linux-kernel - [PATCH] cifs: smbd: Calculate the correct maximum packet size for segmented SMBDirect send/receive

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Message-Id: <1585164614-123696-1-git-send-email-longli@linuxonhyperv.com>
Date:   Wed, 25 Mar 2020 12:30:14 -0700
From:   longli@...uxonhyperv.com
To:     Steve French <sfrench@...ba.org>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org
Cc:     Long Li <longli@...rosoft.com>
Subject: [PATCH] cifs: smbd: Calculate the correct maximum packet size for segmented SMBDirect send/receive

From: Long Li <longli@...rosoft.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@...rosoft.com>
---
 fs/cifs/smb2ops.c   | 38 ++++++++++++++++----------------------
 fs/cifs/smbdirect.c |  3 +--
 2 files changed, 17 insertions(+), 24 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 4c0922596467..9043d34eef43 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -332,16 +332,6 @@ 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);
 
@@ -360,8 +350,15 @@ 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
+			 * SMB2_READ/SMB2_WRITE (49) and possible encryption
+			 * headers
+			 */
 			wsize = min_t(unsigned int,
-				wsize, server->smbd_conn->max_fragmented_send_size);
+				wsize,
+				server->smbd_conn->max_fragmented_send_size -
+					49 - sizeof(struct smb2_transform_hdr));
 		else
 			wsize = min_t(unsigned int,
 				wsize, server->smbd_conn->max_readwrite_size);
@@ -382,16 +379,6 @@ 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);
@@ -411,8 +398,15 @@ 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
+			 * SMB2_READ/SMB2_WRITE (49) and possible encryption
+			 * headers
+			 */
 			rsize = min_t(unsigned int,
-				rsize, server->smbd_conn->max_fragmented_recv_size);
+				rsize,
+				server->smbd_conn->max_fragmented_recv_size -
+					49 - sizeof(struct smb2_transform_hdr));
 		else
 			rsize = min_t(unsigned int,
 				rsize, server->smbd_conn->max_readwrite_size);
diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index eb1e40af9f3a..0327b575ab87 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