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-rw-r--r--block/blk-merge.c20
-rw-r--r--include/linux/bio.h7
2 files changed, 25 insertions, 2 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 908d3e1..8681cd6 100644
--- a/block/blk-merge.c
+++ b/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;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index ff5b4cf..dc3cec3 100644
--- a/include/linux/bio.h
+++ b/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 */
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