IB/iser: Enable iser when FMRs are not supported

Reuse the "SG unaligned for FMR" driver flow to make the initiator
functional when running over driver instance which doesn't support
FMRs, such as a mlx4 virtual function.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Alex Tabachnik <alext@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/iser/iser_memory.c

@@ -369,10 +369,11 @@ int iser_reg_rdma_mem(struct iscsi_iser_task *iser_task,
 	regd_buf = &iser_task->rdma_regd[cmd_dir];
 
 	aligned_len = iser_data_buf_aligned_len(mem, ibdev);
-	if (aligned_len != mem->dma_nents) {
+	if (aligned_len != mem->dma_nents ||
+	    (!ib_conn->fmr_pool && mem->dma_nents > 1)) {
 		iscsi_conn->fmr_unalign_cnt++;
-		iser_warn("rdma alignment violation %d/%d aligned\n",
-			 aligned_len, mem->size);
+		iser_warn("rdma alignment violation (%d/%d aligned) or FMR not supported\n",
+			  aligned_len, mem->size);
 		iser_data_buf_dump(mem, ibdev);
 
 		/* unmap the command data before accessing it */

drivers/infiniband/ulp/iser/iser_verbs.c

@@ -242,10 +242,14 @@ static int iser_create_ib_conn_res(struct iser_conn *ib_conn)
 				    IB_ACCESS_REMOTE_READ);
 
 	ib_conn->fmr_pool = ib_create_fmr_pool(device->pd, &params);
-	if (IS_ERR(ib_conn->fmr_pool)) {
-		ret = PTR_ERR(ib_conn->fmr_pool);
+	ret = PTR_ERR(ib_conn->fmr_pool);
+	if (IS_ERR(ib_conn->fmr_pool) && ret != -ENOSYS) {
 		ib_conn->fmr_pool = NULL;
 		goto out_err;
+	} else if (ret == -ENOSYS) {
+		ib_conn->fmr_pool = NULL;
+		iser_warn("FMRs are not supported, using unaligned mode\n");
+		ret = 0;
 	}
 
 	memset(&init_attr, 0, sizeof init_attr);