This messages indicate that you should be run fsck with "force" option.

"-o f"

Normally, ehen you execute the fsck command, first step for check the FS integrity is verify the "clean flag" in the superblock, if this flag indicate that FS is OK the fsck command return a successfull state, the "-o f" tells to the command that ignore this flag and execute one "full" fsck over FS.