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, 12 insertions, 11 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 61457bffa55f..d89383847d09 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1764,14 +1764,15 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 	}
 }
 
-static void blk_mq_bio_to_request(struct request *rq, struct bio *bio)
+static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
+		unsigned int nr_segs)
 {
 	if (bio->bi_opf & REQ_RAHEAD)
 		rq->cmd_flags |= REQ_FAILFAST_MASK;
 
 	rq->__sector = bio->bi_iter.bi_sector;
 	rq->write_hint = bio->bi_write_hint;
-	blk_rq_bio_prep(rq->q, rq, bio);
+	blk_rq_bio_prep(rq, bio, nr_segs);
 
 	blk_account_io_start(rq, true);
 }
@@ -1941,20 +1942,20 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 	struct request *rq;
 	struct blk_plug *plug;
 	struct request *same_queue_rq = NULL;
+	unsigned int nr_segs;
 	blk_qc_t cookie;
 
 	blk_queue_bounce(q, &bio);
-
-	blk_queue_split(q, &bio);
+	__blk_queue_split(q, &bio, &nr_segs);
 
 	if (!bio_integrity_prep(bio))
 		return BLK_QC_T_NONE;
 
 	if (!is_flush_fua && !blk_queue_nomerges(q) &&
-	    blk_attempt_plug_merge(q, bio, &same_queue_rq))
+	    blk_attempt_plug_merge(q, bio, nr_segs, &same_queue_rq))
 		return BLK_QC_T_NONE;
 
-	if (blk_mq_sched_bio_merge(q, bio))
+	if (blk_mq_sched_bio_merge(q, bio, nr_segs))
 		return BLK_QC_T_NONE;
 
 	rq_qos_throttle(q, bio);
@@ -1977,7 +1978,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 	plug = current->plug;
 	if (unlikely(is_flush_fua)) {
 		blk_mq_put_ctx(data.ctx);
-		blk_mq_bio_to_request(rq, bio);
+		blk_mq_bio_to_request(rq, bio, nr_segs);
 
 		/* bypass scheduler for flush rq */
 		blk_insert_flush(rq);
@@ -1991,7 +1992,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 		struct request *last = NULL;
 
 		blk_mq_put_ctx(data.ctx);
-		blk_mq_bio_to_request(rq, bio);
+		blk_mq_bio_to_request(rq, bio, nr_segs);
 
 		if (!request_count)
 			trace_block_plug(q);
@@ -2006,7 +2007,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 
 		blk_add_rq_to_plug(plug, rq);
 	} else if (plug && !blk_queue_nomerges(q)) {
-		blk_mq_bio_to_request(rq, bio);
+		blk_mq_bio_to_request(rq, bio, nr_segs);
 
 		/*
 		 * We do limited plugging. If the bio can be merged, do that.
@@ -2035,11 +2036,11 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 	} else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator &&
 			!data.hctx->dispatch_busy)) {
 		blk_mq_put_ctx(data.ctx);
-		blk_mq_bio_to_request(rq, bio);
+		blk_mq_bio_to_request(rq, bio, nr_segs);
 		blk_mq_try_issue_directly(data.hctx, rq, &cookie);
 	} else {
 		blk_mq_put_ctx(data.ctx);
-		blk_mq_bio_to_request(rq, bio);
+		blk_mq_bio_to_request(rq, bio, nr_segs);
 		blk_mq_sched_insert_request(rq, false, true, true);
 	}