drbd: fix bitmap writeout after aborted resync

{

	int i;

	int bits;

	int changed = 0;

	unsigned long *paddr = kmap_atomic(b->bm_pages[page_nr], KM_IRQ1);

	for (i = first_word; i < last_word; i++) {

		bits = hweight_long(paddr[i]);

		paddr[i] = ~0UL;

		b->bm_set += BITS_PER_LONG - bits;

		changed += BITS_PER_LONG - bits;

	}

	kunmap_atomic(paddr, KM_IRQ1);

	if (changed) {

		/* We only need lazy writeout, the information is still in the

		 * remote bitmap as well, and is reconstructed during the next

		 * bitmap exchange, if lost locally due to a crash. */

		bm_set_page_lazy_writeout(b->bm_pages[page_nr]);

		b->bm_set += changed;

	}

}

/* Same thing as drbd_bm_set_bits,