A computer system for sharing objects comprises multiple front-end nodes and a back-end node for providing a namespace shared by the front-end nodes. A first front-end node that is any one of the front-end nodes manages local-lock counts for each of objects managed by the first front-end node. The local-lock count is the number of locks taken by operations to the objects including the directory and sub-objects thereof. Every time receiving a request for processing a target object from a client, the front-end node requests the back-end node to lock a parent directory of the target object if the parent directory has not been locked by the back-end node. The front-end node sends a response of the received request to the client regardless of whether or not the parent directory has been unlocked by the back-end node. If the local-lock count of the parent directory is zero, the first front-end node requests the back-end node to unlock the parent directory.