1. A method for use in rapid incremental backup of changed files in a file system, the method comprising: scanning a file system hierarchy of a file system in a top-down manner for determining a list of changed files for performing incremental backup of the file system; evaluating a directory tree modification attribute of each directory hierarchy of the file system hierarchy of the file system in the top-down manner, wherein the file system hierarchy includes a set of directory hierarchies, each directory hierarchy including a set of directories, each directory of the set of directories including a set of files, wherein the directory tree modification attribute of each directory hierarchy indicates whether at least one file in respective entire directory hierarchy has changed since a last backup, wherein the directory tree modification attribute is updated upon finding at least one changed file in the respective directory hierarchy since the last backup and without changing a modification time of a directory associated with the respective directory tree hierarchy; based on the evaluation, determining whether a directory hierarchy of the file system hierarchy has been changed since the last backup; and based on the determination, skip traversing files included in a directory hierarchy during the scanning of the file system hierarchy upon determining that the directory tree modification attribute associated with the directory hierarchy has not been updated since the last backup.