[PATCH v2 1/3] block: Split blk_recalc_rq_segments()

[Bart Van Assche <bvanassche@xxxxxxx>]

Prepare for adding an additional call to bio_chain_nr_segments().

Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
Cc: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 block/blk-merge.c | 26 ++++++++++++++++----------
 block/blk.h       |  2 ++
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 65e75efa9bd3..d6f8552ef209 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -409,22 +409,22 @@ struct bio *bio_split_to_limits(struct bio *bio)
 }
 EXPORT_SYMBOL(bio_split_to_limits);
 
-unsigned int blk_recalc_rq_segments(struct request *rq)
+/* Calculate the number of DMA segments in a bio chain. */
+unsigned int bio_chain_nr_segments(struct bio *bio,
+				   const struct queue_limits *lim)
 {
 	unsigned int nr_phys_segs = 0;
 	unsigned int bytes = 0;
-	struct req_iterator iter;
+	struct bvec_iter iter;
 	struct bio_vec bv;
 
-	if (!rq->bio)
+	if (!bio)
 		return 0;
 
-	switch (bio_op(rq->bio)) {
+	switch (bio_op(bio)) {
 	case REQ_OP_DISCARD:
 	case REQ_OP_SECURE_ERASE:
-		if (queue_max_discard_segments(rq->q) > 1) {
-			struct bio *bio = rq->bio;
-
+		if (lim->max_discard_segments > 1) {
 			for_each_bio(bio)
 				nr_phys_segs++;
 			return nr_phys_segs;
@@ -436,12 +436,18 @@ unsigned int blk_recalc_rq_segments(struct request *rq)
 		break;
 	}
 
-	rq_for_each_bvec(bv, rq, iter)
-		bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes,
-				UINT_MAX, UINT_MAX);
+	for_each_bio(bio)
+		bio_for_each_bvec(bv, bio, iter)
+			bvec_split_segs(lim, &bv, &nr_phys_segs, &bytes,
+					UINT_MAX, UINT_MAX);
 	return nr_phys_segs;
 }
 
+unsigned int blk_recalc_rq_segments(struct request *rq)
+{
+	return bio_chain_nr_segments(rq->bio, &rq->q->limits);
+}
+
 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
 		struct scatterlist *sglist)
 {
diff --git a/block/blk.h b/block/blk.h
index d65d96994a94..ea15b1a4c2b7 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -330,6 +330,8 @@ int ll_back_merge_fn(struct request *req, struct bio *bio,
 		unsigned int nr_segs);
 bool blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 				struct request *next);
+unsigned int bio_chain_nr_segments(struct bio *bio,
+				   const struct queue_limits *lim);
 unsigned int blk_recalc_rq_segments(struct request *rq);
 void blk_rq_set_mixed_merge(struct request *rq);
 bool blk_rq_merge_ok(struct request *rq, struct bio *bio);