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, 14 insertions, 18 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index d1c7c69a20dd..ef998a724b27 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -550,15 +550,15 @@ void blk_put_request(struct request *req)
 }
 EXPORT_SYMBOL(blk_put_request);
 
-bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
-			    struct bio *bio)
+bool bio_attempt_back_merge(struct request *req, struct bio *bio,
+		unsigned int nr_segs)
 {
 	const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
 
-	if (!ll_back_merge_fn(q, req, bio))
+	if (!ll_back_merge_fn(req, bio, nr_segs))
 		return false;
 
-	trace_block_bio_backmerge(q, req, bio);
+	trace_block_bio_backmerge(req->q, req, bio);
 
 	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
 		blk_rq_set_mixed_merge(req);
@@ -571,15 +571,15 @@ bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
 	return true;
 }
 
-bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
-			     struct bio *bio)
+bool bio_attempt_front_merge(struct request *req, struct bio *bio,
+		unsigned int nr_segs)
 {
 	const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
 
-	if (!ll_front_merge_fn(q, req, bio))
+	if (!ll_front_merge_fn(req, bio, nr_segs))
 		return false;
 
-	trace_block_bio_frontmerge(q, req, bio);
+	trace_block_bio_frontmerge(req->q, req, bio);
 
 	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
 		blk_rq_set_mixed_merge(req);
@@ -621,6 +621,7 @@ no_merge:
  * blk_attempt_plug_merge - try to merge with %current's plugged list
  * @q: request_queue new bio is being queued at
  * @bio: new bio being queued
+ * @nr_segs: number of segments in @bio
  * @same_queue_rq: pointer to &struct request that gets filled in when
  * another request associated with @q is found on the plug list
  * (optional, may be %NULL)
@@ -639,7 +640,7 @@ no_merge:
  * Caller must ensure !blk_queue_nomerges(q) beforehand.
  */
 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
-			    struct request **same_queue_rq)
+		unsigned int nr_segs, struct request **same_queue_rq)
 {
 	struct blk_plug *plug;
 	struct request *rq;
@@ -668,10 +669,10 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 
 		switch (blk_try_merge(rq, bio)) {
 		case ELEVATOR_BACK_MERGE:
-			merged = bio_attempt_back_merge(q, rq, bio);
+			merged = bio_attempt_back_merge(rq, bio, nr_segs);
 			break;
 		case ELEVATOR_FRONT_MERGE:
-			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);
@@ -1427,14 +1428,9 @@ bool blk_update_request(struct request *req, blk_status_t error,
 }
 EXPORT_SYMBOL_GPL(blk_update_request);
 
-void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
-		     struct bio *bio)
+void blk_rq_bio_prep(struct request *rq, struct bio *bio, unsigned int nr_segs)
 {
-	if (bio_has_data(bio))
-		rq->nr_phys_segments = bio_phys_segments(q, bio);
-	else if (bio_op(bio) == REQ_OP_DISCARD)
-		rq->nr_phys_segments = 1;
-
+	rq->nr_phys_segments = nr_segs;
 	rq->__data_len = bio->bi_iter.bi_size;
 	rq->bio = rq->biotail = bio;
 	rq->ioprio = bio_prio(bio);