Some clean-ups for bio merge

index d9d6326..ed79109 100644
@@ -642,162 +642,6 @@ void blk_put_request(struct request *req)
 }
 EXPORT_SYMBOL(blk_put_request);
 
-static void blk_account_io_merge_bio(struct request *req)
-{
-	if (!blk_do_io_stat(req))
-		return;
-
-	part_stat_lock();
-	part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
-	part_stat_unlock();
-}
-
-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(req, bio, nr_segs))
-		return false;
-
-	trace_block_bio_backmerge(req->q, req, bio);
-	rq_qos_merge(req->q, req, bio);
-
-	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
-		blk_rq_set_mixed_merge(req);
-
-	req->biotail->bi_next = bio;
-	req->biotail = bio;
-	req->__data_len += bio->bi_iter.bi_size;
-
-	bio_crypt_free_ctx(bio);
-
-	blk_account_io_merge_bio(req);
-	return true;
-}
-
-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(req, bio, nr_segs))
-		return false;
-
-	trace_block_bio_frontmerge(req->q, req, bio);
-	rq_qos_merge(req->q, req, bio);
-
-	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
-		blk_rq_set_mixed_merge(req);
-
-	bio->bi_next = req->bio;
-	req->bio = bio;
-
-	req->__sector = bio->bi_iter.bi_sector;
-	req->__data_len += bio->bi_iter.bi_size;
-
-	bio_crypt_do_front_merge(req, bio);
-
-	blk_account_io_merge_bio(req);
-	return true;
-}
-
-bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
-		struct bio *bio)
-{
-	unsigned short segments = blk_rq_nr_discard_segments(req);
-
-	if (segments >= queue_max_discard_segments(q))
-		goto no_merge;
-	if (blk_rq_sectors(req) + bio_sectors(bio) >
-	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
-		goto no_merge;
-
-	rq_qos_merge(q, req, bio);
-
-	req->biotail->bi_next = bio;
-	req->biotail = bio;
-	req->__data_len += bio->bi_iter.bi_size;
-	req->nr_phys_segments = segments + 1;
-
-	blk_account_io_merge_bio(req);
-	return true;
-no_merge:
-	req_set_nomerge(q, req);
-	return false;
-}
-
-/**
- * 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)
- *
- * Determine whether @bio being queued on @q can be merged with a request
- * on %current's plugged list.  Returns %true if merge was successful,
- * otherwise %false.
- *
- * Plugging coalesces IOs from the same issuer for the same purpose without
- * going through @q->queue_lock.  As such it's more of an issuing mechanism
- * than scheduling, and the request, while may have elvpriv data, is not
- * added on the elevator at this point.  In addition, we don't have
- * reliable access to the elevator outside queue lock.  Only check basic
- * merging parameters without querying the elevator.
- *
- * Caller must ensure !blk_queue_nomerges(q) beforehand.
- */
-bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
-		unsigned int nr_segs, struct request **same_queue_rq)
-{
-	struct blk_plug *plug;
-	struct request *rq;
-	struct list_head *plug_list;
-
-	plug = blk_mq_plug(q, bio);
-	if (!plug)
-		return false;
-
-	plug_list = &plug->mq_list;
-
-	list_for_each_entry_reverse(rq, plug_list, queuelist) {
-		bool merged = false;
-
-		if (rq->q == q && same_queue_rq) {
-			/*
-			 * Only blk-mq multiple hardware queues case checks the
-			 * rq in the same queue, there should be only one such
-			 * rq in a queue
-			 **/
-			*same_queue_rq = rq;
-		}
-
-		if (rq->q != q || !blk_rq_merge_ok(rq, bio))
-			continue;
-
-		switch (blk_try_merge(rq, bio)) {
-		case ELEVATOR_BACK_MERGE:
-			merged = bio_attempt_back_merge(rq, bio, nr_segs);
-			break;
-		case ELEVATOR_FRONT_MERGE:
-			merged = bio_attempt_front_merge(rq, bio, nr_segs);
-			break;
-		case ELEVATOR_DISCARD_MERGE:
-			merged = bio_attempt_discard_merge(q, rq, bio);
-			break;
-		default:
-			break;
-		}
-
-		if (merged)
-			return true;
-	}
-
-	return false;
-}
-
 static void handle_bad_sector(struct bio *bio, sector_t maxsector)
 {
 	char b[BDEVNAME_SIZE];

166 lines not on this page · raw message

index 3aa2de5..b09e9fc 100644
@@ -1052,3 +1052,47 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 
 	return false;
 }
+
+/*
+ * Iterate list of requests and see if we can merge this bio with any
+ * of them.
+ */
+bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
+			struct bio *bio, unsigned int nr_segs)
+{
+	struct request *rq;
+	int checked = 8;
+
+	list_for_each_entry_reverse(rq, list, queuelist) {
+		bool merged = false;
+
+		if (!checked--)
+			break;
+
+		if (!blk_rq_merge_ok(rq, bio))
+			continue;
+
+		switch (blk_try_merge(rq, bio)) {
+		case ELEVATOR_BACK_MERGE:
+			if (blk_mq_sched_allow_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(rq, bio,
+						nr_segs);
+			break;
+		case ELEVATOR_DISCARD_MERGE:
+			merged = bio_attempt_discard_merge(q, rq, bio);
+			break;
+		default:
+			continue;
+		}
+
+		return merged;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(blk_bio_list_merge);

58 lines not on this page · raw message

index 49e2928..d6152d2 100644
@@ -177,6 +177,8 @@ bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
 		struct bio *bio);
 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs, struct request **same_queue_rq);
+bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
+			struct bio *bio, unsigned int nr_segs);
 
 void blk_account_io_start(struct request *req);
 void blk_account_io_done(struct request *req, u64 now);

index a38c5ab..6d4ba0e 100644
@@ -573,7 +573,7 @@ static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
 	bool merged;
 
 	spin_lock(&kcq->lock);
-	merged = blk_mq_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
+	merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
 	spin_unlock(&kcq->lock);
 
 	return merged;

index 9d2d5ad..21a02e0 100644
@@ -489,8 +489,6 @@ static inline int blk_mq_request_completed(struct request *rq)
 void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs);
 void blk_mq_complete_request(struct request *rq);
 bool blk_mq_complete_request_remote(struct request *rq);
-bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
-			   struct bio *bio, unsigned int nr_segs);
 bool blk_mq_queue_stopped(struct request_queue *q);
 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx);

index b09e9fc..80c9744 100644
@@ -907,13 +907,14 @@ static void blk_account_io_merge_bio(struct request *req)
 	part_stat_unlock();
 }
 
-bool bio_attempt_back_merge(struct request *req, struct bio *bio,
-		unsigned int nr_segs)
+enum bio_merge_status 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(req, bio, nr_segs))
-		return false;
+		return BIO_MERGE_FAILED;
 
 	trace_block_bio_backmerge(req->q, req, bio);
 	rq_qos_merge(req->q, req, bio);

@@ -928,16 +929,17 @@ bool bio_attempt_back_merge(struct request *req, struct bio *bio,
 	bio_crypt_free_ctx(bio);
 
 	blk_account_io_merge_bio(req);
-	return true;
+	return BIO_MERGE_OK;
 }
 
-bool bio_attempt_front_merge(struct request *req, struct bio *bio,
-		unsigned int nr_segs)
+enum bio_merge_status 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(req, bio, nr_segs))
-		return false;
+		return BIO_MERGE_FAILED;
 
 	trace_block_bio_frontmerge(req->q, req, bio);
 	rq_qos_merge(req->q, req, bio);

@@ -954,11 +956,12 @@ bool bio_attempt_front_merge(struct request *req, struct bio *bio,
 	bio_crypt_do_front_merge(req, bio);
 
 	blk_account_io_merge_bio(req);
-	return true;
+	return BIO_MERGE_OK;
 }
 
-bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
-		struct bio *bio)
+enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
+						struct request *req,
+						struct bio *bio)
 {
 	unsigned short segments = blk_rq_nr_discard_segments(req);
 

@@ -976,10 +979,39 @@ bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
 	req->nr_phys_segments = segments + 1;
 
 	blk_account_io_merge_bio(req);
-	return true;
+	return BIO_MERGE_OK;
 no_merge:
 	req_set_nomerge(q, req);
-	return false;
+	return BIO_MERGE_FAILED;
+}
+
+static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
+						   struct request *rq,
+						   struct bio *bio,
+						   unsigned int nr_segs,
+						   bool sched_allow_merge)
+{
+	if (!blk_rq_merge_ok(rq, bio))
+		return BIO_MERGE_NONE;
+
+	switch (blk_try_merge(rq, bio)) {
+	case ELEVATOR_BACK_MERGE:
+		if (!sched_allow_merge ||
+		    (sched_allow_merge && blk_mq_sched_allow_merge(q, rq, bio)))
+			return bio_attempt_back_merge(rq, bio, nr_segs);
+		break;
+	case ELEVATOR_FRONT_MERGE:
+		if (!sched_allow_merge ||
+		    (sched_allow_merge && blk_mq_sched_allow_merge(q, rq, bio)))
+			return bio_attempt_front_merge(rq, bio, nr_segs);
+		break;
+	case ELEVATOR_DISCARD_MERGE:
+		return bio_attempt_discard_merge(q, rq, bio);
+	default:
+		return BIO_MERGE_NONE;
+	}
+
+	return BIO_MERGE_FAILED;
 }
 
 /**

@@ -1018,8 +1050,6 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 	plug_list = &plug->mq_list;
 
 	list_for_each_entry_reverse(rq, plug_list, queuelist) {
-		bool merged = false;
-
 		if (rq->q == q && same_queue_rq) {
 			/*
 			 * Only blk-mq multiple hardware queues case checks the

@@ -1029,24 +1059,11 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 			*same_queue_rq = rq;
 		}
 
-		if (rq->q != q || !blk_rq_merge_ok(rq, bio))
+		if (rq->q != q)
 			continue;
 
-		switch (blk_try_merge(rq, bio)) {
-		case ELEVATOR_BACK_MERGE:
-			merged = bio_attempt_back_merge(rq, bio, nr_segs);
-			break;
-		case ELEVATOR_FRONT_MERGE:
-			merged = bio_attempt_front_merge(rq, bio, nr_segs);
-			break;
-		case ELEVATOR_DISCARD_MERGE:
-			merged = bio_attempt_discard_merge(q, rq, bio);
-			break;
-		default:
-			break;
-		}
-
-		if (merged)
+		if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
+		    BIO_MERGE_OK)
 			return true;
 	}
 

@@ -1064,33 +1081,18 @@ bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
 	int checked = 8;
 
 	list_for_each_entry_reverse(rq, list, queuelist) {
-		bool merged = false;
-
 		if (!checked--)
 			break;
 
-		if (!blk_rq_merge_ok(rq, bio))
-			continue;
-
-		switch (blk_try_merge(rq, bio)) {
-		case ELEVATOR_BACK_MERGE:
-			if (blk_mq_sched_allow_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(rq, bio,
-						nr_segs);
-			break;
-		case ELEVATOR_DISCARD_MERGE:
-			merged = bio_attempt_discard_merge(q, rq, bio);
-			break;
-		default:
+		switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
+		case BIO_MERGE_NONE:
 			continue;
+		case BIO_MERGE_OK:
+			return true;
+		case BIO_MERGE_FAILED:
+			return false;
 		}
 
-		return merged;
 	}
 
 	return false;

index 82acff9..94db0c9 100644
@@ -368,7 +368,7 @@ 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(rq, bio, nr_segs))
+		if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
 			return false;
 		*merged_request = attempt_back_merge(q, rq);
 		if (!*merged_request)

@@ -377,14 +377,14 @@ 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(rq, bio, nr_segs))
+		if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
 			return false;
 		*merged_request = attempt_front_merge(q, rq);
 		if (!*merged_request)
 			elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
 		return true;
 	case ELEVATOR_DISCARD_MERGE:
-		return bio_attempt_discard_merge(q, rq, bio);
+		return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
 	default:
 		return false;
 	}

index d6152d2..a180443 100644
@@ -29,6 +29,12 @@ struct blk_flush_queue {
 	spinlock_t		mq_flush_lock;
 };
 
+enum bio_merge_status {
+	BIO_MERGE_OK,
+	BIO_MERGE_NONE,
+	BIO_MERGE_FAILED,
+};
+
 extern struct kmem_cache *blk_requestq_cachep;
 extern struct kobj_type blk_queue_ktype;
 extern struct ida blk_queue_ida;

@@ -169,12 +175,15 @@ static inline void blk_integrity_del(struct gendisk *disk)
 unsigned long blk_rq_timeout(unsigned long timeout);
 void blk_add_timer(struct request *req);
 
-bool bio_attempt_front_merge(struct request *req, struct bio *bio,
-		unsigned int nr_segs);
-bool bio_attempt_back_merge(struct request *req, struct bio *bio,
-		unsigned int nr_segs);
-bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
-		struct bio *bio);
+enum bio_merge_status bio_attempt_front_merge(struct request *req,
+					      struct bio *bio,
+					      unsigned int nr_segs);
+enum bio_merge_status bio_attempt_back_merge(struct request *req,
+					     struct bio *bio,
+					     unsigned int nr_segs);
+enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
+						struct request *req,
+						struct bio *bio);
 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs, struct request **same_queue_rq);
 bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,

index 94db0c9..205d971 100644
@@ -391,28 +391,6 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
 }
 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
 
-/*
- * Reverse check our software queue for entries that we could potentially
- * merge with. Currently includes a hand-wavy stop count of 8, to not spend
- * too much time checking for merges.
- */
-static bool blk_mq_attempt_merge(struct request_queue *q,
-				 struct blk_mq_hw_ctx *hctx,
-				 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_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) {
-		ctx->rq_merged++;
-		return true;
-	}
-
-	return false;
-}
-
 bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs)
 {

@@ -426,14 +404,24 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
 		return e->type->ops.bio_merge(hctx, bio, nr_segs);
 
 	type = hctx->type;
-	if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
-			!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, nr_segs);
-		spin_unlock(&ctx->lock);
+	if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE) ||
+	    list_empty_careful(&ctx->rq_lists[type]))
+		return false;
+
+	/* default per sw-queue merge */
+	spin_lock(&ctx->lock);
+	/*
+	 * Reverse check our software queue for entries that we could
+	 * potentially merge with. Currently includes a hand-wavy stop
+	 * count of 8, to not spend too much time checking for merges.
+	 */
+	if (blk_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) {
+		ctx->rq_merged++;
+		ret = true;
 	}
 
+	spin_unlock(&ctx->lock);
+
 	return ret;
 }