diff --git a/block/blk-map.c b/block/blk-map.c index 66da9e2b19ab..ddc10bcedc6d 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -531,7 +531,7 @@ 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 d2e9dfb03ceb..f6e59cd7cfa1 100644 --- a/block/blk.h +++ b/block/blk.h @@ -91,6 +91,24 @@ 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) {