svcrdma: Make RDMA_ERROR messages work

Fix several issues with svc_rdma_send_error():

 - Post a receive buffer to replace the one that was consumed by
   the incoming request
 - Posting a send should use DMA_TO_DEVICE, not DMA_FROM_DEVICE
 - No need to put_page _and_ free pages in svc_rdma_put_context
 - Make sure the sge is set up completely in case the error
   path goes through svc_rdma_unmap_dma()
 - Replace the use of ENOSYS, which has a reserved meaning

Related fixes in svc_rdma_recvfrom():

 - Don't leak the ctxt associated with the incoming request
 - Don't close the connection after sending an error reply
 - Let svc_rdma_send_error() figure out the right header error code

As a last clean up, move svc_rdma_send_error() to svc_rdma_sendto.c
with other similar functions. There is some common logic in these
functions that could someday be combined to reduce code duplication.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Devesh Sharma <devesh.sharma@broadcom.com>
Tested-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

include/linux/sunrpc/svc_rdma.h

@@ -228,11 +228,11 @@ extern int svc_rdma_map_xdr(struct svcxprt_rdma *, struct xdr_buf *,
 extern int svc_rdma_sendto(struct svc_rqst *);
 extern struct rpcrdma_read_chunk *
 	svc_rdma_get_read_chunk(struct rpcrdma_msg *);
+extern void svc_rdma_send_error(struct svcxprt_rdma *, struct rpcrdma_msg *,
+				int);
 
 /* svc_rdma_transport.c */
 extern int svc_rdma_send(struct svcxprt_rdma *, struct ib_send_wr *);
-extern void svc_rdma_send_error(struct svcxprt_rdma *, struct rpcrdma_msg *,
-				enum rpcrdma_errcode);
 extern int svc_rdma_post_recv(struct svcxprt_rdma *, gfp_t);
 extern int svc_rdma_repost_recv(struct svcxprt_rdma *, gfp_t);
 extern int svc_rdma_create_listen(struct svc_serv *, int, struct sockaddr *);

net/sunrpc/xprtrdma/svc_rdma_marshal.c

@@ -162,7 +162,7 @@ int svc_rdma_xdr_decode_req(struct rpcrdma_msg **rdma_req,
 	}
 
 	if (rmsgp->rm_vers != rpcrdma_version)
-		return -ENOSYS;
+		return -EPROTONOSUPPORT;
 
 	/* Pull in the extra for the padded case and bump our pointer */
 	if (rmsgp->rm_type == rdma_msgp) {

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

@@ -612,7 +612,6 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 	struct svc_rdma_op_ctxt *ctxt = NULL;
 	struct rpcrdma_msg *rmsgp;
 	int ret = 0;
-	int len;
 
 	dprintk("svcrdma: rqstp=%p\n", rqstp);
 
@@ -654,15 +653,10 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 	rdma_build_arg_xdr(rqstp, ctxt, ctxt->byte_len);
 
 	/* Decode the RDMA header. */
-	len = svc_rdma_xdr_decode_req(&rmsgp, rqstp);
-	rqstp->rq_xprt_hlen = len;
-
-	/* If the request is invalid, reply with an error */
-	if (len < 0) {
-		if (len == -ENOSYS)
-			svc_rdma_send_error(rdma_xprt, rmsgp, ERR_VERS);
-		goto close_out;
-	}
+	ret = svc_rdma_xdr_decode_req(&rmsgp, rqstp);
+	if (ret < 0)
+		goto out_err;
+	rqstp->rq_xprt_hlen = ret;
 
 	if (svc_rdma_is_backchannel_reply(xprt, rmsgp)) {
 		ret = svc_rdma_handle_bc_reply(xprt->xpt_bc_xprt, rmsgp,
@@ -698,6 +692,11 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 	svc_xprt_copy_addrs(rqstp, xprt);
 	return ret;
 
+out_err:
+	svc_rdma_send_error(rdma_xprt, rmsgp, ret);
+	svc_rdma_put_context(ctxt, 0);
+	return 0;
+
  close_out:
 	if (ctxt)
 		svc_rdma_put_context(ctxt, 1);

net/sunrpc/xprtrdma/svc_rdma_sendto.c

@@ -652,3 +652,65 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
 	return -ENOTCONN;
 }
+
+void svc_rdma_send_error(struct svcxprt_rdma *xprt, struct rpcrdma_msg *rmsgp,
+			 int status)
+{
+	struct ib_send_wr err_wr;
+	struct page *p;
+	struct svc_rdma_op_ctxt *ctxt;
+	enum rpcrdma_errcode err;
+	__be32 *va;
+	int length;
+	int ret;
+
+	ret = svc_rdma_repost_recv(xprt, GFP_KERNEL);
+	if (ret)
+		return;
+
+	p = alloc_page(GFP_KERNEL);
+	if (!p)
+		return;
+	va = page_address(p);
+
+	/* XDR encode an error reply */
+	err = ERR_CHUNK;
+	if (status == -EPROTONOSUPPORT)
+		err = ERR_VERS;
+	length = svc_rdma_xdr_encode_error(xprt, rmsgp, err, va);
+
+	ctxt = svc_rdma_get_context(xprt);
+	ctxt->direction = DMA_TO_DEVICE;
+	ctxt->count = 1;
+	ctxt->pages[0] = p;
+
+	/* Prepare SGE for local address */
+	ctxt->sge[0].lkey = xprt->sc_pd->local_dma_lkey;
+	ctxt->sge[0].length = length;
+	ctxt->sge[0].addr = ib_dma_map_page(xprt->sc_cm_id->device,
+					    p, 0, length, DMA_TO_DEVICE);
+	if (ib_dma_mapping_error(xprt->sc_cm_id->device, ctxt->sge[0].addr)) {
+		dprintk("svcrdma: Error mapping buffer for protocol error\n");
+		svc_rdma_put_context(ctxt, 1);
+		return;
+	}
+	atomic_inc(&xprt->sc_dma_used);
+
+	/* Prepare SEND WR */
+	memset(&err_wr, 0, sizeof(err_wr));
+	ctxt->wr_op = IB_WR_SEND;
+	err_wr.wr_id = (unsigned long)ctxt;
+	err_wr.sg_list = ctxt->sge;
+	err_wr.num_sge = 1;
+	err_wr.opcode = IB_WR_SEND;
+	err_wr.send_flags = IB_SEND_SIGNALED;
+
+	/* Post It */
+	ret = svc_rdma_send(xprt, &err_wr);
+	if (ret) {
+		dprintk("svcrdma: Error %d posting send for protocol error\n",
+			ret);
+		svc_rdma_unmap_dma(ctxt);
+		svc_rdma_put_context(ctxt, 1);
+	}
+}

net/sunrpc/xprtrdma/svc_rdma_transport.c

@@ -1433,57 +1433,3 @@ int svc_rdma_send(struct svcxprt_rdma *xprt, struct ib_send_wr *wr)
 	}
 	return ret;
 }
-
-void svc_rdma_send_error(struct svcxprt_rdma *xprt, struct rpcrdma_msg *rmsgp,
-			 enum rpcrdma_errcode err)
-{
-	struct ib_send_wr err_wr;
-	struct page *p;
-	struct svc_rdma_op_ctxt *ctxt;
-	__be32 *va;
-	int length;
-	int ret;
-
-	p = alloc_page(GFP_KERNEL);
-	if (!p)
-		return;
-	va = page_address(p);
-
-	/* XDR encode error */
-	length = svc_rdma_xdr_encode_error(xprt, rmsgp, err, va);
-
-	ctxt = svc_rdma_get_context(xprt);
-	ctxt->direction = DMA_FROM_DEVICE;
-	ctxt->count = 1;
-	ctxt->pages[0] = p;
-
-	/* Prepare SGE for local address */
-	ctxt->sge[0].addr = ib_dma_map_page(xprt->sc_cm_id->device,
-					    p, 0, length, DMA_FROM_DEVICE);
-	if (ib_dma_mapping_error(xprt->sc_cm_id->device, ctxt->sge[0].addr)) {
-		put_page(p);
-		svc_rdma_put_context(ctxt, 1);
-		return;
-	}
-	atomic_inc(&xprt->sc_dma_used);
-	ctxt->sge[0].lkey = xprt->sc_pd->local_dma_lkey;
-	ctxt->sge[0].length = length;
-
-	/* Prepare SEND WR */
-	memset(&err_wr, 0, sizeof err_wr);
-	ctxt->wr_op = IB_WR_SEND;
-	err_wr.wr_id = (unsigned long)ctxt;
-	err_wr.sg_list = ctxt->sge;
-	err_wr.num_sge = 1;
-	err_wr.opcode = IB_WR_SEND;
-	err_wr.send_flags = IB_SEND_SIGNALED;
-
-	/* Post It */
-	ret = svc_rdma_send(xprt, &err_wr);
-	if (ret) {
-		dprintk("svcrdma: Error %d posting send for protocol error\n",
-			ret);
-		svc_rdma_unmap_dma(ctxt);
-		svc_rdma_put_context(ctxt, 1);
-	}
-}