diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
index eb243ed..2102e2d 100644
--- a/fs/lockd/mon.c
+++ b/fs/lockd/mon.c
@@ -225,16 +225,13 @@
 #define SM_monres_sz	2
 #define SM_unmonres_sz	1
 
-#ifndef MAX
-# define MAX(a, b)	(((a) > (b))? (a) : (b))
-#endif
-
 static struct rpc_procinfo	nsm_procedures[] = {
 [SM_MON] = {
 		.p_proc		= SM_MON,
 		.p_encode	= (kxdrproc_t) xdr_encode_mon,
 		.p_decode	= (kxdrproc_t) xdr_decode_stat_res,
-		.p_bufsiz	= MAX(SM_mon_sz, SM_monres_sz) << 2,
+		.p_arglen	= SM_mon_sz,
+		.p_replen	= SM_monres_sz,
 		.p_statidx	= SM_MON,
 		.p_name		= "MONITOR",
 	},
@@ -242,7 +239,8 @@
 		.p_proc		= SM_UNMON,
 		.p_encode	= (kxdrproc_t) xdr_encode_unmon,
 		.p_decode	= (kxdrproc_t) xdr_decode_stat,
-		.p_bufsiz	= MAX(SM_mon_id_sz, SM_unmonres_sz) << 2,
+		.p_arglen	= SM_mon_id_sz,
+		.p_replen	= SM_unmonres_sz,
 		.p_statidx	= SM_UNMON,
 		.p_name		= "UNMONITOR",
 	},
diff --git a/fs/lockd/xdr.c b/fs/lockd/xdr.c
index 6aac4b2..9702956 100644
--- a/fs/lockd/xdr.c
+++ b/fs/lockd/xdr.c
@@ -534,10 +534,6 @@
 #define NLM_res_sz		NLM_cookie_sz+1
 #define NLM_norep_sz		0
 
-#ifndef MAX
-# define MAX(a, b)		(((a) > (b))? (a) : (b))
-#endif
-
 /*
  * For NLM, a void procedure really returns nothing
  */
@@ -548,7 +544,8 @@
 	.p_proc      = NLMPROC_##proc,					\
 	.p_encode    = (kxdrproc_t) nlmclt_encode_##argtype,		\
 	.p_decode    = (kxdrproc_t) nlmclt_decode_##restype,		\
-	.p_bufsiz    = MAX(NLM_##argtype##_sz, NLM_##restype##_sz) << 2,	\
+	.p_arglen    = NLM_##argtype##_sz,				\
+	.p_replen    = NLM_##restype##_sz,				\
 	.p_statidx   = NLMPROC_##proc,					\
 	.p_name      = #proc,						\
 	}
diff --git a/fs/lockd/xdr4.c b/fs/lockd/xdr4.c
index 7c8b679..ce1efdb 100644
--- a/fs/lockd/xdr4.c
+++ b/fs/lockd/xdr4.c
@@ -544,10 +544,6 @@
 #define NLM4_res_sz		NLM4_cookie_sz+1
 #define NLM4_norep_sz		0
 
-#ifndef MAX
-# define MAX(a,b)		(((a) > (b))? (a) : (b))
-#endif
-
 /*
  * For NLM, a void procedure really returns nothing
  */
@@ -558,7 +554,8 @@
 	.p_proc      = NLMPROC_##proc,					\
 	.p_encode    = (kxdrproc_t) nlm4clt_encode_##argtype,		\
 	.p_decode    = (kxdrproc_t) nlm4clt_decode_##restype,		\
-	.p_bufsiz    = MAX(NLM4_##argtype##_sz, NLM4_##restype##_sz) << 2,	\
+	.p_arglen    = NLM4_##argtype##_sz,				\
+	.p_replen    = NLM4_##restype##_sz,				\
 	.p_statidx   = NLMPROC_##proc,					\
 	.p_name      = #proc,						\
 	}
diff --git a/fs/nfs/mount_clnt.c b/fs/nfs/mount_clnt.c
index f75fe72..ca5a266 100644
--- a/fs/nfs/mount_clnt.c
+++ b/fs/nfs/mount_clnt.c
@@ -133,13 +133,15 @@
 
 #define MNT_dirpath_sz		(1 + 256)
 #define MNT_fhstatus_sz		(1 + 8)
+#define MNT_fhstatus3_sz	(1 + 16)
 
 static struct rpc_procinfo	mnt_procedures[] = {
 [MNTPROC_MNT] = {
 	  .p_proc		= MNTPROC_MNT,
 	  .p_encode		= (kxdrproc_t) xdr_encode_dirpath,	
 	  .p_decode		= (kxdrproc_t) xdr_decode_fhstatus,
-	  .p_bufsiz		= MNT_dirpath_sz << 2,
+	  .p_arglen		= MNT_dirpath_sz,
+	  .p_replen		= MNT_fhstatus_sz,
 	  .p_statidx		= MNTPROC_MNT,
 	  .p_name		= "MOUNT",
 	},
@@ -150,7 +152,8 @@
 	  .p_proc		= MOUNTPROC3_MNT,
 	  .p_encode		= (kxdrproc_t) xdr_encode_dirpath,
 	  .p_decode		= (kxdrproc_t) xdr_decode_fhstatus3,
-	  .p_bufsiz		= MNT_dirpath_sz << 2,
+	  .p_arglen		= MNT_dirpath_sz,
+	  .p_replen		= MNT_fhstatus3_sz,
 	  .p_statidx		= MOUNTPROC3_MNT,
 	  .p_name		= "MOUNT",
 	},
diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index 3be4e72..abd9f8b 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -687,16 +687,13 @@
 	return nfs_errtbl[i].errno;
 }
 
-#ifndef MAX
-# define MAX(a, b)	(((a) > (b))? (a) : (b))
-#endif
-
 #define PROC(proc, argtype, restype, timer)				\
 [NFSPROC_##proc] = {							\
 	.p_proc	    =  NFSPROC_##proc,					\
 	.p_encode   =  (kxdrproc_t) nfs_xdr_##argtype,			\
 	.p_decode   =  (kxdrproc_t) nfs_xdr_##restype,			\
-	.p_bufsiz   =  MAX(NFS_##argtype##_sz,NFS_##restype##_sz) << 2,	\
+	.p_arglen   =  NFS_##argtype##_sz,				\
+	.p_replen   =  NFS_##restype##_sz,				\
 	.p_timer    =  timer,						\
 	.p_statidx  =  NFSPROC_##proc,					\
 	.p_name     =  #proc,						\
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 0ace092..b51df8e 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -1102,16 +1102,13 @@
 }
 #endif  /* CONFIG_NFS_V3_ACL */
 
-#ifndef MAX
-# define MAX(a, b)	(((a) > (b))? (a) : (b))
-#endif
-
 #define PROC(proc, argtype, restype, timer)				\
 [NFS3PROC_##proc] = {							\
 	.p_proc      = NFS3PROC_##proc,					\
 	.p_encode    = (kxdrproc_t) nfs3_xdr_##argtype,			\
 	.p_decode    = (kxdrproc_t) nfs3_xdr_##restype,			\
-	.p_bufsiz    = MAX(NFS3_##argtype##_sz,NFS3_##restype##_sz) << 2,	\
+	.p_arglen    = NFS3_##argtype##_sz,				\
+	.p_replen    = NFS3_##restype##_sz,				\
 	.p_timer     = timer,						\
 	.p_statidx   = NFS3PROC_##proc,					\
 	.p_name      = #proc,						\
@@ -1153,7 +1150,8 @@
 		.p_proc = ACLPROC3_GETACL,
 		.p_encode = (kxdrproc_t) nfs3_xdr_getaclargs,
 		.p_decode = (kxdrproc_t) nfs3_xdr_getaclres,
-		.p_bufsiz = MAX(ACL3_getaclargs_sz, ACL3_getaclres_sz) << 2,
+		.p_arglen = ACL3_getaclargs_sz,
+		.p_replen = ACL3_getaclres_sz,
 		.p_timer = 1,
 		.p_name = "GETACL",
 	},
@@ -1161,7 +1159,8 @@
 		.p_proc = ACLPROC3_SETACL,
 		.p_encode = (kxdrproc_t) nfs3_xdr_setaclargs,
 		.p_decode = (kxdrproc_t) nfs3_xdr_setaclres,
-		.p_bufsiz = MAX(ACL3_setaclargs_sz, ACL3_setaclres_sz) << 2,
+		.p_arglen = ACL3_setaclargs_sz,
+		.p_replen = ACL3_setaclres_sz,
 		.p_timer = 0,
 		.p_name = "SETACL",
 	},
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index f02d522..b8c28f2 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4546,16 +4546,13 @@
 	return stat;
 }
 
-#ifndef MAX
-# define MAX(a, b)	(((a) > (b))? (a) : (b))
-#endif
-
 #define PROC(proc, argtype, restype)				\
 [NFSPROC4_CLNT_##proc] = {					\
 	.p_proc   = NFSPROC4_COMPOUND,				\
 	.p_encode = (kxdrproc_t) nfs4_xdr_##argtype,		\
 	.p_decode = (kxdrproc_t) nfs4_xdr_##restype,		\
-	.p_bufsiz = MAX(NFS4_##argtype##_sz,NFS4_##restype##_sz) << 2,	\
+	.p_arglen = NFS4_##argtype##_sz,			\
+	.p_replen = NFS4_##restype##_sz,			\
 	.p_statidx = NFSPROC4_CLNT_##proc,			\
 	.p_name   = #proc,					\
     }
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index fb14d68..32ffea0 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -315,16 +315,13 @@
 /*
  * RPC procedure tables
  */
-#ifndef MAX
-# define MAX(a, b)      (((a) > (b))? (a) : (b))
-#endif
-
 #define PROC(proc, call, argtype, restype)                              \
 [NFSPROC4_CLNT_##proc] = {                                      	\
         .p_proc   = NFSPROC4_CB_##call,					\
         .p_encode = (kxdrproc_t) nfs4_xdr_##argtype,                    \
         .p_decode = (kxdrproc_t) nfs4_xdr_##restype,                    \
-        .p_bufsiz = MAX(NFS4_##argtype##_sz,NFS4_##restype##_sz) << 2,  \
+        .p_arglen = NFS4_##argtype##_sz,                                \
+        .p_replen = NFS4_##restype##_sz,                                \
         .p_statidx = NFSPROC4_CB_##call,				\
 	.p_name   = #proc,                                              \
 }
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index c7a78eef2..32c48a0 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -84,7 +84,8 @@
 	u32			p_proc;		/* RPC procedure number */
 	kxdrproc_t		p_encode;	/* XDR encode function */
 	kxdrproc_t		p_decode;	/* XDR decode function */
-	unsigned int		p_bufsiz;	/* req. buffer size */
+	unsigned int		p_arglen;	/* argument hdr length (u32) */
+	unsigned int		p_replen;	/* reply hdr length (u32) */
 	unsigned int		p_count;	/* call count */
 	unsigned int		p_timer;	/* Which RTT timer to use */
 	u32			p_statidx;	/* Which procedure to account */
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index f780e72..7aa2950 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -84,7 +84,9 @@
 	struct list_head	rq_list;
 
 	__u32 *			rq_buffer;	/* XDR encode buffer */
-	size_t			rq_bufsize;
+	size_t			rq_bufsize,
+				rq_callsize,
+				rq_rcvsize;
 
 	struct xdr_buf		rq_private_buf;		/* The receive buffer
 							 * used in the softirq.
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..c45fc4c 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);