If the segment size is smaller than the page size there may be multiple
segments per bvec even if a bvec only contains a single page. Hence this
patch.
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 | 2 +-
block/blk.h | 18 ++++++++++++++++++
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/block/blk-map.c b/block/blk-map.c
index 9ee4be4ba2f1..eb059d3a1be2 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -534,7 +534,7 @@ 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.h b/block/blk.h
index 9a56d7002efc..b39938255d13 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -86,6 +86,24 @@ 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);
+/* Number of DMA segments required to transfer @bytes data. */
+static inline unsigned int blk_segments(const struct queue_limits *limits,
+ unsigned int bytes)
+{
+ if (!blk_queue_sub_page_limits(limits))
+ return 1;
+
+ {
+ 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;
+ }
+}
+
static inline bool biovec_phys_mergeable(struct request_queue *q,
struct bio_vec *vec1, struct bio_vec *vec2)
{
