nfsd4: remove redundant encode buffer size checking

Now that all op encoders can handle running out of space, we no longer
need to check the remaining size for every operation; only nonidempotent
operations need that check, and that can be done by
nfsd4_check_resp_size.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4proc.c

@@ -1279,7 +1279,6 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
 	struct nfsd4_compound_state *cstate = &resp->cstate;
 	struct svc_fh *current_fh = &cstate->current_fh;
 	struct svc_fh *save_fh = &cstate->save_fh;
-	int		slack_bytes;
 	u32		plen = 0;
 	__be32		status;
 
@@ -1333,19 +1332,6 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
 			goto encode_op;
 		}
 
-		/* We must be able to encode a successful response to
-		 * this operation, with enough room left over to encode a
-		 * failed response to the next operation.  If we don't
-		 * have enough room, fail with ERR_RESOURCE.
-		 */
-		slack_bytes = (char *)resp->xdr.end - (char *)resp->xdr.p;
-		if (slack_bytes < COMPOUND_SLACK_SPACE
-				+ COMPOUND_ERR_SLACK_SPACE) {
-			BUG_ON(slack_bytes < COMPOUND_ERR_SLACK_SPACE);
-			op->status = nfserr_resource;
-			goto encode_op;
-		}
-
 		opdesc = OPDESC(op);
 
 		if (!current_fh->fh_dentry) {

fs/nfsd/nfs4xdr.c

@@ -3753,13 +3753,11 @@ static nfsd4_enc nfsd4_enc_ops[] = {
 __be32 nfsd4_check_resp_size(struct nfsd4_compoundres *resp, u32 pad)
 {
 	struct xdr_buf *buf = &resp->rqstp->rq_res;
-	struct nfsd4_session *session = NULL;
+	struct nfsd4_session *session = resp->cstate.session;
 	struct nfsd4_slot *slot = resp->cstate.slot;
+	int slack_bytes = (char *)resp->xdr.end - (char *)resp->xdr.p;
 
-	if (!nfsd4_has_session(&resp->cstate))
-		return 0;
-
-	session = resp->cstate.session;
+	if (nfsd4_has_session(&resp->cstate)) {
 
 		if (buf->len + pad > session->se_fchannel.maxresp_sz)
 			return nfserr_rep_too_big;
@@ -3767,6 +3765,12 @@ __be32 nfsd4_check_resp_size(struct nfsd4_compoundres *resp, u32 pad)
 		if ((slot->sl_flags & NFSD4_SLOT_CACHETHIS) &&
 		    buf->len + pad > session->se_fchannel.maxresp_cached)
 			return nfserr_rep_too_big_to_cache;
+	}
+
+	if (pad > slack_bytes) {
+		WARN_ON_ONCE(nfsd4_has_session(&resp->cstate));
+		return nfserr_resource;
+	}
 
 	return 0;
 }