cifs: smbd: Calculate the correct maximum packet size for segmented SMBDirect send/receive

The packet size needs to take account of SMB2 header size and possible
encryption header size. This is only done when signing is used and it is for
RDMA send/receive, not read/write.

Also remove the dead SMBD code in smb2_negotiate_r(w)size.
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2ops.c

@@ -328,16 +328,6 @@ smb2_negotiate_wsize(struct cifs_tcon *tcon, struct smb_vol *volume_info)
 	/* start with specified wsize, or default */
 	wsize = volume_info->wsize ? volume_info->wsize : CIFS_DEFAULT_IOSIZE;
 	wsize = min_t(unsigned int, wsize, server->max_write);
-#ifdef CONFIG_CIFS_SMB_DIRECT
-	if (server->rdma) {
-		if (server->sign)
-			wsize = min_t(unsigned int,
-				wsize, server->smbd_conn->max_fragmented_send_size);
-		else
-			wsize = min_t(unsigned int,
-				wsize, server->smbd_conn->max_readwrite_size);
-	}
-#endif
 	if (!(server->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU))
 		wsize = min_t(unsigned int, wsize, SMB2_MAX_BUFFER_SIZE);
 
@@ -356,8 +346,15 @@ smb3_negotiate_wsize(struct cifs_tcon *tcon, struct smb_vol *volume_info)
 #ifdef CONFIG_CIFS_SMB_DIRECT
 	if (server->rdma) {
 		if (server->sign)
+			/*
+			 * Account for SMB2 data transfer packet header and
+			 * possible encryption header
+			 */
 			wsize = min_t(unsigned int,
-				wsize, server->smbd_conn->max_fragmented_send_size);
+				wsize,
+				server->smbd_conn->max_fragmented_send_size -
+					SMB2_READWRITE_PDU_HEADER_SIZE -
+					sizeof(struct smb2_transform_hdr));
 		else
 			wsize = min_t(unsigned int,
 				wsize, server->smbd_conn->max_readwrite_size);
@@ -378,16 +375,6 @@ smb2_negotiate_rsize(struct cifs_tcon *tcon, struct smb_vol *volume_info)
 	/* start with specified rsize, or default */
 	rsize = volume_info->rsize ? volume_info->rsize : CIFS_DEFAULT_IOSIZE;
 	rsize = min_t(unsigned int, rsize, server->max_read);
-#ifdef CONFIG_CIFS_SMB_DIRECT
-	if (server->rdma) {
-		if (server->sign)
-			rsize = min_t(unsigned int,
-				rsize, server->smbd_conn->max_fragmented_recv_size);
-		else
-			rsize = min_t(unsigned int,
-				rsize, server->smbd_conn->max_readwrite_size);
-	}
-#endif
 
 	if (!(server->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU))
 		rsize = min_t(unsigned int, rsize, SMB2_MAX_BUFFER_SIZE);
@@ -407,8 +394,15 @@ smb3_negotiate_rsize(struct cifs_tcon *tcon, struct smb_vol *volume_info)
 #ifdef CONFIG_CIFS_SMB_DIRECT
 	if (server->rdma) {
 		if (server->sign)
+			/*
+			 * Account for SMB2 data transfer packet header and
+			 * possible encryption header
+			 */
 			rsize = min_t(unsigned int,
-				rsize, server->smbd_conn->max_fragmented_recv_size);
+				rsize,
+				server->smbd_conn->max_fragmented_recv_size -
+					SMB2_READWRITE_PDU_HEADER_SIZE -
+					sizeof(struct smb2_transform_hdr));
 		else
 			rsize = min_t(unsigned int,
 				rsize, server->smbd_conn->max_readwrite_size);

fs/cifs/smb2pdu.h

@@ -120,6 +120,9 @@ struct smb2_sync_hdr {
 	__u8   Signature[16];
 } __packed;
 
+/* The total header size for SMB2 read and write */
+#define SMB2_READWRITE_PDU_HEADER_SIZE (48 + sizeof(struct smb2_sync_hdr))
+
 struct smb2_sync_pdu {
 	struct smb2_sync_hdr sync_hdr;
 	__le16 StructureSize2; /* size of wct area (varies, request specific) */

fs/cifs/smbdirect.c

@@ -2097,8 +2097,7 @@ int smbd_send(struct TCP_Server_Info *server,
 	for (i = 0; i < num_rqst; i++)
 		remaining_data_length += smb_rqst_len(server, &rqst_array[i]);
 
-	if (remaining_data_length + sizeof(struct smbd_data_transfer) >
-		info->max_fragmented_send_size) {
+	if (remaining_data_length > info->max_fragmented_send_size) {
 		log_write(ERR, "payload size %d > max size %d\n",
 			remaining_data_length, info->max_fragmented_send_size);
 		rc = -EINVAL;