An apparatus and a method for maintaining a file system is described. A method may include receiving a request for allocating a first block of a file system to a file, the first block comprising a first data and computing, by a processing device, a first hash value of the first block. The method also includes comparing, by the processing device, the first hash value with a plurality of hash values in a tree structure, wherein each of the plurality of values correspond to a block among a plurality of blocks stored in the file system. The method further includes in response to determining that a match exists between the first hash value and at least one of the plurality of hash values in the tree structure, allocating, by the processing device, the corresponding block to the file; and updating, by the processing device, a reference count of the corresponding block in the tree structure.