---

yaml
---
r: 115483
b: refs/heads/master
c: 8677142
h: refs/heads/master
i:
  115481: 31dd883
  115479: d213e5f
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 0fc71e3d6520ba7abad5cfbc9a33db0190e4d5b8
+refs/heads/master: 8677142710516d986d932d6f1fba7be8382c1fec

trunk/block/blk-merge.c

@@ -77,12 +77,20 @@ void blk_recalc_rq_segments(struct request *rq)
 			continue;
 		}
 new_segment:
+		if (nr_phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
+			rq->bio->bi_seg_front_size = seg_size;
+
 		nr_phys_segs++;
 		bvprv = bv;
 		seg_size = bv->bv_len;
 		highprv = high;
 	}
 
+	if (nr_phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
+		rq->bio->bi_seg_front_size = seg_size;
+	if (seg_size > rq->biotail->bi_seg_back_size)
+		rq->biotail->bi_seg_back_size = seg_size;
+
 	rq->nr_phys_segments = nr_phys_segs;
 }
 
@@ -106,7 +114,8 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
 		return 0;
 
-	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
+	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
+	    q->max_segment_size)
 		return 0;
 
 	if (!bio_has_data(bio))
@@ -309,6 +318,8 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 				struct request *next)
 {
 	int total_phys_segments;
+	unsigned int seg_size =
+		req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
 
 	/*
 	 * First check if the either of the requests are re-queued
@@ -324,8 +335,13 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 		return 0;
 
 	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
-	if (blk_phys_contig_segment(q, req->biotail, next->bio))
+	if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
+		if (req->nr_phys_segments == 1)
+			req->bio->bi_seg_front_size = seg_size;
+		if (next->nr_phys_segments == 1)
+			next->biotail->bi_seg_back_size = seg_size;
 		total_phys_segments--;
+	}
 
 	if (total_phys_segments > q->max_phys_segments)
 		return 0;

trunk/include/linux/bio.h

@@ -79,6 +79,13 @@ struct bio {
 
 	unsigned int		bi_size;	/* residual I/O count */
 
+	/*
+	 * To keep track of the max segment size, we account for the
+	 * sizes of the first and last mergeable segments in this bio.
+	 */
+	unsigned int		bi_seg_front_size;
+	unsigned int		bi_seg_back_size;
+
 	unsigned int		bi_max_vecs;	/* max bvl_vecs we can hold */
 
 	unsigned int		bi_comp_cpu;	/* completion CPU */