smb3: fix large reads on encrypted connections

When passing a large read to receive_encrypted_read(), ensure that the
demultiplex_thread knows that a MID was processed.  Without this, those
operations never complete.

This is a similar issue/fix to lease break handling:
commit 7af929d6
("smb3: fix lease break problem introduced by compounding")

CC: Stable <stable@vger.kernel.org> # 4.19+
Fixes: b24df3e3 ("cifs: update receive_encrypted_standard to handle compounded responses")
Signed-off-by: Paul Aurich <paul@darkrain42.org>
Tested-by: Yves-Alexis Perez <corsac@corsac.net>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

fs/cifs/smb2ops.c

@@ -3472,8 +3472,10 @@ smb3_receive_transform(struct TCP_Server_Info *server,
 	}
 
 	/* TODO: add support for compounds containing READ. */
-	if (pdu_length > CIFSMaxBufSize + MAX_HEADER_SIZE(server))
+	if (pdu_length > CIFSMaxBufSize + MAX_HEADER_SIZE(server)) {
+		*num_mids = 1;
 		return receive_encrypted_read(server, &mids[0]);
+	}
 
 	return receive_encrypted_standard(server, mids, bufs, num_mids);
 }