1. A method for unmapping logical block addresses (“LBAs”) for a system comprising a non-volatile memory (“NVM”), the method comprising: storing mapping statuses of a plurality of LBAs in a bitmap stored in volatile memory; receiving a request from a file system to unmap a first LBA; changing a mapping status or the first LBA to unmapped by only updating the bitmap; and decreasing a validity counter for a super block corresponding to the first LBA.