Since multi-page bvecs are supported there can be multiple segments per
bvec (see also bvec_split_segs()). Hence this patch that calculates the
number of segments per bvec instead of assuming that there is only one
segment per bvec.
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Keith Busch <kbusch@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
block/blk-map.c | 14 +++++++++++++-
block/blk-mq.c | 2 ++
block/blk.h | 3 +++
3 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/block/blk-map.c b/block/blk-map.c
index 4505307d758e..2976a8d68992 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -529,6 +529,18 @@ static struct bio *bio_copy_kern(struct request_queue *q, void *data,
return ERR_PTR(-ENOMEM);
}
+/* Number of DMA segments required to transfer @bytes data. */
+unsigned int blk_segments(const struct queue_limits *limits, unsigned int bytes)
+{
+ const unsigned int mss = limits->max_segment_size;
+
+ if (bytes <= mss)
+ return 1;
+ if (is_power_of_2(mss))
+ return round_up(bytes, mss) >> ilog2(mss);
+ return (bytes + mss - 1) / mss;
+}
+
/*
* Append a bio to a passthrough request. Only works if the bio can be merged
* into the request based on the driver constraints.
@@ -540,7 +552,7 @@ int blk_rq_append_bio(struct request *rq, struct bio *bio)
unsigned int nr_segs = 0;
bio_for_each_bvec(bv, bio, iter)
- nr_segs++;
+ nr_segs += blk_segments(&rq->q->limits, bv.bv_len);
if (!rq->bio) {
blk_rq_bio_prep(rq, bio, nr_segs);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8070b6c10e8d..82ae8099afdd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2883,6 +2883,8 @@ void blk_mq_submit_bio(struct bio *bio)
bio = blk_queue_bounce(bio, q);
if (bio_may_exceed_limits(bio, &q->limits))
bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
+ else if (bio->bi_vcnt == 1)
+ nr_segs = blk_segments(&q->limits, bio->bi_io_vec[0].bv_len);
if (!bio_integrity_prep(bio))
return;
diff --git a/block/blk.h b/block/blk.h
index 7f9e089ab1f7..342ba7d86e87 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -81,6 +81,9 @@ struct bio_vec *bvec_alloc(mempool_t *pool, unsigned short *nr_vecs,
gfp_t gfp_mask);
void bvec_free(mempool_t *pool, struct bio_vec *bv, unsigned short nr_vecs);
+unsigned int blk_segments(const struct queue_limits *limits,
+ unsigned int bytes);
+
static inline bool biovec_phys_mergeable(struct request_queue *q,
struct bio_vec *vec1, struct bio_vec *vec2)
{
