RPCSEC_GSS: cleanup au_rslack calculation

 Various xdr encode routines use au_rslack to guess where the reply argument
 will end up, so we can set up the xdr_buf to recieve data into the right place
 for zero copy.

 Currently we calculate the au_rslack estimate when we check the verifier.
 Normally this only depends on the verifier size.  In the integrity case we add
 a few bytes to allow for a length and sequence number.

 It's a bit simpler to calculate only the verifier size when we check the
 verifier, and delay the full calculation till we unwrap.

 Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h
index 04ebc24..b68c11a 100644
--- a/include/linux/sunrpc/auth.h
+++ b/include/linux/sunrpc/auth.h
@@ -66,7 +66,12 @@
 
 struct rpc_auth {
 	unsigned int		au_cslack;	/* call cred size estimate */
-	unsigned int		au_rslack;	/* reply verf size guess */
+				/* guess at number of u32's auth adds before
+				 * reply data; normally the verifier size: */
+	unsigned int		au_rslack;
+				/* for gss, used to calculate au_rslack: */
+	unsigned int		au_verfsize;
+
 	unsigned int		au_flags;	/* various flags */
 	struct rpc_authops *	au_ops;		/* operations */
 	rpc_authflavor_t	au_flavor;	/* pseudoflavor (note may