US Patent 9552382 Reference counter integrity checking

Disclosed is a method for checking the integrity of a reference counter for objects in a file system. A unique identifier can be associated with the reference referring to the object. A reference check can be associated with the object and set to a predefined initial value before any references referring to the object are added. When a new reference referring to the object is added, the reference counter is increased by one and the identifier associated with the new reference is added to the reference check. When an existing reference referring to the object is about to be removed, the reference counter is decreased by one and the identifier associated with the existing reference is subtracted from the reference check. If the reference check is not equal to the initial value when the reference counter is zero, then an error message is sent to the file system.