md: teach sync_page_io about new_data_offset.

Some code in raid1 and raid10 use sync_page_io to
read/write pages when responding to read errors.
As we will shortly support changing data_offset for
raid10, this function must understand new_data_offset.

So add that understanding.
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -888,6 +888,10 @@ int sync_page_io(struct md_rdev *rdev, sector_t sector, int size,
 		rdev->meta_bdev : rdev->bdev;
 	if (metadata_op)
 		bio->bi_sector = sector + rdev->sb_start;
+	else if (rdev->mddev->reshape_position != MaxSector &&
+		 (rdev->mddev->reshape_backwards ==
+		  (sector >= rdev->mddev->reshape_position)))
+		bio->bi_sector = sector + rdev->new_data_offset;
 	else
 		bio->bi_sector = sector + rdev->data_offset;
 	bio_add_page(bio, page, size, 0);