Before this change a copy operation with cp(1) would not update the
file access times.
According to the POSIX mmap(2) documentation: the st_atime field
of the mapped file may be marked for update at any time between the
mmap() call and the corresponding munmap() call. The initial read
or write reference to a mapped region shall cause the file's st_atime
field to be marked for update if it has not already been marked for
update.
c066055957