bio: make use of bvec_nr_vecs

Since introduced in 7ba1ba12eee, it should be made use of.

Signed-off-by: Denis ChengRq <crquan@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/bio.c

diff --git a/fs/bio.c b/fs/bio.c
index 25f1af0..8000e2f 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -77,11 +77,8 @@
 	 */
 
 	bvl = mempool_alloc(bs->bvec_pools[*idx], gfp_mask);
-	if (bvl) {
-		struct biovec_slab *bp = bvec_slabs + *idx;
-
-		memset(bvl, 0, bp->nr_vecs * sizeof(struct bio_vec));
-	}
+	if (bvl)
+		memset(bvl, 0, bvec_nr_vecs(*idx) * sizeof(struct bio_vec));
 
 	return bvl;
 }
@@ -149,7 +146,7 @@
 				goto out;
 			}
 			bio->bi_flags |= idx << BIO_POOL_OFFSET;
-			bio->bi_max_vecs = bvec_slabs[idx].nr_vecs;
+			bio->bi_max_vecs = bvec_nr_vecs(idx);
 		}
 		bio->bi_io_vec = bvl;
 	}