diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 396cdbe..12487aa 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -36,8 +36,6 @@
 #include <linux/sunrpc/metrics.h>
 
 
-#define RPC_SLACK_SPACE		(1024)	/* total overkill */
-
 #ifdef RPC_DEBUG
 # define RPCDBG_FACILITY	RPCDBG_CALL
 #endif
@@ -747,21 +745,37 @@
 static void
 call_allocate(struct rpc_task *task)
 {
+	unsigned int slack = task->tk_auth->au_cslack;
 	struct rpc_rqst *req = task->tk_rqstp;
 	struct rpc_xprt *xprt = task->tk_xprt;
-	unsigned int	bufsiz;
+	struct rpc_procinfo *proc = task->tk_msg.rpc_proc;
 
 	dprint_status(task);
 
+	task->tk_status = 0;
 	task->tk_action = call_bind;
+
 	if (req->rq_buffer)
 		return;
 
-	/* FIXME: compute buffer requirements more exactly using
-	 * auth->au_wslack */
-	bufsiz = task->tk_msg.rpc_proc->p_bufsiz + RPC_SLACK_SPACE;
+	if (proc->p_proc != 0) {
+		BUG_ON(proc->p_arglen == 0);
+		if (proc->p_decode != NULL)
+			BUG_ON(proc->p_replen == 0);
+	}
 
-	if (xprt->ops->buf_alloc(task, bufsiz << 1) != NULL)
+	/*
+	 * Calculate the size (in quads) of the RPC call
+	 * and reply headers, and convert both values
+	 * to byte sizes.
+	 */
+	req->rq_callsize = RPC_CALLHDRSIZE + (slack << 1) + proc->p_arglen;
+	req->rq_callsize <<= 2;
+	req->rq_rcvsize = RPC_REPHDRSIZE + slack + proc->p_replen;
+	req->rq_rcvsize <<= 2;
+
+	xprt->ops->buf_alloc(task, req->rq_callsize + req->rq_rcvsize);
+	if (req->rq_buffer != NULL)
 		return;
 
 	dprintk("RPC: %5u rpc_buffer allocation failed\n", task->tk_pid);
@@ -788,6 +802,17 @@
 	task->tk_rqstp->rq_snd_buf.len = 0;
 }
 
+static inline void
+rpc_xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
+{
+	buf->head[0].iov_base = start;
+	buf->head[0].iov_len = len;
+	buf->tail[0].iov_len = 0;
+	buf->page_len = 0;
+	buf->len = 0;
+	buf->buflen = len;
+}
+
 /*
  * 3.	Encode arguments of an RPC call
  */
@@ -795,28 +820,17 @@
 call_encode(struct rpc_task *task)
 {
 	struct rpc_rqst	*req = task->tk_rqstp;
-	struct xdr_buf *sndbuf = &req->rq_snd_buf;
-	struct xdr_buf *rcvbuf = &req->rq_rcv_buf;
-	unsigned int	bufsiz;
 	kxdrproc_t	encode;
 	__be32		*p;
 
 	dprint_status(task);
 
-	/* Default buffer setup */
-	bufsiz = req->rq_bufsize >> 1;
-	sndbuf->head[0].iov_base = (void *)req->rq_buffer;
-	sndbuf->head[0].iov_len  = bufsiz;
-	sndbuf->tail[0].iov_len  = 0;
-	sndbuf->page_len	 = 0;
-	sndbuf->len		 = 0;
-	sndbuf->buflen		 = bufsiz;
-	rcvbuf->head[0].iov_base = (void *)((char *)req->rq_buffer + bufsiz);
-	rcvbuf->head[0].iov_len  = bufsiz;
-	rcvbuf->tail[0].iov_len  = 0;
-	rcvbuf->page_len	 = 0;
-	rcvbuf->len		 = 0;
-	rcvbuf->buflen		 = bufsiz;
+	rpc_xdr_buf_init(&req->rq_snd_buf,
+			 req->rq_buffer,
+			 req->rq_callsize);
+	rpc_xdr_buf_init(&req->rq_rcv_buf,
+			 (char *)req->rq_buffer + req->rq_callsize,
+			 req->rq_rcvsize);
 
 	/* Encode header and provided arguments */
 	encode = task->tk_msg.rpc_proc->p_encode;
diff --git a/net/sunrpc/pmap_clnt.c b/net/sunrpc/pmap_clnt.c
index d9f7653..c45fc4c9 100644
--- a/net/sunrpc/pmap_clnt.c
+++ b/net/sunrpc/pmap_clnt.c
@@ -335,7 +335,8 @@
 	  .p_proc		= PMAP_SET,
 	  .p_encode		= (kxdrproc_t) xdr_encode_mapping,
 	  .p_decode		= (kxdrproc_t) xdr_decode_bool,
-	  .p_bufsiz		= 4,
+	  .p_arglen		= 4,
+	  .p_replen		= 1,
 	  .p_count		= 1,
 	  .p_statidx		= PMAP_SET,
 	  .p_name		= "SET",
@@ -344,7 +345,8 @@
 	  .p_proc		= PMAP_UNSET,
 	  .p_encode		= (kxdrproc_t) xdr_encode_mapping,
 	  .p_decode		= (kxdrproc_t) xdr_decode_bool,
-	  .p_bufsiz		= 4,
+	  .p_arglen		= 4,
+	  .p_replen		= 1,
 	  .p_count		= 1,
 	  .p_statidx		= PMAP_UNSET,
 	  .p_name		= "UNSET",
@@ -353,7 +355,8 @@
 	  .p_proc		= PMAP_GETPORT,
 	  .p_encode		= (kxdrproc_t) xdr_encode_mapping,
 	  .p_decode		= (kxdrproc_t) xdr_decode_port,
-	  .p_bufsiz		= 4,
+	  .p_arglen		= 4,
+	  .p_replen		= 1,
 	  .p_count		= 1,
 	  .p_statidx		= PMAP_GETPORT,
 	  .p_name		= "GETPORT",
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 456a145..432ee92 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -823,7 +823,6 @@
 	req->rq_task	= task;
 	req->rq_xprt    = xprt;
 	req->rq_buffer  = NULL;
-	req->rq_bufsize = 0;
 	req->rq_xid     = xprt_alloc_xid(xprt);
 	req->rq_release_snd_buf = NULL;
 	xprt_reset_majortimeo(req);