smb/client: fix rdma usage in smb2_async_writev()

rqst.rq_iter needs to be truncated otherwise we'll
also send the bytes into the stream socket...

This is the logic behind rqst.rq_npages = 0, which was removed in
"cifs: Change the I/O paths to use an iterator rather than a page list"
(d08089f6).

Cc: stable@vger.kernel.org
Fixes: d08089f6 ("cifs: Change the I/O paths to use an iterator rather than a page list")
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/smb2pdu.c

@@ -4913,6 +4913,13 @@ smb2_async_writev(struct cifs_io_subrequest *wdata)
 	if (rc)
 		goto out;
 
+	rqst.rq_iov = iov;
+	rqst.rq_iter = wdata->subreq.io_iter;
+
+	rqst.rq_iov[0].iov_len = total_len - 1;
+	rqst.rq_iov[0].iov_base = (char *)req;
+	rqst.rq_nvec += 1;
+
 	if (smb3_encryption_required(tcon))
 		flags |= CIFS_TRANSFORM_REQ;
 
@@ -4924,6 +4931,7 @@ smb2_async_writev(struct cifs_io_subrequest *wdata)
 	req->WriteChannelInfoOffset = 0;
 	req->WriteChannelInfoLength = 0;
 	req->Channel = SMB2_CHANNEL_NONE;
+	req->Length = cpu_to_le32(io_parms->length);
 	req->Offset = cpu_to_le64(io_parms->offset);
 	req->DataOffset = cpu_to_le16(
 				offsetof(struct smb2_write_req, Buffer));
@@ -4943,7 +4951,6 @@ smb2_async_writev(struct cifs_io_subrequest *wdata)
 	 */
 	if (smb3_use_rdma_offload(io_parms)) {
 		struct smbd_buffer_descriptor_v1 *v1;
-		size_t data_size = iov_iter_count(&wdata->subreq.io_iter);
 		bool need_invalidate = server->dialect == SMB30_PROT_ID;
 
 		wdata->mr = smbd_register_mr(server->smbd_conn, &wdata->subreq.io_iter,
@@ -4952,9 +4959,10 @@ smb2_async_writev(struct cifs_io_subrequest *wdata)
 			rc = -EAGAIN;
 			goto async_writev_out;
 		}
+		/* For RDMA read, I/O size is in RemainingBytes not in Length */
+		req->RemainingBytes = req->Length;
 		req->Length = 0;
 		req->DataOffset = 0;
-		req->RemainingBytes = cpu_to_le32(data_size);
 		req->Channel = SMB2_CHANNEL_RDMA_V1_INVALIDATE;
 		if (need_invalidate)
 			req->Channel = SMB2_CHANNEL_RDMA_V1;
@@ -4966,30 +4974,22 @@ smb2_async_writev(struct cifs_io_subrequest *wdata)
 		v1->offset = cpu_to_le64(wdata->mr->mr->iova);
 		v1->token = cpu_to_le32(wdata->mr->mr->rkey);
 		v1->length = cpu_to_le32(wdata->mr->mr->length);
+
+		rqst.rq_iov[0].iov_len += sizeof(*v1);
+
+		/*
+		 * We keep wdata->subreq.io_iter,
+		 * but we have to truncate rqst.rq_iter
+		 */
+		iov_iter_truncate(&rqst.rq_iter, 0);
 	}
 #endif
-	iov[0].iov_len = total_len - 1;
-	iov[0].iov_base = (char *)req;
 
-	rqst.rq_iov = iov;
-	rqst.rq_nvec = 1;
-	rqst.rq_iter = wdata->subreq.io_iter;
 	if (test_bit(NETFS_SREQ_RETRYING, &wdata->subreq.flags))
 		smb2_set_replay(server, &rqst);
-#ifdef CONFIG_CIFS_SMB_DIRECT
-	if (wdata->mr)
-		iov[0].iov_len += sizeof(struct smbd_buffer_descriptor_v1);
-#endif
-	cifs_dbg(FYI, "async write at %llu %u bytes iter=%zx\n",
-		 io_parms->offset, io_parms->length, iov_iter_count(&rqst.rq_iter));
 
-#ifdef CONFIG_CIFS_SMB_DIRECT
-	/* For RDMA read, I/O size is in RemainingBytes not in Length */
-	if (!wdata->mr)
-		req->Length = cpu_to_le32(io_parms->length);
-#else
-	req->Length = cpu_to_le32(io_parms->length);
-#endif
+	cifs_dbg(FYI, "async write at %llu %u bytes iter=%zx\n",
+		 io_parms->offset, io_parms->length, iov_iter_count(&wdata->subreq.io_iter));
 
 	if (wdata->credits.value > 0) {
 		shdr->CreditCharge = cpu_to_le16(DIV_ROUND_UP(wdata->subreq.len,