bio: get rid of bio_vec clearing

We don't need to clear the memory used for adding bio_vec entries,
since nobody should be looking at members unitialized. Any valid
use should be below bio->bi_vcnt, and that members up until that count
must be valid since they were added through bio_add_page().
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/bio.c

@@ -180,7 +180,7 @@ struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned long *idx,
 	 * kzalloc() for the exact number of vecs right away.
 	 */
 	if (!bs)
-		bvl = kzalloc(nr * sizeof(struct bio_vec), gfp_mask);
+		bvl = kmalloc(nr * sizeof(struct bio_vec), gfp_mask);
 
 	/*
 	 * see comment near bvec_array define!
@@ -237,9 +237,6 @@ fallback:
 		}
 	}
 
-	if (bvl)
-		memset(bvl, 0, bvec_nr_vecs(*idx) * sizeof(struct bio_vec));
-
 	return bvl;
 }
 
@@ -325,7 +322,6 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
 				idx = 0;
 				bvl = bio->bi_inline_vecs;
 				nr_iovecs = BIO_INLINE_VECS;
-				memset(bvl, 0, BIO_INLINE_VECS * sizeof(*bvl));
 			} else {
 				bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx,
 							bs);