Revert commit 
6de9843dab3f2a1d4d66d80aa9e5782f80977d20, since it
caused a data corruption regression with BitTorrent downloads.  Thanks
to Damien for discovering and bisecting to find the problem commit.
https://bugzilla.kernel.org/show_bug.cgi?id=32972
Reported-by: Damien Grassart <damien@grassart.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
                 * for partial write.
                 */
                set_buffer_new(bh);
+               set_buffer_mapped(bh);
        }
        return 0;
 }