nfsd4: better reservation of head space for krb5

RPC_MAX_AUTH_SIZE is scattered around several places. Better to set it
once in the auth code, where this kind of estimate should be made. And
while we're at it we can leave it zero when we're not using krb5i or
krb5p.

Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfsd/nfs4proc.c

···
 	xdr->buf = buf;
 	xdr->iov = head;
 	xdr->p   = head->iov_base + head->iov_len;
-	xdr->end = head->iov_base + PAGE_SIZE - 2 * RPC_MAX_AUTH_SIZE;
+	xdr->end = head->iov_base + PAGE_SIZE - rqstp->rq_auth_slack;
 	/* Tail and page_len should be zero at this point: */
 	buf->len = buf->head[0].iov_len;
 	xdr->scratch.iov_len = 0;
 	xdr->page_ptr = buf->pages;
 	buf->buflen = PAGE_SIZE * (1 + rqstp->rq_page_end - buf->pages)
-		- 2 * RPC_MAX_AUTH_SIZE;
+		- rqstp->rq_auth_slack;
 }
 
 /*

fs/nfsd/nfs4state.c

···
 			session->se_fchannel.maxresp_sz;
 	status = (seq->cachethis) ? nfserr_rep_too_big_to_cache :
 				    nfserr_rep_too_big;
-	if (xdr_restrict_buflen(xdr, buflen - 2 * RPC_MAX_AUTH_SIZE))
+	if (xdr_restrict_buflen(xdr, buflen - rqstp->rq_auth_slack))
 		goto out_put_session;
 	svc_reserve(rqstp, buflen);
 

fs/nfsd/nfs4xdr.c

···
 	DECODE_HEAD;
 	struct nfsd4_op *op;
 	bool cachethis = false;
-	int max_reply = 2 * RPC_MAX_AUTH_SIZE + 8; /* opcnt, status */
+	int auth_slack= argp->rqstp->rq_auth_slack;
+	int max_reply = auth_slack + 8; /* opcnt, status */
 	int readcount = 0;
 	int readbytes = 0;
 	int i;
···
 	svc_reserve(argp->rqstp, max_reply + readbytes);
 	argp->rqstp->rq_cachetype = cachethis ? RC_REPLBUFF : RC_NOCACHE;
 
-	if (readcount > 1 || max_reply > PAGE_SIZE - 2*RPC_MAX_AUTH_SIZE)
+	if (readcount > 1 || max_reply > PAGE_SIZE - auth_slack)
 		argp->rqstp->rq_splice_ok = false;
 
 	DECODE_TAIL;

include/linux/sunrpc/svc.h

···
 	void *			rq_argp;	/* decoded arguments */
 	void *			rq_resp;	/* xdr'd results */
 	void *			rq_auth_data;	/* flavor-specific data */
-
+	int			rq_auth_slack;	/* extra space xdr code
+						 * should leave in head
+						 * for krb5i, krb5p.
+						 */
 	int			rq_reserved;	/* space on socket outq
 						 * reserved for this request
 						 */
···
  */
 static inline void svc_reserve_auth(struct svc_rqst *rqstp, int space)
 {
-	int added_space = 0;
-
-	if (rqstp->rq_authop->flavour)
-		added_space = RPC_MAX_AUTH_SIZE;
-	svc_reserve(rqstp, space + added_space);
+	svc_reserve(rqstp, space + rqstp->rq_auth_slack);
 }
 
 #endif /* SUNRPC_SVC_H */

net/sunrpc/auth_gss/svcauth_gss.c

···
 			if (unwrap_integ_data(rqstp, &rqstp->rq_arg,
 					gc->gc_seq, rsci->mechctx))
 				goto garbage_args;
+			rqstp->rq_auth_slack = RPC_MAX_AUTH_SIZE;
 			break;
 		case RPC_GSS_SVC_PRIVACY:
 			/* placeholders for length and seq. number: */
···
 			if (unwrap_priv_data(rqstp, &rqstp->rq_arg,
 					gc->gc_seq, rsci->mechctx))
 				goto garbage_args;
+			rqstp->rq_auth_slack = RPC_MAX_AUTH_SIZE * 2;
 			break;
 		default:
 			goto auth_err;

net/sunrpc/svcauth.c

···
 	}
 	spin_unlock(&authtab_lock);
 
+	rqstp->rq_auth_slack = 0;
+
 	rqstp->rq_authop = aops;
 	return aops->accept(rqstp, authp);
 }