[PATCHv3 06/10] blk-integrity: simplify counting segments

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

The segments are already packed to the queue limits when adding them to
the bio, so each vector is already its own segment. No need to attempt
compacting them even more. And give the function a more appropriate
name, since we're counting segments, not scatter-gather elements.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 block/blk-integrity.c         | 33 ++++++---------------------------
 block/blk-mq.c                |  2 +-
 include/linux/blk-integrity.h |  5 ++---
 3 files changed, 9 insertions(+), 31 deletions(-)

diff --git a/block/blk-integrity.c b/block/blk-integrity.c
index 4365960153b91..c180141b7871c 100644
--- a/block/blk-integrity.c
+++ b/block/blk-integrity.c
@@ -17,39 +17,18 @@
 #include "blk.h"
 
 /**
- * blk_rq_count_integrity_sg - Count number of integrity scatterlist elements
- * @q:		request queue
+ * blk_rq_count_integrity_segs - Count number of integrity segments
  * @bio:	bio with integrity metadata attached
  *
  * Description: Returns the number of elements required in a
  * scatterlist corresponding to the integrity metadata in a bio.
  */
-int blk_rq_count_integrity_sg(struct request_queue *q, struct bio *bio)
+int blk_rq_count_integrity_segs(struct bio *bio)
 {
-	struct bio_vec iv, ivprv = { NULL };
 	unsigned int segments = 0;
-	unsigned int seg_size = 0;
-	struct bvec_iter iter;
-	int prev = 0;
-
-	bio_for_each_integrity_vec(iv, bio, iter) {
 
-		if (prev) {
-			if (!biovec_phys_mergeable(q, &ivprv, &iv))
-				goto new_segment;
-			if (seg_size + iv.bv_len > queue_max_segment_size(q))
-				goto new_segment;
-
-			seg_size += iv.bv_len;
-		} else {
-new_segment:
-			segments++;
-			seg_size = iv.bv_len;
-		}
-
-		prev = 1;
-		ivprv = iv;
-	}
+	for_each_bio(bio)
+		segments += bio->bi_integrity->bip_vcnt;
 
 	return segments;
 }
@@ -62,7 +41,7 @@ int blk_rq_count_integrity_sg(struct request_queue *q, struct bio *bio)
  *
  * Description: Map the integrity vectors in request into a
  * scatterlist.  The scatterlist must be big enough to hold all
- * elements.  I.e. sized using blk_rq_count_integrity_sg().
+ * elements.  I.e. sized using blk_rq_count_integrity_segs().
  */
 int blk_rq_map_integrity_sg(struct request_queue *q, struct bio *bio,
 			    struct scatterlist *sglist)
@@ -145,7 +124,7 @@ bool blk_integrity_merge_bio(struct request_queue *q, struct request *req,
 		return false;
 
 	bio->bi_next = NULL;
-	nr_integrity_segs = blk_rq_count_integrity_sg(q, bio);
+	nr_integrity_segs = blk_rq_count_integrity_segs(bio);
 	bio->bi_next = next;
 
 	if (req->nr_integrity_segments + nr_integrity_segs >
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3ed5181c75610..79cc66275f1cd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2548,7 +2548,7 @@ static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
 	blk_rq_bio_prep(rq, bio, nr_segs);
 #if defined(CONFIG_BLK_DEV_INTEGRITY)
 	if (bio->bi_opf & REQ_INTEGRITY)
-		rq->nr_integrity_segments = blk_rq_count_integrity_sg(rq->q, bio);
+		rq->nr_integrity_segments = blk_rq_count_integrity_segs(bio);
 #endif
 
 	/* This can't fail, since GFP_NOIO includes __GFP_DIRECT_RECLAIM. */
diff --git a/include/linux/blk-integrity.h b/include/linux/blk-integrity.h
index de98049b7ded9..0de05278ac824 100644
--- a/include/linux/blk-integrity.h
+++ b/include/linux/blk-integrity.h
@@ -27,7 +27,7 @@ static inline bool queue_limits_stack_integrity_bdev(struct queue_limits *t,
 #ifdef CONFIG_BLK_DEV_INTEGRITY
 int blk_rq_map_integrity_sg(struct request_queue *, struct bio *,
 				   struct scatterlist *);
-int blk_rq_count_integrity_sg(struct request_queue *, struct bio *);
+int blk_rq_count_integrity_segs(struct bio *);
 
 static inline bool
 blk_integrity_queue_supports_integrity(struct request_queue *q)
@@ -91,8 +91,7 @@ static inline struct bio_vec rq_integrity_vec(struct request *rq)
 				 rq->bio->bi_integrity->bip_iter);
 }
 #else /* CONFIG_BLK_DEV_INTEGRITY */
-static inline int blk_rq_count_integrity_sg(struct request_queue *q,
-					    struct bio *b)
+static inline int blk_rq_count_integrity_segs(struct bio *b)
 {
 	return 0;
 }
-- 
2.43.5