commit cf9a6784 upstream.

Without this copy-up of a file can be forced, even without actually being
allowed to do anything on the file.

[Arnd Bergmann] include <linux/pagemap.h> for PAGE_CACHE_SIZE (used by
MAX_LFS_FILESIZE definition).
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>