For a front merge, the maximum number of sectors of the
request must be checked against the front merge BIO sector,
not the current sector of the request.
Signed-off-by: NDamien Le Moal <damien.lemoal@hgst.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>