IB/hfi1: check for user backed iterator, not specific iterator type

In preparation for switching single segment iterators to using ITER_UBUF,
swap the check for whether we are user backed or not. While at it, move
it outside the srcu locking area to clean up the code a bit.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/infiniband/hw/hfi1/file_ops.c

@@ -267,18 +267,15 @@ static ssize_t hfi1_write_iter(struct kiocb *kiocb, struct iov_iter *from)
 
 	if (!HFI1_CAP_IS_KSET(SDMA))
 		return -EINVAL;
+	if (!from->user_backed)
+		return -EINVAL;
 	idx = srcu_read_lock(&fd->pq_srcu);
 	pq = srcu_dereference(fd->pq, &fd->pq_srcu);
 	if (!cq || !pq) {
 		srcu_read_unlock(&fd->pq_srcu, idx);
 		return -EIO;
 	}
 
-	if (!iter_is_iovec(from) || !dim) {
-		srcu_read_unlock(&fd->pq_srcu, idx);
-		return -EINVAL;
-	}
-
 	trace_hfi1_sdma_request(fd->dd, fd->uctxt->ctxt, fd->subctxt, dim);
 
 	if (atomic_read(&pq->n_reqs) == pq->n_max_reqs) {