svcrdma: Post Receives in the Receive completion handler

Web:        https://git.kernel.org/torvalds/c/482725027ff32bc857f5527fb17feda5361265fe
Commit:     482725027ff32bc857f5527fb17feda5361265fe
Parent:     66282ec1cf004c09083c29cb5e49019037937bbd
Refname:    refs/heads/master
Author:     Chuck Lever <[email protected]>
AuthorDate: Wed Jan 3 15:42:18 2018 -0500
Committer:  J. Bruce Fields <[email protected]>
CommitDate: Thu Jan 18 11:52:51 2018 -0500

    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 <[email protected]>
    Signed-off-by: J. Bruce Fields <[email protected]>
---
 include/linux/sunrpc/svc_rdma.h            |  2 --
 net/sunrpc/xprtrdma/svc_rdma_backchannel.c |  5 -----
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c    |  9 +--------
 net/sunrpc/xprtrdma/svc_rdma_sendto.c      |  6 ------
 net/sunrpc/xprtrdma/svc_rdma_transport.c   | 25 +++++++------------------
 5 files changed, 8 insertions(+), 39 deletions(-)

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index 995c6fe9ee90..4b731b046bcd 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/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);
diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
index af7893501e40..a73632ca9048 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
@@ -95,7 +95,6 @@ out_shortreply:
 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.
 	 */
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index ad4bd62eebf1..19e9c6b33042 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/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 @@ out_postfail:
 
 out_drop:
 	svc_rdma_put_context(ctxt, 1);
-repost:
-	return svc_rdma_repost_recv(rdma_xprt, GFP_KERNEL);
+	return 0;
 }
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 7c3a211e0e9a..649441d5087d 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/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;
diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 46ec069150d5..9ad12a215b51 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/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;
-}