NLM: Shrink the maximum request size of NLM4 requests

NLM version 4 requests estimate the call and reply header sizes rather
conservatively, using the very maximum size allowed in the protocol even
though Linux always uses only a small fraction of the allowable space.

Reduce the size of caller and lock arguments to conserve RPC buffer space
while XDR encoding NLM4 arguments.  Add compile-time checks to ensure the
hostname string won't overflow NLM protocol maximums.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/lockd/xdr4.c

@@ -516,17 +516,24 @@ nlm4clt_decode_res(struct rpc_rqst *req, __be32 *p, struct nlm_res *resp)
 	return 0;
 }
 
+#if (NLMCLNT_OHSIZE > XDR_MAX_NETOBJ)
+#  error "NLM host name cannot be larger than XDR_MAX_NETOBJ!"
+#endif
+
+#if (NLMCLNT_OHSIZE > NLM_MAXSTRLEN)
+#  error "NLM host name cannot be larger than NLM's maximum string length!"
+#endif
+
 /*
  * Buffer requirements for NLM
  */
 #define NLM4_void_sz		0
 #define NLM4_cookie_sz		1+XDR_QUADLEN(NLM_MAXCOOKIELEN)
-#define NLM4_caller_sz		1+XDR_QUADLEN(NLM_MAXSTRLEN)
-#define NLM4_netobj_sz		1+XDR_QUADLEN(XDR_MAX_NETOBJ)
-/* #define NLM4_owner_sz		1+XDR_QUADLEN(NLM4_MAXOWNER) */
+#define NLM4_caller_sz		1+XDR_QUADLEN(NLMCLNT_OHSIZE)
+#define NLM4_owner_sz		1+XDR_QUADLEN(NLMCLNT_OHSIZE)
 #define NLM4_fhandle_sz		1+XDR_QUADLEN(NFS3_FHSIZE)
-#define NLM4_lock_sz		5+NLM4_caller_sz+NLM4_netobj_sz+NLM4_fhandle_sz
-#define NLM4_holder_sz		6+NLM4_netobj_sz
+#define NLM4_lock_sz		5+NLM4_caller_sz+NLM4_owner_sz+NLM4_fhandle_sz
+#define NLM4_holder_sz		6+NLM4_owner_sz
 
 #define NLM4_testargs_sz	NLM4_cookie_sz+1+NLM4_lock_sz
 #define NLM4_lockargs_sz	NLM4_cookie_sz+4+NLM4_lock_sz