The "surplus" bits of the old (smaller) bitmap must be clean
in case of online-grow without resync.
Note: Reverted 
67ae8b80d4a116ab3b7094eb3723506b20c06dff as
well, since the lines added by this patch are redundant. The
bits get set by the bm_set_surplus(b) call before that.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
        obits  = b->bm_bits;
 
        growing = bits > obits;
-       if (opages)
+       if (opages && growing && set_new_bits)
                bm_set_surplus(b);
 
        b->bm_pages = npages;
                if (set_new_bits) {
                        bm_memset(b, owords, 0xff, words-owords);
                        b->bm_set += bits - obits;
-                       __bm_change_bits_to(mdev, obits,
-                                           ALIGN(obits, BITS_PER_LONG),
-                                           1, KM_IRQ1);
                } else
                        bm_memset(b, owords, 0x00, words-owords);