nvdimm-blk: use bvec_kmap_local in nd_blk_rw_integrity

Using local kmaps slightly reduces the chances to stray writes, and
the bvec interface cleans up the code a little bit.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20220303111905.321089-6-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvdimm/blk.c

@@ -88,10 +88,9 @@ static int nd_blk_rw_integrity(struct nd_namespace_blk *nsblk,
 		 */
 
 		cur_len = min(len, bv.bv_len);
-		iobuf = kmap_atomic(bv.bv_page);
-		err = ndbr->do_io(ndbr, dev_offset, iobuf + bv.bv_offset,
-				cur_len, rw);
-		kunmap_atomic(iobuf);
+		iobuf = bvec_kmap_local(&bv);
+		err = ndbr->do_io(ndbr, dev_offset, iobuf, cur_len, rw);
+		kunmap_local(iobuf);
 		if (err)
 			return err;