block: remove the bi_phys_segments field in struct bio

We only need the number of segments in the blk-mq submission path.
Remove the field from struct bio, and return it from a variant of
blk_queue_split instead of that it can passed as an argument to
those functions that need the value.

This also means we stop recounting segments except for cloning
and partial segments.

To keep the number of arguments in this how path down remove
pointless struct request_queue arguments from any of the functions
that had it and grew a nr_segs argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 15 insertions, 11 deletions

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 2766066a15db..956a7aa9a637 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -224,7 +224,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 }
 
 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
-			    struct request **merged_request)
+		unsigned int nr_segs, struct request **merged_request)
 {
 	struct request *rq;
 
@@ -232,7 +232,7 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
 	case ELEVATOR_BACK_MERGE:
 		if (!blk_mq_sched_allow_merge(q, rq, bio))
 			return false;
-		if (!bio_attempt_back_merge(q, rq, bio))
+		if (!bio_attempt_back_merge(rq, bio, nr_segs))
 			return false;
 		*merged_request = attempt_back_merge(q, rq);
 		if (!*merged_request)
@@ -241,7 +241,7 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
 	case ELEVATOR_FRONT_MERGE:
 		if (!blk_mq_sched_allow_merge(q, rq, bio))
 			return false;
-		if (!bio_attempt_front_merge(q, rq, bio))
+		if (!bio_attempt_front_merge(rq, bio, nr_segs))
 			return false;
 		*merged_request = attempt_front_merge(q, rq);
 		if (!*merged_request)
@@ -260,7 +260,7 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
  * of them.
  */
 bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
-			   struct bio *bio)
+			   struct bio *bio, unsigned int nr_segs)
 {
 	struct request *rq;
 	int checked = 8;
@@ -277,11 +277,13 @@ bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
 		switch (blk_try_merge(rq, bio)) {
 		case ELEVATOR_BACK_MERGE:
 			if (blk_mq_sched_allow_merge(q, rq, bio))
-				merged = bio_attempt_back_merge(q, rq, bio);
+				merged = bio_attempt_back_merge(rq, bio,
+						nr_segs);
 			break;
 		case ELEVATOR_FRONT_MERGE:
 			if (blk_mq_sched_allow_merge(q, rq, bio))
-				merged = bio_attempt_front_merge(q, rq, bio);
+				merged = bio_attempt_front_merge(rq, bio,
+						nr_segs);
 			break;
 		case ELEVATOR_DISCARD_MERGE:
 			merged = bio_attempt_discard_merge(q, rq, bio);
@@ -304,13 +306,14 @@ EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge);
  */
 static bool blk_mq_attempt_merge(struct request_queue *q,
 				 struct blk_mq_hw_ctx *hctx,
-				 struct blk_mq_ctx *ctx, struct bio *bio)
+				 struct blk_mq_ctx *ctx, struct bio *bio,
+				 unsigned int nr_segs)
 {
 	enum hctx_type type = hctx->type;
 
 	lockdep_assert_held(&ctx->lock);
 
-	if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio)) {
+	if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) {
 		ctx->rq_merged++;
 		return true;
 	}
@@ -318,7 +321,8 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
 	return false;
 }
 
-bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
+bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
+		unsigned int nr_segs)
 {
 	struct elevator_queue *e = q->elevator;
 	struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
@@ -328,7 +332,7 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
 
 	if (e && e->type->ops.bio_merge) {
 		blk_mq_put_ctx(ctx);
-		return e->type->ops.bio_merge(hctx, bio);
+		return e->type->ops.bio_merge(hctx, bio, nr_segs);
 	}
 
 	type = hctx->type;
@@ -336,7 +340,7 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
 			!list_empty_careful(&ctx->rq_lists[type])) {
 		/* default per sw-queue merge */
 		spin_lock(&ctx->lock);
-		ret = blk_mq_attempt_merge(q, hctx, ctx, bio);
+		ret = blk_mq_attempt_merge(q, hctx, ctx, bio, nr_segs);
 		spin_unlock(&ctx->lock);
 	}