1. A method for cloning a source filesystem object in a file storage system, the source filesystem object including at least one data block and a set of pointers directly or indirectly referencing the at least one data block, the method comprising: creating in the file storage system a read-only data-stream-snapshot object and storing a copy of the set of pointers in the data-stream-snapshot object; and creating in the file storage system a mutable clone object and storing a copy of the set of pointers in the clone object, wherein the data-stream-snapshot object and the clone object share the at least one data block with the source filesystem object without making separate copies of the at least one data block for the data-stream-snapshot object and the clone object, and wherein the source filesystem object and the clone object effectively become mutable versions of the data-stream-snapshot object and effectively store changes from the read-only copy of the object represented by the data-stream-snapshot object.