svcrdma: Another sendto chunk list parsing update

Commit 5fdca6531434 ("svcrdma: Renovate sendto chunk list parsing")
missed a spot. svc_rdma_xdr_get_reply_hdr_len() also assumes the
Write list has only one Write chunk. There's no harm in making this
code more general.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

include/linux/sunrpc/rpc_rdma.h

@@ -109,6 +109,15 @@ struct rpcrdma_msg {
 	} rm_body;
 };
 
+/*
+ * XDR sizes, in quads
+ */
+enum {
+	rpcrdma_fixed_maxsz	= 4,
+	rpcrdma_segment_maxsz	= 4,
+	rpcrdma_readchunk_maxsz	= 2 + rpcrdma_segment_maxsz,
+};
+
 /*
  * Smallest RPC/RDMA header: rm_xid through rm_type, then rm_nochunks
  */

include/linux/sunrpc/svc_rdma.h

@@ -218,7 +218,7 @@ extern void svc_rdma_xdr_encode_reply_header(struct svcxprt_rdma *,
 					     struct rpcrdma_msg *,
 					     struct rpcrdma_msg *,
 					     enum rpcrdma_proc);
-extern int svc_rdma_xdr_get_reply_hdr_len(struct rpcrdma_msg *);
+extern unsigned int svc_rdma_xdr_get_reply_hdr_len(__be32 *rdma_resp);
 
 /* svc_rdma_recvfrom.c */
 extern int svc_rdma_recvfrom(struct svc_rqst *);

net/sunrpc/xprtrdma/svc_rdma_marshal.c

@@ -260,32 +260,35 @@ int svc_rdma_xdr_encode_error(struct svcxprt_rdma *xprt,
 	return (int)((unsigned long)va - (unsigned long)startp);
 }
 
-int svc_rdma_xdr_get_reply_hdr_len(struct rpcrdma_msg *rmsgp)
+/**
+ * svc_rdma_xdr_get_reply_hdr_length - Get length of Reply transport header
+ * @rdma_resp: buffer containing Reply transport header
+ *
+ * Returns length of transport header, in bytes.
+ */
+unsigned int svc_rdma_xdr_get_reply_hdr_len(__be32 *rdma_resp)
 {
-	struct rpcrdma_write_array *wr_ary;
+	unsigned int nsegs;
+	__be32 *p;
 
-	/* There is no read-list in a reply */
+	p = rdma_resp;
 
-	/* skip write list */
-	wr_ary = (struct rpcrdma_write_array *)
-		&rmsgp->rm_body.rm_chunks[1];
-	if (wr_ary->wc_discrim)
-		wr_ary = (struct rpcrdma_write_array *)
-			&wr_ary->wc_array[be32_to_cpu(wr_ary->wc_nchunks)].
-			wc_target.rs_length;
-	else
-		wr_ary = (struct rpcrdma_write_array *)
-			&wr_ary->wc_nchunks;
-
-	/* skip reply array */
-	if (wr_ary->wc_discrim)
-		wr_ary = (struct rpcrdma_write_array *)
-			&wr_ary->wc_array[be32_to_cpu(wr_ary->wc_nchunks)];
-	else
-		wr_ary = (struct rpcrdma_write_array *)
-			&wr_ary->wc_nchunks;
-
-	return (unsigned long) wr_ary - (unsigned long) rmsgp;
+	/* RPC-over-RDMA V1 replies never have a Read list. */
+	p += rpcrdma_fixed_maxsz + 1;
+
+	/* Skip Write list. */
+	while (*p++ != xdr_zero) {
+		nsegs = be32_to_cpup(p++);
+		p += nsegs * rpcrdma_segment_maxsz;
+	}
+
+	/* Skip Reply chunk. */
+	if (*p++ != xdr_zero) {
+		nsegs = be32_to_cpup(p++);
+		p += nsegs * rpcrdma_segment_maxsz;
+	}
+
+	return (unsigned long)p - (unsigned long)rdma_resp;
 }
 
 void svc_rdma_xdr_encode_write_list(struct rpcrdma_msg *rmsgp, int chunks)

net/sunrpc/xprtrdma/svc_rdma_sendto.c

@@ -476,7 +476,8 @@ static int send_reply(struct svcxprt_rdma *rdma,
 
 	/* Prepare the SGE for the RPCRDMA Header */
 	ctxt->sge[0].lkey = rdma->sc_pd->local_dma_lkey;
-	ctxt->sge[0].length = svc_rdma_xdr_get_reply_hdr_len(rdma_resp);
+	ctxt->sge[0].length =
+	    svc_rdma_xdr_get_reply_hdr_len((__be32 *)rdma_resp);
 	ctxt->sge[0].addr =
 	    ib_dma_map_page(rdma->sc_cm_id->device, page, 0,
 			    ctxt->sge[0].length, DMA_TO_DEVICE);