svcrdma: Prevent page release when nothing was received

I noticed that svc_rqst_release_pages() was still unnecessarily
releasing a page when svc_rdma_recvfrom() returns zero.

Fixes: a53d5cb ("svcrdma: Avoid releasing a page in svc_xprt_release()")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: chucklever

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

@@ -792,6 +792,12 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 	struct svc_rdma_recv_ctxt *ctxt;
 	int ret;
 
+	/* Prevent svc_xprt_release() from releasing pages in rq_pages
+	 * when returning 0 or an error.
+	 */
+	rqstp->rq_respages = rqstp->rq_pages;
+	rqstp->rq_next_page = rqstp->rq_respages;
+
 	rqstp->rq_xprt_ctxt = NULL;
 
 	ctxt = NULL;
@@ -815,12 +821,6 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 				   DMA_FROM_DEVICE);
 	svc_rdma_build_arg_xdr(rqstp, ctxt);
 
-	/* Prevent svc_xprt_release from releasing pages in rq_pages
-	 * if we return 0 or an error.
-	 */
-	rqstp->rq_respages = rqstp->rq_pages;
-	rqstp->rq_next_page = rqstp->rq_respages;
-
 	ret = svc_rdma_xdr_decode_req(&rqstp->rq_arg, ctxt);
 	if (ret < 0)
 		goto out_err;