smb3: increase initial number of credits requested to allow write

Compared to other clients the Linux smb3 client ramps up
credits very slowly, taking more than 128 operations before a
maximum size write could be sent (since the number of credits
requested is only 2 per small operation, causing the credit
limit to grow very slowly).

This lack of credits initially would impact large i/o performance,
when large i/o is tried early before enough credits are built up.
Signed-off-by: Steve French <stfrench@gmail.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

fs/cifs/smb2pdu.c

@@ -990,8 +990,9 @@ SMB2_sess_alloc_buffer(struct SMB2_sess_data *sess_data)
 	req->PreviousSessionId = sess_data->previous_session;
 
 	req->Flags = 0; /* MBZ */
-	/* to enable echos and oplocks */
-	req->sync_hdr.CreditRequest = cpu_to_le16(3);
+
+	/* enough to enable echos and oplocks and one max size write */
+	req->sync_hdr.CreditRequest = cpu_to_le16(130);
 
 	/* only one of SMB2 signing flags may be set in SMB2 request */
 	if (server->sign)