RDMA/rtrs-srv: Correct the checking of ib_map_mr_sg

We should check with nr_sgt, also the only successful case is that
all sg elements are mapped, so make it explicitly.
Acked-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Link: https://lore.kernel.org/r/20221117101945.6317-4-guoqing.jiang@linux.devSigned-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/ulp/rtrs/rtrs-srv.c

@@ -622,7 +622,7 @@ static int map_cont_bufs(struct rtrs_srv_path *srv_path)
 		}
 		nr = ib_map_mr_sg(mr, sgt->sgl, nr_sgt,
 				  NULL, max_chunk_size);
-		if (nr < 0 || nr < sgt->nents) {
+		if (nr != nr_sgt) {
 			err = nr < 0 ? nr : -EINVAL;
 			goto dereg_mr;
 		}