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 <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-16-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 38 insertions, 0 deletions

diff --git a/block/blk.h b/block/blk.h
index f24569980905..fa90691cfdab 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -96,6 +96,44 @@ static inline bool bvec_gap_to_prev(struct request_queue *q,
 	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 *);