svcrdma: Fix backchannel return code

Way back when I was writing the RPC/RDMA server-side backchannel code, I misread the TCP backchannel reply handler logic. When svc_tcp_recvfrom() successfully receives a backchannel reply, it does not return -EAGAIN. It sets XPT_DATA and returns zero. Update svc_rdma_recvfrom() to return zero. Here, XPT_DATA doesn't need to be set again: it is set whenever a new message is received, behind a spin lock in a single threaded context. Also, if handling the cb reply is not successful, the message is simply dropped. There's no special message framing to deal with as there is in the TCP case. Now that the handle_bc_reply() return value is ignored, I've removed the dprintk call sites in the error exit of handle_bc_reply() in favor of trace points in other areas that already report the error cases.

Chuck Lever committed 6 years ago

Commit ea740bd1 parent dbc17ac3 files · +17 −37Browse files

Unified · Split

3 files

include/linux/sunrpc/svc_rdma.h +2 −3
net/sunrpc/xprtrdma/svc_rdma_backchannel.c +10 −28
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +5 −6

include/linux/sunrpc/svc_rdma.h+2−3

@@ -160,9 +160,8 @@ struct svc_rdma_send_ctxt { · 159 unmodified lines
160	160	};
161	161
162	162	/* svc_rdma_backchannel.c */
163		−extern int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt,
164		− __be32 *rdma_resp,
165		− struct xdr_buf *rcvbuf);
	163	+extern void svc_rdma_handle_bc_reply(struct svc_rqst *rqstp,
	164	+ struct svc_rdma_recv_ctxt *rctxt);
166	165
167	166	/* svc_rdma_recvfrom.c */
168	167	extern void svc_rdma_recv_ctxts_destroy(struct svcxprt_rdma *rdma);

net/sunrpc/xprtrdma/svc_rdma_backchannel.c+10−28

@@ -15,26 +15,25 @@ · 14 unmodified lines
15	15	#undef SVCRDMA_BACKCHANNEL_DEBUG
16	16
17	17	/**
18		− * svc_rdma_handle_bc_reply - Process incoming backchannel reply
19		− * @xprt: controlling backchannel transport
20		− * @rdma_resp: pointer to incoming transport header
21		− * @rcvbuf: XDR buffer into which to decode the reply
	18	+ * svc_rdma_handle_bc_reply - Process incoming backchannel Reply
	19	+ * @rqstp: resources for handling the Reply
	20	+ * @rctxt: Received message
22	21	*
23		− * Returns:
24		− * %0 if @rcvbuf is filled in, xprt_complete_rqst called,
25		− * %-EAGAIN if server should call ->recvfrom again.
26	22	*/
27		−int svc_rdma_handle_bc_reply(struct rpc_xprt xprt, __be32 rdma_resp,
28		− struct xdr_buf *rcvbuf)
	23	+void svc_rdma_handle_bc_reply(struct svc_rqst *rqstp,
	24	+ struct svc_rdma_recv_ctxt *rctxt)
29	25	{
	26	+ struct svc_xprt *sxprt = rqstp->rq_xprt;
	27	+ struct rpc_xprt *xprt = sxprt->xpt_bc_xprt;
30	28	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	29	+ struct xdr_buf *rcvbuf = &rqstp->rq_arg;
31	30	struct kvec dst, src = &rcvbuf->head[0];
	31	+ __be32 *rdma_resp = rctxt->rc_recv_buf;
32	32	struct rpc_rqst *req;
33	33	u32 credits;
34	34	size_t len;
35	35	__be32 xid;
36	36	__be32 *p;
37		− int ret;
38	37
39	38	p = (__be32 *)src->iov_base;
40	39	len = src->iov_len;
@@ -49,14 +48,10 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt xprt, __be32 rdma_resp, · 8 unmodified lines
49	48	__func__, (int)len, p);
50	49	#endif
51	50
52		− ret = -EAGAIN;
53		− if (src->iov_len < 24)
54		− goto out_shortreply;
55		−
56	51	spin_lock(&xprt->queue_lock);
57	52	req = xprt_lookup_rqst(xprt, xid);
58	53	if (!req)
59		− goto out_notfound;
	54	+ goto out_unlock;
60	55
61	56	dst = &req->rq_private_buf.head[0];
62	57	memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
@@ -77,25 +72,12 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt xprt, __be32 rdma_resp, · 14 unmodified lines
77	72	spin_unlock(&xprt->transport_lock);
78	73
79	74	spin_lock(&xprt->queue_lock);
80		− ret = 0;
81	75	xprt_complete_rqst(req->rq_task, rcvbuf->len);
82	76	xprt_unpin_rqst(req);
83	77	rcvbuf->len = 0;
84	78
85	79	out_unlock:
86	80	spin_unlock(&xprt->queue_lock);
87		−out:
88		− return ret;
89		−
90		−out_shortreply:
91		− dprintk("svcrdma: short bc reply: xprt=%p, len=%zu\n",
92		− xprt, src->iov_len);
93		− goto out;
94		−
95		−out_notfound:
96		− dprintk("svcrdma: unrecognized bc reply: xprt=%p, xid=%08x\n",
97		− xprt, be32_to_cpu(xid));
98		− goto out_unlock;
99	81	}
100	82
101	83	/* Send a backwards direction RPC call.

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c+5−6

@@ -878,12 +878,9 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp) · 877 unmodified lines
878	878	goto out_drop;
879	879	rqstp->rq_xprt_hlen = ret;
880	880
881		− if (svc_rdma_is_backchannel_reply(xprt, p)) {
882		− ret = svc_rdma_handle_bc_reply(xprt->xpt_bc_xprt, p,
883		− &rqstp->rq_arg);
884		− svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
885		− return ret;
886		− }
	881	+ if (svc_rdma_is_backchannel_reply(xprt, p))
	882	+ goto out_backchannel;
	883	+
887	884	svc_rdma_get_inv_rkey(rdma_xprt, ctxt);
888	885
889	886	p += rpcrdma_fixed_maxsz;
@@ -913,6 +910,8 @@ out_postfail: · 23 unmodified lines
913	910	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
914	911	return ret;
915	912
	913	+out_backchannel:
	914	+ svc_rdma_handle_bc_reply(rqstp, ctxt);
916	915	out_drop:
917	916	svc_rdma_recv_ctxt_put(rdma_xprt, ctxt);
918	917	return 0;