+ - startup.
  -}
 onAdd :: Handler
-onAdd file False = do
-	showStart "add" file
-	handle =<< Command.Add.ingest file
-	noChange
+onAdd file = do
+	ifM (Annex.getState Annex.fast)
+		( go -- initial directory scan is complete
+		, do -- expensive check done only during startup scan
+			ifM (null <$> inRepo (Git.LsFiles.notInRepo False [file]))
+				( noChange
+				, go
+				)
+		)
 	where
+		go = do
+			showStart "add" file
+			handle =<< Command.Add.ingest file
+			noChange
 		handle Nothing = showEndFail
 		handle (Just key) = do
 			Command.Add.link file key True
 			showEndOk
-{- During initial directory scan, this will be run for any files that
- - are already checked into git. We don't want to turn those into symlinks,
- - so do a check. This is rather expensive, but only happens during
- - startup, and when a directory is moved into the tree. -}
-onAdd file True = do
-	liftIO $ putStrLn $ "expensive check for " ++ file
-	ifM (null <$> inRepo (Git.LsFiles.notInRepo False [file]))
-		( noChange
-		, onAdd file False
-		)
 
 {- A symlink might be an arbitrary symlink, which is just added.
  - Or, if it is a git-annex symlink, ensure it points to the content
  - before adding it.
  -}
 onAddSymlink :: Handler
-onAddSymlink file _inscan = go =<< Backend.lookupFile file
+onAddSymlink file = go =<< Backend.lookupFile file
 	where
 		go Nothing = addlink =<< liftIO (readSymbolicLink file)
 		go (Just (key, _)) = do
@@ -260,7 +271,7 @@ onAddSymlink file _inscan = go =<< Backend.lookupFile file
 			madeChange file "link"
 
 onDel :: Handler
-onDel file _inscan = do
+onDel file = do
 	Annex.Queue.addUpdateIndex =<<
 		inRepo (Git.UpdateIndex.unstageFile file)
 	madeChange file "rm"
@@ -273,14 +284,14 @@ onDel file _inscan = do
  - command to get the recursive list of files in the directory, so rm is
  - just as good. -}
 onDelDir :: Handler
-onDelDir dir _inscan = do
+onDelDir dir = do
 	Annex.Queue.addCommand "rm"
 		[Params "--quiet -r --cached --ignore-unmatch --"] [dir]
 	madeChange dir "rmdir"
 
 {- Called when there's an error with inotify. -}
 onErr :: Handler
-onErr msg _inscan = do
+onErr msg = do
 	warning msg
 	return Nothing
 

Utility/Inotify.hs

@@ -15,11 +15,7 @@ import qualified System.Posix.Files as Files
 import System.IO.Error
 import Control.Exception (throw)
 
-{- A hook is passed some value to act on.
- -
- - The Bool is False when we're in the intial scan of a directory tree,
- - rather than having received a genuine inotify event. -}
-type Hook a = Maybe (a -> Bool -> IO ())
+type Hook a = Maybe (a -> IO ())
 
 data WatchHooks = WatchHooks
 	{ addHook :: Hook FilePath
@@ -94,8 +90,8 @@ watchDir i dir ignored hooks
 				Nothing -> return ()
 				Just s
 					| Files.isDirectory s -> recurse fullf
-					| Files.isSymbolicLink s -> addSymlinkHook <@?> f
-					| Files.isRegularFile s -> addHook <@?> f
+					| Files.isSymbolicLink s -> addSymlinkHook <@> f
+					| Files.isRegularFile s -> addHook <@> f
 					| otherwise -> return ()
 
 		-- Ignore creation events for regular files, which won't be
@@ -130,11 +126,10 @@ watchDir i dir ignored hooks
 
 		hashook h = isJust $ h hooks
 
-		runhook h f inscan
+		runhook h f
 			| ignored f = noop
-			| otherwise = maybe noop (\a -> a (indir f) inscan) (h hooks)
-		h <@> f = runhook h f False
-		h <@?> f = runhook h f True
+			| otherwise = maybe noop (\a -> a $ indir f) (h hooks)
+		h <@> f = runhook h f
 
 		indir f = dir </> f
 
@@ -149,10 +144,10 @@ watchDir i dir ignored hooks
 					Just hook -> tooManyWatches hook dir
 			| otherwise = throw e
 
-tooManyWatches :: (String -> Bool -> IO ()) -> FilePath -> IO ()
+tooManyWatches :: (String -> IO ()) -> FilePath -> IO ()
 tooManyWatches hook dir = do
 	sysctlval <- querySysctl [Param maxwatches] :: IO (Maybe Integer)
-	hook (unlines $ basewarning : maybe withoutsysctl withsysctl sysctlval) False
+	hook $ unlines $ basewarning : maybe withoutsysctl withsysctl sysctlval
 	where
 		maxwatches = "fs.inotify.max_user_watches"
 		basewarning = "Too many directories to watch! (Not watching " ++ dir ++")"