block: open code blk_max_size_offset in blk_rq_get_max_sectors

blk_rq_get_max_sectors always uses q->limits.chunk_sectors as the
chunk_sectors argument, and already checks for max_sectors through the
call to blk_queue_get_max_sectors.  That means much of
blk_max_size_offset is not needed and open coding it simplifies the code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220614090934.570632-4-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-merge.c

@@ -566,17 +566,18 @@ static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
 						  sector_t offset)
 {
 	struct request_queue *q = rq->q;
+	unsigned int max_sectors;
 
 	if (blk_rq_is_passthrough(rq))
 		return q->limits.max_hw_sectors;
 
+	max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
 	if (!q->limits.chunk_sectors ||
 	    req_op(rq) == REQ_OP_DISCARD ||
 	    req_op(rq) == REQ_OP_SECURE_ERASE)
-		return blk_queue_get_max_sectors(q, req_op(rq));
-
-	return min(blk_max_size_offset(q, offset, 0),
-			blk_queue_get_max_sectors(q, req_op(rq)));
+		return max_sectors;
+	return min(max_sectors,
+		   blk_chunk_sectors_left(offset, q->limits.chunk_sectors));
 }
 
 static inline int ll_new_hw_segment(struct request *req, struct bio *bio,