NLM: Don't hang forever on NLM unlock requests

If the NLM daemon is killed on the NFS server, we can currently end up
hanging forever on an 'unlock' request, instead of aborting. Basically,
if the rpcbind request fails, or the server keeps returning garbage, we
really want to quit instead of retrying.

Tested-by: Vasily Averin <vvs@sw.ru>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
call_decode(struct rpc_task *task)
{
	struct rpc_clnt	*clnt = task->tk_client;
	struct rpc_rqst	*req = task->tk_rqstp;
	kxdrdproc_t	decode = task->tk_msg.rpc_proc->p_decode;
	__be32		*p;

	dprintk("RPC: %5u call_decode (status %d)\n",
			task->tk_pid, task->tk_status);

	if (task->tk_flags & RPC_CALL_MAJORSEEN) {
		if (clnt->cl_chatty)
			printk(KERN_NOTICE "%s: server %s OK\n",
				clnt->cl_protname, clnt->cl_server);
		task->tk_flags &= ~RPC_CALL_MAJORSEEN;
	}

	/*
	 * Ensure that we see all writes made by xprt_complete_rqst()
	 * before it changed req->rq_reply_bytes_recvd.
	 */
	smp_rmb();
	req->rq_rcv_buf.len = req->rq_private_buf.len;

	/* Check that the softirq receive buffer is valid */
	WARN_ON(memcmp(&req->rq_rcv_buf, &req->rq_private_buf,
				sizeof(req->rq_rcv_buf)) != 0);

	if (req->rq_rcv_buf.len < 12) {
		if (!RPC_IS_SOFT(task)) {
			task->tk_action = call_bind;
			clnt->cl_stats->rpcretrans++;
			goto out_retry;
		}
		dprintk("RPC:       %s: too small RPC reply size (%d bytes)\n",
				clnt->cl_protname, task->tk_status);
		task->tk_action = call_timeout;
		goto out_retry;
	}

	p = rpc_verify_header(task);
	if (IS_ERR(p)) {
		if (p == ERR_PTR(-EAGAIN))
			goto out_retry;
		return;
	}

	task->tk_action = rpc_exit_task;

	if (decode) {
		task->tk_status = rpcauth_unwrap_resp(task, decode, req, p,
						      task->tk_msg.rpc_resp);
	}
	dprintk("RPC: %5u call_decode result %d\n", task->tk_pid,
			task->tk_status);
	return;
out_retry:
	task->tk_status = 0;
	/* Note: rpc_verify_header() may have freed the RPC slot */
	if (task->tk_rqstp == req) {
		req->rq_reply_bytes_recvd = req->rq_rcv_buf.len = 0;
		if (task->tk_client->cl_discrtry)
			xprt_conditional_disconnect(task->tk_xprt,
					req->rq_connect_cookie);
	}
}

call_decode(struct rpc_task *task)
{
	struct rpc_clnt	*clnt = task->tk_client;
	struct rpc_rqst	*req = task->tk_rqstp;
	kxdrdproc_t	decode = task->tk_msg.rpc_proc->p_decode;
	__be32		*p;

	dprintk("RPC: %5u call_decode (status %d)\n",
			task->tk_pid, task->tk_status);

	if (task->tk_flags & RPC_CALL_MAJORSEEN) {
		if (clnt->cl_chatty)
			printk(KERN_NOTICE "%s: server %s OK\n",
				clnt->cl_protname, clnt->cl_server);
		task->tk_flags &= ~RPC_CALL_MAJORSEEN;
	}

	/*
	 * Ensure that we see all writes made by xprt_complete_rqst()
	 * before it changed req->rq_reply_bytes_recvd.
	 */
	smp_rmb();
	req->rq_rcv_buf.len = req->rq_private_buf.len;

	/* Check that the softirq receive buffer is valid */
	WARN_ON(memcmp(&req->rq_rcv_buf, &req->rq_private_buf,
				sizeof(req->rq_rcv_buf)) != 0);

	if (req->rq_rcv_buf.len < 12) {
		if (!RPC_IS_SOFT(task)) {
			task->tk_action = call_bind;
			clnt->cl_stats->rpcretrans++;
			goto out_retry;
		}
		dprintk("RPC:       %s: too small RPC reply size (%d bytes)\n",
				clnt->cl_protname, task->tk_status);
		task->tk_action = call_timeout;
		goto out_retry;
	}

	p = rpc_verify_header(task);
	if (IS_ERR(p)) {
		if (p == ERR_PTR(-EAGAIN))
			goto out_retry;
		return;
	}

	task->tk_action = rpc_exit_task;

	if (decode) {
		task->tk_status = rpcauth_unwrap_resp(task, decode, req, p,
						      task->tk_msg.rpc_resp);
	}
	dprintk("RPC: %5u call_decode result %d\n", task->tk_pid,
			task->tk_status);
	return;
out_retry:
	task->tk_status = 0;
	/* Note: rpc_verify_header() may have freed the RPC slot */
	if (task->tk_rqstp == req) {
		req->rq_reply_bytes_recvd = req->rq_rcv_buf.len = 0;
		if (task->tk_client->cl_discrtry)
			xprt_conditional_disconnect(task->tk_xprt,
					req->rq_connect_cookie);
	}
}
