SUNRPC: Add rpc_auth::au_ralign field

Currently rpc_inline_rcv_pages() uses au_rslack to estimate the
size of the upper layer reply header. This is fine for auth flavors
where au_verfsize == au_rslack.

However, some auth flavors have more going on. krb5i for example has
two more words after the verifier, and another blob following the
RPC message. The calculation involving au_rslack pushes the upper
layer reply header too far into the rcv_buf.

au_rslack is still valuable: it's the amount of buffer space needed
for the reply, and is used when allocating the reply buffer. We'll
keep that.

But, add a new field that can be used to properly estimate the
location of the upper layer header in each RPC reply, based on the
auth flavor in use.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h
index 359dfdd..5f9076f 100644
--- a/include/linux/sunrpc/auth.h
+++ b/include/linux/sunrpc/auth.h
@@ -74,13 +74,12 @@ struct rpc_cred_cache;
 struct rpc_authops;
 struct rpc_auth {
 	unsigned int		au_cslack;	/* call cred size estimate */
-				/* guess at number of u32's auth adds before
-				 * reply data; normally the verifier size: */
-	unsigned int		au_rslack;
+	unsigned int		au_rslack;	/* reply cred size estimate */
 	unsigned int		au_verfsize;	/* size of reply verifier */
+	unsigned int		au_ralign;	/* words before UL header */
 
-	unsigned int		au_flags;	/* various flags */
-	const struct rpc_authops *au_ops;		/* operations */
+	unsigned int		au_flags;
+	const struct rpc_authops *au_ops;
 	rpc_authflavor_t	au_flavor;	/* pseudoflavor (note may
 						 * differ from the flavor in
 						 * au_ops->au_flavor in gss