block: move a few merge helpers out of <linux/blkdev.h>

These are block-layer internal helpers, so move them to block/blk.h and
block/blk-merge.c. Also update a comment a bit to use better grammar.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Johannes Thumshirn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

block/blk-merge.c

···
 	return queue_max_segments(rq->q);
 }
 
+static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
+						  sector_t offset)
+{
+	struct request_queue *q = rq->q;
+
+	if (blk_rq_is_passthrough(rq))
+		return q->limits.max_hw_sectors;
+
+	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)));
+}
+
 static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
 		unsigned int nr_phys_segs)
 {
···
 		return ELEVATOR_BACK_MERGE;
 
 	return ELEVATOR_NO_MERGE;
+}
+
+static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
+{
+	if (bio_page(a) == bio_page(b) && bio_offset(a) == bio_offset(b))
+		return true;
+	return false;
 }
 
 /*

block/blk.h

···
 	return __bvec_gap_to_prev(q, bprv, offset);
 }
 
+static inline bool rq_mergeable(struct request *rq)
+{
+	if (blk_rq_is_passthrough(rq))
+		return false;
+
+	if (req_op(rq) == REQ_OP_FLUSH)
+		return false;
+
+	if (req_op(rq) == REQ_OP_WRITE_ZEROES)
+		return false;
+
+	if (req_op(rq) == REQ_OP_ZONE_APPEND)
+		return false;
+
+	if (rq->cmd_flags & REQ_NOMERGE_FLAGS)
+		return false;
+	if (rq->rq_flags & RQF_NOMERGE_FLAGS)
+		return false;
+
+	return true;
+}
+
+/*
+ * There are two different ways to handle DISCARD merges:
+ *  1) If max_discard_segments > 1, the driver treats every bio as a range and
+ *     send the bios to controller together. The ranges don't need to be
+ *     contiguous.
+ *  2) Otherwise, the request will be normal read/write requests.  The ranges
+ *     need to be contiguous.
+ */
+static inline bool blk_discard_mergable(struct request *req)
+{
+	if (req_op(req) == REQ_OP_DISCARD &&
+	    queue_max_discard_segments(req->q) > 1)
+		return true;
+	return false;
+}
+
 #ifdef CONFIG_BLK_DEV_INTEGRITY
 void blk_flush_integrity(void);
 bool __bio_integrity_endio(struct bio *);

include/linux/blkdev.h

···
 	return op_is_sync(rq->cmd_flags);
 }
 
-static inline bool rq_mergeable(struct request *rq)
-{
-	if (blk_rq_is_passthrough(rq))
-		return false;
-
-	if (req_op(rq) == REQ_OP_FLUSH)
-		return false;
-
-	if (req_op(rq) == REQ_OP_WRITE_ZEROES)
-		return false;
-
-	if (req_op(rq) == REQ_OP_ZONE_APPEND)
-		return false;
-
-	if (rq->cmd_flags & REQ_NOMERGE_FLAGS)
-		return false;
-	if (rq->rq_flags & RQF_NOMERGE_FLAGS)
-		return false;
-
-	return true;
-}
-
-static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
-{
-	if (bio_page(a) == bio_page(b) &&
-	    bio_offset(a) == bio_offset(b))
-		return true;
-
-	return false;
-}
-
 static inline unsigned int blk_queue_depth(struct request_queue *q)
 {
 	if (q->queue_depth)
···
 		chunk_sectors -= sector_div(offset, chunk_sectors);
 
 	return min(q->limits.max_sectors, chunk_sectors);
-}
-
-static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
-						  sector_t offset)
-{
-	struct request_queue *q = rq->q;
-
-	if (blk_rq_is_passthrough(rq))
-		return q->limits.max_hw_sectors;
-
-	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)));
 }
 
 static inline unsigned int blk_rq_count_bios(struct request *rq)
···
 
 	/* Turn it back into bytes, gaah */
 	return offset << SECTOR_SHIFT;
-}
-
-/*
- * Two cases of handling DISCARD merge:
- * If max_discard_segments > 1, the driver takes every bio
- * as a range and send them to controller together. The ranges
- * needn't to be contiguous.
- * Otherwise, the bios/requests will be handled as same as
- * others which should be contiguous.
- */
-static inline bool blk_discard_mergable(struct request *req)
-{
-	if (req_op(req) == REQ_OP_DISCARD &&
-	    queue_max_discard_segments(req->q) > 1)
-		return true;
-	return false;
 }
 
 static inline int bdev_discard_alignment(struct block_device *bdev)