/usr/lib/ghc-doc/hoogle/mmap.txt is in libghc-mmap-doc 0.5.8-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-mmap-doc/html/mmap.txt
/usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-mmap-doc/html/mmap.txt