- /*
- * for each bio in rq
- */
- sg = NULL;
- rq_for_each_segment(bvec, rq, iter) {
- __blk_segment_map_sg(q, &bvec, sglist, &bvprv, &sg,
- &nsegs, &cluster);
- } /* segments in rq */
+ if (bio->bi_rw & REQ_DISCARD) {
+ /*
+ * This is a hack - drivers should be neither modifying the
+ * biovec, nor relying on bi_vcnt - but because of
+ * blk_add_request_payload(), a discard bio may or may not have
+ * a payload we need to set up here (thank you Christoph) and
+ * bi_vcnt is really the only way of telling if we need to.
+ */
+
+ if (bio->bi_vcnt)
+ goto single_segment;
+
+ return 0;
+ }
+
+ if (bio->bi_rw & REQ_WRITE_SAME) {
+single_segment:
+ *sg = sglist;
+ bvec = bio_iovec(bio);
+ sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
+ return 1;
+ }
+
+ for_each_bio(bio)
+ bio_for_each_segment(bvec, bio, iter)
+ __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
+ &nsegs, &cluster);