SUNRPC: Move svc_xprt_received() call sites

Currently, XPT_BUSY is not cleared until xpo_recvfrom returns.
That effectively blocks the receipt and handling of the next RPC
message until the current one has been taken off the transport.
This strict ordering is a requirement for socket transports.

For our kernel RPC/RDMA transport implementation, however, dequeuing
an ingress message is nothing more than a list_del(). The transport
can safely be marked un-busy as soon as that is done.

To keep the changes simpler, this patch just moves the
svc_xprt_received() call site from svc_handle_xprt() into the
transports, so that the actual optimization can be done in a
subsequent patch.

Signed-off-by: Chuck Lever <[email protected]>

Author: chucklever

net/sunrpc/svc_xprt.c

@@ -820,8 +820,10 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
 			newxpt->xpt_cred = get_cred(xprt->xpt_cred);
 			svc_add_new_temp_xprt(serv, newxpt);
 			trace_svc_xprt_accept(newxpt, serv->sv_name);
-		} else
+		} else {
 			module_put(xprt->xpt_class->xcl_owner);
+		}
+		svc_xprt_received(xprt);
 	} else if (svc_xprt_reserve_slot(rqstp, xprt)) {
 		/* XPT_DATA|XPT_DEFERRED case: */
 		dprintk("svc: server %p, pool %u, transport %p, inuse=%d\n",
@@ -836,8 +838,6 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
 		rqstp->rq_reserved = serv->sv_max_mesg;
 		atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
 	}
-	/* clear XPT_BUSY: */
-	svc_xprt_received(xprt);
 out:
 	trace_svc_handle_xprt(xprt, len);
 	return len;
@@ -1248,6 +1248,7 @@ static noinline int svc_deferred_recv(struct svc_rqst *rqstp)
 	rqstp->rq_xprt_hlen   = dr->xprt_hlen;
 	rqstp->rq_daddr       = dr->daddr;
 	rqstp->rq_respages    = rqstp->rq_pages;
+	svc_xprt_received(rqstp->rq_xprt);
 	return (dr->argslen<<2) - dr->xprt_hlen;
 }
 

net/sunrpc/svcsock.c

@@ -519,6 +519,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 	if (serv->sv_stats)
 		serv->sv_stats->netudpcnt++;
 
+	svc_xprt_received(rqstp->rq_xprt);
 	return len;
 
 out_recv_err:
@@ -527,7 +528,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 		set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 	}
 	trace_svcsock_udp_recv_err(&svsk->sk_xprt, err);
-	return 0;
+	goto out_clear_busy;
 out_cmsg_err:
 	net_warn_ratelimited("svc: received unknown control message %d/%d; dropping RPC reply datagram\n",
 			     cmh->cmsg_level, cmh->cmsg_type);
@@ -536,6 +537,8 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 	local_bh_enable();
 out_free:
 	kfree_skb(skb);
+out_clear_busy:
+	svc_xprt_received(rqstp->rq_xprt);
 	return 0;
 }
 
@@ -1033,6 +1036,7 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
 	if (serv->sv_stats)
 		serv->sv_stats->nettcpcnt++;
 
+	svc_xprt_received(rqstp->rq_xprt);
 	return rqstp->rq_arg.len;
 
 err_incomplete:
@@ -1050,13 +1054,14 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
 	if (len != -EAGAIN)
 		goto err_delete;
 	trace_svcsock_tcp_recv_eagain(&svsk->sk_xprt, 0);
-	return 0;
+	goto err_noclose;
 err_nuts:
 	svsk->sk_datalen = 0;
 err_delete:
 	trace_svcsock_tcp_recv_err(&svsk->sk_xprt, len);
 	svc_xprt_deferred_close(&svsk->sk_xprt);
 err_noclose:
+	svc_xprt_received(rqstp->rq_xprt);
 	return 0;	/* record not complete */
 }
 

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

@@ -846,6 +846,7 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 		/* No new incoming requests, terminate the loop */
 		clear_bit(XPT_DATA, &xprt->xpt_flags);
 		spin_unlock(&rdma_xprt->sc_rq_dto_lock);
+		svc_xprt_received(xprt);
 		return 0;
 	}
 	list_del(&ctxt->rc_list);
@@ -883,28 +884,33 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
 	rqstp->rq_xprt_ctxt = ctxt;
 	rqstp->rq_prot = IPPROTO_MAX;
 	svc_xprt_copy_addrs(rqstp, xprt);
+	svc_xprt_received(xprt);
 	return rqstp->rq_arg.len;
 
 out_readlist:
 	ret = svc_rdma_process_read_list(rdma_xprt, rqstp, ctxt);
 	if (ret < 0)
 		goto out_readfail;
+	svc_xprt_received(xprt);
 	return 0;
 
 out_err:
 	svc_rdma_send_error(rdma_xprt, ctxt, ret);
 	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
+	svc_xprt_received(xprt);
 	return 0;
 
 out_readfail:
 	if (ret == -EINVAL)
 		svc_rdma_send_error(rdma_xprt, ctxt, ret);
 	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
+	svc_xprt_received(xprt);
 	return ret;
 
 out_backchannel:
 	svc_rdma_handle_bc_reply(rqstp, ctxt);
 out_drop:
 	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
+	svc_xprt_received(xprt);
 	return 0;
 }