svcrdma: Post Receives in the Receive completion handler

This change improves Receive efficiency by posting Receives only
on the same CPU that handles Receive completion. Improved latency
and throughput has been noted with this change.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

include/linux/sunrpc/svc_rdma.h

@@ -185,8 +185,6 @@ extern void svc_rdma_wc_reg(struct ib_cq *, struct ib_wc *);
 extern void svc_rdma_wc_read(struct ib_cq *, struct ib_wc *);
 extern void svc_rdma_wc_inv(struct ib_cq *, struct ib_wc *);
 extern int svc_rdma_send(struct svcxprt_rdma *, struct ib_send_wr *);
-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 *);
 extern struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *);
 extern void svc_rdma_put_context(struct svc_rdma_op_ctxt *, int);

net/sunrpc/xprtrdma/svc_rdma_backchannel.c

@@ -95,7 +95,6 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
 out_notfound:
 	dprintk("svcrdma: unrecognized bc reply: xprt=%p, xid=%08x\n",
 		xprt, be32_to_cpu(xid));
-
 	goto out_unlock;
 }
 
@@ -129,10 +128,6 @@ static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
 	if (ret < 0)
 		goto out_err;
 
-	ret = svc_rdma_repost_recv(rdma, GFP_NOIO);
-	if (ret)
-		goto out_err;
-
 	/* Bump page refcnt so Send completion doesn't release
 	 * the rq_buffer before all retransmits are complete.
 	 */

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

@@ -400,10 +400,6 @@ static void svc_rdma_send_error(struct svcxprt_rdma *xprt,
 	struct page *page;
 	int ret;
 
-	ret = svc_rdma_repost_recv(xprt, GFP_KERNEL);
-	if (ret)
-		return;
-
 	page = alloc_page(GFP_KERNEL);
 	if (!page)
 		return;
@@ -554,8 +550,6 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 		ret = svc_rdma_handle_bc_reply(xprt->xpt_bc_xprt, p,
 					       &rqstp->rq_arg);
 		svc_rdma_put_context(ctxt, 0);
-		if (ret)
-			goto repost;
 		return ret;
 	}
 
@@ -590,6 +584,5 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 
 out_drop:
 	svc_rdma_put_context(ctxt, 1);
-repost:
-	return svc_rdma_repost_recv(rdma_xprt, GFP_KERNEL);
+	return 0;
 }

net/sunrpc/xprtrdma/svc_rdma_sendto.c

@@ -674,9 +674,6 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 		svc_rdma_xdr_encode_reply_chunk(rdma_resp, rp_ch, ret);
 	}
 
-	ret = svc_rdma_post_recv(rdma, GFP_KERNEL);
-	if (ret)
-		goto err1;
 	ret = svc_rdma_send_reply_msg(rdma, rdma_argp, rdma_resp, rqstp,
 				      wr_lst, rp_ch);
 	if (ret < 0)
@@ -687,9 +684,6 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
 	if (ret != -E2BIG && ret != -EINVAL)
 		goto err1;
 
-	ret = svc_rdma_post_recv(rdma, GFP_KERNEL);
-	if (ret)
-		goto err1;
 	ret = svc_rdma_send_error_msg(rdma, rdma_resp, rqstp);
 	if (ret < 0)
 		goto err0;

net/sunrpc/xprtrdma/svc_rdma_transport.c

@@ -58,6 +58,7 @@
 
 #define RPCDBG_FACILITY	RPCDBG_SVCXPRT
 
+static int svc_rdma_post_recv(struct svcxprt_rdma *xprt);
 static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *, int);
 static struct svc_xprt *svc_rdma_create(struct svc_serv *serv,
 					struct net *net,
@@ -320,6 +321,8 @@ static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc)
 	list_add_tail(&ctxt->list, &xprt->sc_rq_dto_q);
 	spin_unlock(&xprt->sc_rq_dto_lock);
 
+	svc_rdma_post_recv(xprt);
+
 	set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
 	if (test_bit(RDMAXPRT_CONN_PENDING, &xprt->sc_flags))
 		goto out;
@@ -404,7 +407,8 @@ static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *serv,
 	return cma_xprt;
 }
 
-int svc_rdma_post_recv(struct svcxprt_rdma *xprt, gfp_t flags)
+static int
+svc_rdma_post_recv(struct svcxprt_rdma *xprt)
 {
 	struct ib_recv_wr recv_wr, *bad_recv_wr;
 	struct svc_rdma_op_ctxt *ctxt;
@@ -423,7 +427,7 @@ int svc_rdma_post_recv(struct svcxprt_rdma *xprt, gfp_t flags)
 			pr_err("svcrdma: Too many sges (%d)\n", sge_no);
 			goto err_put_ctxt;
 		}
-		page = alloc_page(flags);
+		page = alloc_page(GFP_KERNEL);
 		if (!page)
 			goto err_put_ctxt;
 		ctxt->pages[sge_no] = page;
@@ -459,21 +463,6 @@ int svc_rdma_post_recv(struct svcxprt_rdma *xprt, gfp_t flags)
 	return -ENOMEM;
 }
 
-int svc_rdma_repost_recv(struct svcxprt_rdma *xprt, gfp_t flags)
-{
-	int ret = 0;
-
-	ret = svc_rdma_post_recv(xprt, flags);
-	if (ret) {
-		pr_err("svcrdma: could not post a receive buffer, err=%d.\n",
-		       ret);
-		pr_err("svcrdma: closing transport %p.\n", xprt);
-		set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
-		ret = -ENOTCONN;
-	}
-	return ret;
-}
-
 static void
 svc_rdma_parse_connect_private(struct svcxprt_rdma *newxprt,
 			       struct rdma_conn_param *param)
@@ -833,7 +822,7 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
 
 	/* Post receive buffers */
 	for (i = 0; i < newxprt->sc_max_requests; i++) {
-		ret = svc_rdma_post_recv(newxprt, GFP_KERNEL);
+		ret = svc_rdma_post_recv(newxprt);
 		if (ret) {
 			dprintk("svcrdma: failure posting receive buffers\n");
 			goto errout;