1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2015-2020, Oracle and/or its affiliates.
4  *
5  * Support for reverse-direction RPCs on RPC/RDMA.
6  */
7 
8 #include <linux/sunrpc/xprt.h>
9 #include <linux/sunrpc/svc.h>
10 #include <linux/sunrpc/svc_xprt.h>
11 #include <linux/sunrpc/svc_rdma.h>
12 
13 #include "xprt_rdma.h"
14 #include <trace/events/rpcrdma.h>
15 
16 #undef RPCRDMA_BACKCHANNEL_DEBUG
17 
18 /**
19  * xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
20  * @xprt: transport associated with these backchannel resources
21  * @reqs: number of concurrent incoming requests to expect
22  *
23  * Returns 0 on success; otherwise a negative errno
24  */
25 int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
26 {
27 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
28 
29 	r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
30 	trace_xprtrdma_cb_setup(r_xprt, reqs);
31 	return 0;
32 }
33 
34 /**
35  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
36  * @xprt: transport
37  *
38  * Returns maximum size, in bytes, of a backchannel message
39  */
40 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
41 {
42 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
43 	struct rpcrdma_ep *ep = r_xprt->rx_ep;
44 	size_t maxmsg;
45 
46 	maxmsg = min_t(unsigned int, ep->re_inline_send, ep->re_inline_recv);
47 	maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
48 	return maxmsg - RPCRDMA_HDRLEN_MIN;
49 }
50 
51 unsigned int xprt_rdma_bc_max_slots(struct rpc_xprt *xprt)
52 {
53 	return RPCRDMA_BACKWARD_WRS >> 1;
54 }
55 
56 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
57 {
58 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
59 	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
60 	__be32 *p;
61 
62 	rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
63 	xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
64 			rdmab_data(req->rl_rdmabuf), rqst);
65 
66 	p = xdr_reserve_space(&req->rl_stream, 28);
67 	if (unlikely(!p))
68 		return -EIO;
69 	*p++ = rqst->rq_xid;
70 	*p++ = rpcrdma_version;
71 	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
72 	*p++ = rdma_msg;
73 	*p++ = xdr_zero;
74 	*p++ = xdr_zero;
75 	*p = xdr_zero;
76 
77 	if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
78 				      &rqst->rq_snd_buf, rpcrdma_noch_pullup))
79 		return -EIO;
80 
81 	trace_xprtrdma_cb_reply(r_xprt, rqst);
82 	return 0;
83 }
84 
85 /**
86  * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
87  * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
88  *
89  * Caller holds the transport's write lock.
90  *
91  * Returns:
92  *	%0 if the RPC message has been sent
93  *	%-ENOTCONN if the caller should reconnect and call again
94  *	%-EIO if a permanent error occurred and the request was not
95  *		sent. Do not try to send this message again.
96  */
97 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
98 {
99 	struct rpc_xprt *xprt = rqst->rq_xprt;
100 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
101 	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
102 	int rc;
103 
104 	if (!xprt_connected(xprt))
105 		return -ENOTCONN;
106 
107 	if (!xprt_request_get_cong(xprt, rqst))
108 		return -EBADSLT;
109 
110 	rc = rpcrdma_bc_marshal_reply(rqst);
111 	if (rc < 0)
112 		goto failed_marshal;
113 
114 	if (frwr_send(r_xprt, req))
115 		goto drop_connection;
116 	return 0;
117 
118 failed_marshal:
119 	if (rc != -ENOTCONN)
120 		return rc;
121 drop_connection:
122 	xprt_rdma_close(xprt);
123 	return -ENOTCONN;
124 }
125 
126 /**
127  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
128  * @xprt: transport associated with these backchannel resources
129  * @reqs: number of incoming requests to destroy; ignored
130  */
131 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
132 {
133 	struct rpc_rqst *rqst, *tmp;
134 
135 	spin_lock(&xprt->bc_pa_lock);
136 	list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
137 		list_del(&rqst->rq_bc_pa_list);
138 		spin_unlock(&xprt->bc_pa_lock);
139 
140 		rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
141 
142 		spin_lock(&xprt->bc_pa_lock);
143 	}
144 	spin_unlock(&xprt->bc_pa_lock);
145 }
146 
147 /**
148  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
149  * @rqst: request to release
150  */
151 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
152 {
153 	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
154 	struct rpcrdma_rep *rep = req->rl_reply;
155 	struct rpc_xprt *xprt = rqst->rq_xprt;
156 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
157 
158 	rpcrdma_rep_put(&r_xprt->rx_buf, rep);
159 	req->rl_reply = NULL;
160 
161 	spin_lock(&xprt->bc_pa_lock);
162 	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
163 	spin_unlock(&xprt->bc_pa_lock);
164 	xprt_put(xprt);
165 }
166 
167 static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
168 {
169 	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
170 	struct rpcrdma_req *req;
171 	struct rpc_rqst *rqst;
172 	size_t size;
173 
174 	spin_lock(&xprt->bc_pa_lock);
175 	rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
176 					rq_bc_pa_list);
177 	if (!rqst)
178 		goto create_req;
179 	list_del(&rqst->rq_bc_pa_list);
180 	spin_unlock(&xprt->bc_pa_lock);
181 	return rqst;
182 
183 create_req:
184 	spin_unlock(&xprt->bc_pa_lock);
185 
186 	/* Set a limit to prevent a remote from overrunning our resources.
187 	 */
188 	if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
189 		return NULL;
190 
191 	size = min_t(size_t, r_xprt->rx_ep->re_inline_recv, PAGE_SIZE);
192 	req = rpcrdma_req_create(r_xprt, size, GFP_KERNEL);
193 	if (!req)
194 		return NULL;
195 	if (rpcrdma_req_setup(r_xprt, req)) {
196 		rpcrdma_req_destroy(req);
197 		return NULL;
198 	}
199 
200 	xprt->bc_alloc_count++;
201 	rqst = &req->rl_slot;
202 	rqst->rq_xprt = xprt;
203 	__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
204 	xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
205 	return rqst;
206 }
207 
208 /**
209  * rpcrdma_bc_receive_call - Handle a reverse-direction Call
210  * @r_xprt: transport receiving the call
211  * @rep: receive buffer containing the call
212  *
213  * Operational assumptions:
214  *    o Backchannel credits are ignored, just as the NFS server
215  *      forechannel currently does
216  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
217  *      No replay detection is done at the transport level
218  */
219 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
220 			     struct rpcrdma_rep *rep)
221 {
222 	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
223 	struct svc_serv *bc_serv;
224 	struct rpcrdma_req *req;
225 	struct rpc_rqst *rqst;
226 	struct xdr_buf *buf;
227 	size_t size;
228 	__be32 *p;
229 
230 	p = xdr_inline_decode(&rep->rr_stream, 0);
231 	size = xdr_stream_remaining(&rep->rr_stream);
232 
233 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
234 	pr_info("RPC:       %s: callback XID %08x, length=%u\n",
235 		__func__, be32_to_cpup(p), size);
236 	pr_info("RPC:       %s: %*ph\n", __func__, size, p);
237 #endif
238 
239 	rqst = rpcrdma_bc_rqst_get(r_xprt);
240 	if (!rqst)
241 		goto out_overflow;
242 
243 	rqst->rq_reply_bytes_recvd = 0;
244 	rqst->rq_xid = *p;
245 
246 	rqst->rq_private_buf.len = size;
247 
248 	buf = &rqst->rq_rcv_buf;
249 	memset(buf, 0, sizeof(*buf));
250 	buf->head[0].iov_base = p;
251 	buf->head[0].iov_len = size;
252 	buf->len = size;
253 
254 	/* The receive buffer has to be hooked to the rpcrdma_req
255 	 * so that it is not released while the req is pointing
256 	 * to its buffer, and so that it can be reposted after
257 	 * the Upper Layer is done decoding it.
258 	 */
259 	req = rpcr_to_rdmar(rqst);
260 	req->rl_reply = rep;
261 	trace_xprtrdma_cb_call(r_xprt, rqst);
262 
263 	/* Queue rqst for ULP's callback service */
264 	bc_serv = xprt->bc_serv;
265 	xprt_get(xprt);
266 	spin_lock(&bc_serv->sv_cb_lock);
267 	list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
268 	spin_unlock(&bc_serv->sv_cb_lock);
269 
270 	wake_up(&bc_serv->sv_cb_waitq);
271 
272 	r_xprt->rx_stats.bcall_count++;
273 	return;
274 
275 out_overflow:
276 	pr_warn("RPC/RDMA backchannel overflow\n");
277 	xprt_force_disconnect(xprt);
278 	/* This receive buffer gets reposted automatically
279 	 * when the connection is re-established.
280 	 */
281 	return;
282 }
283