assistant: More robust inotify handling; avoid crashing if a directory cannot be read.

Utility/INotify.hs

@@ -54,11 +54,12 @@ watchDir i dir ignored hooks
 		-- scan come before real inotify events.
 		lock <- newLock
 		let handler event = withLock lock (void $ go event)
-		void (addWatch i watchevents dir handler)
-			`catchIO` failedaddwatch
-		withLock lock $
-			mapM_ scan =<< filter (not . dirCruft) <$>
-				getDirectoryContents dir
+		flip catchNonAsync failedwatch $ do
+			void (addWatch i watchevents dir handler)
+				`catchIO` failedaddwatch
+			withLock lock $
+				mapM_ scan =<< filter (not . dirCruft) <$>
+					getDirectoryContents dir
   where
 	recurse d = watchDir i d ignored hooks
 
@@ -149,12 +150,14 @@ watchDir i dir ignored hooks
 		-- disk full error.
 		| isFullError e =
 			case errHook hooks of
-				Nothing -> throw e
+				Nothing -> error $ "failed to add inotify watch on directory " ++ dir ++ " (" ++ show e ++ ")"
 				Just hook -> tooManyWatches hook dir
 		-- The directory could have been deleted.
 		| isDoesNotExistError e = return ()
 		| otherwise = throw e
 
+	failedwatch e = hPutStrLn stderr $ "failed to add watch on directory " ++ dir ++ " (" ++ show e ++ ")"
+
 tooManyWatches :: (String -> Maybe FileStatus -> IO ()) -> FilePath -> IO ()
 tooManyWatches hook dir = do
 	sysctlval <- querySysctl [Param maxwatches] :: IO (Maybe Integer)

debian/changelog

@@ -26,6 +26,8 @@ git-annex (4.20130921) UNRELEASED; urgency=low
     yet knowing about the new remote.
   * OSX: Bundled gpg upgraded, now compatible with config files
     written by MacGPG.
+  * assistant: More robust inotify handling; avoid crashing if a directory
+    cannot be read.
 
  -- Joey Hess <joeyh@debian.org>  Sun, 22 Sep 2013 19:42:29 -0400
 

doc/todo/wishlist:_display_name_of_object_when_addWatcher_gets_a_permission_denied.mdwn

@@ -1 +1,6 @@
 When addWatcher gets a permission denied, it would be helpful to display the name of the object on which the permission was denied, in the error message which shows in the webapp.
+
+> I have made the inotify code more robust; now it doesn't crash if it
+> cannot read a directory or a file, and only logs a warning, which includes
+> the directory name.
+> [[done]] --[[Joey]]