SUNRPC: remove printk when back channel request not found

If the client interface is down, or there is a network partition between
the client and server that prevents the callback request to reach the
client, TCP on the server will keep re-transmitting the callback for about
~9 minutes before giving up and closing the connection.

If the connection between the client and the server is re-established
before the connection is closed and after the callback timed out (9 secs)
then the re-transmitted callback request will arrive at the client. When
the server receives the reply of the callback, receive_cb_reply prints the
"Got unrecognized reply..." message in the system log since the callback
request was already removed from the server xprt's recv_queue.

Even though this scenario has no effect on the server operation, a
malfunctioning or malicious client can fill up the server's system log.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: daimngo

net/sunrpc/svcsock.c

@@ -1049,18 +1049,14 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	struct rpc_rqst *req = NULL;
 	struct kvec *src, *dst;
 	__be32 *p = (__be32 *)rqstp->rq_arg.head[0].iov_base;
-	__be32 xid;
-	__be32 calldir;
-
-	xid = *p++;
-	calldir = *p;
+	__be32 xid = *p;
 
 	if (!bc_xprt)
 		return -EAGAIN;
 	spin_lock(&bc_xprt->queue_lock);
 	req = xprt_lookup_rqst(bc_xprt, xid);
 	if (!req)
-		goto unlock_notfound;
+		goto unlock_eagain;
 
 	memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
 	/*
@@ -1077,12 +1073,6 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	rqstp->rq_arg.len = 0;
 	spin_unlock(&bc_xprt->queue_lock);
 	return 0;
-unlock_notfound:
-	printk(KERN_NOTICE
-		"%s: Got unrecognized reply: "
-		"calldir 0x%x xpt_bc_xprt %p xid %08x\n",
-		__func__, ntohl(calldir),
-		bc_xprt, ntohl(xid));
 unlock_eagain:
 	spin_unlock(&bc_xprt->queue_lock);
 	return -EAGAIN;