raid1: use bio_copy_data()

This doesn't really delete any code _yet_, but once immutable bvecs are
done we can just delete the rest of the code in that loop.
Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
CC: NeilBrown <neilb@suse.de>

drivers/md/raid1.c

@@ -1906,10 +1906,9 @@ static int process_checks(struct r1bio *r1_bio)
 			else
 				bi->bv_len = size;
 			size -= PAGE_SIZE;
-			memcpy(page_address(bi->bv_page),
-			       page_address(pbio->bi_io_vec[j].bv_page),
-			       PAGE_SIZE);
 		}
+
+		bio_copy_data(sbio, pbio);
 	}
 	return 0;
 }