[Patch v2] cifs: smbd: Calculate the correct maximum packet size for segmented SMBDirect send/receive

[longli@linuxonhyperv.com]

From: Long Li <longli@microsoft.com>

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>
---

Change since v1: defined SMB2_READWRITE_PDU_HEADER_SIZE for header size and corrected miscalculation

 fs/cifs/smb2ops.c   | 38 ++++++++++++++++----------------------
 fs/cifs/smb2pdu.h   |  3 +++
 fs/cifs/smbdirect.c |  3 +--
 3 files changed, 20 insertions(+), 24 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 9c9258fc8756..b36c46f48705 100644
--- a/fs/cifs/smb2ops.c
+++ b/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);
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index dda928d05c13..10acf90f858d 100644
--- a/fs/cifs/smb2pdu.h
+++ b/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) */
diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index 5b1b97e9e0c9..a6ae29b3c4e7 100644
--- a/fs/cifs/smbdirect.c
+++ b/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;
-- 
2.17.1