splice: adjust balance_dirty_pages_ratelimited() call

As we have potentially dirtied more than 1 page, we should indicate as
such to the dirty page balancing. So call
balance_dirty_pages_ratelimited_nr() and pass in the approximate number
of pages we dirtied.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
1 file changed