remove non existing files from the cache when rescanning a folder

lib/filecache.php

@@ -522,6 +522,9 @@ class OC_FileCache{
 			$view=new OC_FilesystemView(($root=='/')?'':$root);
 		}
 		self::scanFile($path,$root);
+		if(self::inCache($path)){
+			self::updateFolder($path,$root);
+		}else{
 			$dh=$view->opendir($path.'/');
 			$totalSize=0;
 			if($dh){
@@ -543,6 +546,7 @@ class OC_FileCache{
 			}
 			self::increaseSize($view->getRoot().$path,$totalSize);
 		}
+	}
 
 	/**
 	 * scan a single file

lib/filesystem.php

@@ -275,6 +275,7 @@ class OC_Filesystem{
 		if(class_exists($class)){
 			return new $class($arguments);
 		}else{
+			OC_Log::write('core','storage backend '.$class.' not found',OC_Log::ERROR);
 			return false;
 		}
 	}