CIFS: SMBD: Set SMB Direct maximum read or write size for I/O

When connecting over SMB Direct, the transport negotiates its maximum I/O sizes
with the server and determines how to choose to do RDMA send/recv vs
read/write. Expose these maximum I/O sizes to upper layer so we will get the
correct sized payloads.
Signed-off-by: NLong Li <longli@microsoft.com>
Signed-off-by: NSteve French <smfrench@gmail.com>
Reviewed-by: NPavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: NRonnie Sahlberg <lsahlber@redhat.com>

fs/cifs/smb2ops.c

@@ -32,6 +32,7 @@
 #include "smb2status.h"
 #include "smb2glob.h"
 #include "cifs_ioctl.h"
+#include "smbdirect.h"
 
 static int
 change_conf(struct TCP_Server_Info *server)
@@ -250,7 +251,11 @@ 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)
+		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);
 
@@ -266,6 +271,11 @@ 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)
+		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);